1950's Fender Princeton 5F2-A Home-Built Guitar Amplifier
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- Опубліковано 23 сер 2024
- This video features a completely home-built guitar amplifier utilizing the circuit from a 1950's Fender Princeton chassis, model number 5F2-A. All aspects of design and construction will be explained, and the sound quality of the amplifier will be demonstrated. If you enjoy videos like this, please subscribe to view the many videos I have already posted, and to be notified whenever a new video is released. Thanks for watching !!!
....if you don't know that is the on switch, and that is the volume knob and tone knob, you have no businesses foolin' around with amplifiers.......you rock Uncle Doug!
I couldn't have said it better myself, Rebelde ;)
You're the only person I found who actually explains all clearly and doesn't avoid the important details. I'm sure I'll comeback with some doubts, since i'm going to do this one. Thank you!
You're welcome, LM, and thanks for your nice comments. We're glad you enjoy our videos :)
Ok, 4 months later but, I've done it. As soon as I solve some ground problems, I'll do a video and post it, thank you so much again!
You're welcome, David. Bending and forming the chassis is a real nightmare without proper equipment (that most people don't have). I'm glad you like the "assembled chassis" method. It also allows you to drill holes in flat plates, rather than wrestling with a metal 'can'. Please also consider using aluminum for the fabrication. It conducts both heat and electricity much better than steel....and it doesn't rust. Please keep me posted on your progress if you start the project. Good luck !!!
I score sheet alumimun on my bends first on a table saw with a cheap 7" panel blade . The bends come out smooth because the scoring leaves a void so you get a smooth even bend. Clamp a piece of angle steel behind bend. I use alumimun solder with a propane torch to weld my corners. Very strong and looks like a expensive factory chassis.
Thanks for the helpful tips, David.
You're a scientist AND an artist Doug. My hat's off.
Thanks so much, Dwight. I truly appreciate your kind assessment.
Thanks, Warchol. Yes, it does indeed matter which output transformer lead is used for the negative feedback (NFB) loop. If you use the wrong lead for NFB, it becomes POSITIVE feedback and will cause the amp to howl like a siren. It's sometimes hard to tell which OPT lead is which, and no harm is done (other than to your ears :) if you're wrong, so you can use trial and error to find the right one. Believe me, you will know immediately if you guessed right or not :D
Such a beautiful amplifier, love the cabinet tolex and baffle design. Only made sweeter by the Jensen speaker and how it was acquired.
Thanks so much, Hadley. You're right about the speaker......saved from oblivion, which made it even better :)
Doug, you are a true craftsman. #highfive
Jason Thorpe Thanks, Jason :)
Wow… this is saaweeet! Beautifully clean design and attention to detail!! Very impressive!
Thanks so much, Justin.
I love your work Sir, Just Beautiful!!!!! I love the way you recycle old parts, and that speaker was a great find!!! Just Amazing, Thank you for Posting!!!!
Thanks so much, Chance. I really appreciate your kind words and am glad you liked the amp :)
To my ear this one sounds the best! Just love it.
Wow.....very high praise for one of my home-made amps, Tom. Thanks !!!
Hi Uncle doug & Rusty, I've watched this video numerous times, and, it always brings a smile to my face. Happy Summer, Be good, C.
Thanks, Cass, and likewise to you :)
Really sweet! I love those 5F2As....
Thanks, HG :)
And I said - "Do you ever use a soup spoon to scoop out your eyes?" Nailed it!
Thanks, Kley.....I guess we have the same sense of humor :)
I laughed outloud. Amazing.
Oh my God, I just caught that "soup spoon to scoop out your eye" line. Deadpan and unexpected. Made me laugh for about 10 minutes! BTW, love your videos.
oh man!!! That first little part you played, the sound is just amazing to my ears. It's awesome!
Thanks, CT. Glad you liked it. It's an old Barrett Strong tune called "Money (That's What I Want)".
Beautiful,Uncle Doug!A true masterpiece!
