Stereomour power supply mod?

[tpatton]

When I built my second Seduction, I put in one Hammond 155J choke to replace the innermost 1K ohms resistor in the CRCRC power supply.  On advice from Caucasian Blackplate, I later replaced the other 1K ohms resistor with another Hammond 155J, which allowed me to reduce the C size drastically--for me it was down from 200 uF to 100 uF, but CB said it could go down much further, so film caps could be used.

I see that the Steremour has a CRC power supply.  I wonder if replacing that R with a choke would allow for a similar reduction in the C size, and whether there might be any advantage in doing this.  I haven't yet seen the Stereomour circuit diagram, but would need expert advice even if I had.

Any advise on this would be welcome.  I'm thinking about coming out of kit-building retirement since the Stereomour seems like such a neat, well designed amp, which could compete with my Paramour II's.

 

[Paul Joppa]

The Stereomour has a "pseudo-dual-mono" power supply, with an RC section for each channel. Using 2A3s that is 270 ohms/100uF each channel, which is similar to the Paramour II. In the Paramour II the upgrade was to use new iron, and re-purpose the 10H/90mA plate choke (Triad C7-X) as a power supply choke. You can do the same thing with the Stereomour. A cap as small as 10uF should still provide lower ripple than the original. The cap will react with the plate choke/parafeed cap/output transformer in ways that are difficult to analyze reliably, so I can't say what value would actually be workable in practice, but the potential is there.

A little tricky to place the new PSU chokes where they won't get ihn the way or pick up or radiate magnetic hum fields - once again, experimentation would be needed even if you had a good analysis to provide a starting point.

 

[tpatton]

Thanks for this, Paul.  I plan a custom chassis anyway, and could make it big enough to permit lots of location alternatives for the chokes.  If I get to the point of doing it, could you tell me, in detail that a circuitry ignoramus can follow, (a) what chokes I should get, and (b) where to connect them in?  I can easily go above 10 uF, in Obbligato film/oil caps, for example.  Would bypassing these with Russian Teflon FT-3 0.1 uF 600V caps further help sound quality?  Sounds like overkill to me, but why not ask?  I've found no film cap that betters those Russian Teflon FT-3's, not even Mundorf Supreme silver/oil.  As reported in this Forum, I even found that using them to bypass a fancy grade of Black Gates worked.

No need to reply to this, at this point.  I'm still undecided about whether to end my retirement.