Tweed overdrive special - some guidance needed

[bepone]

. Also my 5881 Tung Sols are getting hotter than any tube i have ever seen. Like burn you hot. They are not red plating or arcing though. I

how i'm reading, it is too much current.. and too much power dissipation..

first reduce bias, make cathode resistor around 500 ohms to fix that, and read again cathode voltage (pin 8 out tubes)

[bepone]

early clipping can be fixed with 1.5 in cathode of V1a tube, shrill OD must be possible to tube with tone control, otherwise there is mistake..

anode and cathode wiring together all the way.. i would split them

[johnnyreece]

I measured again and did get a drop in voltage with the MV change.
All the way up i get 422v and down im at 444v, its late and i may have mixed that up.

Hey! We're getting somewhere! My guess is you'll want to remeasure voltages with the MV all the way up (I only build stuff that's not so loud that I need a MV, so my inexperience shows there).

[Fictitiousfreedom]

. Also my 5881 Tung Sols are getting hotter than any tube i have ever seen. Like burn you hot. They are not red plating or arcing though. I

how i'm reading, it is too much current.. and too much power dissipation..

first reduce bias, make cathode resistor around 500 ohms to fix that, and read again cathode voltage (pin 8 out tubes)

Thanks man, i will try the 500ohm but ill have to order one. The schematic calls for 430r but i used 400 because thats all i could find. I do have some 430r 10w ww i bought on ebay but they looked questionable so i didnt use it. Its like a sandy brown color and looks very low quality but i have no idea. Ill try it first. I also used 1/2watt 1R between the cathodes and the cathode resistor because thats what the BOM specified but the schematic shows them as 2w, that may be a problem but idk. If i understand correctly those resisters are there for checking the bias?

early clipping can be fixed with 1.5 in cathode of V1a tube, shrill OD must be possible to tube with tone control, otherwise there is mistake..

anode and cathode wiring together all the way.. i would split them

Ok so are you saying to add a 1k5 resister between V1A pin 3 and the 2k2 resister and the 2u2 cathode bypass cap? Ill give that a shot too.

As far as the twisted preamp wiring. I was trying to follow that chapter in Merlins book that i mentioned earlier, it says it can help with noise If you keep everything separated and it can give a visual indication of each half of the tube. If its not hurting id rather keep it like that mostly because i like the way it looks. I originally had almost everything twisted but in my troubleshooting i untwisted a lot of them. Come to find out there was no problem, my pots were backwards so i had every knob dimed instead of off. 🫠 i usually spend a huge ammount of time and effort in making everything very thought out and well done only to do something completely moronic anyway lol

I think most of the problem with the shrill overdrive and the early clipping has to do with the MV. I may try a VVR for once, ive not used them yet but i keep running into problems with MVs.
Today after work ill have a chance to really crank the amp and ill get a much better picture of how it sounds.
Im almost finished with a live room ive been building in my basement, once thats done volume will never be a problem again. Does anyone see a problem with removing the MV completely?

[Fictitiousfreedom]

I measured again and did get a drop in voltage with the MV change.
All the way up i get 422v and down im at 444v, its late and i may have mixed that up.

Hey! We're getting somewhere! My guess is you'll want to remeasure voltages with the MV all the way up (I only build stuff that's not so loud that I need a MV, so my inexperience shows there).

Yeah i will do all my voltage measurements again once i swap out my output tube cathode resister and ill be sure to check with the MV up and down. Thanks again, that really was great advice and i appreciate you taking the time. Everyone on this forum is so willing to share their knowledge its truly beautiful. I wouldn’t be able to make a single amp if it wasn’t for all of you fine folks, if your willing and motivated you can learn at an amazing pace.

Im kinda over MVs, they never sound good at low volume and i find myself trying anyway and just being left un satisfied. I tried purchasing a Fryette power station and after a year of waiting while on backorder fedex lost my package and then i got placed back on backorder so i just got a refund. My solution was a live room in my basement. I ran audio over cat6a and speaker cable from my studio down into a semi soundproofed room i built. Should be great for recording i just worry losing the amp in the room will zap the feel of everything so i may run a small cab as well.

Thanks again!

[Fictitiousfreedom]

Now that im home i see that even those crappy ebay resisters are only 5w. I have two 470ohm 5watts. The only other 10w i have are 250ohm and 10k. I thought about splitting them so i could use the 470w 5 watts but im assuming id then need two 250 ohm which i only have one of. I also am assuming id have to split the 147uF cap as well? I guess im just going to have to order some of the correct value. Unless i could use the 250ohm in series with the 400 but ive read that the more resistance you add to the cathode the higher your B+ will be. I may try anyway and check.

[Fictitiousfreedom]

Sorry im replying so much lol

I added the 250R in series with the 400R and tested again. My B plus was raised slightly so my plates are at exactly the same voltage but id have to assume my bias is now not ideal. Strange thing is that the MV had no effect on the voltage this time.

[sluckey]

Strange thing is that the MV had no effect on the voltage this time.

Your checking the bias under static conditions. The mv should have zero effect.

[10thTx]

The OD Channel just sounds bad, its shrill and has no bottom end at all.

