How to Scratch-Build A Vintage Amp, Part2: Schematic Review and Modifications
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- Опубліковано 24 вер 2015
- This is the second video in this series and features a review of the schematic for a Supro S6422RT that is the basis for the scratch-build. In addition, proposed alterations to the circuit will be presented and explained. At the end of the video, Jack the Cat demonstrates his uncanny retrieval skills.....you won't believe your eyes.
Link to final version of modified schematic and layout diagram: app.box.com/s/u945p1s2dv7ffro...
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Thanks for watching.
What's with all the generosity? We're supposed to be selfishly self-serving and then you go and post all of these super informative videos?!
Thanks a thousand!
+jrcenina85 Rusty, Jack, and I are just hooked on show biz, I guess.....and why not "Thanks a million" , JR? Are you being selfish ? :))
+Uncle Doug Haha, well a crowd of pupils are here to feed your addiction!
I think we ampoholics all share the same chassis-binging addiction. Our wives and friends may not understand us, but we all understand each other.....unless it gets too technical, and then Rusty and I fall asleep :)
@@UncleDoug You should get Cafe Press or similar to do a limited run 'Ampoholics' tshirt! They only print whats ordered so you can just send them a drawing and the rest is automatic.
Uncle Doug , It was while watching THIS video that I finally had my “aha” moment; when the mystery of tube amp design and building that had been eluding me finally crystallized in perfect focus. Thank you for sharing your knowledge.
That's great to hear, Shimmy. Glad it was informative :)
Hi, Doug I m pretty sure that many viewers around the world are learning from your videos. I m french speaking , you explain very easily . Generous of you giving all your good information. My study in electronics repairs did not included the study of tubes. Now, i m confident on restoring my Guild S-200 stereo guitar amp. Merci beaucoup M. Doug pour votre générosité.
+Mathieu Coletta You are quite welcome, Mathieu. Rusty and I sincerely hope that our videos are clear and helpful to all those who are interested in tube amplifiers. Best of luck with your restoration project.
This little series tasted even better the second time around.
Glad you enjoyed it, AZ.
Brilliant mods, loved them. I am very happy that you are allowing your own muse guide your decisions for modding here. Love every modification proposed. On to the next in this series.
Thanks, Mod.....glad you are enjoying the series.
since the lock downs I started building guitars,I have 9 now..I'm gonna try my hand at this...never had a tube amp since childhood..traded one of my guitars for 1by12 cab and an orange hybrid tiny terror I cannot believe the tone I'm getting now..it is my fav.rig now....your very generous. ,thanks again
You're welcome, WJ. Best of luck with your new hobby.
Just finished my first build - scratch build- Cathode follower buffer amp, couldn't have done it without your videos dude! Thanks to you I don't just solder on components and hope it works, I know know what everything does and how to recognise and fix problems. Thanks a ton man!
Congratulations on completing your first scratch-build, AT. We're really glad to hear that our videos were helpful.
Great mod suggestions! Looking forward to part 3!
+redfishbum Thanks, Red. It should be posted in the next few days.
Jack just isn't cooperating. But, I got to thank you for the videos. I have a friend who repairs tube amps and builds cutoms, too. I'm learning from him a lot, hanging out in his shop. Having your videos is a real boost to my ability to understand what my friend is doing. I am so glad to be learning this craft. Thanks again.
You're welcome, Allen. Good luck with your continued acquisition of knowledge.
This is my favorite part....the.."walk-thru"....I put it on a loop....love it....favorite part..... the walk thru....so clear....the schematic stuff is the best........thks unk
+William Earney We're glad you like it, William. I focus on schematics to help people learn how to interpret them on their own. It's like learning a new language, and essential to understand how circuits work.
I'm at the edge of my seat! great series!
Excellent series and I like the approach to use an existing design and improve along the way. I've been looking for this type of amp (single ended with reverb and tremolo) for a long time and will probably break out the old soldering iron now...Hats off to Uncle Doug (and to Rusty and Jack)!!!
+Joachim Schranzhofer Thanks, Joachim. It is an interesting circuit and concept, and I'm glad you share my interest in it. Best of luck if you choose to make your own version.
Thanks for sharing all your knowledge with us. I have learned a ton from your videos. I am very excited that you are documenting a scratch build. I am sure it will inspire many hobbyists and pros alike.
+donktonk1 You're welcome, DT. Thanks for watching.
It has been such a blessing to have you and your helpers teach us in such a delightful way. It's the first time I have ever found a use for algebra and I love it.
Thanks Doug for you generous time and God given talents.
Marcel
+Marcel Pacheco You're welcome, Marcel, and thanks for your very kind and generous appraisal of our videos. We sincerely appreciate the time you have spent watching and commenting :)
This is why I love you Uncle Doug. I've been unsuccessfully amp hunting for years (including watching lots of your videos) and resigned myself to just learning how to design and build my dream amp instead... and then you come along and not only incorporate all of the elements I want, but you show me how to build it. Thanks!!!
+Moods_Tunes You're welcome, M_T. I highly recommend the final modified circuit for this amp project. It exceeded expectations in every way. Best of luck if you choose to build one.
+Uncle Doug Will Do. I've been searching for a low wattage single ended amp with good reverb and tremolo, so this looks perfect! i'm hoping this will pair nicely with a guitar i'm building with a p13 and supro pickup complement. Time to get working...
Good luck with your project. Let us know how it turns out.
Diggin the proposed changes UD. Looking forward to part 3! Thanks again for your vids
+wreckoningday You're welcome, WD. Let's hope it all works out in the end :)
The only bad thing I see about this part two is we have to wait for part three. Other than that, it's straight out of the cool beans dept. Thanks UD..............Carl
+skycarl I second that
+skycarl Thanks, Carl. You won't have to wait too long, it's almost finished.
Congrats on your PDF schematic and build plans, Very professional looking. And again lol Thank you for sharing your knowledge, seems like I say that to you a lot.
You're welcome, Pat :)
just watching this series for the first time....really enjoying it...your choice of mods is exactly what I thought as well so this is fun to watch!
We're glad to hear that.....thanks for watching :)
This is great. Can't wait to see the build. Love the pets too!
+Barnekkid Thanks, BK :)
I agree with the unknown scratch build design that you propose; can't wait to see the results.
+John Cunningham I think you will like it, John.....so stay tuned.