Thanks so much, Charles :)
The best things in life are free. On that winter's night in London, 1966 Chas said to Jimi "C'mon, mate, let's go meet Cream" and hoo boy/girl can you for one second imagine what Jimi felt at that moment? He was probably Eric's biggest fan so he grabbed his upside-down Strat and off the duo went. Chas and Jimi stepped into the cavernous club - I forget the name, it was a large club, probably 500 capacity. Cream was doing a soundcheck (there are kids who really don't know what a soundcheck is) and Jimi just stepped right up and he introduced himself to the band who were no doubt gobsmacked that any bloke on earth would dare to ask to sit in with Cream. Jack said "plug in here, mate" and he offered up a channel in his Marshall stack. That's Jack Bruce, kids, who singularly made bass players the coolest beings on earth. Jimi plugged in and Eric was thinking "who is this wildman from the colonies? What the bloody hell is Jack doing?" and Jimi called out "Killin'Floor!" by Willie Dixon (Dixon wrote the greatest blues songs in history of blues - I always play Spoonful when I perform - it is my favorite song on earth and it is TWO BLOODY NOTES. Sorry to shout. I am unweaving the mess that the "music stars" have created). One or two notes, kids, that's all you need to transform stupidity into high vi-bration. So Jimi shouted "Killin' Floor in A" and he played it at triple the tempo of the Howlin' Wolf version of the song and of course Jack and Ginger fell right into the maniac groove that Jimi created at that moment. Eric just stood there. His hands dropped to his sides and his knees wobbled. He was no longer god. He shuffled to the dressing room and his roadie had to light his fag for him as he was shaking so much. Jack and Ginger and Jimi finished the song. Jack and Ginger both thought "this bloke is a force of nature - we have just participated in a bloody miracle". Jimi thanked the boys and called out to the corridor - "thank you Eric!" and Chas and Jimi left the club. True story.
Well told, B. What I would have given to be a fly on the wall during that epic moment.
GEEEZ ... THIS Is really brilliant in it's design Uncle Doug ... Simply Brilliant ... Compact And very clean ... Well Well done ... )))
Thanks, TA. It has become one of my favorite amps.....for the reasons you mentioned.
Thanks much for the video. I have always wanted to build a tube amp and I can solder and read schematics and use tools, but I could never figure out how to build the chassis. I had the idea to maybe use a cake tin, but that is so skeezy--and I didn't know how to do with without an angle bender. Your idea of using two or more seperate pieces with a right angle connector is pure genius. You got me seriously thinking about this as a real thing, now, not just dreaming in the dark. Thanks.
Hi Doug, just stumbled on your video today. I am retired now but spent my whole career in electronics started with tubes in the mid 60's.. Anyway, I am now learning to play guitar and want a tube amp. Since I have the skills and understand the circuitry, I think J will give this amp build a try. Its is a beautiful little gem and it should fit my needs quite well.... BTW, I play mostly Jazz so I think this will be a nice clean amp for my style of play.. I spent most of career with Tektronix.
Welcome to our channel, Stan. This is a great little amp and I think you'll be quite glad you built one. Best of luck with your project.
@@UncleDoug I will build it. Just one question, any recommendation for a good speaker, I am thinking an 8 or 10 inch.... Thanks for your site, it is great.
Go with the 10", Stan. With speakers, size really does matter. Best of luck with your project.
Yes, JZ. The Princeton evolved from the Champ and the added tone control was the first of many evolutionary changes.
"...except in this case you have a bunch of electrolytic capacitors in your sock drawer."
Glad you liked it, Max :)
Beautiful job!
Thanks, Henry. It's always good to hear from you. I hope all is well :)
Another beautiful amp --
Flawless. Love the aluminum.
Thanks so much, dB. We're glad you liked it :) ^. .^
Very nice, Doug! You did an outstanding job!!
Regards,
Mick
Thanks so much, Mick. I'm glad you liked the amp :)
Beautiful work Doug. Love the upholstery work too.
Coming from a fellow amp builder, your kind appraisal means a lot. I have watched several of your videos, particularly those featuring your AO-44 conversions, and must return the compliment. Thanks so much.
thats a nice looking and good sounding amp. I always enjoy this channel
Thanks, Jason :)
yeah you made a gem of an amp & that speaker is great so a top remake doug if fender did the same i might get a reissue,but masterful sounding clean,crisp tones with nice break up great post doug regards jamie...
Thanks so much, Jamie.
What a beauty!
+Fuga Mante Thanks, Fuga :)
I can describe the process briefly: Brush two heavy coats of Weldwood Original Contact Cement (the one with toxic fumes, not the sissy latex garbage) on the wood, allowing each coat to dry until only slightly tacky. Spray the back of the Tolex with V&S 185 or 581 spray adhesive.....a heavy coat. While it's still sticky, apply Tolex to wood and roll with a linoleum roller.....applying as much pressure as you can. There are minor details, but this is the general process.
