0:15 Intro 1:56 First look inside 4:32 Cleaning is underway 9:29 First look at the schematic. This is a good design 12:58 A closer look at the amplifier section & some theory 22:49 Comparing the 2240 vs 2240b 26:00 Some changes that were done to the later production of the 2240 28:34 Modifying the original design & making a modified schematic 40:42 First look at the modified amp module and initial tests 44:27 Some square wave stability tests on the modified module 45:37 Same square wave test on original unmodified module 46:53 THD test on modified amp module 47:19 THD test on original stock amp module 47:45 First thoughts on how the two modules compare in performance 48:45 Adjusting the gain of the modified amp module to match the original module 55:04 Frequency analysis of the modified module 56:03 Final comments on the modified module 58:47 Modifying the second module - step by step 1:14:00 All I want is a-just be free, to live my life the way I wan a-be 1:14:43 The finished product & making some final tests/closing comments
Haven’t watched the full video yet but I really like your way of explaining everything. Keep up the good work and keep those devices away of the landfill.
Wow, that really cleaned up nicely. It is a testament to how well built those were. You figure living in that garage environment for decades, probably on 10 hours a day, through thunderstorms and wind storms, and just kept going.
Wooo!!...Astonishing ! Never seen such a transformation. You brought it back for trash to treasure. GREAT stuff... and huge and patience here between the cleaning and the electronics refurb/modding.
I love doing amps in this condition, I almost enjoy the cleaning up as much as the fixing the electronics especially if they are in good condition under the grime, it's very therapeutic 👍
Awesome video Tony, love the master class on the LTP and changes you made. These receivers are true gems and need to be preserved, which you did well. Looking forward to your future vids, thank you!
I know this an older video, but after following Tony through building and modifying those cheap foreign amplifiers, I’m beginning to understand what he’s talking about. I can find my way around on the schematic drawings. Now I’m scared! 🙂🙂🙂🙂
I can not BELIEVE how clean you got the inside of that amp/receiver! The before and after is beyond belief. Great job, not just cosmetic but performance. Thanks for the fun as always 🤩
I've been waiting for a channel like this for years. Thank you Tony for being so giving in your knowledge. There's so much to learn from this vid, I've watched it 3 times.
I had bought a new Marantz 1050 amplifier, cassette deck and tuner when I was 17 years old.I always thought they were wonderful things, until then after years there were some problems.To my great regret I consigned the amplifier to the scrapyard. After seeing all those videos what is possible. Regret regret regret regret....:-(
A Fantastic video for Marantz owners who want to work on their own gear. I have a Marantz 2235 and have been lost trying to get a basic understanding of what I'm looking at in the schematics.
I miss my Marantz that I lost in the divorce 20 years ago :-). Fantastic video! I really enjoy the time you take with the schematic and talking about Theory. Keep it up I may have found my favorite channel.
This video offers a terrific analysis of the power amplifier circuit design (thanks!) The quasi-complementary output stage (as seen in this model) dates back to the late 1950’s before the existence of complementary power transistors (matched NPN & PNP). At that time all germanium power transistors were PNP & all silicon power transistors were NPN. Matching complementary silicon power transistors were first introduced in the mid 1970’s. The quasi-complementary output stage circuit design in the original factory version of this model produces sufficient crossover notch distortion to be heard, especially when listening at low and moderate loudness. Crossover notch distortion is heard as a “buzzy” or “harsh” tonality and is a main reason why some listeners prefer tube amplifiers. However, crossover notch distortion can be greatly reduced by proper circuit design.
Тhank you Tony for sharing this interesting video. I have designed several quasi-complementary output stages in the past and they really sound and perform good when well thought out. Let me make couple of short notes here: 1) It is not the Vbe of the output transistor H002 but the Vbe of the driver H715 that is taken into account with the bias of 3xVbe drops in this topology. 2)Adding the current source upgrade will also improve the common-mode rejection ratio (CMRR) in this amplifier. It will not affect the closed loop gain of the amplifier. So it doesn't make sense to lose gain using it. The closed loop gain is determined by the ratio (R714+R710) / R710 , which is 19.3 (25.7dB). So increasing R710 lowers the closed loop gain and the implementation of the current source has nothing to do with it. 3)Changing R720, R721, R723, R724 will only move the trigger point for the over-current protection. 4)This amplifier can be much more improved (adding current mirror, emitter follower on the VAS stage...etc) but I agree with you that it is already a well designed one. Regards, Tony B (namesake 😄)
HI Toni, Thank you for the comment! Looking back at this video, I really did a pretty lousy job of explaining the diff amp section of the receiver. I should have spoken more about common mode vs differential mode signals. I also should have explained more clearly how one transistor in the pair amplifies the input signal and the other receives the negative feedback form the output of the amp and how they add together at the differential output. I also didn't do a very good job on how these signals interact and how varying the common mode current can affect the linearity of the pair (although it is usually only slightly). I have the next project already on the bench, but I may clear the deck for a moment and get out the breadboard for a quick follow-up video. It would probably do me some good as well, because I haven't done this since college in the 1980's. Besides, my son is now in college studying EE and is starting to call and ask questions as he sees this stuff in class. It just reminds me of how little I remember ;( Thanks again for the comment. You were spot-on!
I really like your channel. It gave me the courage to get into this hobby. I have been watching your channel for years and my first time commenting. I had to after the nonferatu comment. It was really funny. I really appreciate the great entertainment.
Great restoration mod, the receiver looked nasty indeed. Way better now! Nice mods too. By the way, as for CCS in tube projects, I prefer tube-based. Got one in my amp, in the LTP phase inverter's tail. Now the amp is undergoing some redesign and I'm switching from triode-based CCS to pentode--based using EF80.
I wish I could find something like this to fix up. I have a working Sherwood S-7100A I am going to do a partial recap on just as a learning exercise. Ordered the caps today. Hope to work on more in the future.
I love how it look and how it cleaned up, it seems to sound really good too. However I do miss some of the midrange but that's something that I like personally, I love when the midrange really pops so when you hear a bass you hear a bit of it on the midrange too, you know that pop sound, that's what I love. Could be the mic you're using or it is actually what I heard, I do have 2 big Infinity Studio Monitors, model SM 155... Those have 2 midrange speakers so my midrange is already big compared to normal speakers and I still miss the midrange when you played the track on the amplifier but it UA-cam and there are so many variables that I can't tell you if I'm correct or not.