Whow! You are speaking directly to the heart of all ampaholics. Why did Fender put both halves of the 12AT7 together for the first stage of the reverb circuit? Does it double the amplification factor of the stage? Does the reverb tank require that much to preform well? You are doing what I and many amp builders have been dreaming of for series from you and Rusty and Jack. What a production crew! Thank you so much for these jewels! Thankz
+Audio Tech Labs A 12AX7 can tickle the (reverb) tank, but a double-barreled 12AT7 should kick the heck out of it. I imagine that a large 17" tank would take a lot more signal input (than the small, original one) to really shake up the springs. I've built Fender reverb amps before, but never grafted in a complete reverb circuit, so this will be a new experience for me too. I just don't see how it can help but sound wonderful :)
Uncle Doug With parallel 12AT7 sections,
You get half the source impedance, double the current delivery compared to using one section triode. Slightly improved
performance can be had with hard parallel plates by separating the cathodes from each other, each with its own cathode resistor and bypass cap. Grids should have a stopper of 1k to 300 ohms on each grid, with drive signal appearing at the junction of the 2 stoppers. Stoppers of higher ohm value only add noise, but with so many other high value resistors everywhere, it really only makes a very tiny difference.
Excellent explanations and good ideas! I can't wait to see the finished product!
+Learner-Learns Thanks, L-L. Neither can Rusty or I :)
This amp...is going to sound awesome! Also, my wife now likes your videos, due to the fact that our first cat was also a black Bombay...named Jack! No lie. Our Jack was a bit less of an accomplished soccer goalie, though. Relocating the tremolo intensity makes sense (can't say I would have spied the problem myself, though). Can't wait to hear the "Supro Tremol-(Fender)-Verb a la Uncle Doug-tube-switchable Amp!"
+Andy Reeves Thanks so much, Andy. In my haste to scrawl out a diagram of the intensity control, I showed its simple design, but was remiss in its location within the circuit. It's nice to get little glitches like this out of the way before the construction begins. Thanks for watching :)
Great video. Many thanks Doug.
I own this amp, it's an Airline sold by Monkey Ward but is the same amp internally. I have played with this circuit extensively, even had it going strong as an acoustic guitar amp at one point. You are doing what I did, basically making it a fender amp. I opted for dual 10's, I made a new speaker mount board and reclothed it, I believe I did a push pull 6v6 circuit in the end. I would have to dig it out and check, it's been awhile.
Let us know what you find, Tom.
UD, your videos are top notch! Looking forward to the further details, including the Jack & Rusty Show segment.
+GmanMusicProductions Thanks, G-Man. They are busily planning their next performances :)
Keep it up Doug, always love your videos - greetings from northern NSW Australia
+BaseandGlider We will, B&G. Thanks for the kind words and best regards from West Texas, USA.
Hello Doug. Fantastic video. Well thought out and explained. Rusty and Jack will steal the show if your not careful :) Jack is the Male version of my cat Molly. I lost my last Dog around 2002 and just haven't had the heart to adopt another one. I am very much looking forward to your next video in this series. Till then,
Take care Doug.
Bobby
+Bobby Tectalabyss Thanks so much, Bobby. I fully understand the attachment to and mourning of lost pets. Over the years, I have had to cope with it many times and it never gets easier. Meanwhile, and on a happier note, thanks for watching :)
Uncle Doug
You are very welcome Doug :) I had a young wild Raccoon climb up on my knee tonight. What a great feeling :) to be trusted by something so wild.
Take care Doug.
Bobby
I had a wild young pole dancer climb on my knee once.....and it felt really good (as I recall). Seriously, it's good to hear that others share my love of animals, Bobby. They are one of life's greatest pleasures. Thanks for watching.
Uncle Doug
The pole dancer sounds wonderful too :) Took my brother in-law to a topless bar for his Bachelor party years ago. We almost had to knock my wife's uncle out to get him out of the place Lol. Thank you for bringing back that good memory
You're welcome, Bobby :)
Looks like Jack has the same agent as Rusty......er..... uh.... I mean Mr Rusty! Looking forward to Part 3!
+Tim Dockery Yes, indeed. "Mr." Rusty and "His Highness" Jack do have the same agent, and he has been squeezing my $@&%$ for salary raises and more (and more) perks. Pretty soon, I'll be working for them :)
Love this proposal very much! Thank you for your work!
You're welcome, KM :)
Omg! The Fender Twin Reverb is the best sounding reverb in my opinion too! I used to jam, when I played drums more than guitar, with a guy who had one. It was absolutely incredible! Nothing like it that I heard before or since. I tried so many times to buy that amp off him...wouldn't sell. Smart man!
They are wonderful amps for sure.
I think Jack and Rusty are co-conspirators in the "No Shits Given" movement.. gotta love em.. great series so far... as always, your videos are well thought out and always a pleasure to watch.. Thanks again for the effort..
+kujawat You're welcome, Kuja. I think you're right about Rusty and Jack.....about the only sh*ts they give are in the catbox and the back yard :)
I am so glad I found your channel. You are one of the best teachers I have ever ran across. Keep up the good work.
Thanks, Robert. We will..... :)
Hi Uncle Doug, With the changes you have outlined I bet your amp will have a lot more Va Va Voom. Can't wait.
+Jeff M I hope, Jeff. I guess we'll find out in a few weeks. Keep your fingers crossed :)
Great video series Uncle Doug. Waiting to see more...
+Olli Kivelä Thanks, Olli. I am uploading Part 3 as we speak. It should be available in a few hours.
Merry Xmas and a superb 2018 to Uncle Doug, Jack and Rusty.
May all your wishes be amplified : )
Thanks so much, FB. Same to you, from all of us :)
Great video, thanks Uncle Doug!
+TVtubeamps You're welcome, TV :)
This is great stuff! Can't wait for the rest of the series! Thanks for this. I'm actually a bass man, and would love to do a B15 clone of some variety in the future. This is all good info. Best regards.
+Julian Higgs You're welcome, Julian. Bass amps follow all the same rules, but often incorporate slightly different tone circuitry and higher power. Rusty and I hope you give it a try :)
The Uncle Doug 001 amp circuit. Cool!
+Greg's Garage Thanks, GG. I hope it works when I'm finished :)
can't wait for part 3!
+JJ Kentala You won't have to wait long, JJ. I am uploading it as we speak. It should be available in a few hours.
Great video as always. I am really excited since this project has a 6L6/6V6 option. Something like this will make a great addition to my own amp collection. Can't wait! Thanks
+Steve Dewitt You're welcome, Steve. I'm doing this mostly out of curiosity regarding the uniqueness of an SE amp with Trem and Reverb, as well as why you almost never see a SE amp with 6L6 output. There is a chance that the 6L6 won't sound as good as the 6V6.....but at least we'll find out. Thanks for watching.
+Uncle Doug maybe we've not seen the SE 6L6 with Trem & Verb because its probably too Awesome and the kept it hidden away like the Kecksburg Acorn UFO---Can't wait to see and hear the results. Thanks again for all your hard work....tubing around!
