I don't use tubes in output stages only in preamps. In the preamp I contour the sound I want and my power amp is simply a current amp. My thinking is that once you get the tube sound (read distortion) in an amp there's no reason to use it in the power end. I make my power amps as neutral as possible. I don't like the idea of wasting all that energy with fat hi current tubes or expensive transformers.
With that said preamp tubes only run a few ma on the plate and there's no reason to double the B+ for that. In fact I use voltage multipliers that gradually build to a point and then regulate the result with a three terminal regulator. I don't use rectifier tubes either, you can really contour the filaments with three terminal regulators if you know what you're doing. My 6SN7's are current limited to slightly above 600 ma ( the max current at 6.3 volts is slightly lower than 600 ma so limiting slightly over that value ensures the tube will get to the 6.3 volt running voltage.) Once the tube builds to 6.3 volts regulators lock it in.
Bottom line is no rectifier tube, and B+ that's no more than 5 or 10% above the tube working voltage. This also reduces my transformer needs. For example I run 180 volt plates with a 40 volt transformer. ($2.50 at Allelectronics)
Rob
ps:
The down side of diodes is their fixed insertion loss. A few mV going through a 6SN7 has little if any voltage fluctuation with a couple of hundred uF cap across it in the cathode circuit. If you read the old RCA tube manuals you'll see they get away with 3 or 4 uF in cathode circuits.
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Yes it is possible. Just make sure your output transformer is powerful enough to handle up to 5W. The add on circuit:
An externally hosted image should be here but it was not working when we last tested it.
K-12G In A Wine Box
The $189 K-12G tube amp (by S-5 Electronics) is a terrific sounding amplifier and a huge bargain. The only downside is that its stock chasis is nothing more than a board.
So I got rid of the board and found an inexpensive enclosure to mount it in.
The $189 K-12G tube amp (by S-5 Electronics) is a terrific sounding amplifier and a huge bargain. The only downside is that its stock chasis is nothing more than a board.
So I got rid of the board and found an inexpensive enclosure to mount it in.
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I built the earlier version of the K-12 the "M" I think. I did upgrade the OPTs and power tranny plus Sprague oringe drops throughout. Also beefed up PS.
They do sound good and offer lots of opertunities for tweaking. And as you have done, mount the components on the back of the cct. brd. you can get the tubes to protude.
Click here for the image
They do sound good and offer lots of opertunities for tweaking. And as you have done, mount the components on the back of the cct. brd. you can get the tubes to protude.
Click here for the image
Thanks for the nice comments.That's a nice looking build you've done. I like your site as well!
Thanks!
The regimen of Gu50 was set according to Your recommendations (plate 300V 85 mA, bias -40V).
Cool!One more version: "Big Brother's Amp"
It's quite benevolent actually..At least that's what it tells me.