well i was talking to nik, since all the voltages check out its probably not any of the resistors or caps.  most likely a wiring issue.  maybe a cold solder or a bad ground that's attenuating the signal.  i'm in the process of re-dressing the amp anyway, so any wiring issues should get fixed.  i built the amp 2 years ago and was new to the field.  i've since learned a lot about tubes and wiring, so i figured this amp needs to get updated.

i suspected the volume pots could be acting up, but they checked out.  i am replacing them anyway with PEC pots as part of the re-dress.  i'm currently desoldering the amp right now.  i'll keep you guys updated on what happens.  thanks.

for best performance, yes they should be matched.  matching makes sure the tubes have similar cathode currents.  matching will definitely get you more power, and some people say a better sound.  better is all relative in my book, but power is measurable.

i would say though mixed tubes won't hurt the amp, although it could hurt the tube.  since the dc30 is cathode biased all the tubes are biased by the same resistors, so if they are different one can be biased too hot while the other too cold.  it's not that much to get biased tubes, so its probably worth it.  i like the jj tubes.  good price for good performance.  its not worth it for me to blow a bunch of money on power tubes with the way the matchless burns through them.  tubedepot will make sure you get a matched quad.  just ask for it in the comments section when you checkout.

Hi All,

I am having problems with low gain on channel 1.  I understand that channel 1 should be slightly quieter than channel 2, but I'm talking way quieter.  Channel 1 isn't loud enough to play any type of club, or even a band practice.  I've checked the plate voltages for the tubes and everything is in 5% tolerance of spec.  I've checked the pots to make sure they are working properly.  Both the 1.5 K resistor and the 220 K resistor are within tolerance.  I've also replaced all the preamp tubes.  I can't think of anything else, short of changes to component values to increase gain.

Does anyone else have a severe gain difference between channels?  Anyone have suggestions on what to change or test?  The amp has a great sound, but at this volume is useless.  Any help is appreciated.  Thanks!