You may be on to something, Mike. Maybe it's so fantastic that amp manufacturers are keeping it hidden, and only Eric, Jimmy, Jeff, and Stevie Ray were ever allowed to use one.....in the studio :)
can't wait to see how you wire this up!
+EXPLORING AUDIO I'm machining the chassis at the moment. Wiring should begin soon :)
I have been watching you for some time and wanted to let you know how in debt to you so many of us are for your time and knowledge. The truth is I feel I know nothing (very little). I set out to learn so long ago but with several kids and life happening all around me the learning has gone slow. I can not take a college class, just do not have the time. This is so valuable to most of us and I thought that is was time to really let you know how much I appreciate these videos. I have learned more from you and your kind demeanor than anywhere else. I love you brother, Thank you.
My 9 year old boy is learning from you and it is fun to watch.
I would like to ask you, if it is possible for you, to walk through a schematic and an amp from beginning to end and explain what happens as the signal path moves through the input, tone stack and power section. I have spoken to some other guys in chat rooms and it is our missing link. It would put in perspective how all this works. I understand how most of the parts are comprised...such as caps, resistors, transformers etc. I do not completely understand the circuit from beginning to end. . . . .
I have two Marshall Major amps with some obvious design flaws in the ultra linear circuit and as simple as this amp looks, I still do not fully understand it. (yes the plate voltage in this amp is about 580- yikes!!) It is the best sounding guitar amp I have ever heard hands down. I think I like the kt88s and the openness of the ultra linear circuit. I want to build some of these. I just feel I need to fully understand what is going on. I'm open to your thoughts. I make changes in resistors and caps but never know that what I'm doing is right, if that makes sense. I want to mod my amp but the understanding of this (resistor value or cap value) that makes this or that happen, is still not clear to me...I hope I do not sound as dumb as this makes me look...
If you have the time, please feel free to respond in length, I would love to hear your and Rustys thoughts....ALL MY LOVE AND AGAIN THANK YOU SO MUCH
+Tonelives Greetings to you and your son, TL. I'm glad to hear that the videos have been helpful, and will keep your suggestion in mind for the future. Thanks for watching and commenting.
Thanks a lot for the video, the tension is building on the build. You make things look so simple Doug, great explanations as ever. All the best to you and Jack ha ha cats are a funny lot and a high to Rusty too. Colin
+mixolydian2010 You're welcome, Colin. It's always good to hear from you. Glad you're enjoying the videos :)
Absolutely love the project! Just about any Valco amp is interesting. I was hoping for a Premier Reverb instead of the standard Fender. They are just so dark and rich and sound like nothing else. Other than that oh so minor disappointment I cannot wait for further videos. You are giving me confidence for a nice winter project----Thank you!!
+notanotherchad Thanks so much, Chad. To be honest, I never thought of using a Premier reverb circuit. I'm not familiar with the type of transformer or tank they use, and these parts may not still be available, so I would have probably used a Fender transformer and MOD or Accutronics tank anyway. I hope your disappointment fades when you hear it in action.
@@UncleDoug If I remember a comment correctly on Part One. there was the implication that the smaller reverb tank and its associated lower 'power' tube gave a kind of alternative reverb not found on other amps. While your mods dont stop anyone else trying a more original design, or sourcing an original amp, one wonders if you would have liked to have tried something that is theoretically 'weak' to see exactly how it sounds with a variety of pick-up input combinations.
I can't wait to see how this series turns out. Thanks again Uncle Doug, great to have you back!
Just a heads up, the link at the end of this video seemed to take us to a video from last year instead of Part 3. You might want to fix that.
Cheers!
+Admiral Quality You're welcome, AQ. I didn't add a link to the end, maybe YT did, simply because at the time I had not created or posted the follow-up video to which to link. I'm sorry if it happened and will look into it. Thanks for the tip.
+Uncle Doug Ah, YT decides itself what the next video is? It's algorithm must be failing. (Worked for the first video in this series though. I've never made a series so I haven't actually used the feature yet, if it's even offered.)
Anyway, no biggie! I survived the considerably mild confusion with my sanity intact! ;)
That's good news, AQ. More than most of us can say :)
+Uncle Doug (It is quite possible that I'm not enough of an objective observer to have a right to form that opinion. ;)
I guess we'll have to poll your associates to verify (or negate) your assertion.....
Very good information. Thank you
Glad it was helpful, Adriano.
Great work and thanks for sharing it all . have to say i recently built a SE champ workalike ,with a 5 watt OT which i plugged a 6L6 into and it worked quite nicely with a 470 ohm and 22uF bypass cap . no more power , just a different tone. Then just for giggles i tied pin 1 and pin 8 , and shoved an EL34 in there ,which yielded some of the charm of that tube .again no more power just different tone . all i did was borrow a bit more current to cope with the demand for the heater..Gotta love that self bias resistor.. Cheers..
+steeveejay Thanks for the input, Steevee. I gather that the bias switch is probably not necessary for tube exchanges, and that the cathode biasing can compensate for the differences between the 6V6, 6L6, and even an EL34. I thought this might be a possibility, but was going to test it to see, once the circuit was completed. I wonder if more power will be evident with a stouter (15W) OPT ??
Uncle Doug Always good for more headroom , Then if you build a silicon diode rectifier into an old octal socket your larger power tubes would be 50 or 60 volts happier . And good choice going to Triode elec for the transformers. i believe Valco got all their transformers in Chicago .I sourced the Magnetic bits there for the amp i mentioned .
A good suggestion, Steevee, and thumbs up to Triode.....they're my favorite transformer source.
I think I mention to you before that I have a Fender Hot Rod Deville. This is the 4 10 inch speaker version. It's very heavy and very loud. Anyway, I've never been very happy with the tone of it, and in retrospect, I should have bought a deluxe reverb. So a little while back I gutted the circuitry, and I'm going to put my own handwired circuit in there, based on a Deluxe Reverb with a few modifications. I left the tremolo part of the circuit out, but when it come to the reverb I ran into problems. I only had room on the chassis for 1 extra pre-amp tube, which meant I had to figure out a way to drive the whole reverb circuit with 1 pre-amp tube. It ended up being a reverb circuit that's all tube driven, but does not use a driving transformer. I hope to finish assembling this amp over the next few weeks, and I'll report back on how it turned out. All in all, it ended up being a very different approach to the classic tube driven reverb circuit used by Fender on those blackface amps.
