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
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