Hey Doug, love your work.
I have a 5f2a clone that a local guy here in Australia put together. As second owner I bought it from the original customer for a song. I put an Eminence Legend 10" ceramic (not quite rescued from a dumpster, admittedly) and it sings. I reckon the single ended Princeton is a bit special. It's amongst my faves, has a special sound compared to the 6V6 dual tube amps.
(BTW my first dog back in '71 was also called Rusty - almost brings a tear to my eye)
twerpeater Thanks so much, TP. I definitely share your enthusiasm for the SE Princeton circuit, and for loyal old hound dogs. We really appreciate hearing from you and wish you the best.
@ :54 I think you named it, Uncle Doug. The DaniSonic Prince-Clone! Excellent work, btw and it sounds great.
Thanks for posting this. =)
You're welcome, Dean. Thanks so much.
So cool man, wish I was smart enough to be able to do this, well done!
Don't be hesitant, HA. Study up, then give it a try......just be careful :)
Love that tone!
Thanks, James :)
Nice job!
Thanks, Rob.
Sounds Great!!!
Thanks, 49V :)
Doug - I own a 5F2A amp and have recently watched an interview with the founder of Dr Z amplifiers where he was remarking on how he substitutes certain power tubes for improved performance in his amplifiers. The two examples he mentions are using a 6n14n for a EL84 and a 7591A for a 6V6. In the 7591 example, he stressed that it is a high fidelity tube and more powerful.
All of my amplifier circuit knowledge has come from watching your excellent videos and studying (as you suggest) the original circuit diagrams. I obtained the tube data charts for the 7591A and 6V6GT and compared them. They do seem pretty similar, and the 7591 does appear to produce a little more power. It also appears (to this CPA that is not an electrical engineer) that the tube socket wiring is somewhat different between the two.The charts I compared were both for the Tung Sol branding of the tubes.
Are these tubes actually "swap-able" in my 5F2-A to give it a try, or would that be a mistake? If mods have to be made, are they extensive?
Thank you for your videos. As a lifelong guitar player it has been absolutely fascinating to have the mysteries of these amps I've owned explained in such a thorough and understandable manner. I'm having a builder make me a Princeton Reverb clone, but thanks to your videos with that amp, I'm having a bias pot installed and feel confident I will be able to correctly (and safely) bias my own amp to my preference.
Thanks for your very nice letter, Stan. It's human nature to experiment with equipment, from auto engines to amplifiers, trying to improve upon performance.....but often the results of these experiments are exaggerated to justify the time and effort involved. Is the result simply "different" or actually "better"? Generally, the appraisal is purely subjective and possibly biased. Bottom line: I have no problem with any competent tech modifying their gear, seeking improvement.....but, I would be very hesitant to encourage anyone to pay a lot of money to have it done, based on someone else's subjective opinion. One possibility is that adapters are made to allow different tubes to be used in a socket, without any rewiring. This way you could make a direct comparison and draw your own conclusions as to the benefit (or not) of the swap.
@@UncleDoug Thanks Doug. I appreciate your answer and will return to the real source of tone, my fingers. When I raised this topic with the fellow building the PR, he responded that most of his customers are after the character of the PR and suggested that the 7591 power tubes would require more voltage than the circuit would provide using the normal transformer. This sounded reasonable, especially since I haven't a clue, so your input is all that more trusted and valuable.
Thanks for your prompt response.
@@stanwatkins975 It's true. Changing to more powerful output tubes may well require upgrading of the power transformer and possibly the output transformer too. Lots of effort and money spent.....for what ??? I don't get it.
@@UncleDoug Thanks (again) Doug. Your points are well received on this end. The builder that is helping me with the PR and I discussed your comments and agreed that using the 7591A tubes in this amp didn't make sense. When I mentioned that I had reached out to you on this matter, he shared that he was a huge Uncle Doug video fan, too. He told me that his ability to install the bias pot in my PR chassis was based on the video you made explaining that modification. The balance of our conversation turned into an Uncle Doug Fan Club meeting. Thanks again for doing the videos and providing guidance to us. Your presentation of this technical information is clear and understandable, even for those of us that are not electrical engineers. You're a star.