Great knowledgeable and confident repairmen are never afraid to completely disassemble and clean first before repair. Its always a lot more comfortable to work on clean equipment. Cleaning can solve problems for example I had an Akai amp that did not have bad components it only had conductive glue and corrosion that stopped it from working. You and I can build one of these from scratch let alone repair it. ....It might take a couple of years😆. The secretary where I work at refers me to customers as a technician. I hate the word technician. I am a repairman. Technicians do technical work and still not fix a thing.
the other week i found a 'sponge spacer' in a not so old receiver (vsx-40?) that became slightly conductive as it dried out by touching the heat sink. it was right on the soldered posts of the preamp input board connector... many years ago we had a wave of customers complaining about erratic mouse and keyboard behavior after buying a batch of imported Dell PCs. after swapping mice and keyboards, reinstalling and logging errors, we discovered there were minuscule metal shavings under the mainboards for whatever reasons. that fix took longer than anyone wanted.. cleaning and visual inspection are underrated :} ps: how about 'technologist'? :}
This was amazing. Love that you experiment, for the fun of it, and still are able to learn/teach. I learned a lot and I was highly entertained so fantastisk video. So happy i stumbled over this channel. You mentioned some books are you planning on doing some reviews?
Great video as always. Gives me the motivation to go look for the Marantz 1530 I have somewhere. Would live to know more about the ultrasonic cleaning of boards. Do you just use water or do you add a few drops of dish soap or something else? How long too? I guess boards with certain types of components should not get wet like relays and pots am I right? Can’t believe you did the tuning cap what great idea assuming one can do the alignment over of course.
I would have loved to see you repeat the tests after reducing the feedback. I am curious about whether the distortion increased and how the amplifier handled capacitive loads.
The interaction between speaker and amplifier is something I see consistently ignored by everyone. I'd like to see more content about how the amp controls the speaker and doesn't just merely drive it. I think that explains what you are hearing.
Proving once again that I will never achieve friend of the electron status. I did notice that before attacking the second board you didn't see if temperatures were overall better with the first one.
Tony, thanks for the informative video. I have a Marantz 2250B since purchasing it in 1976. My balance slider stopped functioning and I took it to a tech in North Carolina and he had to bypass it since he said it was not functioning. The receiver still sounds great but I did not know if you had any experience on repairing the balance slider? My other option is to just continue to look on line for the part 500 ohm RS0504002 of the parting out sale. Thanks Dave
Hi Tony, I think the reduced gain on the "modified" version is due to the change you made to R710 (increased to 2.7k, as can be seen in your schematic at 1:00:05 and confirmed at 1:07:48), instead of having a current source feeding the diff. If you calculate the theoretical gain of the whole amplifier (R714/R710), you'll find Av = 19.3 > 1+(33k/1k8) and Av = 13.2 > 1+(33k/2k7) for the modified version, prior to change R714 to 51k. I also recommend to maintain R714 equal to R702 (33k both) to prevent differential pair base currents inbalance. Work on R710 instead, if you really need to change gain of the whole amplifier. What's your thinking about ?
Hello Tony .................what would happen if instead of using a CCS in place of the resistor.........you should add a capacitor bypass on the original resistor ?
i had the 4240 Quadraphonic Receiver in the mid 70's 2x40 watt 4x17 watt with Dolby FM and a Dolby processor so you could Record Dolby B to Reel to Reel Tape Recorders
Same with me, i loved my old equipement, mp3's came, moved house through work and had to sell my gear as part of the move...... completely regret the life choices i made at the time....
Love your videos Tony, But I have a non electronics related question, How the hell do mice get into an amp with 2mm wide vent holes? Its always puzzled me .
Did you manually enter the schematic into a drawing or circuit design program on your pc? If so, what program? Or did you just scan the original schematic as an image and then enlarge on the pc?
Hello Tony I need some expert advice. I had a customer brought in a Kenwood KR-5010 receiver. The STK Darlington power packs were shorted so I went to eBay and ordered from dalbani two STK-0050 and one TA-1001 trio voltage amplifier. I replaced all three ICs and connected the AC to a 40watt dim bulb tester and the voltages on the TA-1001 are as follows starting from pin one to fifteen; 0.1 volt, -0.3 volt, 28.4 volt, 28.7 volt, -10 volt, -10 volt, -30 volt, 0 volt, 30 volt, -10 volt, -10 volt, 28.7 volt, 28.4 volt, -0.3 volt, 0.1 volt. I think the new TA-1001 is bad. I don't think it's a new one from dalbani but a pulled one from another unit. I paid about $29.00. There is a supposedly "rebuilt" for $21.00 from the same place. I was wondering if you had the same problem
Hey Tony. Great job on the video. I believe my father purchased a 2240 back in '74, so I remember this from being a kid and listening with my dad. With his health no failing, I purchased a 2240 off of ebay, to be in my office as visual reminder of my dad and the happy times we had listening to albums, 8-tracks, and later cassettes. Because I want to keep this forever and will want to check out each board and component (read degree in electronics and an engineer at this time) would you have a link to this schematic or be able to point me to somewhere I could download this file? At work, we have a plotter, so printing this at C-size (that's what it looks like in the video) would be easy once I have the file. Thanks and keep up the great work!
“This has been sitting in a mechanic shop for 20 years.” Me, a mechanic: “Oh, no. This is going to be bad.” Yeah, the stuff that builds up on surfaces in the shops is really stubborn, few things short of brake cleaner will fully clean off the gunk.
That’s a little disgusting 🤢 to see turds 💩 falling out of this radio 📻, onto your bench. Just sterilize your bench, and wash 🧼 your hands 🙌 before eating 🍽. Although your bench isn’t a place you’ll eat, you won’t want the Hantavirus, especially if this is about mice 🐁, or rats 🐀. Just be careful there’s also no urine on any of the circuit boards, this can short them out. That radio 📻 has a VERY IMPRESSIVE set of tuning gangs. I can tell ya that this is a 1970’s receiver, just by the look 👀, possibly mid 1980’s. That transformer is a Marantz. It is definitely worth rebuilding. VERY NICE 👍 schematic, you’ll wanna hold onto it. Your friend, Jeff.
I have a Model 2225 and lately it started crackling and popping in the left channel. It stopped for a while but came back. Do you have any idea what it could be? A failing transistor or the relay?
I hope you get an answer. At the most basic level, excercising the slider after using some Deoxit on it might help? I was told these sliders are not as robust as the channel knobs. I own a 2226B and a 2250 and am learning.
If you remove potentiometers and dont clean the tuner board as the tuning pots can hold water for a long time, i shouldn't think ot would matter.... use a soft toothbrush, that helps and becarefull not to dislodge componants.... no problem 🙂👍🏻
Isn't the output stage of this amplifier similar to that Quasi Complimentary eBay kit that you put together some time ago Tony? As I recall it didn't work out for you back then and I was hoping that you would have a go at it to make it work better but it never reared its head again! I have a few of those eBay Quasi Complimentary amplifiers that I have yet to put together but I'm waiting for someone who knows more than me to fix it and get it to work properly.... I have seen plenty of people put it together and claim that it sounds great! But there's no videos on modifying it to improve it.....
Shango's special indeed. Edit after watching: You had once proper stabistors in the DIP packages, why not use them? Edit2: It seems the in and out front panel sockets, the broken ones, could be substituted with ordinary headphones' 6,3 mm TRS jack sockets. They would fit nice.
