trainwreck highpass filter

[lewilson]

Im interested to hear peoples experience with different values of caps and resistors in the high pass filter in between stage 2 and 3 of the express. doubling the .001 to .002 and lowering the 150k to 50k or so should give the same results as the 150 with the .001, but I have found small differences. I play mainly tele and lp jrs and im afraid once I voice the amp to these it may be useless for a lp with humbuckers. Maybe some of you have some tips . Ive been trying many different combonations, but now neighbors are always calling when I crank mine up and Ive got to stop for a bit.

[jimipage]

I changed the 150k resistor to 75k and I like it better. Bass response is more even and the overall signal is clearer and easier to control. However, my Express is not an exact repro; it uses two 6v6's with a 6.6k OT and choke(instead of the 1k/25W resistor), so I'm guessing that the 75k is likely a naturally better choice in that design -- maybe something KF would have done? (I know, I know: dreams are free... )

[lewilson]

I just put in a new set of some east german rft tubes and its a lot punchier now. I was having trouble with it loosing midrange and punch at high volumes, but now that thats fixed I tried some different r values for the filter. Im at 56k now with .002 cap and its a monster. I could try a 150k but its seems good now. I did have a 33k in there and I liked that too.{with a tele} Mine is a 6.6k output trans also. Mines not exact, I just built it on a whim. I used some 18 watt marshall parts I bought from musical power supplies .com. I was hoping to build a low power version of a wreck. Had to use an aux filiment transformer for the 12ax7s. The output trans is interleaved and very good . Its putting out 36 watts!
{about 17 volts into 8 ohm} it will peak around 23volts .I have had no trouble with it except for those old tubes. Its been up and running for about 3 weeks. The old tubes seemed fine in other amps and tested o.k. ,but apparently the wreck likes good tubes, at least in the first and 3rd stages. Output tubes are el34, Plate voltage is 355, 50 ma. and The first 12ax7 is around 170 vdc. I cant remember the other sections voltages.

[roberto]

Changing from 150k to 33k change the gain of the 2nd stage, also if you scale up the capacitor to say 1n to 4n7. This is due to the fact that the triode can't load 33k as it should do with 1M load, and so it changes the way it sounds.
Have you tried some different caps in parallel on this coupling stage? Maybe one ceramic? Usually this trick makes the amp sound better.

[lewilson]

.001uf ceramic and .001 film? I have about that. I will give it a try. maybe I can gain some mids at higher volumes. Thanks