The Amp Garage

Gaz wrote:Doesn't the bootstrapped MV lower drive to the PI as well break down the feedback loop? It was my understanding it was only beneficial in amps that used a pre-PI master, but even then power amp controls do nothing at lower volumes.

Pursuant to KOC TUT 3 no because it is not in the feedback loop.

My question is what is the better channel on a zodiac ? THey both have a driven pentode but one has the rotary control over the pre that looks complex. I'm not sure what it contributes to the overall tone. The other channel with just a tone control looks very do-able. I see you have to set up the p...

I have four cathode biased amps (2 with EL34s, 2 with EL84s) with both the LarMar PPIMV and a cut control. Works really well. Part of it is that none of these amps have negative feedback around the PI. The reason why the 59 Bassman/Plexi presence control does not work well with a PPIMV is that it re...

What you are doing with this enhance cap is stabilize the amp with respect to its negative feedback loop. This is explained in great detail in chapter 9 (feedback theory) in ValveWizard's preamp design book. Definitely a sensible enhancement.

Cheers Stephan

I actually played Fender amps for a long time because - well - that's what you are almost supposed to use for country (rock). Turned out that I preferred the Vox style amps by far but then I prefer John Jorgensen's tone to say Vince Gill's (both great players BTW). So I Rocket preamp with octal powe...

That's pretty much how I had set up mine for a while - clean channel AB763 and lead channel ODS non HRM. I tried to get around using the existing layout but this is far from optimum IMHO. I have later converted by Bassman head with one of the suggested layouts here in this forum and the amp sounded ...

In a fixed bias amp like the 2204, these resistors have two functions: (1) pass the negative voltage to the power tube grids for biasing purposes - essential for the power tubes to survive - and (2) act as grid leak resistors for the power tubes. Together with the PI output coupling caps they form a...

Mark,

I just rechecked the second picture you posted, and from that picture you did it exactly as I stated. That connection is safe and I cannot see a conduct violation from that.

Sorry if my earlier post caused any confusion.

Cheers Stephan

The ground connection on the IEC connector is fixed to one of the IEC connector screws. Also the ground wire from the IEC connector is the shortest one running from the connector. Dangerous, and also a code violation. Agree to the first one. The ground connection from the IEC connnector should 1) b...

Gain I is a 1 meg audio pot with a 1000pf bright cap. Gain II is also a 1 meg audio pot but wired as a variable resistor to a 47k and from there to ground. The output of Gain I connects to a 470k resistor and from there to the top of Gain II. Together they form a voltage divider. This double gain po...

LarryLarry wrote:Hans, what do you mean by 'drill your anode wires'?

Sounds like the Zener diodes needed for dropping overall voltage are not the common type (NTE5125A)...

He meant "twist".

Cheers Stephan

wsaraceni wrote:gain stage - volume - gain stage - tone stack (tmb) - gain stage - PI

That's a Lee Jackson in the low gain mode without the effects loop.

It does cut a lot of volume and mids but that is the heart of its clean tone. As an owner of an S series Dr Z Stangray with open back 212 blue/gold this statement makes me confused because I don't find the tone control affecting volume at all and have not noticed mid frequency problems. I use the c...

But the stock tone control IMHO is really what sets this amp apart from others. It does cut a lot of volume and mids but that is the heart of its clean tone. Just for curiosity I replaced the Stangray tone control with a Chieftain tone control which does not cut as much volume and which only cuts mi...

I never tried a CCS tail (nor the choke tail). I only heard that the CCS tail would sound terrible when overdriven.

The choke tail looks interesting. The obvious downside is that you have to get the choke mounted somewhere but in most cases it should be manageable.

Cheers Stephan