• 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.

6L6 for a beginner, plus ECL86/6GW8

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Jump to Latest
Miles Prower

Miles Prower

Member
Joined 2005
dolphin-hsl.com
It motor boats and then oscilates real high pitched if I have the feedback resistor connected from the output transformer, I cut that line and it works pretty good. But I should have some feedback shouldn't I?
Click to expand...

If your component values are correct, then I'm not surprised. Your B-factor is: 0.595, and that's a whole order of magnitude greater than it needs to be. Get that 6K8 feedback resistor out of there are replace it with something like 470K or 680K.

While 6L6s are probably one of the best performers so far as THD is concerned, it's still a pentode, and it still produces that pentode nastiness, as well as woofer underdamping. You need some NFB to correct those problems. Without NFB, it'll still sound lots better than many a "Big Box" SS amp. Get that NFB working, and you will notice the improvement.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Top Bottom