The Tweed Overdrive Special "OD" should sound something like this: https://soundclick.com/share.cfm?id=9488477

and this: https://soundclick.com/share.cfm?id=11332809

Did you note on the original schematic that V2 is a 12AY7?

With respect, 10thtx

[Fictitiousfreedom]

Strange thing is that the MV had no effect on the voltage this time.

Your checking the bias under static conditions. The mv should have zero effect.

I was checking plate voltage of the output tubes. The first time it really did change a small amount depending on where the MV was set but the last time it stayed the same.

The OD Channel just sounds bad, its shrill and has no bottom end at all.

The Tweed Overdrive Special "OD" should sound something like this: https://soundclick.com/share.cfm?id=9488477

and this: https://soundclick.com/share.cfm?id=11332809

Did you note on the original schematic that V2 is a 12AY7?

With respect, 10thtx

I have an 12AY7 in both V1 and V2 and a 12AX7 in V4.

Thanks for all of the designs and info you have contributed! I have learned so much from you. Its very very generous of you to share all of your work.
My TOS sounds absolutely incredible now that i understand the way everything operates! The main problem was the MV. It sounds very bad below about half on mine. Im gathering the parts for a VVR now. I love both the clean and the OD. You really managed to design an incredible amp. I can get really beautiful clean sounds, great blues slightly overdriven sounds, crunchy rhythms, and super high gain lead and heavy heavy rhythm tones, all in this one crazy amp. The way you configured everything is extremely inovative. Im pretty blown away man. Ill post a video of a few recordings ive done once i get everything sorted.

FYI… Im not trying to kiss your ass, i really mean it.

My only problems now are that my 5881s are running too hot as well as my power xformer getting hot after an hour or two of playing. Hopefully the 500R bias resister will solve that. The second problem is that my PI voltages are way off from the schematic. I posted them earlier. Idk if its really a problem or something i dont understand yet.

Again thank you for everything! 🫡

[johnnyreece]

With the new cathode resistor combination in there, what’s the measurement between the plate and cathode?

[10thTx]

A few thoughts about the Tweed Overdrive Special ...............

I've always thought of this as an amp to build and then change to personal taste in tone. So if you experiment I would do small changes and do them ONE at a time. Then play it that way for a few hrs or days and then decide what to keep or change.

I have built amps with VVR and I do think the VVR preserves a good tone at a lower volume than the PPIMV. I think the PPIMV dialed in between 5-7 sounds excellent but I agree that the PPIMV dialed down below 5 loses some good tone. I think the VVR helps in recording an OD tone at low volumes.

Having said that, I found the PPIMV to be more reliable. I had a VVR develop some hum after using it a few yrs and removed it.

IF I were experimenting these would be some changes I might try. I would definitely add the 220p "enhance cap" on that LTPI plate resistor. It seems to smooth out the high end harshness that amps sometimes will have.

I always thought the design going into the first gain stage of the OD channel was sort of convoluted. IIRC, I think I eventually removed a bunch of parts there and put in a 100ka pot instead? Not sure if I'm remembering correctly but that's what I think I did? However, I sure don't think it's necessary to remove those parts. It's simply more convenient.

I might also try a .01 coupling cap into the LTPI instead of the .02 simply to see what sounded the better to me.

You might want to try a 12AT7 in V4 (the LTPI)?

None of these ideas are things you "should" do. They're simply a starting place to tweak stuff IF you're inclined to do things that way.

It's critical in my thinking that the changes are small and done one at a time.

With respect, 10thtx

[dorrisant]

I don't know if anyone else already stated it, but it looks like your PI tail resistor is 100k and should be 10k. That may solve your PI voltage issues. I see brown black black orange brown... It should be brown black black RED brown

When you wired all of your pots backwards you taught yourself a huge lesson. You'll probably not do that much anymore. And don't worry... There aren't many members here who haven't made mistakes like that. If they haven't, they will if they build enough, and then they'll learn. Keep going. You will learn more with every build. Your attitude will get you almost all of the answers around here.

As far as bepone's comments... He is absolutely right. But you can worry about that after you get it to function without the voltage issues and with better tone/less unwanted noise. What he is telling you is what you will learn is best. You can always rework it later and hear for yourself. I used to build with a bunch of metal film resistors, I learned to build differently. Keep reading and that stuff will come to you.

The topology of this amp is very much like a Dumble... You have to think of it as a clean amp, and when you change channels, it is much like kicking in an OD pedal. Except it is tube (much better). Look at the switch and realize that it functions much like a stomp switch in a pedal. That makes it easier to wrap your head around it.

Nice to meet you,
Tony

[Fictitiousfreedom]

Thanks for all the help I really appreciate it, Sorry I am just responding I was attempting to make a video of my recorded sounds to share but kept losing the files somehow but ill post it on here soon. Also its music festival season so ive been enjoying that. I have ordered a variety of I0 watt wire wound resisters from multiple sources and they almost all are on back order 'i think I have at least one 470 R coming today.