+Alva Goldbook I have heard of purely tube-driven reverbs, Alva. I believe that some early Gibson amps did this, but to be honest, I have not heard much good about the resulting reverb tone and intensity. Fender used both triodes of a 12AT7 (a single pre-amp tube) to drive most of their reverbs, but then you need a 12AX7 triode to recover the signal. If you made the Deluxe Reverb circuit one-channel (Vibrato only, no Normal) perhaps you could "borrow" the Normal's 12AX7 for that purpose.
+Uncle Doug In researching this, I found a few circuits that did this, and Gibson was one of them. Oddly, one Gibson circuit (I forget which one) used a cathode follower to drive the reverb.
The existing Hot Rod amp had 3 pre-amps, and the chassis has room for 1 more. I figured I would need 3 12ax7 gain stages for the main part of the pre-amp, and plus 2 more for the phase inverter. I opted to use the other gain stage for an added gain stage for more distortion, which is pretty similar to the Mesa Boogie Mark 1.
So this left me with just 1 pre-amp tube for the entire reverb. Paul Faucett from the AX84 forum was nice enough to help me out with developing this circuit, he ran the SPICE simulations for me.
The basic idea is to drive a reverb pan using one half of a 12AT7 using a standard gain stage. The 500pf grid cap filter is omitted, and a cathode bias cap and a coupling capacitor is used to filter out the undesirable frequencies. A resistor shunt to ground follows the plate, which filters other frequencies, but also drains the caps of voltage when the amp is turned off.
The biggest problem is dealing with output impendence. But it's important to note that the input impendence of any reverb pan is only listed as it's impendence at 1kHZ. The pan itself acts as a _inductor_, and it's input impendence varies at different frequencies. Ohm's Law allows us to use this characteristic to drive current, which is what reverb pans really need to function.
Since we need resistance to drive current, low impendence reverb tanks, like 8 ohms, won't work well. Luckily, higher impendence tanks are made, which are meant to be driven with solid state drivers. The tank that came on my Hot Rod amp is such a tank (Type E I believe), as it was driven by an op-amp in the original circuit. I think I'm going to replace it with a Type F.
The reverb recovery will be the other half of the 12at7, and plus there is a final 12ax7 stage that will amplify it again, now mixed with the rest of the pre-amp circuit before the phase inverter.
Here's a schematic.
i.imgur.com/jIFd292.png
Very interesting, Alva. I was aware that the tube-driven (and solid-state-driven) tanks had much higher input impedance, but I was not aware of many of the details you provided. Using a cathode follower (as Gibson did) makes sense because they tend to convert voltage to current much like an output transformer does. Thanks so much for this information and be sure to let us know how it turns out.
Every time I rewatch your video's something I can't wrap my adled brain around becomes clearer!! This time??? How to low power high power an amp. My fantasy amp is a super reverb that runs 2 6v6's or 6l6's that can emulate all the black face amps in the 22 to 35 watt range by having various hand built speaker cabs! But the wife says no way!
Your plan is not all that bad, Russell. Give it a try. Tell your wife it's either amp experimentation or booze, gambling, and prostitutes. She'll change her tune ;)
I built a 2 x 12AU7 preamp and the tremolo unit but haven't finished it to the push pull stage yet. (got a little heart trouble, slowed me up).
A really great tool I use is LTSpice modelling and schematic software. The actual real amp turned out within a few percent of the modelled values.
Another great thing is you can feed a guitar riff wav file to the model and get a wav file output, (Not real time of course) and I have to say the output file sounded fantastic, like the real thing. The only 'iffy' part was getting the right model software script for the particular tube behaviour, but it's out there and the result is a really impressive model. It's a lot of fun and you don't burn up good parts testing, well not until the very end ...
:-)
Wow, that sounds pretty sophisticated to me. Maybe someday, Jack will give that software a try :)
@@UncleDoug
Well it's free from Analog Devices
www.analog.com/en/design-center/design-tools-and-calculators/ltspice-simulator.html
... although Jack will probably use it for Op Amp n Solid State stuff
:-)
Love the jack as you call him, Master Doug. A fishing pole with felines i use. puspus love. Your next lesson i await...
+R HEIDEMAN Thanks, RH. We have a fishing-pole-like device with a stuffed mouse in the "bait" position, and he loves it. We wear him out playing with it at night so he'll sleep.....just like a baby.
Awesome
good upgrade choices.. seems lile a very promising project
It was, Emmett. Thanks.
@@UncleDoug since watching your scratch built tube amp mini series, i'm better equipped to do a project that I've been wanting to do once i get some spare cash. I plan on gutting an old tube console radio and replacing the guts with a tube guitar amp section and a midfi stereo section. then i can run them simultaneously for music or separately for guitar
@@sherpadelgatos That sounds like an interesting project, Emmett. Please let us know how it turns out.
@@UncleDoug yes ill let u know. it'll be a while tho since i don't have the money yet
The proposed circuit at 03:50 connecting the cathode of V4 through a pot to cathode of V1 would alter the cathode bias. When then pot is turned toward ground it would jumper the resister and bypass cap at v1 cathode. Otherwise I get what you want to achieve. Very nice build by the way.
Thanks, Daniel. That was previously discussed and corrected in the schematic.
@@UncleDoug Sorry, I must have missed that. I'll have to check it out again. I did watch the whole series and the end product is extraordinary! You are amazing at cabinetry as well as tube electronics. Any further issues regarding CAThodes, ask Jack, he is the expert.
I often post my plans for projects in a video and then let knowledgeable viewers (like you) chime in with helpful suggestions in the Comments section, Daniel. That's what happened in this case and the schematic was altered as a result. Thanks for your very nice comments, both from me......and from Jack :)
Well, it all sounds pretty darn good to me (considering I know next to nothing about electronics design) BUT has Rusty approved the substitution of the 6V6 with the 6L6? Another stellar project Uncle Doug, I learn so much from watching your videos. Many thanks.
You're welcome, Stony, and thanks for your nice comments. Yes, both Rusty and Jack signed off on the tube substitution long before the video was produced :)
WOW!! Excited for this build this what I want to do but can't seem to get the connection from the schematic to the build.
Thank You again !!!!
For your teaching.
+scott entrekin You're welcome, Scott. I think the transition from schematic to build is an obstacle for many people. Hopefully, this video series will help to remove it. Thanks for watching :)
just got around to this part. I find schematics always interesting. Very simple Class A circuit. As sa230e comments,
putting an intensity pot in the cathode circuit may cause some issues depending on where the pot is in relation to ground,]as
it acts as just a variable resistor and you turn it to minimum, the cathode will be grounded.
Fender used a isolation neon/light dependent resistor (LDR) taken from the plate of the LFO phase shifting oscillator via the neon coupled LDR , into the wiper of a 50K pot and into the grid i/p signal of one half of the phasesplitter/driver.
splitter.
