Key to the "touch sensitivity" of TWs - 1st gain s

[mojo]

I'm just wondering if anyone has any easily understood insight into the ability of the TW to "clean up" from the guitar volume. I would imagine the layout of the passive parts surrounding the first preamp gain stage would be the main key - primarily the bias of the tube. If I use the same passive component layout on another amp's first gain stage would I not achieve some of the same ability to alter the distortion from the guitar, or am I missing something?

[kindred]

from what ive read, the main reason the tw cleans up so well is because the tubes get pushed over the edge prety much at the same time. starting slightly with the powers and moving backward to v1. then again i have never tested that theory so i could be out to lunch.

[tubetek]

I've re-wired a blackface Bassman channel to the Twreck scheme; The key is, as you said, you can get "some" of the vibe. The Wreck as a whole is pretty much balanced from end to end, though. I also figure that the distortion really begins in the output stage in spite of the un-throttled third stage (100kP, 10kC no bypass)...Hard to duplicate without using the whole circuit, IMO.
Tom

[dave g]

Yes, the key to the "touch sensitivity" is that most of the clipping comes from only one stage (the output tubes) and it's at the very end. If you look at the output of the preamp on a scope at the settings that most people use, it's pretty clean. When you clip early on in the signal path a la a lot of high gain designs, you really can't get the same clean-up effect with the guitar's volume knob.

[geetarpicker]

I also think another part of this is the power supply and output stage. There is a fair amount of sag to these, almost like a rectifier tube feel about the amp. It makes the amp compress downward when pushed, but spring back with fairly dynamic clean tones when you back off.

[Firestorm]

I've been studying this a little: absolutey nothing happens at V1A -- even with hot humbuckers, you only get 7-10 volts and that stage can pass 20-30. The tone stack drops a LOT of signal so the second stage is still mostly tone recovery (but MIGHT clip a little at full-tilt). V2 though, has no attenuation and no cathode bypass cap, so it is low in gain and will compress. I think subtle distortion begins at that stage. But most, as was said, happens at the output.

[jjman]

On my build the PI and the output clip 1st on the dial. I'm using cathode biased 6v6s which I assumed would make the outputs clip before the PI. Then the 3rd stage clips asymetrically from being driven into some cutoff after some more turning of the dial.

[RJ Guitars]

I also think another part of this is the power supply and output stage. There is a fair amount of sag to these, almost like a rectifier tube feel about the amp. It makes the amp compress downward when pushed, but spring back with fairly dynamic clean tones when you back off.

Glen, That's an interesting observation... do you have any idea why it would do that? I can't see anything in the power supply that should contribute to sag but your ears and experience would make us all sit back and ponder that a bit.

rj

[leaveitalone84]

I also think another part of this is the power supply and output stage. There is a fair amount of sag to these, almost like a rectifier tube feel about the amp. It makes the amp compress downward when pushed, but spring back with fairly dynamic clean tones when you back off.

Glen, That's an interesting observation... do you have any idea why it would do that? I can't see anything in the power supply that should contribute to sag but your ears and experience would make us all sit back and ponder that a bit.

rj

It's in PT and OT. The PT will drop some what when the amp is clipping but it'll keep up when you turn down the volume and run it in clean. The OT is smaller and tends to saturate quickly compared to something with larger irons.