Hi Tony. Excellent video. Recently, I bought the Marantz 2226. It is in a similar condition to the 2240 in your video, and it requires a good clean and parts (which unfortunately are scarce in Melbourne, Australia). You mentioned how the real improvement - in terms of cleaning - was when ultrasonic cleaning. was used. I am new to this so my question is this: do I need to disassemble the entire unit and clean the different parts separately, or can the entire unit be cleaned as one (eg I have seen the guy from AhFixIt use a powerwash at a car wash outlet)? Any risk involved in damaging key components ie you mention transistors? Any assistance would be fantastic. Thanking you, or anyone who can help, in advance. Regards. Sam
@dohmesam Hay Sam... 🙂👋🏼 I dont think i would run an amplifier board through the "car wash" lol.... (i too saw the video and was horrified)... I think the strength of the power lance could eaisily dislodge componants on the board or damadge anything that dosent like water (like volume, balance, bass and trebble controls, and parts of the tuners adjustment pots), i think that video was just made for fun and entertainment, it would be something i would never do to my own equipement. If you are able to remove certain boards (and remove atleast the potentiometers off the tone board), then a "bubble cleaner" 😂 should be safe enough. Best wishes from UK... 🙂
I think a customer brought in a unit like that to me, they would have to want it restored pretty bad, because just the cost of cleaning for me, would be the worth of the amp.
@@xraytonyb I wish all receivers had been designed so that the tuning dial as well as the dial pointer did not illuminate unless you were using the tuner. Not only would the lamps last a lot longer but the receivers would be less likely to have badly baked, discolored, and melted plastic decades later (unless of course the tuner was the only function that the unit's owner ever used, as is likely in a mechanic garage. I don't imagine they were playing records very much, perhaps some cassette tapes or the occasional CD). You can usually tell what function was the most frequently used because the indicator lamp for that function will be burned out or much darker and blackened than the others.
Of course it's not working, it doesn't have any LoL... The Two meters are for the tuner, not the output power... I personally would have preferred output power meters but in the end, you get what you are given LoL.
I think the 2240 is an incorrect designation - or - the faceplate fasteners have been replaced. The hex fasteners are typically an indication of a "B" model.
what about the noise floor you didn't measure that? and it's in the listening more than measurements interesting to see what it sounds like compared to the original. what would be nice maybe on the next one,!! is to run the gain stage with a valve like a12ax7 that would be good. is it like two-phase is that why they flip to increase greater voltage draw ?
Carlos, you've deleted your posts, so I'll take the opportunity remaining ones present. I can only see a snippet of your answer. Amp is simply inverting both outputs, hence they are in phase in relation to each other ! The jump you see on the Bode plot is the phase plot going above or below 180°, this undulation is there for crushing majority of amps and would look perfectly normal, if plotted at 0° line in the midrange instead. All it takes to restore absolute phase is to swap both speaker connections. Simply connect plus terminals to negative and minus to positive and your output signal will be in phase with the input. As to "bass control", you never use them if the goal is to increase sound quality! You either set them to zero (good), engage tone defeat (better), or use an amplifier without any of that nonsense (best).
Avoid tv technicians who beg for Google review for extra high special price. They drill holes into the relais (!) and spray Teslanol T6 trough it and knot dial cords in the middle.
So you added the costs of the restoration by putting in unnecessary parts, you lowered the value of the unit by modifying it from its original form. For your efforts you got the same performance with a theoretically more stable unit. and learned that you can mod anything?
I thought I made it abundantly clear that this was an experiment to see how the two designs compared. I am charging no one for this project and am funding it myself. I took the time to share the results with all of you. I learned that by studying the original circuit design as well as the changes made by the manufacturer on later models, we can modify an already well-designed circuit to improve stability and/or performance. I also learned that not all changes will make a difference that can be seen on an oscilloscope or other test equipment. Another thing I learned when I opened the cover of this receiver was that there was no way that this mouse turd encrusted device will ever be a museum quality example of a Marantz 2240, but with a lot of work could become a very good performing receiver that can be used every day for its intended purpose to enjoy music and good sounding audio for years to come. For me, the value in this unit was in what I have learned from rebuilding it and the satisfaction that it is now a useable piece of audio gear instead of part of a landfill. Thank you for the comment.
@StevenTheElder Sir, I think you mistake my intent. I merely trying to point out the costs of the lesson involved here. There is no value judgement attached on my part.
No offense taken. This is not what I would suggest doing for a customer, nor is it something I would want to have done as a customer. I think it just proves what I said: Marantz did an exceptional job designing this receiver, especially when you consider that this was not their top of the line unit.
I didn't know that Nichicon capacitors from Mouser were made in China and other places sell Nichicon capacitors made in Japan. Is this true? I buy a lot of product from Digikey, Newark and Allied Electronics as well. Are their Nichicon caps made in China or Japan? I'm now also wondering about Cornell/Sprague/Kemet/Panasonic/etc. Do some distributers get products made in different countries than the others? Also, if they were made in China to the same spec, how would they be different? I've never heard this before. Please explain???
@@xraytonyb I have been asking Mouser where are your Electrolytic capacitors made never reply never. Made in China caps quality are not as good as made in Japan.I have had Nichicon. Rubycon caps from china that have very bad ESR and fail. Its all about the material Tony simple. I have a top suppler in Australia that buys direct from W/Sale in Japan, and are 100% made in Japan. Cost is high but the quality is as you accept products that is MFG in Japan.
IMHO the country of origin isn’t as important as the specifications. Over the past 30 years I’ve purchased huge amounts of electrolytic capacitors from both Digikey & Mouser. I haven’t observed any significant failures yet from either source. Both Mouser & Digikey publish complete specs and offer manufacturer’s data sheets. Although the “great capacitor plague” in the early 2000’s affected many brands, those issues were all corrected & haven’t reoccurred. For power supply applications I select capacitors with a high ripple current rating. This also corresponds to a very low ESR. I check ESR routinely for both old & new capacitors. Surprisingly I have found some 60-year old electrolytics to be totally within all specs. I have also seen failed electrolytics that were
@@electricboyo Yes it is. Very important very as you will be paying for quality for your customers repairs simple not counter fit. Mouser is large due to caps mfg in Thailand simple and China. The best caps in the world are Made in Japan.We do 100s repairs every year and when I was using Mauser there caps always gone bad.
Your explanation of how the differential input circuit works is wrong! The current in emitter resistor is constant regardless of the signal swing! The current through the collectors is the same at idle! As the current increases in the input transistor, it decreases by the same amount in the second transistor! So the current in the emitter resistor remains constant!! The differential amplifier is biased class A. Current is flowing in both transistors at all times!
If you did'nt use the offensive language, one might be encouraged to review Tony's explanation and your argument. Maybe you look to other comments here to see how to express yourself.