The 12AT7 (low mu) as a reverb tank driver is a good idea.
+SuperCarver2011 Thanks, SC. The Intensity Control placement has been altered for the reasons you stated. Here is a schematic of the circuit in its current state of evolution: www.tommyfoley.com/theuncledougtremoloreverb.jpg
I had no idea I loved tube amps until I started watching your videos! I've just been getting into building my own electronics and, honest to goodness, watching the videos you make is getting me pretty excited about the whole concept.
That being said, not sure I'm quite ready to build a full amp. If I could make a request: Could you maybe make a small headphone amplifier, just something really simple that I (and probably several other novices) could try and reproduce as a first step towards building a full guitar amp?
If I could make a secondary request...it'd be nice if the parts list could come in under $50, I only have so much to throw at this new found hobby of mine...
Rusty and I stick strictly with tube guitar amps, Jay, but we have posted a video series on how to build a Fender Champ from scrap parts (i.e. found at garage sales, junk stores, etc.) that may be helpful. With some luck it may end up in your price range, but considering the current cost of tubes and speakers, it will probably end up higher. You could try the Internet for ideas on small headphone amps.
Hmmm, well, maybe if I just keep watching these things I can figure out a basic schematic on my own ^_^. I'll give the Champ series a look after I get through this one (heck, maybe I'll be ridiculous and modify a champ to do stereo and output to a 1/4" stereo). If it's over $50 well...just means I have to save a bit longer, that's fine :).
Thanks a bunch for doing these videos! It's really helping bring everything I've learned over the last couple months into focus.
You're welcome, Jay. Modifying any guitar amp to become stereo would probably not be practical or feasible.....but don't let that stop you :)
Uncle Doug Huh, why is that? (If you have a link to something that explains it, I'd be just as happy to read up on it. I don't want to turn this into a game of 20 questions or anything...)
I would assume though, at very least, that there are a lot of similarities between tube guitar amps and tube headphone amps, right? The big different being how much power is involved and the whole stereo v. mono thing?
A stereo amp is basically two separate amps that may or may not share a power supply. To convert an existing tube monaural guitar amp into a stereo amp, you would have to double the circuit, completely redesign the power supply, and find a cabinet that could hold it all. Then, since the vast majority of guitar outputs are not in stereo, your efforts would be wasted.
It was apparent just how entrenched both Jack and Rusty were in their traditionalist leanings at the outset. Something tells me they could be won over to a more flexible outlook.
They made the difficult transition from rigid fundamentalists to open-minded visionaries......not an easy one to make.
Excellent series, Uncle Doug! Thanks very much for sharing all of your knowledge. I've been looking for something special to do with all of the spare amp parts I've accumulated over the years and I think I've found it! The tremolo in Part 8 is unbelievable! I'd like to try it with a 4xEL84 output section left over from a previous build. I'll keep you posted. I'd also like to experiment with the second half of V1 to work by 'jumpering' pins 1-6, 2-7, and 3-8 similar to the AT7 in V3. I'm curious how that additional gain would affect the V1 tremolo.
+Bryan Ellis Thanks, Bryan. Glad you enjoyed the video series. The four output tube modification sounds interesting. I tried running the two triodes of the 12AX7 in parallel and got a small increase in gain, but a noticeable decrease in tone quality. Perhaps you can experiment and come up with a way to make it work. Best of luck.
It's funny how less is more when it comes to great tone. We are reminded of it regularly. Thanks for your reply.
You're welcome, Bryan. I guess the venerable old Fender Champ is a good example of the benefits of simplicity.....no frills at all, just great tone (in the right hands).
Awesome cat
Thanks, Robert :)
thanks doug, well im gona do the drive circit of a marshall drop the trem and do the reverb and trem valves to be overdrive. cheers doug. i got a zenith 30watt selmer amp combo with a good trem on it. like the 6l6 6v6 config.
+freak55beat You're welcome, Jon. Thanks for watching. Best of luck with your projects.
Hi Doug, watching this series for the 3rd time and really getting the bug to do something like it. I happen to have a Hammond Organ Amp that was repurposed for a guitar but i want to add in the reverb and tremelo that you show in this video. does that make sense. It seems if i can isolate the circuit and make the two circuits on separate boards. I hope all is well i see this is an old video i hope you are still doing this great videos. Thanks for sharing and educating us all so much. D
You can't add extra circuits unless your power supply can handle their current requirements, Dennis. Be careful not to overburden your power supply.
Thank you for you reply. I am talking to the original builder of the Hammonds conversion. He said the same thing. We may like at them as a EFX out/in and add all the circuits to support them. Not sure but really enjoy your videos and your great way of explaining it is so good. D
@@DennisMurphey It's easier to simply use a reverb/tremolo pedal, Dennis......if all else fails.
I don't know if your drawings are only to illustrate the concept or if those are the actual circuits you plan to use but I noticed the tremolo intensity control will also affect the bias of the first 12AX7. If you dial it down to zero it will ground the cathode of the first stage, bias the triode very hot and probably cause a lot of distortion. I would put the intensity pot at the grid of the tremolo cathode follower.
I have the same concern, and was thinking he needs 2k to 3k resistor on pin 3 of the intensity pot to prevent grounding the cathode of V1.
+sa230e Excellent observations.....I see your point(s) and appreciate your input. The diagram was something I whipped up quickly to help viewers visualize how an Intensity control could work, but it does appear to alter the bias and enable grounding the V1 cathode. I think I'll follow your suggestion and move the pot connection to the grid. Thanks again.
+Uncle Doug Cool! It's fun to collaborate on this stuff. I'm thinking making that 220k resistor variable would be the easiest and most effective way to implement the intensity control.
Best of luck on your build.
I agree. Several minds can produce a far better product than a single mind can :) Your suggestion would probably be the simplest approach. Are you thinking a 250KA pot, wired as a variable resistor (wiper and one side) ?
Exactly so, and the other problem is that the final 12AX7 section in the tremolo oscillator shares the 100R cathode resistor and bypass of the input 12AX7. It is not going to like having a 1M cathode resistor. It will probably over-bias itself into complete cutoff. NB Doug this section is a cathode follower, it doesn't provide any gain, only a low output impedance, which again you would mess up with the 1M pot. The suggestion to put it at the grid is a good one. Note also that as the tremolo oscillator only outputs subsonics, it doesn't really need a shield.
LOL! "Rare, Vintage" - the battle cry of Ebay! :-D
Amen, Dave. The problem with rarity and age is that they don't automatically equate to "valuable". I have some really unusual old shirts in my closet.....but no one seems very interested in buying they from me :)
It would be great to have independent treble and bass tone controls, thank you for the videos
You're welcome, Joch. You can easily tailor the circuit to suit your needs.
