TS100 [TubeStereo 50x2] possible design flaws

[Guitarist]

These are decent amps —basically a Fender Deluxe x 2 —but lifeless due to the many caps shunting highs. I've been leaning towards brighter pickups and the sound just wasn't happening so I traced it to this power amp. Tubes are fine.

I've lifted some pF shunting caps to brighten things up but see that the designers were perhaps forced to add these to compensate for some power supply shortcomings somewhere. Now there is enough hiss for me to revisit this and swap in some upgrades such as metal film on a all preamp plates and if available through the power supply string, swap in FREDs, double the DC heater caps...

Any other ideas? I wish I kept my old VHT!

[soundguruman]

you sold your VHT and bought a Carvin?
You young Whippersnappers....
They put those caps in to stop the thing from oscillating to infinity and beyond.
And you wind up with 2K frequency response.

Never "did" like Carvins. Seems like a funny concept for a guitar amp.
Never liked the layout or the parts they use.

Yeah, you take out the "tone prevent-er" caps, one at a time. Then test with some guitar playing.
When it starts wheezing, you put the "last one" back in.

You might get 4K frequency response before it upchucks. Depends on how many you can get away with, taking out...

I had a high school professor in electronics classes. He showed us that we could take parts out of a TV, and it would still keep working.
We took out about 45 parts and it still worked just fine. Hahahahahahahahahahahahhahahha!
Makes you wonder what the heck all those parts are there for?

PS where's the rest of the schematic?
I think it's the preamp you need to look at.

Yeah, metal film, bulk metal foil is the lowest noise, and somebody said wire wound was better.
I am OK with wire wound. It's the coat hanger wire that appeals to me.
Isn't obsolete technology wonderful? I love it.

But besides just low noise parts, it's the layout that makes a big difference in the noise.
With a PC board, its the layout that suffers.

[Guitarist]

Hey Oldtimer

Well, I sold the 4U high VHT a few years before this one and it was super and super HEAVY too. That is the whole schematic, basically a neutered Fender. I'll see if CE Dist has those resistors. I did run shielded cables from back to front and wrapped some foil around one ribbon cable. Back then I was going to call Carvin with what I did but forgot most of it now...
The transformers are all rather close to things it seems. I wonder if injecting DC to the heaters would help more.
Without those pF caps it doesn't oscillate at all just the "sssh" in the background. It's worth it for now as the BurstBucker and single coils show their mettle now. It was about 2K, OK for high gain I suppose.
Sounds like you had a great electronics teacher too, I was a bad student though This electronics necessity is rather endless!

[soundguruman]

Hey Oldtimer

Well, I sold the 4U high VHT a few years before this one and it was super and super HEAVY too. That is the whole schematic, basically a neutered Fender. I'll see if CE Dist has those resistors. I did run shielded cables from back to front and wrapped some foil around one ribbon cable. Back then I was going to call Carvin with what I did but forgot most of it now...
The transformers are all rather close to things it seems. I wonder if injecting DC to the heaters would help more.
Without those pF caps it doesn't oscillate at all just the "sssh" in the background. It's worth it for now as the BurstBucker and single coils show their mettle now. It was about 2K, OK for high gain I suppose.
Sounds like you had a great electronics teacher too, I was a bad student though This electronics necessity is rather endless!

Many Carvins already have DC heaters.
This is necessary because the filament power is too close to the audio path.
Otherwise there is too much heater buzz.

This is another layout problem, The Filament needs to be as far from the audio path as possible.
A DC bench power supply is handy to check that.

You can get metal film from CED / tubes and more. Bulk metal foil is better, but it costs too much to be practical.
But one of these days I'm going to use bulk metal for the whole amp, just for fun. Another one of those projects...

I got a Marshall 2204 board for a Fender HRD chassis. I might try bulk metal on that build, just for grins.
And Black Gate Capacitors, Millen Sockets, DC filaments, is what I was planning for that one. Just this one time, a splurge.

[Guitarist]

That Marshall board installed should really raise eyebrows in a Fender chassis, I've been there and it's fun. It was a Princeton with a Marshall relayed in. I stuffed the online cart on CE Dist and it be up to $300 so I may wait a month yet. Parts add up. There should be a simple-quality amp for versatile tones but easy build. Perhaps, 6K11 switched in, in series for crunch ala Marshall ---> loop jack ---> pentode 6u8 using its additional triode side as a cathodyne PI and maybe a single KT88. You'd have few cap spots to fill perhaps only four.

[Guitarist]

Parts came in and I upgraded many power supply and plate resistors, caps and better shielded the input cable. The amp is far more usable now. The HISS which was annoying the soundman and I too, is gone. Carvin could easily improve this otherwise disappointing amp..

[TimmyP1955]

Are the grid stoppers on the sockets, or on the board? If the latter, move them to the sockets. I had to do this to a Fender custom shop amp (WTF Fender?!). Fixed it.

[Guitarist]

The grid stoppers are fairly close to the sockets. I also removed the first triode from the circuit as it wasn't required for full power and was adding noise. Sure, had to increase some later grid-bias resistors that were 100k and the like. So the amp certainly does the job, but with the hours spent, I would been further ahead getting a used Freyette 2/90; another example that 'you get what you pay for'.