@@cjay2 the reason I said BS is because he is misinforming his viewers and fans of his channel!! This man is a professional and should know better!! I changed BS to wrong as you suggested!
@Raul I will try to explain you why the current through the differential pair input is not constant and depends on the voltage swing. If you have 1V p-p input signal then the voltage on the differential pairs emitters will vary + - 1 Vbe drop i.e. from -0.3V to 1.7V Vp-p therefore the current through the 6.8k resistor will vary form 2.3mA to 2.6mA. That's why we use better current sources (usually active loads) than a single resistor.
@@RaulHernandez-lg5nw online communication is tricky as it lacks so much of the nuances of the spoken word (not to mention language and cultural barriers)... what works best for me is to observe the tone the community members use and adapt.. it's like walking into a party and checking if ppl wear their shoes or not, are they loud talking, am i the last one to be sober, etc i myself dwell in profanity and your choice of words doesn't register as offensive language BUT i'm not the one hosting the party. it's nice of you editing the comment as it hints to your intentions/temperament. the vast majority of internet users have the opposite reaction (almost never works) :} hope this helps, i know it may appear annoying but it works. wish you the best.
There is absolutely no difference between the original version and the one with the constant current. So, other than heating problems how can anyone claim that "the bass here sounds better" when the scope shows no difference whatsoever? Besides, it's only the bass, and the terms they use are so subjective that it can't be nothing else than pseudo-science... Sorry Tony, you're usually a quite reliable and competent technician, if I had to hand my equipment to someone here on UA-cam I'd probably hand it over to you, but please do not fall through the audiofoolery rabbit hole, even more when you use a test music that clearly has been recorded and mixed digitally...
Thanks for the comment. This is the reason I did this video. From what we can see on the test equipment, there is little to no difference in the performance of the stock design vs the modified design. Sound quality of any audio gear will always be subjective. As a repair technician, our job is to make sure the amp is performing up to spec. What I can say about this particular project is this: The CCS will keep the diff amp stage a bit more stable, especially when it comes to music with a lot of dynamics. In addition, the transistor pair will be less likely to drift because of temperature changes. The circuit would be improved with the addition of a current mirror at the collectors, but it is not practical to do on this amp. Many other designs make this same compromise by using a CCS at the tail with no current mirror at the collectors. As for the improved bass, I can only report what I hear when compared to stock versions of this amp. Is it placebo effect and I'm just crazy? Perhaps. I rarely say things like this, as I am someone who likes to be able to "view" what I am hearing through the use of test equipment. The recording didn't do justice to the real thing (it never does). This amp really sounds good to my bad ears. Anyway, this is the kind of stuff I really like to discuss with others. This is how we learn. Thanks again for the comment!
I don't recall that he compared the bass response of the modified to the unmodified, but the amp in general to other amps. Speakers are NOT simple resistive loads. But all testing I've seen (from everyone) fails to look a the complex interaction between amp and speaker. Looking at dampening factor is a start.
13:59 exactly, both transistors show NPN; yet you called one a PNP despite the diagram, why? This is why such videos are extremely confusing and indeciperable to amateurs who know nothing, and likely never will thanks to the contradictions and lack of clear explanations.
Before you start insulting me, please listen to the video again. What I said is that there are 4 similar models of this receiver; the 2240, 2240b, 2238 and 2238b. The main difference is the output transistor configuration. The 2240 uses a "quasi-complimentary " output stage, while the others use a "true complimentary" output stage. The main difference is that quasi-complimentary output stages use two NPN transistors and true complimentary output stages use an NPN for the positive side and PNP for the negative side. If you search "quasi complimentary vs True complimentary output stage" you will most likely find a lot more info. There is no contradiction if you listen to what was said just before the time marker you listed. If you are willing to ask questions instead of assuming that everything is wrong, you may find that you can learn this. I am more than happy to answer any other questions you may have, within reason.
@@xraytonyb No insult was intended. Your uploads are very informative, and I mainly watch them to learn as that's the best anyone can do with one's time. Thanks very much for taking the time and effort to explain. Don't know how you dealt with the mouse leftovers, but somewhere I heard that you should never vacuum rodent feces as minute particles can go through the vacuum filter and become air born, potentially leading to serious health problems.
But....but.... the purity of the sound .... ("never mind the width... feel the quality" !).... lol This gear at whatever wattage sounds far better then the "modern" switched mode class d amplifiers ..... stick with your bluetooth crapple ear buds and enjoy your life,and let the rest of us enjoy something far superior 😎
0:15 Intro
1:56 First look inside
4:32 Cleaning is underway
9:29 First look at the schematic. This is a good design
12:58 A closer look at the amplifier section & some theory
22:49 Comparing the 2240 vs 2240b
26:00 Some changes that were done to the later production of the 2240
28:34 Modifying the original design & making a modified schematic
40:42 First look at the modified amp module and initial tests
44:27 Some square wave stability tests on the modified module
45:37 Same square wave test on original unmodified module
46:53 THD test on modified amp module
47:19 THD test on original stock amp module
47:45 First thoughts on how the two modules compare in performance
48:45 Adjusting the gain of the modified amp module to match the original module
55:04 Frequency analysis of the modified module
56:03 Final comments on the modified module
58:47 Modifying the second module - step by step
1:14:00 All I want is a-just be free, to live my life the way I wan a-be
1:14:43 The finished product & making some final tests/closing comments
Haven’t watched the full video yet but I really like your way of explaining everything. Keep up the good work and keep those devices away of the landfill.
Randy Sloane (RIP) has two great books also. 1) The Audiophiles Project Source Book and 2) High Power Audio Amplifier Construction Manual.
Wow, that really cleaned up nicely. It is a testament to how well built those were. You figure living in that garage environment for decades, probably on 10 hours a day, through thunderstorms and wind storms, and just kept going.
I think the garage had a roof on it, as i dont think they would have left it outside in the rain powered up lol.......
Amazing comment...
Hi Tony,
Once again - always the best from your basement!!!
Out of many YT audio channels, you are a true mentor.
Many Thanks and Best Regards,
Jack
Looove the theory and schematic sections of your vids. Like a look into the past, and just inspires. Thanks
I used to service these back in the day. Memories.
Wooo!!...Astonishing ! Never seen such a transformation. You brought it back for trash to treasure. GREAT stuff... and huge and patience here between the cleaning and the electronics refurb/modding.
Hello from Columbus Ohio USA
I love doing amps in this condition, I almost enjoy the cleaning up as much as the fixing the electronics especially if they are in good condition under the grime, it's very therapeutic 👍
Awesome video Tony, love the master class on the LTP and changes you made. These receivers are true gems and need to be preserved, which you did well.
Looking forward to your future vids, thank you!