@@stanwatkins975 Wow.....thanks so much, Stan. It's great to know that our videos really offer practical benefits for our viewers.
I used particle board for my amp box, (not MDF) simply as I had a spare 6ft shelf and it balanced out just right, and two old ex GPO equipment cabinet plywood doors for the back and front, it only runs out a tiny ex radio rola speaker , does the job , probably 5watts.
I see no problem with particle board for small amp cabinets, HP, but it gets real heavy and tends to come apart in larger cabinets.
That's beautiful!
Joseph Van Yush Thanks :)
I love that amp but I hate to tell you, fender started making the princeton way before the 5F2 circuit. I'm using the 5C2 (circa 1954) for my princeton clone and I've seen a 5B2 schematic labeled as a princeton. Still a great video.
Thanks, Jeremy.
Sorry for the delay, Cat, but I've been busier than a crocodile at a pool party lately. I'll put it on my to-do list.
barge cement is what they use to glue soles on shoes....
as well as barge all purpose thinner..... sounds like you have a great adhesive combination.....
brian foley Thanks, Brian. It seems to work well for us.
I loved the soup spoon comment.
Beautiful work Doug. Gorgeous looking and sounding amp. I know this is an old video... are you still a fan of your slide in drawer design? Any downsides to it? I like the clean look of your amp and am considering building something similar and was wondering if you've found any issues with that layout. Thanks for any insights.
Thanks, Mark. No issues at all......the design has served me well in multiple cabinets and with small to large chassis.
I want one!!!
It could be yours, Diego, but domestic (USA) shipping only.
Again, very very nice!
Thanks, Jennifer :)
Don't forget that the other major difference between the Champ and Princeton was the 8" speaker in the Champ versus the 10" speaker in the Princeton. Of course recording engineers still love those 8" speakers anyway... BTW, the way I end up with parts all over the place it would not surprise me to find electrolytic capacitors in my sock drawer. I can never have enough parts storage it seems.
BuzzCrumhunger Good point, Buzz. I really prefer the 10" myself. Thanks for your input :)
CuteKittyMeep that's incorrect. Tweed Princeton's came with 8" spkrs, just in a bigger cabinet.
Uncle Doug builds an amazingly well-designed and crafted Fender style amp, then claims to be too lazy to label the knobs. Well played, good sir!
Robert Lewis Thanks, Robert ;) With only two knobs, there is a 50/50 chance of guessing right......pretty good odds nowadays :)
That's right, Joseph.....only those with high level security clearance can be briefed on them.
Don't forget the power cord, Joseph. It's important not to plug it into your toaster slot.....unless you want your tubes to pop out of their sockets every 60 seconds ;)
great build. I'm building one and putting it in an old radio cab. what is the purpose of adding the 1k resistor? would it be a 1 or 2 watt resistor? thanks for your videos.
Is the resistor you mentioned the bias resistor? See my video on Cathode Biasing, Jim. One watt is fine, two watt is a little better ;)
Sir,
Loved this video, very informative.
One question though: Does it matter which speaker lead is connected to the negative feedback loop?
Hi Uncle Doug,I built a Princeton 5F2A amp a couple of years ago and just now going to install it into a cabinet. What I plan on doing is installing a tremolo circuit once the amp is up and running. I looked at the Vibrochamp amp schematic and will be using the circuit that Fender uses. I will have to install the 25uf/50v cap and the 47Ω resistor on the cathode of the 12AX7 and feed the speaker from the 47/1.5kΩ spot. There is a 2.7K resistor going to the speaker and the one in the 5F2A is a 22K. Can you give me any tips if I'm doing this correctly or incorrectly. I have some pictures of the 5F2A if you want to see them. You can contact me via e-mail address to further discuss this "upgrade". I also built a 6G15 reverb unit to go along with the 5F2A...your video(s) on the tolex installation will be a tremendous help as I have not done this before as I am a better carpenter/electronic tech than a tolex installer ;-))Again, many thanks for the videoTom...
You're welcome, Tom. The addition of the tremolo should be fairly straightforward. I would connect it to the cathode of the second 12AX7 stage, just like in the VC, and then experiment with component values (if necessary) to optimize its performance. Anytime you make a modification like this, some minor tweaking is generally necessary. Good luck.