First, I added a VVR. It works much better now. I added It right after the choke. It has definitly made the amp more usable and sometimes it sounds great. The clean channel almost always sounds great. I think i have a solid grasp on the way the amp works now. The advice to treat it like a clean amp and the OD channel like a pedal is great advice and helped me a lot. Once I get home and tweak a few things ill take my voltages and post them.

The OD channel is usually somehow too dark and at the same time too shrill and its always lacking in bottom end. The Voltage is a little better now but still too high. I placed two 5 watt wire wounds in parallel and then those in series with a ten watt but i forget the exact values, i think i am somewhere around 470R. Once i get some more 10 watts finally ill experiment. Another problem i had was with the fx loop jacks. I almost always have a delay and reverb hooked up while playing. Last night i unplugged all my pedals and the amp sounded 1000 times better but slowly started to make a sound as if the speaker in my cab was lose or blown. I checked and one of the switch terminals on my jack was bent and hopefully once i replace that jack it will be fixed. I tried my pedals in true bypass vs buffered ect… but it never sounded as good as it did without anything in the loop.

I don't know if anyone else already stated it, but it looks like your PI tail resistor is 100k and should be 10k. That may solve your PI voltage issues. I see brown black black orange brown... It should be brown black black RED brown

When you wired all of your pots backwards you taught yourself a huge lesson. You'll probably not do that much anymore. And don't worry... There aren't many members here who haven't made mistakes like that. If they haven't, they will if they build enough, and then they'll learn. Keep going. You will learn more with every build. Your attitude will get you almost all of the answers around here.

As far as bepone's comments... He is absolutely right. But you can worry about that after you get it to function without the voltage issues and with better tone/less unwanted noise. What he is telling you is what you will learn is best. You can always rework it later and hear for yourself. I used to build with a bunch of metal film resistors, I learned to build differently. Keep reading and that stuff will come to you.

The topology of this amp is very much like a Dumble... You have to think of it as a clean amp, and when you change channels, it is much like kicking in an OD pedal. Except it is tube (much better). Look at the switch and realize that it functions much like a stomp switch in a pedal. That makes it easier to wrap your head around it.

Nice to meet you,
Tony

Thanks for the kind words and also all the work you have done in this community! It is nice to meet you as well! The PI resistor was a 10k, I replaced it anyway but i appreciate you looking at everything so closely. I am all for learning and try and take in as much as possible. I really want to design an amp myself at some point but that will be a good while from now. The advice you give to treat the OD channel as a pedal is great advice and really helped me approach the amp in a much better way. Again, thank you!!

A few thoughts about the Tweed Overdrive Special ...............

I've always thought of this as an amp to build and then change to personal taste in tone. So if you experiment I would do small changes and do them ONE at a time. Then play it that way for a few hrs or days and then decide what to keep or change.

I have built amps with VVR and I do think the VVR preserves a good tone at a lower volume than the PPIMV. I think the PPIMV dialed in between 5-7 sounds excellent but I agree that the PPIMV dialed down below 5 loses some good tone. I think the VVR helps in recording an OD tone at low volumes.

Having said that, I found the PPIMV to be more reliable. I had a VVR develop some hum after using it a few yrs and removed it.

IF I were experimenting these would be some changes I might try. I would definitely add the 220p "enhance cap" on that LTPI plate resistor. It seems to smooth out the high end harshness that amps sometimes will have.

I always thought the design going into the first gain stage of the OD channel was sort of convoluted. IIRC, I think I eventually removed a bunch of parts there and put in a 100ka pot instead? Not sure if I'm remembering correctly but that's what I think I did? However, I sure don't think it's necessary to remove those parts. It's simply more convenient.

I might also try a .01 coupling cap into the LTPI instead of the .02 simply to see what sounded the better to me.

You might want to try a 12AT7 in V4 (the LTPI)?

None of these ideas are things you "should" do. They're simply a starting place to tweak stuff IF you're inclined to do things that way.

It's critical in my thinking that the changes are small and done one at a time.

With respect, 10thtx

I will Try a few of your suggestions, one at a time of course. I like the idea of removing those parts and once i get everything working properly ill see if i can find a way to remove them but only if i can easily reverse it.
I have tried an 12aT7 in the PI, it sounds good but the best setup i have gotten so far has been
V1 - EH12AX7
V2 - TAD12AY7
V3 - 5879
V4 - JJ12AX7
V5 - Sovtek 5881
V6 - Sovtek 5881
V7 - 5Y3* I prefer the SS rectifier but The 5Y3 drops the voltage so thats how ive been running it to keep it as low as possible.
Thanks again for your time man! Even with it not working perfectly i have managed to get some amazing tones from this design. Its the best clean/slightly overdriven tone ive ever gotten from any amp so i really thank you sir!

[Fictitiousfreedom]

Ok i added the 500R 10watt and now my voltages are way better and after fixing the fx loop jack everything sounds great. Im working on a video/sound clips now and once i know everything is the way i want it ill post a multipage pdf including bookmarks with all the information on relays/vvrs ect that helped me so that if anyone else makes this amp it will help a little.

I injected a 500hz signal into the input, had a scope on the output, and had the VVR at max setting for these voltage tests. Thanks again eveyone here for everything. Your the most helpful, sharing, wonderful community of people and i really am super grateful for your time.