I know this an older video, but after following Tony through building and modifying those cheap foreign amplifiers, I’m beginning to understand what he’s talking about. I can find my way around on the schematic drawings. Now I’m scared! 🙂🙂🙂🙂
I can not BELIEVE how clean you got the inside of that amp/receiver! The before and after is beyond belief. Great job, not just cosmetic but performance. Thanks for the fun as always 🤩
I like the feedback resistor trick. Ratio and proportion.
I've been waiting for a channel like this for years.
Thank you Tony for being so giving in your knowledge. There's so much to learn from this vid, I've watched it 3 times.
Thanks Tony for the educational and skill teaching you have done with this tuner. Totally enjoyed!
I had bought a new Marantz 1050 amplifier, cassette deck and tuner when I was 17 years old.I always thought they were wonderful things, until then after years there were some problems.To my great regret I consigned the amplifier to the scrapyard. After seeing all those videos what is possible.
Regret regret regret regret....:-(
Loudness does not equal fidelity... i wish i had one of these and will be looking foe one, Great video as always Tony, Thanks!
A Fantastic video for Marantz owners who want to work on their own gear. I have a Marantz 2235 and have been lost trying to get a basic understanding of what I'm looking at in the schematics.
Great Job. Beautiful looking piece of equipment.
I miss my Marantz that I lost in the divorce 20 years ago :-). Fantastic video! I really enjoy the time you take with the schematic and talking about Theory. Keep it up I may have found my favorite channel.
Marantz should have put a blank prenup form in the appendix of the owners manual ;)
This video offers a terrific analysis of the power amplifier circuit design (thanks!) The quasi-complementary output stage (as seen in this model) dates back to the late 1950’s before the existence of complementary power transistors (matched NPN & PNP). At that time all germanium power transistors were PNP & all silicon power transistors were NPN. Matching complementary silicon power transistors were first introduced in the mid 1970’s. The quasi-complementary output stage circuit design in the original factory version of this model produces sufficient crossover notch distortion to be heard, especially when listening at low and moderate loudness. Crossover notch distortion is heard as a “buzzy” or “harsh” tonality and is a main reason why some listeners prefer tube amplifiers. However, crossover notch distortion can be greatly reduced by proper circuit design.
Well done! Tony
Тhank you Tony for sharing this interesting video.
I have designed several quasi-complementary output stages in the past and they really sound and perform good when well thought out.
Let me make couple of short notes here:
1) It is not the Vbe of the output transistor H002 but the Vbe of the driver H715 that is taken into account with the bias of 3xVbe drops in this topology.
2)Adding the current source upgrade will also improve the common-mode rejection ratio (CMRR) in this amplifier.
It will not affect the closed loop gain of the amplifier. So it doesn't make sense to lose gain using it. The closed loop gain is determined by the ratio (R714+R710) / R710 , which is 19.3 (25.7dB). So increasing R710 lowers the closed loop gain and the implementation of the current source has nothing to do with it.
3)Changing R720, R721, R723, R724 will only move the trigger point for the over-current protection.
4)This amplifier can be much more improved (adding current mirror, emitter follower on the VAS stage...etc) but I agree with you that it is already a well designed one.
Regards,
Tony B (namesake 😄)
HI Toni,
Thank you for the comment! Looking back at this video, I really did a pretty lousy job of explaining the diff amp section of the receiver. I should have spoken more about common mode vs differential mode signals. I also should have explained more clearly how one transistor in the pair amplifies the input signal and the other receives the negative feedback form the output of the amp and how they add together at the differential output. I also didn't do a very good job on how these signals interact and how varying the common mode current can affect the linearity of the pair (although it is usually only slightly). I have the next project already on the bench, but I may clear the deck for a moment and get out the breadboard for a quick follow-up video. It would probably do me some good as well, because I haven't done this since college in the 1980's. Besides, my son is now in college studying EE and is starting to call and ask questions as he sees this stuff in class. It just reminds me of how little I remember ;( Thanks again for the comment. You were spot-on!
I really like your channel. It gave me the courage to get into this hobby. I have been watching your channel for years and my first time commenting. I had to after the nonferatu comment. It was really funny. I really appreciate the great entertainment.
Excellent work and thank you for all your videos!
I have had a 2245 since 1971.
Schematics, TonyTalk, GoodAmp, .. = joyful/inspirational/happiness ..Thanks for interesting video(s)
Greetings from Mt. Lebanon. Loved the Shango shootout at the beginning.
Great restoration mod, the receiver looked nasty indeed. Way better now! Nice mods too.
By the way, as for CCS in tube projects, I prefer tube-based. Got one in my amp, in the LTP phase inverter's tail. Now the amp is undergoing some redesign and I'm switching from triode-based CCS to pentode--based using EF80.
That is the first time I have heard The Seeds in a repair/restore video! "Pushin' too hard, on meeeeeeee"
the ring camera ring kept making me look at my phone. lol. Great job Tony
I wish I could find something like this to fix up. I have a working Sherwood S-7100A I am going to do a partial recap on just as a learning exercise. Ordered the caps today. Hope to work on more in the future.
It sounds So much better then UA-cam's audio Clip..Very Good Amp..
thanks for the vid tony
I love how it look and how it cleaned up, it seems to sound really good too. However I do miss some of the midrange but that's something that I like personally, I love when the midrange really pops so when you hear a bass you hear a bit of it on the midrange too, you know that pop sound, that's what I love.
Could be the mic you're using or it is actually what I heard, I do have 2 big Infinity Studio Monitors, model SM 155... Those have 2 midrange speakers so my midrange is already big compared to normal speakers and I still miss the midrange when you played the track on the amplifier but it UA-cam and there are so many variables that I can't tell you if I'm correct or not.
I just bought Art of Electronics, and you're right, excellent book 😉 I also recommend Douglas Self's books 😉
I do wish I could get my turntable to you your work is superb.
CLR calcium, lime, rust remover... saw Bandersentv using that and works too
Great knowledgeable and confident repairmen are never afraid to completely disassemble and clean first before repair. Its always a lot more comfortable to work on clean equipment. Cleaning can solve problems for example I had an Akai amp that did not have bad components it only had conductive glue and corrosion that stopped it from working. You and I can build one of these from scratch let alone repair it. ....It might take a couple of years😆. The secretary where I work at refers me to customers as a technician. I hate the word technician. I am a repairman. Technicians do technical work and still not fix a thing.
the other week i found a 'sponge spacer' in a not so old receiver (vsx-40?) that became slightly conductive as it dried out by touching the heat sink. it was right on the soldered posts of the preamp input board connector...
many years ago we had a wave of customers complaining about erratic mouse and keyboard behavior after buying a batch of imported Dell PCs. after swapping mice and keyboards, reinstalling and logging errors, we discovered there were minuscule metal shavings under the mainboards for whatever reasons. that fix took longer than anyone wanted..
cleaning and visual inspection are underrated :}
ps: how about 'technologist'? :}
This was amazing. Love that you experiment, for the fun of it, and still are able to learn/teach.
