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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: Design question... posted by Vinnie on November 29, 2008 at 05:29:52:
Hi Vinnie,
Yes it certainly can !
A 300B has the most difficult drive requirement, so look to a 6GK5 as the 300B driver tube, Eli Duttmans' driver choice. Of those three finals you mention, I prefer a 300B the least.
The 2A3 and the 45 can use the 6SL7 paralleled, (or even a 12AX7 or other mu of 70 and higher tubes) as the driver. Both the 2A3 and the 45 finals are easy to drive in a two stage direct couple. Obviously, the 45 is the easiest to drive of the three, and it sounds great on efficient speakers.
Vinnie, even a modest 6AQ5 is worthwhile, and can "do a number" on a lot of other amps you might ever hear, as a trioded final tube in a two stage direct coupled amp.
I must warn you Vinnie, in my opinion, the JC Morrison Micro is not documented well enough circuit-wise, in the schematic shown in Sound Practices magazine. One can NOT build an amp from that partial schematic, and know the direct couple operating points are optimal. I've recently seen some that are pretty far off !!
(If, someone has a fully documented schematic of a properly operating Morrison Micro, please do this group a favor and post it up here, for analysis.)
Two other amp circuits for you to look at are the Nobu Shushido and Isamu Asano Loftin-White amps. Unlike the Morrison Micro, these circuits are documented well enough to do a DIY build. The Asano even has a kit available from EIFL. About the only big complaint I have is that both original circuits' power supplies are inadequate, burdened with high series resistances, the usual problem. For a circuit of this power and draw, the L.S.E.S. (Dennis' supply idea) in practice, is totally excellent.
An other place to read about these types of amps Vinnie, the seminal article that got many building two stage DC amps, is "A Direct Coupled Single Triode Amplifier" by Ciro Marzio and Cristiano Jelasi, in the Spring 1994 issue of Sound Practices. Its a truly excellent article. My above-expressed suggestion on improving the power supply, reducing series resistances, etc., would equally apply to the Italians' circuit.
I agree with your thinking Vinnie, KISS and less ........ is more !!
Jeff Medwin
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Follow Ups
- RE: Design question... - drlowmu 11/29/0810:35:09 11/29/08 (1)
- RE: Design question... - Vinnie 11:11:38 11/29/08 (0)
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