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finally finished another tube amp


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Got a couple pictures last night at last. It's been running for a few weeks now, I kept tinkering with it, but it's pretty much done for now. Built mostly from parts on hand, plus an old scsi drive chassis. I did buy a few resistors once I had settled on working values, if only to replace a couple series and parallel conglomerations.

Obligatory off and on shots...

e2_amp_off.jpg

e2_amp_on.jpg

Started with this lumber and chassis...

[ATTACH=CONFIG]3086[/ATTACH] [ATTACH=CONFIG]3087[/ATTACH]

There is another thread (dead bug psu) that shows some other pics along the way.

The amp is derivation of the mapletree design; it has higher operating voltage, similar to his super, though the operating point and bias are different. The PSU has three chokes, one common to both channels, then it splits. First PSU stage for output tubes is electrolytic with poly bypass, the second PSU stage for the input is poly in oil only.

post-1464-12951157334003_thumb.jpg

post-1464-12951157334651_thumb.jpg

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Thanks guys! It's pretty dark in appearance as compared to the other amp, it being stainless and birch. This one has a graphite-like hammered paint on the top, and I still don't know what the wood is for certain, but it's plenty dark. Both this and the stainless amp have just plain watco on them, nothing else.

It sounds very nice to me, but I'm going to need help comparing between the two, so I'm reserving any other comments. I am going to put together a little a/b box with a toggle switch that I can plug one pair of cans into and flip back and forth between two headphone jacks, which should help some. I like them both a lot, but there are differences between them.

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We might have to do something about that knob though, I've got a few bits "laying around" that might be suitable.

I agree completely! The only others I had in black were your typical knurled thang, which was a little too large in diameter for the layout, and then I have the hafler knobs, which look great, but did not quite cover the peg for the pot. I should have just snipped off the peg like I usually do.

So, you have something in mind?

This amp is a bit different for me, having everything on the top plate. I think I would have spaced the inputs and output a bit more from the pot if I did it over, which would give more room for the knob. But I do like the directness of the wiring path.

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What do you figure is the max reasonable diameter for the knob?

You do realize that's like throwing peanuts to scare the squirrels away? Sometimes I feel my reputation on here is ill-deserved, it's simply that I'm so often baited like this.

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Thanks Ari! I should try to clarify though- it's not a separate PSU for the gain, just a separate filter stage. If you take two of the original Mapletree PSUs after the first filter cap, and put one of them on each of the output legs of Ciuffoli's PSU, it's pretty close to what I have. I did not use a Graetz bridge this time as Ciuffoli does, just a normal FW setup with an 80 rectifier. My other amp does have the Graetz bridge, using two hexfreds and a 12X4 rectifier.

Ciuffoli's PSU:

[ATTACH=CONFIG]3094[/ATTACH]

The separate chokes on each channel do seem to work quite well. My output stage would be tagged on at the terminus of the above schematic, then there is another r/c filter composed of the poly in oil caps on each channel before tagging on the input stage. It's very quiet, but is still very fast, without excessive overshoot or ringing on transients. The output is pretty heavily biased, too.

Nate- a 1.25d knob will fit okay, it's just that I didn't like the knob I had on hand in that size- it was too short for good vertical use I think. The Kilo is a good height, but a little too skinny, not to mention odd looking. The fluted bakelite communications knob that Lloyd uses on his amps looks very good on it, but feels weird when used vertically.

I think an ideal size would be about 1.125d x .65 tall, or something along that line.

post-1464-12951157364166_thumb.jpg

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Nate- a 1.25d knob will fit okay, it's just that I didn't like the knob I had on hand in that size- it was too short for good vertical use I think. The Kilo is a good height, but a little too skinny, not to mention odd looking. The fluted bakelite communications knob that Lloyd uses on his amps looks very good on it, but feels weird when used vertically.

I think an ideal size would be about 1.125d x .65 tall, or something along that line.

I'll rummage through the bin this weekend and see what I've got, I think I might have a little something.

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