I learned a lot and I was highly entertained so fantastisk video. So happy i stumbled over this channel.
You mentioned some books are you planning on doing some reviews?
Good...we see that recap is not always needed
Sounds very good
Great video as always. Gives me the motivation to go look for the Marantz 1530 I have somewhere. Would live to know more about the ultrasonic cleaning of boards. Do you just use water or do you add a few drops of dish soap or something else? How long too? I guess boards with certain types of components should not get wet like relays and pots am I right? Can’t believe you did the tuning cap what great idea assuming one can do the alignment over of course.
I've got a 2252b, wonder if those types of mods are available in that amp, love the Maranz sound.
Beautiful
I would have loved to see you repeat the tests after reducing the feedback. I am curious about whether the distortion increased and how the amplifier handled capacitive loads.
distortion may change but also create less other distortions due to NFB! depends also on the load of different LS if they need more or less NFB !
Before I store things away I wrap it with plastic wrap. This keeps my steel clean and dry.
The interaction between speaker and amplifier is something I see consistently ignored by everyone. I'd like to see more content about how the amp controls the speaker and doesn't just merely drive it. I think that explains what you are hearing.
Great apparatus 👍👍👍
Proving once again that I will never achieve friend of the electron status.
I did notice that before attacking the second board you didn't see if temperatures were overall better with the first one.
Tony, thanks for the informative video. I have a Marantz 2250B since purchasing it in 1976. My balance slider stopped functioning and I took it to a tech in North Carolina and he had to bypass it since he said it was not functioning. The receiver still sounds great but I did not know if you had any experience on repairing the balance slider? My other option is to just continue to look on line for the part 500 ohm RS0504002 of the parting out sale. Thanks Dave
very cool, how about a baxandall diode on this one?
Hi Tony, I think the reduced gain on the "modified" version is due to the change you made to R710 (increased to 2.7k, as can be seen in your schematic at 1:00:05 and confirmed at 1:07:48), instead of having a current source feeding the diff.
If you calculate the theoretical gain of the whole amplifier (R714/R710), you'll find Av = 19.3 > 1+(33k/1k8) and Av = 13.2 > 1+(33k/2k7) for the modified version, prior to change R714 to 51k.
I also recommend to maintain R714 equal to R702 (33k both) to prevent differential pair base currents inbalance.
Work on R710 instead, if you really need to change gain of the whole amplifier.
What's your thinking about ?
Hello Tony .................what would happen if instead of using a CCS in place of the resistor.........you should add a capacitor bypass on the original resistor ?
i had the 4240 Quadraphonic Receiver in the mid 70's 2x40 watt 4x17 watt with Dolby FM and a Dolby processor so you could Record Dolby B to Reel to Reel Tape Recorders
I had a 2270, then upgraded to a 4270 (QUAD), and then a 4300. I would love to have them back. but life goes on.
Same with me, i loved my old equipement, mp3's came, moved house through work and had to sell my gear as part of the move...... completely regret the life choices i made at the time....
i have same radio but tuner section not works. what may be problem??
Love your videos Tony, But I have a non electronics related question, How the hell do mice get into an amp with 2mm wide vent holes? Its always puzzled me .
The mouse poop falls through the slots.
Did you manually enter the schematic into a drawing or circuit design program on your pc? If so, what program? Or did you just scan the original schematic as an image and then enlarge on the pc?
Thanks Tony fun with out the mouse poop
The guts on that Marantz look a lot like whats inside my Pioneer SX3700.
Negative. I have been inside many Marantz units, and I also own a SX3700. To my eyes, they are entirely different.
Hello Tony I need some expert advice. I had a customer brought in a Kenwood KR-5010 receiver. The STK Darlington power packs were shorted so I went to eBay and ordered from dalbani two STK-0050 and one TA-1001 trio voltage amplifier. I replaced all three ICs and connected the AC to a 40watt dim bulb tester and the voltages on the TA-1001 are as follows starting from pin one to fifteen; 0.1 volt, -0.3 volt, 28.4 volt, 28.7 volt, -10 volt, -10 volt, -30 volt, 0 volt, 30 volt, -10 volt, -10 volt, 28.7 volt, 28.4 volt, -0.3 volt, 0.1 volt. I think the new TA-1001 is bad. I don't think it's a new one from dalbani but a pulled one from another unit. I paid about $29.00. There is a supposedly "rebuilt" for $21.00 from the same place. I was wondering if you had the same problem
Hey Tony. Great job on the video. I believe my father purchased a 2240 back in '74, so I remember this from being a kid and listening with my dad. With his health no failing, I purchased a 2240 off of ebay, to be in my office as visual reminder of my dad and the happy times we had listening to albums, 8-tracks, and later cassettes. Because I want to keep this forever and will want to check out each board and component (read degree in electronics and an engineer at this time) would you have a link to this schematic or be able to point me to somewhere I could download this file? At work, we have a plotter, so printing this at C-size (that's what it looks like in the video) would be easy once I have the file. Thanks and keep up the great work!
Go to hifiengine.com . They have the service manual available there for download. You have to have an account to download, but it's free.
@@xraytonyb Thank you so much!
FYI, registration is closed to new members.😐
That sucks. Thanks for letting me know. I was unaware. You can also try elektrotanya.com
@@jonathanjackson669 keep checking periodically you will eventually get in.
Xraytonyb your Marantz 2240 is cool
I have a Yamaha streo mw fm receiver
I have a shortwave receiver ssb mw lw fm air band
“This has been sitting in a mechanic shop for 20 years.”
Me, a mechanic: “Oh, no. This is going to be bad.”
Yeah, the stuff that builds up on surfaces in the shops is really stubborn, few things short of brake cleaner will fully clean off the gunk.
That’s a little disgusting 🤢 to see turds 💩 falling out of this radio 📻, onto your bench. Just sterilize your bench, and wash 🧼 your hands 🙌 before eating 🍽. Although your bench isn’t a place you’ll eat, you won’t want the Hantavirus, especially if this is about mice 🐁, or rats 🐀. Just be careful there’s also no urine on any of the circuit boards, this can short them out. That radio 📻 has a VERY IMPRESSIVE set of tuning gangs. I can tell ya that this is a 1970’s receiver, just by the look 👀, possibly mid 1980’s. That transformer is a Marantz. It is definitely worth rebuilding. VERY NICE 👍 schematic, you’ll wanna hold onto it. Your friend, Jeff.
I have a Model 2225 and lately it started crackling and popping in the left channel. It stopped for a while but came back. Do you have any idea what it could be? A failing transistor or the relay?
I hope you get an answer. At the most basic level, excercising the slider after using some Deoxit on it might help? I was told these sliders are not as robust as the channel knobs. I own a 2226B and a 2250 and am learning.
love that song ..showing my age lol
Nice shoutout to shango066 and his usual victims!