Love this series Uncle Doug. It is inspiring me to add a tremolo and reverb circuit to a 5E3 build project I have been planning. I reviewed all the comments - but didn't see this question: Regarding adapting the circuit to accommodate both the 6L6 and 6V6 output tubes. Do both tubes have the same Plate Impedance characteristics - such that a single output transformer will reflect to the same speaker impedance (i.e. 8 Ohms) with out any circuit mods ?? Thanks again for all of the inspiration !!! -- Don
+Donald Filbert Thanks, Don. Glad the series is helpful. Yes, they both have the same load resistance and therefore the tube socket can be connected to the output transformer and will work regardless of which output tube is plugged in. This was essential for the swapping concept to work.
You are awesome
"Show everybody what a brilliant cat you are!"........
"Oh Lord."
hahahahahahahaha ha ha haha ha ha ha ha ha
ha
super good series, are you gonna explain how to make a hifi stereo amp at some time?
+marcus ravn Thanks, Marcus. No, I only work with vintage guitar amps and circuits. I guess I'll have to leave the Hi-Fi to others who know a lot more about it than I do. There are a whole bunch of them on UA-cam and the Internet.
thats cool, i just like the way you explain everything :) keep up the great work :)
We will, Marcus. Thanks for watching :)
Losing the Treble input circuitry might be a backward step. Would not an alternative be to have a couple of switches in the input circuit so that both the hi Z and lo Z can be switched as required through a bass cut (I presume as its not really a treble boost !!?) filter. I am a fan of as many inputs as possible though, having one Telecaster through the normal input and one thru a bass cut option would give an interesting mix signal for a pair of guitarists running harmonies or unison playing. Though of course you can argue as it is in the input stage it is merely replicating what the tone controls are doing on your guitar anyway. like all things it is do you keep the amplification simple, and run the effects as separate items outwith of the unit or move one or more effect and tone into the amplifier circuit at pre-pre amp, pre-amp or pre-output valve stages.
Thanks for your thoughtful input, HP.
Uncle Doug, this really sounds like a plan, it will be so much fun watching it progress in the future... I'm a bit curious, where did you come up with the idea of this particular amplifier? Has this been burning in the back of your mind for years or is it just something you decided on after going thru schematics of single ended amps or something else?
+Buddy Martin I was trying to find a really unique circuit upon which to base another scratch-build, and discovered this one just recently. The concept of a compact, SE amp with both a really good tremolo and reverb has appealed to me for a long while, and this one seemed (potentially.....with reverb modification) to fill the bill.
+Uncle Doug Well, you certainly found one that meets your requisites... I really like the idea of adding the better reverb too. Buddy
Thanks, Buddy. Let's hope it all works out in the end :)
It should be real beast (in a good way)! Jack is much bigger than his first YT appearance, but he fetches the way I play guitar.....going the wrong way. :))
+bullthrush He's a Jimi Hendrix fan, so I guess that explains it :) Yes, I hope it emits something other than just smoke when I'm finished.....but either way, it's more fun than watching re-runs of The View.
+carrierwave I would rather have a battery acid enema than watch it......so I guess we're on the same page, CW.
i found the circuit great design i am going to build a reverb tank unit from this unit
+ian “valve doctor” forster You might be better off using the Super Reverb circuit, Ian. The Supro circuit requires a proprietary reverb tank and is not particularly impressive.
Hey Uncle Doug, What if I wanted to add a tone stack in replace of the tone knob. Something like a Treble and Bass control with a fixed Middle section?
Most amps I've seen have only one or two tone controls, Joseph. Use Google to find a schematic of an amp you like that uses the two controls and replicate the tone circuit.
Uncle Doug ok one last question is where do I start the circuit, do I get rid of the 500pF cap, the .005 uF cap, 470K res, and the 47K res? Thanks for your help. These videos are awesome!
Without a schematic and personal experience with this modification, I can't speculate, Joseph. I suggest that you experiment by removing and altering component values and see if you can't come up with a suitable configuration. Best of luck.
I may not yet fully understand the amp build parts of your videos, I may get there one day if I only applied myself, but, I think I do understand Jack as I`ve been a cat owner for nearly forever. Now for my `substantive` comment/question: What will you call this amp? Suggestions: Ampinstein, Rusty-Jack special, or if it doesn't pan out like you hoped it would, a P.O S. lol. But no, I`m sure you will have a very nice 1st build once you finally have it together and test drive it. BTW, will it come with an Elvis sticker on the cabinet? :-) Cheers Unck.
+Krang Gangs Greetings, Lee. "Ampenstein" sounds pretty good to me, and the sales slogan could be "Fire.....bad. Tone......good" :) This isn't my first build (see my other videos), but it's probably the most exciting one, simply due to the fact that I have no idea what to expect. It all makes sense on paper, but may (or may not) be true of its reality.
+Uncle Doug I`m confident its going to work great. And if it doesn't initially, you will make it so. Cheers!
The best.
+MrMac5150 Thanks :)
Uncle Doug
I did not know kitty cats can play catch.
This will sound like a real "come-on" but under normal circumstances, Jack will retrieve the paper toy quite a few times.....bringing it right back to me each time. Naturally, for the video he did everything wrong, but I thought it was funnier that way.
Uncle Doug
I have never seen a cat respond like yours.
Cheers.
Thanks, Mr.M. He is definitely a gifted retriever....when the camera isn't running :)
Great Video Uncle Doug. I'm on the verge of building a Fender Champ clone.
I'm interested in that mod that you're going to make re: the AB switch for a 6L6 or 6V6 for the output tube. Is it possible to do that with the "Champ" circuit"? Meaning...is it as simple as having a variable bias resistor switch and of course upgrade the output transformer to support the increased current draw from the 6L6?
Great videos!
Thanks,
Joe
Greetings, Joe. Yes, if you provide a switchable bias resistance that suits both output tubes, you can interchange a 6V6 and 6L6. There are two other requirements, however. 1.) The output transformer must be able to handle the higher output power of the 6L6. 2.) The power (not output) transformer must be able to handle the higher current demands of the 6L6. Bear in mind, also, that due to the difference in load resistance between the two tubes, the primary impedance of a single output transformer cannot exactly match both tubes, but the result is generally quite acceptable.
Hello Uncle Doug,
First of all, many thanks for all your videos, have been watching them non-stop for a week. They're so great and I'm learning so much!
Regarding modifications. Would you ever replace/upgrade a tube-rectifier with a solid-state rectifier? Or if this is generally a bad idea, could you enlighten us?
