The Amp Garage

Sonny Landreth "Grant Street" live album. He plays mostly slide Cajun/Swamp/Boogie stuff, about half of which is instrumental. Very good at it, if you like that sort of thing.

I've used it without adjusting any of the other values (except bias resistance). It sounds better to me. I use my Express with 6V6's and it's the only 6V6 amp I've ever had that I like. The 260V tap also sounds good with EL34's, but to my ears, not as good as it does with 6V6's. The slightly lower v...

I'm not sure if it was the fact of a 500pf being in the system, or the particluar caps themselves, but it was driving everyone crazy, so I'm glad it's gone. I tossed the old caps, so there's no way to know for sure. I suppose Cornell-Dublier caps silver mica caps could be microphonic, though this is...

My A1a had been plagued since the first day with a very high-pitched oscillation that would really get loud with the presence and the (post-phase inverter) master volume all the way up, though it was less with a Hotplate in use. I had rebuilt various sections of the amp, shielding the negative feedb...

As I was installing a better bias knob (a really nice one that records which turn of a 10 turn pot you're on, and is calibrated with 100 little numbered notches on the outer edge, so you can make note of exact knob position when you've got the bias right on different sets of tubes, allowing tube swa...

Dobhill, what guitar(s) are you using and through what cab? I've played mostly a Les Paul 57RI with Fralin 8k/9k pickups, and a 335 59RI with WCR Crossroads pickups through mine, and I'm using a Mojave 2x12 cab with one G2H and one Red Fang. It's fairly dark, I need to switch in one or the other of ...

D: I haven't changed any of the A1A power supply architecture, I just used the 260-260 v taps off the Heyboer multitap power transformer after trying it originally with the 300-300. I had to rebias, but didn't do anything else. I think I like the sound better, it's less "hard" sounding.

I have Sozos in my A1A, it sounds spectacular tonally, one of the most amazing sounding amps I've heard. I'm currently using NOS Mullard preamp tubes and NOS Hammond (RCA?) 6v6's with the low-voltage tap off the power transformer, leading to plate voltage on the power tubes around 334, and the high-...

Thanks. I'll try that. I've built a bunch of amps, but not a "big" Marshall, so the reference was going right past me. It's like a "cut" control from a Vox amp, but without the pot to make it adjustable. If I'm trying to phase-cancel out only the highest of high frequencies, presumably I'd use the s...

Gary, please explain the 50pf "across the phase inverter." Exactly where? My A1A sounds great but it's hissy with either of the bright caps switched in, and I get a high pitched, almost ultrasonic, squeal on top of the notes when the treble is turned way up.

If you want the nice aluminum-bodied one, Mouser.com, part number 71-RH25-1.0K

I can't remember where I got the cement type one. I thought it was Mouser as well but I'm not seeing it there now.

I built A1A with a 250K bass pot, and the amp seemed to be a bit lacking in bass unless I turned the bass control way up. Then I changed that bass pot to 1 meg per the Kelly schematic. I'm pretty sure that the bass content of the signal went up a fair amount (not just the sweep of the pot) - I have ...

Weber Mass and THD Hotplate are both fine with an Express clone in my experience.

Well, I finally had time for a debugging session. First I tried shielding the wire from the board to the presence pot and the negative feedback wire from the presence pot (through the 100K resistor) to the output jack. That was either no change or only a slight one. Then I switched to the 260V taps ...

Mark, I've got lots of speaker cabs available, but the one that seems to fit the Express the best is a Mojave 2x12 "slightly" open back, with a Celestion G12H and an Eminence Red Fang currently in it. That cabinet can really pass bass along, so I might tweak my Express clone a bit to reduce some of ...