Hi Uncle Doug,
I have a final question on that 1k grid stopper on pin 5 of the 6v6. What wattage and type would you recommend here? I was thinking likely 1w or 2w carbon comp. Any better ideas? I've read the big factor on grid stoppers is low inductance resistors and not having steel leads or steel caps. What is your experience?
One little tweak: I would have recessed the rear of the chassis, so the toggle switch and knobs aren't protruding and risk getting scraped or knocked off.
Good point, David. When designing cabinets to fit chassis, you need to consider the protruding parts, as you mentioned.
Doug your videos are great. I recently built a junk box 5F1 clone in a cake pan and it sounds sweet; I learned a lot from your version. Thinking of trying a 5C1 next. Two questions: does a tight fit cabinet risk any kind of feedback issues between speaker and transformers? I have nice 280-0-280 150ma power transformer in my junk box, do you think the voltage output would be sufficient for the 6SJ7 version? I know its a bit lower than stock.
Greetings and thanks, Bs. I prefer compact cabinets and have never had a feedback issue. I think feedback is more likely to be an interaction between speaker vibration and a (microphonic) tube rather than a transformer.
Regarding your 280V transformer, I think it would work fine. If you want to maximize your voltage, you might consider solid state rectification or use a GZ34 rectifier tube. Good luck !! :))
Naugahide from a freshly killed nauga. She's a beauty. How much would on cost?
I personally hunted down the nauga's for this amp, Roger, then beat them to death with a canoe paddle and tanned their little hides. I value the amp at $1250.
Hello Uncle Doug,
I've been watching a bunch of your videos. I appreciate you taking the time to make them. Especially the lessons about amp electronics and evolution.
What was your reason for the grid stopper resistor being added to the 6v6???? what determined your resistor value?? I have just watched the resistor vid on grid stoppers where you talked about 12ax7.
What affect would this play in this princeton build?
Would you apply this to other designs such as a champ too?
Thank you,
Stu
+stu mac I believe the answers to your questions are all in my more recent video series on Resistors, including the "Grid Stopper" resistor. Please watch it, and my other 127 videos, whenever you get a chance. They cover all aspects of amplifier circuitry and design.
+Uncle Doug
Thanks for your reply. I did watch the resistor vids prior commenting. I did see the parts about low pass filter and internal cap. of the tube.
I was wondering why you chose to add it to your design. What change would it have in particular?
What about the original were you trying to tweak???
I'm re watching the resistor series.
You did help me with a mistake I made in my 5e1/5f1 adaptation. I had a 0.0005uf mica on my volume to tone pot. I also had a 0.0005 mica on my tone to ground. I missed a decimal I guess. I've just put it to a proper 0.005uf I haven't tried it yet. I wondered why everyone likes the tone control but I thought it sucked on mine.
Cheers!
Stu
+stu mac
That 0.005 cap in place of the 0.0005 from tone to ground changed my whole amp ! completely!
I looked through my stuff and only had a 1.5k resistor as closest value. So I didn't use one yet.
Hi Doug u build lovely amps n stuff I was well impressed with the big tremolo unit but I wouldn't have much room left for my Zoom pedal LOL why do some people love to create things and others like to destroy ?
Thanks for the interesting vids
Regards Steve
SequencerSynth Thanks, SS. You ask a question that many of us wonder about. It would definitely be a better world if everyone just focused on positive things....but then, look at how many law enforcement, military, and other government employees would be out of a job ;)
Another amazing and informative video Doug. I'm trying to finish up a Princeton build 5?2 using a 6sl7 and a bunch of junk parts from around the shop. $0.00 investment. I like the way it sounds however the volume control seems wrong in that after 1/4 or its sweep is way too loud. Its a 1 meg. pot it seems wired correctly. What could be a cure for this? Thanks if you are able to reply.. P.S. I love that speaker cover design it looks like a hamburger.. Best regards Ed
You might experiment with other pot values, Ed. Read the resistance of your pot at the point that the amp becomes too loud and then install a pot that has a little more resistance, i.e. too loud at 220K.....install a 250K pot. Then your VC full sweep will go from silence to just too loud.
@uncledoug Why the 1K grid stopper add?
