Power supply upgrades

I'm not familiar with the Nichicon electrolytics, but assuming they are of at least decent quality I don't think you'll gain anything by replacing them. You might realize some small benefits by paralleling ("bypassing") them with good quality film caps, of lower value, although I agree with Elizabeth that capacitors in the signal path are much more critical.

Electrolytics provide filtering of ac ripple, and energy storage. They almost invariably provide poor performance at high frequencies, so bypassing them with a polypropylene or other good film capacitor will potentially help filter out noise or other garbage before it reaches the components that are in the signal path (where power supply decoupling/bypass capacitors are presumably incorporated as well, but cleaning up the dc voltages as much as possible before they enter those areas can't hurt and might help).

The capacitance values you listed for the electrolytics strike me as adequate for the relatively low and fairly constant current draw of a 3 x 12AX7 phono stage, so I don't think there is anything to be gained by increasing their values. Adding the film bypass capacitors will, of course, provide a bit of added capacitance as an incidental benefit.

Regards,
-- Al

Thanks Al, the film bypass caps have been my first inclination from the start. What value bypass caps should those electrolytics be bypassed with? I've heard various percentages discussed in various forums, or is simply bypassing with .1uf caps good enough?

Also, any suggestions as to best axial resistors for the signal path in the Cayin? The Vishays and Texas Instuments are impossible to fit here.

Thanks again, Scott

Increase your filter capacitance, and replace your rectifiers with FREDs. I've done the former in the past(in tube amps) with excellent results. That's one of the first things most tube amp modders address, as it will improve the amp's bottom end performance and, overall, make everything sound more effortless. I just did the latter in both my SS woofer amp, and two Cary monoblocks. The results/improvements are too numerous to list, but the dynamics, slam and resolution you are seeking will be presented "in spades". I used a pair of IXYS VBE 17-06NO7 in my SS amp, and six IXYS DSEI 12-10A each in my Carys. Those are easily obtained from Digi-Key. How I wish that Black Gate was still manufacturing their large filter caps, or that Sanyo had OS-CONs big enough for amplifier power supplies. Al's filter cap/film cap bypass suggestion will also yield improvments. OOPS- I also recently upgraded the power supply in my TacT pre-amp, using FREDs and OS-CONs. Made a whole new beast out of it. I got carried away, talking about the power amp mods. SORRY! =8^) The tubes you choose will make a dramatic difference in your presentation also. Regarding the resistors: See if any of Caddock's will work in your app: (http://www.caddock.com/Online_catalog/Mrktg_Lit/TypeMK.pdf) Read the bottom of the data sheet.

What value bypass caps should those electrolytics be bypassed with?

I don't think it's particularly critical, as long as the bypass caps are of good quality. Anything from 0.1 to several uf strikes me as reasonable. If you find indications of particular values that worked well for people, in the forums you spoke of, go with those, but quality is probably more important than value.

Rodman -- As I think you indicated towards the end of your post, I'm not sure that the improvements you cited, which were mostly with power amps, would be relevant to a phono stage's power supply, where the current load is much more stable as well as much lower.

Regards,
-- Al

If he could find some Black Gates to directly replace the caps he has, there would definitely be an improvement with regards to dynamics. Some of their old suppliers still have the smaller values in stock, although at a premium. Upgrading to Black Gates, or Sanyo OS-CONs will improve dynamics installed in any circuit that provides gain. I believe he could easily find them for his phono pre. If the pre has rectifiers, replacing them with soft recovery FREDs will yield even greater benefits. These things just hold true, regardless of the power supply's application.