The Amp Garage

pdf64 wrote: ↑Fri Sep 25, 2026 12:10 pm How about if you temporarily rig up a 1M pot as a variable resistor master volume, connected between TP23 and a local ground eg P3B-1 (or the grounded leg of R68), by the LTP phase splitter socket (ie at its input)?

why would that make a difference? its still pre phase inverter.

the master volume doesnt help in the fx loop. Just to be clear, have you already tried an additional master volume patched into the fx loop? Certainly removing C11 will allow more high harmonics, probably making the issue worse. My suggestion, if the above doesn't help, is to increase the value of ...

... with the master lower than 5 the overdrive gets worse as you turn down the master with more unwanted gritty/harsher overdrive. not sure why. It might be parasitic capacitance between the clipping stage and later stages, after the master volume, allowing high frequencies to bleed / leak through....

pdf64 wrote: ↑Thu Sep 24, 2026 6:07 pmSchematic?

i sent you a pm

The HRDIII schematic is in the public domain, I can find that. Is it the same as the IV in regards of your queries? If not, maybe post it here, a user needs to be logged in to see attachments. voltage is the same. c8 is 4.7, r24 is 1.5k, c3 and r27 on v2a gone, c23 is .001, r42 is gone, r20 is 220k...

pdf64 wrote: ↑Thu Sep 24, 2026 6:07 pmSchematic?

https://www.thetubestore.com/lib/thetub ... -Rev-B.pdf

pdf64 wrote: ↑Thu Sep 24, 2026 6:07 pmSchematic?

im not sure if its ok to post the IV schematic here. but i guess its ok to post the III schematic?

I don’t have time in this post I am replying to you with the level of details I would like to , but I will try to get across an important point on clipping/ distortion. A preamp tube like in your amp and many others is biased in class A, it has to be biased in class to some level or another. Circui...

From my experience with messing around with changes like these and in terms of the plate or cathode resistor, you never want to change either more then 25% without changing the other. This is the only way to allow the gain stage to amplify the full sign wave without clipping off the top or bottom o...

i was wondering if i lower v2b plate voltage with a larger plate load resistor r22 will the yellow and red more drive channel have a smoother less gritty and harsh overdrive? i seen someone suggest changing r75 to an 18 or 22k instead of the 10k but that would lower the headroom on the clean channel...

that video is not accurate. not sure what year that one is but the hrd iv i own the dropping resistors have been raised off the board from the factory. you cant go by a video you need to see a schematic.