Good stoppers are always a good addition to any amplifier circuit, Nick.
hi Doug I really enjoy your video.. not to mention your craftsmanship... anyway I am looking for a small champ type amp... however I don't want to pay the big $$$$$$$ that they are asking... anyway do you have one for sale or is there any type of amp you recommend.. small it important for me...champ size.. please let me know thanks
+Jim Johannessen Thanks so much, Jim. I am flattered that you would want to buy one of my amps, but since they are handmade from scratch, they are (much) more expensive than the modern mass-produced Asian-made amps currently for sale at places like the Guitar Center. I would recommend that you take a look at a Fender Excelsior. They cost under $300, have a 15" speaker and tremolo, are a tube amp, and are light and portable. I have no idea how they can be made and sold at this price.
hi uncle Doug thanks for all your great knowledge and great help to every one. I am looking to build a fender 5E9-A Tremloux just looking at the 12AX7. OSC Circuit for the tremlo the plate of that 12AX7is directly coupled to the grid of that same valve therefore there must be. B+ going to the grid that is being fed from 220K. that feeds the plate. Can that circuit be correct.(never herd of B+ on the grid)and also what would be the power O/p of that amp
thanking you for your reply.
Tony
You're welcome, Tony. Yes, the grid can be energized with the B+ voltage in some circuits, particularly the cathode follower configuration. It seems unusual, since in amplification circuits, this isn't done, but this portion of the circuit is a tremolo oscillator (not amplification) circuit......and the unusual connection is required for the oscillator to function.
hi Doug lots of thanks for your prompt reply you are so great with your work and knowledge thanks again
Tony
i looked over the schematic. is the only differnce between this and a champ the added tone control?
I'm about to build a 5F2-A from a mojotone kit and use a Panama 10" cab, then I saw this. I like your chassis and will do the same. But should I be concerned that it's not shielded with an open chassis like that? Will it hum around fluorescent lights...?
+Nor'easter Playa I have 5 large fluorescent light units in my workshop, where the amp was built and tested, and there was absolutely no hum at all. You can use this design without worrying about this problem. Good luck with your project.
Have you had a chance to form an opinion on the 'new' Jensen loud speakers???
Yes, I like them. In fact, they are my preference when ordering replacement speakers.
Hello.
I have a question that should have potentiometers characteristics: linear or logarithmic. The diagram found 1M lin, but I know that voice control should be carried out using a logarithmic potentiometer.
Greetings, Mr.C. I don't see "linear" on the schematic. They probably assumed that people would know that the tone and volume pots should have an audio taper. I did. As a result, both pots in my clone have an audio taper.
Audio for volume, linear for tone
Great video, I love your channel, I learn a lot watching your videos. I just bought a clone of the 5F2A Princeton hand wired amp , I checked the circuit, everything seems correct ( filter caps in mine are a bit bigger value then in original schematic) but there is 1 thing intrigued me, the grid stopper resistor between the input and 12ax7 tube which was used is 1.5k instead 68k . I don't know if it was made by mistake or in purpose, does it can harm the amp? or I should replace it with 68k? I love the sound of this amp as it is, it has a lot of sparkle, tone knob is very effective. When I use the amp with different guitars it works very well, I can get nice sparkle tone from even very dark sounding guitar. Regards. Arthur
+portlaoiseguitar Thanks, PG. I agree that a 1.5K resistor in this position is very "un-Fenderlike", but if the amp works so well with this resistor in place, then I would leave it there. If oscillation problems arise then you might reconsider, but until it happens (which is probably unlikely) I would simply leave it alone.
+Uncle Doug Many Thanks
You're welcome :)
N
Great video, I have the amp with 5F2A circuit, lovely amp, I have a question, is it possible to run this amp with EL84 output tube? VHT currently have EL84 converters for 6v6 sockets, and their website says "The Special 6 EL84 adapter works in other 6V6 amps as well. Check with your amp tech to be sure your amp's voltages don't exceed the maximum ratings for an EL84" . I checked a plate voltage in my amp and it's 302 volts, maximum rating for EL84 i 300v, is it still ok to run the amp like this, or do I need to change other components to accommodate EL84?
Greetings, Artur, and thanks. Bear in mind that your current plate voltage is affected by your plate current, and both will change if you substitute EL84's for 6V6's. That said, any EL84 worth its salt is easily capable of handling a PV of more than 300VDC. Recall that the max PV for 6L6's is 315VDC.....and Fender routinely runs them at well over 400VDC. As long as the Plate Dissipation is within normal limits, you should have no problems.
I will calculate Plate Dissipation so, I think 12W is maximum PD for both 6v6 and EL84, , Many Thanks for your valuable answer.
