• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

6SL7 Phono Preamp

tubewade

Member
2007-06-03 8:54 pm
Hi Denny,

You and I have been thinking along the same lines. As I have researched this subject I have found that higher mu valves like the 6SL7 and 12AX7, especially used in such a simple circuit, do not lend themselves that well to this function. The input capacitance due to miller effect is very high and causes loading of the cartridge which cause a rollercoaster frequency response with many if not most cartridges. Furthermore, with no buffer on the output the amp is only capable of driving high impedance loads, 250k ohms or higher. The best circuit I've found that is basically like the one you are considering is here..

http://www.geocities.com/TimesSquare/1965/phono.html

Best, I say, based on theory and principle rather than on listening tests, though. I have not built that amp yet.

There is a thread with some interesting discussion and some great input from very experienced builders about this very thing here...

http://www.diyaudio.com/forums/showthread.php?s=&threadid=114096&highlight=

Best regards to you,

Wade