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.
I just recieved a GlassWare Bd for 5687. I havent decided on values yet though. Broske suggests around 20mA. I was thinking of running close to 100 ohms Rk at about 125Vp/tube. It's a balance though of what you want to run for the input tube unless you split the supplies? I was thinking maybe a 6FQ7 on the input?
My homebrewed Aikido amp uses 6CG7's as input tube.
Try to find the RCA cleartops. Other brands of couse still ok.
Run the amp with a B+ a little higher then suggested, let's say 200 to 250 Volt. Bias the tube with 4 to 5 mA is a good choice.
My opinion is that a 6CG7 starts to sing wonderfull with a plate voltage of 100 to 150 Volts.
As output tube I tryed the 5687 and 6N6p.
There is almost no sonic difference between these tubes.
Mind the difference in pinning layout between those two!!
Have fun, greetings,
I have some boards that were from a group buy here on the forum. I am using the 6FQ7 as the input tube and 5687 as the output tube. I am running 220 -230 volts with dual mono supplies.
It is very nice listening from Jazz to rock.