Yes, 12W is about right if the tubes are cathode biased. If they were fixed bias (grounded cathodes) the max PD would be 70% or about 8.4W.
Did you wire the neg feedback loop to only one speaker output jack? Thanks in advance love your vids.
Greetings, DWB, and thanks for the kind words. You have a good eye. In the video it appears that only the 8-Ohm jack (green OPT lead) is connected to the NFB loop. After the video was completed, I also connected the NFB loop to the 4-Ohm jack (yellow OPT lead).
Uncle Doug My eyes are old and didn't see green wire.How did you wire both jacks to nf loop ? Do you jumper to other op jack?
To prevent shorting the OPT secondary windings and to enable disconnection of the NFB loop, I used a DTSP switch: up, NFB goes to 4-ohm jack; down, to 8-ohm jack; NFB is off if it's switched to the un-utilized jack.
I have since discovered that simply connecting the NFB to the 8-ohm OPT jack was sufficient. Since the NFB was connected to the entire OPT secondary (via the 8 ohm wire), both output jacks were affected regardless which one was connected to the speaker. Live and learn. I now use the switch simply to turn the NFB on and off.
Thanks for the detailed explanation. I can now wrap my head around this.
It only needs to come off the 4 ohm secondary. It's in place no matter what jack you select. But for correct value, tie it to the 4 as the original circuit used a 4 ohm transformer. To use the 8 ohm tap you'd need to bump the nfb resistor up to 33k to compensate.
Hi Uncle Doug, I tried to look on you home page for a way to contact you about getting a quote on what the cost would be to have an amp like this one built from scratch. I commented about 3 months ago on how I like the sound of it. I am not a member of Facebook, I am not able to contact you that way. Is there another way to contact you about a build? Tom
I don't like to duplicate existing creations, Tom, but would be willing to sell you the original. Provide your e-mail address and I'll contact you directly.
Banjo.frost43@gmail.com I live in Michigan Tom
Awesome! Do you build amps for other people who would supply a chassis for conversion? Thanks.
+Bill Smith I don't do outside work any more, Bill, except for the occasional restoration of an interesting vintage amp (or two).
+Uncle Doug Ok thanks anyway. So you say you like to build a cab as small as possible. Have you found you lose any low end placing a 10" speaker in a cabinet the size of your 5F2? Love the "drawer" idea! As a real novice, I built a 5F1 a number of years ago, but needed help when it didn't work when I fired it up. Made it out of the amp out of a Voice Of Music reel-to-reel.
You're welcome, Bill. Since most guitar cabinets are open at the rear, I don't notice much tone difference between small or large cabinets. In a sealed or ported cabinet, it makes a big difference. Glad you enjoyed the video. Thanks for watching.
+Uncle Doug OK thanks. I'm still a novice, but hope to gain more understanding at some point by watching your videos! Had a great guy I started talking to online years ago make me a blackface Champ circuit with a 6L6 and a switchable in/out NFB. Have a vintage1965 C10Q in the cab I had built (out of solid pine only and dovetailed) about the size of an old Fender Musicmaster Bass amp. My main stage amp last few years (we're old and don't play too loud!). You build some great looking cabinets too!
You're welcome, Bill. By all means, watch the videos and hopefully they will clarify many of the complexities of tube amp circuitry. Perhaps some day you can build your own amp from scratch. Best of luck.
Beautiful amp Doug, Amazing job, HAHA exercise in frustration indeed, For all its good aluminum is not always fun to work with. I lost all faith in 3M spray adhesives, not relevant here but, I use to use a lot of the Super77, which always worked well for what I was using it for till about a year ago, now it can barely stick two sheets of paper together with it, If you want a good laugh, Try calling 3M about a product you been using for years and having the dumb phone technician tell you its not their problem because each run is not made the same way and they can not Garantie that the same line of product will work from batch to batch, Isn't that crazy haha.
Thanks so much, Pat. I've been using a can of Super 77 for a couple years.....I guess it was part of a "good batch".
Doug I'd buy one of your amps. A Tweed deluxe please
I'm currently sold out of that model. What is your next choice ??