+Vincent Herbst Greetings, Vincent, and welcome aboard The Rusty Express :) I am a purist when it comes to tube amps and would never convert from tube rectifier to solid-state (diodes), but I do see the advantages to SS rectification: cheaper, simpler, more efficient, higher voltages, less sag, etc.....but there is a certain, undeniable charm (and tone effect) in old-fashioned, inefficient tube rectification.
+Uncle Doug Thanks for the tought.
+Vincent Herbst You're welcome, Vincent :)
Thanks. Will you be explaining how to connect the tremolo circuit to the grid of your output tube? I'm building a parallel 6v6 amp with 6sl7 preamp. I want to steal the 6sl7 trem circuit from a reverbarocket 2, but not sure how to incorporate it properly. Hope your build will help clarify that for me. Keep up the good work!
+ej222 You're welcome, EJ. As I currently envision it, it will simply be a pot (1 Meg ?) in series between the right end of the 2200 ohm resistor beside V4 (second Trem tube) and ground, with the wiper connected to the tube's grid. This mimics the circuit's Volume Control (directly above, near top).
Uncle Doug. I play thru silverface Twins ect. /w push/pull master vols I disconnect reverb tank and put 220k 1/2 watt resistor across the the hots on the reverb in/outs thus making the reverb pot distortion thus the ( ice cube mod ) with a 4x12 wired parallel it has a compressed heavy sound. Not quite your favorite type of sound. My question is , can that reverb circuit be used in something like what you are building to drive more gain like on the twins? My research shows you using a older reverb design.. thanks
IMHO the reverb circuit is intended purely to drive a reverb tank and recover the signal from it. I cannot see any way to utilize it to increase gain for the regular music signal. I can understand why it would be tempting to use those extra parts for another purpose, but cannot see any way to do it. Sorry.
It was a passing thought when you added the twin reverb circuit to your build. for the house I use a silvertone 1457 and a peavey Bravo, I like the dry and compressed mix of the 6v6 and el 84, I use mkii marshall and twin on stage . I am a true Fan of yours and the Pets thanks for the Reply Uncle Doug.
You're welcome, GTO. Rusty and I really appreciate the nice comments.
Uncle Doug...I follow all your changes....except the output Tubes....Since you are beefing up the output Transformer and going to a 12" speaker...What's the advantage of having the option of running the original 6V6 tubes when you have designed it for the beefy 6L6 ....is there some kind of "sonic" advantage?? Or you just want the option to swap out for some reason like .... a/b testing.??? Just asking.....just curious...B.
+William Earney I'm curious why there are so many SE amps with 6V6's and very, very few with 6L6's. The 6L6 should offer much more power while (hopefully) retaining the SE tone quality.....yet you almost never see it used in this manner. I would like the flexibility to be able to switch the output tubes and compare the sound quality of each. I may even try a 6F6 or some other uncommon tube.
+Uncle Doug Got it.... love to hear your final analysis....even if it's a year down the road...after you've lived with your final selection and tinkered. a bit.......Thanks...
You're welcome, Bill.
Hello, thank you for all the great videos. I am wondering about your tremolo intensity circuit however, I'm not sure it will work the way you envision. If you attach C the cathode of V1a to the wiper of the pot, by turning it down you will be grounding the cathode of V1a eliminating the bias resister and cap from the circuit and changing the gain and frequency response of your input stage. You might be able to do it if you insert a coupling cap between the the pot and V1a but you would also need to add in a bias resister to the tremolo tube since it currently is sharing V1a's bias. If that doesn't work you would have to probably add another stage and inject the tremolo signal down stream somewhere. I noticed there is half of a 12ax7 that is not being used. I would take a look at a Fender Twin tremolo circuit to see how its intensity is done.
Thanks again for all the great content!
+Nick Clarity Thanks, Nick. The Tremolo Intensity problem has already been detected and corrected. I posted a note to this effect in the video. The pot will be attached to the grid of the second tremolo circuit tube, exactly like the volume control above it in the schematic. Also, I will convert the half-utilized 12AX7 into a fully-utilized 12AT7 to drive the reverb circuit.
+Uncle Doug sounds good to me. That's what happens when I don't pay attention.
I really appreciate your input and help, Nick. Always feel free to advise me whenever you see anything questionable. I'm always anxious to benefit from the knowledge of viewers. Thanks.
The cat a brilliant cat......................he/she has a mind of his/her own.
Yes, he does :)
Hi Uncle Doug, you used a Vintage Jensen Ceramic C12Q 35W speaker. What other speakers do you reccomand? I obviously try to put in a good speaker that match this cabinet and circuit. What do you think about Eminence speakers like these 3: Texas Heat, Wizard and CV75?
Choosing speakers for someone is like choosing a wife for them. It's so personal and subjective. You need to do research on each speaker. The Wizard is 8 Ohm 75W but not recommended for open-backed cabinets. The CV75 is 16 Ohm, which would require a different OPT. The Texas Heat is 8 Ohm, OK with open-backed cabinet, but 150W (a bit excessive, but no harm). Thus, from your suggested speakers, the TH would be the best choice.
Uncle Doug thx again for time effort and your input about my suggested speakers. Thx a lot. I agree its a relative thing so not absolute. I decided to put in at least 3 speakers so i have some reference.
Good luck, Stefan.
Hey Uncle Doug, I've been following your videos for a while now... Congrats, they're great! I watched this series a couple of times now and I'm decided to build something like this model. I do not like spring reverbs very much and I'm wondering if the driver/recover stages can be replaced for an active effects loop. I noticed you haven't cover that in your videos, but have you any advice about this subject?
Thanks, Pancho. No, I deal only with vintage tube amp circuits, which rarely, if ever, have effects loops.....relying strictly on built-in spring reverb and tube tremolo effects. Yes, I'm sure you could delete the spring reverb from a circuit and add an effects loop, but I have never done such a conversion.
Hey Uncle Dough, thanks for the video, looking forward to see the result,
I'm wondering though, what do the resistors on the jack-inputs do to your sound? any particular reasons to pick a higher impendance over a lower one? (or is this just to balance out high output pickups vs low output ones?)
+Sander van der Zandt You're welcome, Sander. The higher value resistors really don't affect the incoming signal much in series because the signal is at a very low current level, but if you look at the schematic, these input resistors also provide a pathway to ground through the self-grounding input jacks. Lower values will allow too much signal to leak to ground and you will lose volume and high frequency.
+Uncle Doug any particular reason to use these self grounding jacks?
Yes, when there is no instrument cable plugged into the jack, it automatically self-grounds to prevent any noise or RF interference. They are commonly used on just about all amps.
