Monkeymatic Acetone Princeton

[xtian]

Done! As you point out, I used the 4ohm tap, which reflects 8K on the primary.

Sounds very good! I'm measuring 18 watts before clipping on the OT secondary with 1kHz signal at 1v p-p. 450v on the plates. Bias is now uneven, with 20 and 25mA on the power tubes, but I expected this because of the uncentered CT on the OT primary.

I still think there's something suboptimal about my gain stages, because I expect a little more when I dime the volume, but it's pretty good right now. A little nice crunch with single coils. I'm going to take it to practice this afternoon with my band to see how it hangs.

Thanks, guys!

[cbass]

Cool Looking amp.Bet noone else on the block has one.

Wonder if the old OT was bad or just a POS

[xtian]

Cool Looking amp.Bet noone else on the block has one.

No DOUBT!

Wonder if the old OT was bad or just a POS

It wasn't bad. Wrong impedance, and perhaps a wee bit under powered. New one is clearly better, but only 3-6dB.

Part of this issue of overall volume is perceptual, I think, because this is a pretty clean amp. Doesn't distort nearly as much as my other low-wattage builds. And it has a lot of bass energy. !! Which makes me think I may increase my useful gain by rolling off the bass via interstage coupling cap(s). Hmm.

Anyway, NO MORE CHANGES before I play it with the band!

[JazzGuitarGimp]

Good job! And that's a great looking build. Of course, I've come to expect nothing less from you, Xtian!

[xtian]

Thanks, Lou!

Man, the amp was great at practice. My worries about volume were for nil. Didn't even have to turn it up very loud, and the tone was great. At the end, we played Long Cool Woman in a Black Dress. I dimed the amp and turned on the tremolo, and it was SO kick ass.

When I had the amp on the scope, I noticed that the bias tremolo changes the shape of the sine wave, causing crossover distortion as the bias drops. I think this sounds lovely. A bit dirty and mean if you dig in. Is this how all bias tremolos work?

[JazzGuitarGimp]

No practical experience here, but the circuit looks like it modulates the DC bias (operating point) of the output tubes. If you've biased the tubes at about 70%, the trem oscillator will cause the bias to go hotter than 70% on the positive half of the oscillator waveform, then colder than 70% on the negative half of the oscillator waveform. When it goes colder, you're pushing the bias toward Class B, which yields crossover distortion.

[cbass]

.Yup bias tremolos are cool.I like to bias the amp as cold as I can and still sound good.It increases the tremolo depth

[JazzGuitarGimp]

.Yup bias tremolos are cool.I like to bias the amp as cold as I can and still sound good.It increases the tremolo depth

There ya go! Good advice!

[tribi9]

What a nice looking amp. Congrats.

[cbass]

.Yup bias tremolos are cool.I like to bias the amp as cold as I can and still sound good.It increases the tremolo depth

There ya go! Good advice!

There's a first time for everything

[NickC]

Very