Posted by PakProtector [ 152.163.100.65 ] on December 30, 2005 at 08:07:21:

In Reply to: There is a simple solution to the problem posted by Russ on December 30, 2005 at 07:36:40:

Hey-Hey!!!,
My first foray into a valve pre was quite similar to the foreplay circuit. I added the bipolar supply, and increased the CF tail load. It was running more current, and through a larger resistance. Adding a CCS there made little if any improvement.

The shorting switch for the output is easy, a DPST will do quite well, and eliminated the risk of a large transient.

With VR tubes, a CCS instead of a resistor to feed the VR tube has always worked better for me. Less of a need for a high raw voltage( like the 2x regulated that is suggested ).

While you're building CCS-es, build two more for the plate loads, and do away with the CF stage. The mu-follower output from the MOSFET CCS is going to have lower output Z than most CF's anyway, and it eliminates the need for that extra stage.
cheers,
Douglas

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