Hi there, I m in the middle of building a CNC controller, and my plan is when Ive finished that, is to build a valve amp. Looks like Ive found your videos just in time. I might copy your design if I may. I would however, like to build an elaborate enclosure for it though, and maybe build it as a stand alone head with a separate cab. Im not sure yet. Thank you for the inspiration and education. Kev UK.
+kev keelan You're welcome, Kev. I will be building a vintage-style combo cabinet for this circuit, but a head version would make good sense, so you could avail yourself of an array of large, multiple speakers. I will incorporate a 4 and 8 ohm speaker output jack on the chassis, so that the cabinet speaker can be disconnected and a speaker cab can be used.....the best of both worlds :)
Sounds good, Ill look forward to seeing and hearing your finished project. Tubes in my opinion give a warmer richer sound than that of digital and makes for an interesting project. Best wishes.
Thanks, Kev. I agree with your assessment of tube vs transistor.....it's what makes us the ampoholics we are :)
Not sure if you cover this in another video, but can you explain speaker wattage and impedance and how that relates to amp wattage. I am going to ask another question but before I do, I am trying to understand a bit on how you can build an amp with similar tonal qualities but at a reduced wattage...so with that in mind my next question. Besides picking the amp (pre -existing) of which you want to model after, then is it the tubes you decide on next or the speaker, I saw in another video you talked about knowing the speaker impedance, so you could ge the correct output transformer , than match the selected output transformer to the tubes that will work with it (OT).
Speaker wattage and impedance are covered in several videos. You must be sure the the speaker wattage is adequate to handle the output power of the amp, otherwise the speaker may overheat and be damaged. I would think that any fundamental change in a circuit, i.e. reduction of output power, would alter the tone. If you are modeling another amp, you simply use the same or very similar components.
Hi Uncle Doug, I'm currently building a single ended amp, very similar to your plans here ( I downloaded the schematics). One question please: I have 4 22uF 450V caps available. Do you think I should put all 4 like you did here, and split the resistor of 10K in half? What is the advantage compared to using 3 caps?
PS, my schematics is based on a champ which calls for a 10K resistor in between 1st and 2nd cap.. I hope that makes sense..
It would help if you provided a schematic, Ivan. I have no idea which Champ circuit you are referring to. My suggestion would be to duplicate the schematic. Use the same cap and resistor values that they suggest.
Thank you for your response @@UncleDoug. It's the 5F1 circuit which has 3 filter caps. I modified the 5F1 schematic so I use 3 x 22uF caps (5F1 calls for 16uF-8uF-8uF). I also have one more additional 22uF cap that I could add, so I was wondering - what is the advantage of adding one more additional filter cap? Will this reduce the hum or something? I'm sorry if it's trivial question, I just started with electronics 4 months ago, and couldn't find proper answer on the internet.
I think you may be overdoing it with the filter caps, Ivan. You have doubled the capacitance and are considering adding more. All the circuit needed was 16/8/8uf. The added capacitance will stress your rectifier tube on startup and probably provide no noticeable reduction in hum. It's best to stick with traditional values.
I think you were right when you asked for the schematics, but I feared that I'm going to bother you too much with this, which I did anyway. I hope you don't mind, and I appreciate your help. Could you please check the schematics here: tinyurl.com/y777zo2q, and help me determine if the setup is okay? Thanks..
Thanks I'm not as familiar with them as you but I'll keep trying
The best way to gain experience is to carefully experiment with a circuit. You also need to build and use a current limiter (see my video on how to build one) to prevent damage to the circuit during this process. Good luck.
Uncle doug-- what does the second cap off of the the first plate-do?why is there 2-- is it for coupling-thanks Markus
Could you provide a time at which the capacitor is mentioned or shown on a schematic ?
@@UncleDoug yes--- its on the uncle doug tremoverb off of v1(12ax7) there is a .015uf and then a .005uf-- i think the .015 is a coupling and the
.005uf is a tone stack?-i might have answered my own question thanks for reply-
Doug, just following through with my enquiry about YOUR amps? . . . do you have a site or page etc? . . thanks again
I have a FB page: Uncle Doug's Vintage Amps. All business inquiries should be addressed to me there.
Do you think these or similar modifications could be used with a Champ 5F1?
Yes, definitely.
First! :D
I will watch of later! But I'm sure it will be great ! :)
+LowEndStrings What could possibly be more important than one of Rusty's videos, LES ? He's crying in his dog house as we speak. Seriously, when you do get a chance, we hope you like it :)
Hello, uncle Doug,
I've taken a look at your tremolo intensity mod and I think in the lowest intensity pot position you'll end up grounding V1's cathode? Am I mistaken maybe?
Keep the good work.
+DolganoFF You're not mistaken, D. The error was detected quite rapidly by a viewer, and corrected. The new location for the Intensity control is to replace the 220K resistor (between the grid of the cathode follower, V4, and ground) with a 250K potentiometer. Thanks for your observation and input.
have you tried the plastic springs for cats? my black cat(Echo) loves them.
No, but I'll check them out. Jack needs some new toys.
Hello Uncle Doug, after build my first amp after being inspired by your videos I have come down with a fever and the only cure is to build more! I really would like to build this design as I have accumulated some spare parts like a reverb tank and other various parts as well as an oscilloscope and other testing equipment. I'm a harp player and would like make it more harp friendly at least on one input and was wondering what might be some things I can do to help with this? I use high impedance mics but would like it to be able to be a guitar amp too if that's possible. Thanks for all of your videos!
That's good to hear, Joe. There are sites dedicated to creation of harp-friendly guitar amps which would be more informative than my limited knowledge on the subject. Best of luck with your project.
Hello Doug, I am looking fwd to the next instalment. One question I have in general about vintage tube amps. Why do you think most were manufactured with the tubes facing down. As heat rises I would have thought better heat dissipation from the hottest part of the amp, i.e. the tubes would have been achieved if the tubes were upright. This would also reduce residual heat passing into the chassis via convection.Thus reducing additional heat throughout the other electrical componentry. Space and overall height of the cabinet could be the reason however this does not make too much sense given the heat problem of all tube amps. Do you have any theories? Are you likely to follow an upside down plan?
+allanpennington I completely agree that the best orientation for tubes is upright with their bases down. Upside-down tubes do tend to absorb more of their own heat and to heat the chassis above them. Early amps were almost all configured this way. However, to make the controls convenient for the user (i.e. at the top of the amp), many manufacturers (i.e. Fender) started putting the chassis in the ceiling of the cabinet with the tubes hanging downward. Another option, but more expensive to build, is to put the control panel at the top of the cabinet and the chassis on the floor, with an umbilical cord of (mostly shielded) wires to connect them......like the Kay amp in my recent video series. I am going to hang the Supro tubes upside-down, as they were originally.