• http://www.diyaudio.com/forums/showthread.php?s=&threadid=68267

It sounded really good, but it was a bit more prone to hum than with the CCS. I had to beef up the PS capacitance( 120 uF/330V salvaged photo flash caps from disposable cameras ).
cheers,
Douglas

With the change to smaller output capacitors and the use of disposable camera flash capacitors. It looks as if you have developed a bang for the buck preamplifier.

What type of power supply filter scheme are you using, CLCLRC, or?

How did the overall sound character change, when you changed to the 10k plate load at 10mA and 4 red LED's at the cathode?
This must have reduced the overall gain somewhat?

Now, if I can figure out how to get a cheap power transformer to obtain the 170V without a big series resistor to drop some Voltage.

This preamplifier could be built from mostly junk box parts.

It would be nice to have a great preamplifier with a tiny investment.

As always, thanks for your input.

Norris

I never built this with 12B4 and CCS, so I don't know what the gain *MIGHT* have been. It has a 50k volume pot with a 75k shunt resistor so it is gain-reduced anyway.

Don't worry too much about the B+, with 10k plate loads, there is no dissipation issue until it's over 400 anyway. 4 or 5( or maybe 6 ) LED's will be fine too. Just make sure your plate loads are up to the task. Remember, the output voltage is going to be less than 10 p-p, so we don't need a lot of cathode bias....back to less LED's no?
cheers,
Douglas