Tube Amp Archive

There seems to be some contradiction even within the direct quotes from David Lindley regarding which amp was used on ROE. In the "amps for sale" thread he is quoted as saying it's #008 used on that album and el-rayo X stuff, and has never been modded or upgraded by Dumble. He also states that #002 ...

yes, just consider it a warm-bias for your 12ax7. Marshall uses this, Mesa did also on the old MK series. I've also seen it recommended often by the gurus over at 18watt if there's too much fizz in the overdrive. You could also try 680 if you wanted to stay closer to center. I noticed your earlier d...

dehughes - you might also try lowering the cathode resistor and tail values in your PI to something like a 470 cathode resistor with a 22k tail. I've had good luck warming up tone with these values, which are basically from the blackface design.

jla - I believe your speaker jack should be isolated from the chassis if you have a separate wire going back to the main ground as you mentioned.

thanks voodoo. I've seen some sites that might have the schematic or service manual for sale, might be something I can pursue.

hi folks, I came into a partially working scope yesterday where the horizontal trace only goes halfway across the screen, even at maximum adjustment. I know nothing about these, so just hoping maybe someone's seen a similar kind of problem. it seems otherwise functional, at least the basics anyway. ...

I agree entirely with what heisthl just posted. to that I would add, reading thru all the threads also "introduces" you to the various personalities and skill levels here. I found it to be great fun and developed great respect for the folks here.

I've never built one of these D-style amps, but here's an idea I used recently. the amp was a 2-channel 4-gain-stage variety, and the user is someone who doesn't deal well with complex amp controls. on the 'clean' channel there was a drive and a master, period - no tone controls at all. there was a ...

the caps are new, although they came from a local guy with a really large warehouse of stuff, so I can't be exactly sure how long they may have been on the shelf. it's possible they could be old stock in need of being reformed. I'm definitely going to try and double up for at least the first node, I...

the caps all appear to have correct polarity. none are in series at the moment, so it is running pretty much right at the limit for the first couple. I was thinking of changing the first one for a series pair, but wanted to try and determine if there's some other problem first. is the 200r between t...

looking for help with some strange behavior in a new power supply I'm testing, no tubes currently installed other than the rectifier. after the supply is up and running for about 15 minutes, the first few filter caps are getting fairly warm and the voltage begins to drop. I haven't spotted any kind ...

that's true, although I'm trying to have the reverb on-board, and also have the loop (he uses a lot of FX). I have enough space laid out for two tubes, one each for both a loop and a reverb circuit. what I meant before was that it might be too crowded to use two tubes for the reverb (Fender style), ...

it's not a must-use situation, so I think best bet will be to just use the 12ax7 for the one-tube reverb setup. I'm already at 5 pre's, 2 pwr, and 1 recto tube, so the space is pretty tight already.

thanks to everyone for your helpful replies.

thanks guys.

Bob, do you think the reverb return gain is something that can be attained by using different plate/cathode values, or that we can't really get there from here using this tube ?

hello all - I'm working on adapting the single tube reverb and D'lator loop to a somewhat non-Dumblish design, more like a Mezza C+ actually, for my son. The takeoff point would still be after the master volume and before the PI. Does anyone have experience or insight into using a 12AT7 as the drive...