Reversible tweak to Counterpoint SA-7.1

Tweakers' Asylum

Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ.

Here is my tweak to my Counterpoint SA7.1 preamplifier.
If you have the same preamp, I encourage pyou to do the same and tell me what you think.
It is a reversible tweak. So, if you do not find the sound improved, you simply change it back. No hame done. Just have to be careful not to crack any tube or get electric shock.
- remove the upgrade card that holds just one 6922 tube with MOSFET followers. This plug-in card with MOSFET followers and WIMA cap is a degrade rather than an upgrade to enable using just one tube instead of two in the line stage.
- now plug two 12AU7 into the two tube sockets that suppose to hold two 6DJ8 or 6922 as in the SA-7. I have tried several different RCA and Sylvania 12AU7, 5814 etc, they are all good here.
In my unit there are actually two resistors to drop the filament volage to around 6 volts for the 6DJ8 tubes.
The filament volage applied to the 12AU7 is then much less than the usual 12V but it is okay.
I have been using them like this for a few months with no problem. I could have short out those two resistor to allow 12V to the filament of the 12AU7 but did not bother.
I have also tried two 6DJ8 tubes which are the tubes used in later issue of the SA-7 before the SA-7.1 but like the 12AU7 a lot better.

- I want to try some of those Japanese-issue paper that works similar to StillPoints' ERS cloth as in Zanden Audio DAC but has no assess to such. So I fabricated some ordinary typewriter paper with accetate sandwitched in between and rolled into a cylinder and covered with a layer of aluminum tape. Both 12AU7 tubes are covered by such cylinder. Aluminium tape cut to thin strip is taped over the cylinder and closest ground screw on the main PCB. This may also help bring the temperature of the 12AU7 to be a bit higher to compensate for the lower filament voltage.
- I also removed those two 12AX7 in the RIAA phono (since I do not use my turntable much) to reduce the heat from the transformer.

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Kimber Kable

Topic - Reversible tweak to Counterpoint SA-7.1 - jacky 19:20:38 06/08/05 (5)

Re: Reversible tweak to Counterpoint SA-7.1 - Cougar 20:16:51 06/08/05 (4)

Re: Reversible tweak to Counterpoint SA-7.1 - jacky 13:57:53 06/09/05 (3)

How do you like the Counterpoint SA 7.1 preamp? - Cougar 20:04:43 06/09/05 (2)

Re: How do you like the Counterpoint SA 7.1 preamp? - jacky 08:17:02 06/11/05 (1)

I Put A Mullard E88CC Gold Pin In.. - Cougar 07:46:59 06/13/05 (0)

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