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In Reply to: Re: Tung-Sol, yum! posted by Jim McShane on July 20, 2006 at 13:33:13:
The Machine is in some respects more complex than El Cheapo (170v negative supply, bias supply), and in other respects simpler (no current sources, no caps in the cathode circuits). I would expect that the parts costs would be about the same for equivalent quality.I'm thinking of some sort of sand discreet or chip CCS for the tail, and just build a mongo bias supply to provide for it and the tail; the tail supply has proven remarkably noninfluential to the sound, in my experimentation. As it is, the 5965s draw 3mA each (6mA for the whole amp), so a resistor and cheap toroid is viable. As we discussed privately, I'm eventually going to VHF single triodes for the front end, and they like 5-10mA each, so a very long tail becomes impractical. This is something I got to get after.
I'm not sure what the final design of EC is, Jim. The only place I knew of to reference it was a mongerously long thread over on the other forum, and I didn't have time to wade that far downstream. Is there a more practical way to have a look at it?
Aloha,
Follow Ups:
Poinz,A link to the most current EC schematic is provided below.
At this time, the only change I'm considering is replacing the "Rat Shack" filament trafo with a Triad VPS241800. The Triad trafo's 2X 1.8 A/12 VAC secondaries would provide for both heater power and the B+ boost Jim McShane recommends. The VPS241800 comes with some "baggage": an extra pair of ferrite beads and a change in the 'AQ5 bias resistor value to 350 Ohms.
Eli D.
Speaking of trafo subs, what is the secondary voltage of the Allied 6K27VF used for B- supply?
Eli D.
I was hoping you'd show up here.Listen, if you want to put E C up as a DIY article, I have lots of space on my server, at your disposal. You (or somebody) will have to exposit a rational, um, exposition, and arrange schems and photos, and like that. I can help you. We can put it up on the 'Projects' side of the site. At least then I'll be able to chew on your ankles more efficiently.
:^)
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