Uncle Doug! I didn't see the all important underwriters laboratory stamp on your awesome amp and as per the gospel of Doug, no one in their right mind would play an amplifier that doesn't have one. You must not be in your right mind! Busting chops aside I'm curious about your output transformer. I see that you are using the small fairly small "5 watt or so" size OT like used in the champ. What are you biasing the 6V6 at? I only ask because I was astonished to discover that my homemade vibrochamp was putting out 15W for a few weeks before I got hip to biasing. I had no problems w it but have since upgraded to a heavier OT and biased my single JJ6V6 at 11.5W. Just wondering if you have sage council to offer on OT's and max wattage for this princeton.
Greetings, Mike. I applied to UL for a stamp of approval, but my application was "lost in the mail" as well as my $1000 "donation" to their CEO.
It's typical for small Fender amps to be biased ridiculously "hot" from the factory. In several videos, I have cautioned about this and recommended that owners check the bias of their 6V6(s).
Tube bias (i.e. 11.5W of Plate Dissipation) and output power (i.e. 5 to 8W) are completely different parameters. The first measures the heat generated in the output tube(s), while the second measures the power being applied to the speaker coil. Just because your 6V6 has a PD of 11.5W doesn't mean that the output transformer will ever see this amount of power. In fact, in this case the power applied to the speaker will be much lower.....around "5W or so".
Thanks unk. Your work and guidance is a treasure to the community!
Hey Uncle Doug. I was wondering what the channel bar (L channel) that connects the two pieces of the chassis is made of? Is it also aluminum or steel?
+Nemo Alicunde It's aluminum, Nemo. I bought it at Home Depot. It's best to stick with one type of metal. When two different metals are in contact, electrically-caused corrosion can often occur between them.
ok thanks alot. Is there any specific type of screws I should use? Sheet metal screws?
I would use No. 6 or 8 machine screws with nuts and lock washers, Nemo.
Galvanic reaction. It is a constant concern mostly when building salt water boats and ships, or with anything electrical, like with phone wires and connections that turn green. A dab of dielectric grease will help prevent a galvanic reaction, and prevents signal loss on things like video connections of security systems... This link will explain better. www.fastenal.com/content/feds/pdf/Article%20-%20Corrosion.pdf
Yes, indeed. Thanks so much for this additional information, NP.
Hey there, any problem using a 32uf instead of the two 16uf in the power supply? They're in parallel on the schematic, but I just wanted to make sure I'm not missing anything. Thanks!
I see what you're asking about, Tysen, and the arrangement in the schematic is a little unusual, with no resistor between the caps. I can see no reason why a single 32uf cap wouldn't work just fine.
Great. Thanks Uncle Doug for all these videos. I've almost watched every one!
You're welcome. If, for any reason, it doesn't work, please let me know.
Will do! Last question: How do you feel about 450v in this position? It's a lot cheaper for me to find a 32uf 450v than a 32 500v....and I'm a poor musician.
I use a lot of 450V filter caps with no problem, Tysen. If money were not such an issue, you could go with two 70uf @ 350V caps in series. This would provide the same value as a single 35uf @ 700V cap. It's what Fender does on its larger amps, like the Bassman.
Over time particle board warps 9x what wood will !
Any moister in the air when its old and forget it !
I agree, IS. Particle board is a disgrace, best used in bonfires and as a backboard for targets.
Transformer: please explain "copper flux band"....thank you.
Carl Rudd Carl, according to Triode Electronics, a major seller of transformers for amplifiers, the copper flux band "prevents vibration and buzzing". Here is there site with lots more info: www.classictone.net/About-ClassicTone.html
Thank you, UD.
You're welcome, Carl.
I heard naugas are hard to catch.
They are elusive and vicious when cornered. Sadly, they were hunted to virtual extinction in the 1960's, which is why you never hear about them any more.
Well at least we can still get Corinthian Leather because corinthians reproduce like crazy.
Englehard Dinglefester
Naugas suffered a finyl extinction.
not really- they just hyde.
Love the amp-looks like a hamburger-need to get a fender japan hamburgler strat to go with it!
They would make a great pair, Scott. I should have put some mustard between the bun and burger :)
Ever sell or take commissions?
Was thinking the same!
Yes, I sell vintage and hand-built amps from my collection all the time. I don't build to order, however, so it would have to be an existing amplifier, probably featured in a previous video.
@@UncleDoug Be sure to let us know!
Let you know what, D1970 ?????
@@UncleDoug When you have something up for sale!!!! Your vids are great and would like to get an amp of yours
Soup spoon to scoop out your eyes? BAHAHAHA!
It does conjure up a vivid mental image :)