• 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.

Look for a beefy driver tube.

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Shoog

Shoog

Member
Joined 2002
I went with the 5687 today. Sound beautiful and clean, and has just the right amount of gain.
In the past when I had built with the 5687 I had always encountered hum issues. Forced me to go DC on the filaments. Today I went AC with one side of the winding earthed (not even the centre tap), and have absolutely no hum. The only real difference in implementation was that today I added a 100R anode stopper. Seems that the 5687 is prone to instability.
In the past when I ran a gainclone with a 5687 based preamp it ran unusually hot. I never really thought about it much as I didn't run this combination for long - but it seems logical that the 5687 preamp was unstable in the supersonic frequencies.

Hope that helps, and thanks for the suggestions.

Shoog
 
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