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Their answering machine says "GROM-us".

I never in the world would have guessed that! I've always said GROMZ.

Grommes made some very decent stuff, but it's true that you don't see much of it anymore. Thirty years ago tube buffs turned their noses up at it because it wasn't Marantz or Harman-Kardon, and it looked pretty industrial. They also, believe it or not, turned their noses up at Eico gear.

Or, I have a pair of PC-8412s you can have the end bells from because...well, because they failed, sorry to say. But if yours are good you're welcome to the end bells.

Oh bummer! I think the W4 power tranny is the 54-29, 760VCT. The PC-8412 is 800VCT. What's the number on the other amp's PT?

The tube is fine, I have a pair of GE's just like that, brand new.

Cool, thank you. That's a tanatalizing suggestion at the end, there. Should the input probe be placed differently, grid to cathode?

That looks very good. If it's reasonable stable I'd stop there. ;-) What was the magic formula?

Just as a matter of interest, Tim, how do you "see" or calculate the 60kHz peak from the square wave?

Another thing to try is increasing the the value of the 10K input grid resistor.

Try increasing the resistor in the shelf network, to 1K then go up from there.

No, the original question was, how much AC wattage does the amp draw at idle.

Joe Robert's WE91A was my first DIY project, with the big Magnequest FS-030s. My wife still wonders why I didn't stop there. ;-) You really should check out the DC diy group. I think it would be right up your alley. One of our moderators belongs. The focus is on what really plays music...

So Dave, which way do you use them? SE or PP?

They are, and they're stacked to provide 700 volts tolerance, which means 650uF in capacitance as the first cap (with caps in series, you halve the capacitance). That's rather extraordinary for any tube rectifier. I think they get away with it because they tap the rectified voltage off the 5U4...

Honestly, I think that's a good choice. You can pass those things along to your grandchildren. ;-)

Whatever it was, there isn't much left of it now. ;-) If I had to guess I'd say he converted it to a simple PP 6L6 amp, but that's just a guess. Maybe even a guitar amp, given the ClassicTone output transformer. I sure wouldn't try to fire it up with those loose wires floating around.

Okay, fair enough. You might check eBay for Sylvania or GE 5AR4s, they're twice the price of Chinese ones but half the price of Mullards, and they're tough as nails. The large-bottle Sylvanias are very good, as are the "copper plate" GEs. Otherwise the TAD is probably your best bet, at least...

BTW, are you aware of the DCAudioDIY group? It's an exceptionally well-versed group of audiophiles in MD, DC and VA who also happen to be into DIY and especially tubes on a pretty sophisticated level. http://www.dcaudiodiy.com/phpBB3/

Dave_in_Va, I'm not trying to be snarky--really, I'm not. But with $12K monoblocks and $3K worth of 300Bs, is $250 really too much to spend on rectifier tubes? Seriously. Why go cheap and risk a meltdown in those beautiful amps? Plus, they *do* make a difference in the sound. I find the...

Yes, I agree, though I find it odd that the editor didn't catch the impedance vs. turns ratio thing. Though perhaps in the next issue, someone did...

^^^^Okay, THIS is what I mean! This is hard for me to wrap my head around. Thanks for clearing that up, Dave! Brewer, if I googled the right guy, was an amateur ham operator and not an EE at all. Odd that this wasn't "peer reviewed"!

Another reason to daisy-chain the decoupling stages is that, as you get closer to the high-gain input stages, you get more power supply filtering and ripple reduction. Each decoupling "cell" further reduces the AC ripple in the power supply. The way that fellow has them arranged, in parallel...

So Tim, in your opinion, is this an invitation to trouble? ;-) Based on my experienced, even in triode mode the LS-57 is a bit tricky to stabilize, but not impossible. ;-)

That certainly has value for console collectors, though it's not permitted to discuss prices anywhere except the Dollars and Sense forum. I would strongly advise against trying to turn it on. It's probably not in bad shape electronically but the amp section looks a bit roughed up, and the can...