Posted by Tnuctipun [ 64.12.116.132 ] on January 09, 2005 at 08:33:34:
In Reply to: Re: yell if you want other options... posted by Wayne Parham on January 09, 2005 at 04:56:42:
Hey-Hey!!!,
I have built three like it already. The first was SS rectified and had cheap-o coupling caps. It sounded really good. I built two after that with increasing complexity( like you'd expect anything else, right? ).
I have another in process which I mentioned as having a schematic in hand for. Just got the big PS choke from Heyboer, and the active load valves from Radio Electric Supply and a bunch of other stuff cleaned up from my slavage box. Top plate on Monday...
This gives me a reasonable assurance that it will sound excellent. L-C filter and tube rectifier( either hybrid Graetz-bridge or perhaps get two of the 230V Hammonds and pure valve rectifier...), are definatly an improvement on the all 1N4007 C-R-C-R-C I used at first. One could try the Cree Schottky types. 1A/600V are ~$1 from Tubebuilder in Maryland and are zero recovery time. I tried them in a full bridge amplifier circuit, and found an improvement over Fairchild's Stealth types.
The most important modification will be cascoding the active load circuit. One more gate-stopper and one more 2540 and it is done. The 'top' mosfet is the one which will need the heatsink, so leave room to add another, or swap it.
If you decide on resistive loads, you'll need a second filter stage. move the big oiler to the output end and put a 450vdc 'lytic in its place.
regards,
Douglas
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