What do you use in the ultrasonic cleaner - only water? If yes, can the boards be cleaned by soaking them in the kitchen sink? :)
If you remove potentiometers and dont clean the tuner board as the tuning pots can hold water for a long time, i shouldn't think ot would matter.... use a soft toothbrush, that helps and becarefull not to dislodge componants.... no problem 🙂👍🏻
Isn't the output stage of this amplifier similar to that Quasi Complimentary eBay kit that you put together some time ago Tony?
As I recall it didn't work out for you back then and I was hoping that you would have a go at it to make it work better but it never reared its head again!
I have a few of those eBay Quasi Complimentary amplifiers that I have yet to put together but I'm waiting for someone who knows more than me to fix it and get it to work properly....
I have seen plenty of people put it together and claim that it sounds great! But there's no videos on modifying it to improve it.....
Shango's special indeed.
Edit after watching: You had once proper stabistors in the DIP packages, why not use them?
Edit2: It seems the in and out front panel sockets, the broken ones, could be substituted with ordinary headphones' 6,3 mm TRS jack sockets. They would fit nice.
Why not clean it first, then try turning it on?
Hi Tony. Excellent video. Recently, I bought the Marantz 2226. It is in a similar condition to the 2240 in your video, and it requires a good clean and parts (which unfortunately are scarce in Melbourne, Australia). You mentioned how the real improvement - in terms of cleaning - was when ultrasonic cleaning. was used.
I am new to this so my question is this: do I need to disassemble the entire unit and clean the different parts separately, or can the entire unit be cleaned as one (eg I have seen the guy from AhFixIt use a powerwash at a car wash outlet)? Any risk involved in damaging key components ie you mention transistors? Any assistance would be fantastic. Thanking you, or anyone who can help, in advance. Regards. Sam
@dohmesam
Hay Sam... 🙂👋🏼
I dont think i would run an amplifier board through the "car wash" lol.... (i too saw the video and was horrified)...
I think the strength of the power lance could eaisily dislodge componants on the board or damadge anything that dosent like water (like volume, balance, bass and trebble controls, and parts of the tuners adjustment pots), i think that video was just made for fun and entertainment, it would be something i would never do to my own equipement.
If you are able to remove certain boards (and remove atleast the potentiometers off the tone board), then a "bubble cleaner" 😂 should be safe enough.
Best wishes from UK... 🙂
“Barn fresh.” I understand why xraytonyb is wearing gloves when he goes inside this unit.
Wow howabout dem apples
Tony, Quiet the educational video besides showing repair. Very nice work.
I have the 2240B. What’s the difference,…oooh grab the vacuum.
I think a customer brought in a unit like that to me, they would have to want it restored pretty bad, because just the cost of cleaning for me, would be the worth of the amp.
Is this a class AB amplifier also?
Yes
Just add chrome wheels and metal flake paint chop the roof a little and you could say this is all Foosed up.
Also changed the oil in the capacitors and rotated the knobs.... ;)
It looks as though there's no lighting at the tuning pointer. That surprises me!
It only turns on when am or fm is selected
@@xraytonyb I wish all receivers had been designed so that the tuning dial as well as the dial pointer did not illuminate unless you were using the tuner. Not only would the lamps last a lot longer but the receivers would be less likely to have badly baked, discolored, and melted plastic decades later (unless of course the tuner was the only function that the unit's owner ever used, as is likely in a mechanic garage. I don't imagine they were playing records very much, perhaps some cassette tapes or the occasional CD). You can usually tell what function was the most frequently used because the indicator lamp for that function will be burned out or much darker and blackened than the others.
>>you need to enable language translation
I noticed the level meter is not working.
Of course it's not working, it doesn't have any LoL...
The Two meters are for the tuner, not the output power...
I personally would have preferred output power meters but in the end, you get what you are given LoL.
I think the 2240 is an incorrect designation - or - the faceplate fasteners have been replaced. The hex fasteners are typically an indication of a "B" model.
I’m the owner of a 1974-75 2240 that has the hex fasteners, so probably a transition thing.
what about the noise floor you didn't measure that?
and it's in the listening more than measurements interesting to see what it sounds like compared to the original.
what would be nice maybe on the next one,!! is to run the gain stage with a valve like a12ax7 that would be good.
is it like two-phase is that why they flip to increase greater voltage draw ?
Audio cyclopedia - Tremaine - Amazon books
Imagine reading that diagram
Bass tone control center frequency must be reduced to increase sound quality
Carlos, you've deleted your posts, so I'll take the opportunity remaining ones present.
I can only see a snippet of your answer. Amp is simply inverting both outputs, hence they are in phase in relation to each other ! The jump you see on the Bode plot is the phase plot going above or below 180°, this undulation is there for crushing majority of amps and would look perfectly normal, if plotted at 0° line in the midrange instead. All it takes to restore absolute phase is to swap both speaker connections. Simply connect plus terminals to negative and minus to positive and your output signal will be in phase with the input. As to "bass control", you never use them if the goal is to increase sound quality! You either set them to zero (good), engage tone defeat (better), or use an amplifier without any of that nonsense (best).
Avoid tv technicians who beg for Google review for extra high special price. They drill holes into the relais (!) and spray Teslanol T6 trough it and knot dial cords in the middle.
first
I can't fathom how mice got in there.
They probably were on top of it and some fo their turds fell through the vents!
So you added the costs of the restoration by putting in unnecessary parts, you lowered the value of the unit by modifying it from its original form. For your efforts you got the same performance with a theoretically more stable unit. and learned that you can mod anything?
I thought I made it abundantly clear that this was an experiment to see how the two designs compared. I am charging no one for this project and am funding it myself. I took the time to share the results with all of you. I learned that by studying the original circuit design as well as the changes made by the manufacturer on later models, we can modify an already well-designed circuit to improve stability and/or performance. I also learned that not all changes will make a difference that can be seen on an oscilloscope or other test equipment. Another thing I learned when I opened the cover of this receiver was that there was no way that this mouse turd encrusted device will ever be a museum quality example of a Marantz 2240, but with a lot of work could become a very good performing receiver that can be used every day for its intended purpose to enjoy music and good sounding audio for years to come. For me, the value in this unit was in what I have learned from rebuilding it and the satisfaction that it is now a useable piece of audio gear instead of part of a landfill. Thank you for the comment.
@StevenTheElder Sir, I think you mistake my intent. I merely trying to point out the costs of the lesson involved here. There is no value judgement attached on my part.
No offense taken. This is not what I would suggest doing for a customer, nor is it something I would want to have done as a customer. I think it just proves what I said: Marantz did an exceptional job designing this receiver, especially when you consider that this was not their top of the line unit.
Tony Why do you buy your caps from Mouser. All Mouser capacitors are made in China Thailand not Japan or Taiwan why.
