first build is ready for testing. need to confirm the first reading though.

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I was reading through the page you linked and right under circuit description the designer wanted low sensitivity (700mV) in order to use effects pedals and not overdrive the amp. This is about exactly what I simulated, 18w max clean output power with around 700mV input, that's with the volume maxed out.

Too big a signal in will clip preamp, some people want this some don't it's all preference in the world of guitar amplification.
 
I apologize for the frequent pauses.
I haven't measured output yet. It's one of those things where my guitar is at home, the amp is at home, and my work area is elsewhere. I keep promising myself that i'll bring my meter home but I've been distracted by other projects. (I always have a few projects going)

I am getting to a point where I question the health of the tubes. It seems to me that the EMGs ought to be able to drive the pre-amp valve pretty hard, and the measured voltage values seem reasonable all around. Maybe not perfectly biased, but the difference between 18 tube watts and what I'm actually hearing (which is not even as loud as my new Roland micro-cube) seems too much to be explained by bias problems.

The fact is - these tubes were the only 6L6 tubes that I could scrounge up (at the time) and they were among the pile of used tubes rather than with the NOS tubes. I was originally planning to make use of some NOS 6bg6 tubes but I found out (too late) that they were too tall for my enclosure. I re-wired for 6L6 and went ahead with the build.

I think that's probably the smartest thing to do right now but it's not the cheapest. I don't like to throw money at the problem but I'll never be able to set my mind at ease as long as I'm doubting the health of the power tubes. Those two tubes were found installed in a pa amplifier that may have been removed from service for any number of reasons - including failed tubes.

I was hoping that they were fine and I was briefly convinced that they must be okay when I heard sound from the amp, but I have found some reports of significantly reduced volume in commercial tube amps and the advice that was given to those individuals was frequently along the lines of "check the tubes".

So.....
 
Well I hate it when I'm reading an old forum thread that never gets a conclusion - so here's my conclusion:

Different tubes made a big difference.
I purchased a set of used (but still good) tubes from a nice gentleman. They're marked Mesa. I put the new tubes in and returned the circuit to original configuration and then I turned it up. It sounds pretty good now. It's still barely driven and just a basic clean with no tone stack, but it works and I believe it works as it was built to work, which means victory for me.

Thanks everyone who helped. I'm sure another stage and some kind of a tone stack are in my future but for now I think I'm going to take some time to enjoy my victory.
 
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