I didn't know that Nichicon capacitors from Mouser were made in China and other places sell Nichicon capacitors made in Japan. Is this true? I buy a lot of product from Digikey, Newark and Allied Electronics as well. Are their Nichicon caps made in China or Japan? I'm now also wondering about Cornell/Sprague/Kemet/Panasonic/etc. Do some distributers get products made in different countries than the others? Also, if they were made in China to the same spec, how would they be different? I've never heard this before. Please explain???
@@xraytonyb I have been asking Mouser where are your Electrolytic capacitors made never reply never. Made in China caps quality are not as good as made in Japan.I have had Nichicon. Rubycon caps from china that have very bad ESR and fail. Its all about the material Tony simple. I have a top suppler in Australia that buys direct from W/Sale in Japan, and are 100% made in Japan. Cost is high but the quality is as you accept products that is MFG in Japan.
IMHO the country of origin isn’t as important as the specifications. Over the past 30 years I’ve purchased huge amounts of electrolytic capacitors from both Digikey & Mouser. I haven’t observed any significant failures yet from either source. Both Mouser & Digikey publish complete specs and offer manufacturer’s data sheets. Although the “great capacitor plague” in the early 2000’s affected many brands, those issues were all corrected & haven’t reoccurred. For power supply applications I select capacitors with a high ripple current rating. This also corresponds to a very low ESR. I check ESR routinely for both old & new capacitors. Surprisingly I have found some 60-year old electrolytics to be totally within all specs. I have also seen failed electrolytics that were
@@electricboyo Yes it is. Very important very as you will be paying for quality for your customers repairs simple not counter fit. Mouser is large due to caps mfg in Thailand simple and China. The best caps in the world are Made in Japan.We do 100s repairs every year and when I was using Mauser there caps always gone bad.
Tone control bass capacitors must be increased due to the fact it is amplifying too much high bass tones
Math challenged !
Your explanation of how the differential input circuit works is wrong! The current in emitter resistor is constant regardless of the signal swing! The current through the collectors is the same at idle! As the current increases in the input transistor, it decreases by the same amount in the second transistor! So the current in the emitter resistor remains constant!! The differential amplifier is biased class A. Current is flowing in both transistors at all times!
Perhaps you could edit your 'comment' to say that his explanation is 'wrong', instead of 'BS'. Eh?
If you did'nt use the offensive language, one might be encouraged to review Tony's explanation and your argument. Maybe you look to other comments here to see how to express yourself.
@@cjay2 the reason I said BS is because he is misinforming his viewers and fans of his channel!! This man is a professional and should know better!! I changed BS to wrong as you suggested!
@Raul I will try to explain you why the current through the differential pair input is not constant and depends on the voltage swing.
If you have 1V p-p input signal then the voltage on the differential pairs emitters will vary + - 1 Vbe drop i.e. from -0.3V to 1.7V Vp-p therefore the current through the 6.8k resistor will vary form 2.3mA to 2.6mA.
That's why we use better current sources (usually active loads) than a single resistor.
@@RaulHernandez-lg5nw online communication is tricky as it lacks so much of the nuances of the spoken word (not to mention language and cultural barriers)... what works best for me is to observe the tone the community members use and adapt.. it's like walking into a party and checking if ppl wear their shoes or not, are they loud talking, am i the last one to be sober, etc
i myself dwell in profanity and your choice of words doesn't register as offensive language BUT i'm not the one hosting the party. it's nice of you editing the comment as it hints to your intentions/temperament. the vast majority of internet users have the opposite reaction (almost never works) :}
hope this helps, i know it may appear annoying but it works.
wish you the best.
There is absolutely no difference between the original version and the one with the constant current. So, other than heating problems how can anyone claim that "the bass here sounds better" when the scope shows no difference whatsoever? Besides, it's only the bass, and the terms they use are so subjective that it can't be nothing else than pseudo-science...
Sorry Tony, you're usually a quite reliable and competent technician, if I had to hand my equipment to someone here on UA-cam I'd probably hand it over to you, but please do not fall through the audiofoolery rabbit hole, even more when you use a test music that clearly has been recorded and mixed digitally...
Thanks for the comment. This is the reason I did this video. From what we can see on the test equipment, there is little to no difference in the performance of the stock design vs the modified design. Sound quality of any audio gear will always be subjective. As a repair technician, our job is to make sure the amp is performing up to spec. What I can say about this particular project is this: The CCS will keep the diff amp stage a bit more stable, especially when it comes to music with a lot of dynamics. In addition, the transistor pair will be less likely to drift because of temperature changes. The circuit would be improved with the addition of a current mirror at the collectors, but it is not practical to do on this amp. Many other designs make this same compromise by using a CCS at the tail with no current mirror at the collectors. As for the improved bass, I can only report what I hear when compared to stock versions of this amp. Is it placebo effect and I'm just crazy? Perhaps. I rarely say things like this, as I am someone who likes to be able to "view" what I am hearing through the use of test equipment. The recording didn't do justice to the real thing (it never does). This amp really sounds good to my bad ears. Anyway, this is the kind of stuff I really like to discuss with others. This is how we learn. Thanks again for the comment!
I don't recall that he compared the bass response of the modified to the unmodified, but the amp in general to other amps. Speakers are NOT simple resistive loads. But all testing I've seen (from everyone) fails to look a the complex interaction between amp and speaker. Looking at dampening factor is a start.
13:59 exactly, both transistors show NPN; yet you called one a PNP despite the diagram, why? This is why such videos are extremely confusing and indeciperable to amateurs who know nothing, and likely never will thanks to the contradictions and lack of clear explanations.
Before you start insulting me, please listen to the video again. What I said is that there are 4 similar models of this receiver; the 2240, 2240b, 2238 and 2238b. The main difference is the output transistor configuration. The 2240 uses a "quasi-complimentary " output stage, while the others use a "true complimentary" output stage. The main difference is that quasi-complimentary output stages use two NPN transistors and true complimentary output stages use an NPN for the positive side and PNP for the negative side. If you search "quasi complimentary vs True complimentary output stage" you will most likely find a lot more info. There is no contradiction if you listen to what was said just before the time marker you listed. If you are willing to ask questions instead of assuming that everything is wrong, you may find that you can learn this. I am more than happy to answer any other questions you may have, within reason.
@@xraytonyb No insult was intended. Your uploads are very informative, and I mainly watch them to learn as that's the best anyone can do with one's time. Thanks very much for taking the time and effort to explain. Don't know how you dealt with the mouse leftovers, but somewhere I heard that you should never vacuum rodent feces as minute particles can go through the vacuum filter and become air born, potentially leading to serious health problems.
Under 100 watts goes in the trash 1970s junk
But....but.... the purity of the sound .... ("never mind the width... feel the quality" !).... lol
This gear at whatever wattage sounds far better then the "modern" switched mode class d amplifiers ..... stick with your bluetooth crapple ear buds and enjoy your life,and let the rest of us enjoy something far superior 😎