New Tube Porn!!

[G]

Originally posted by mourip
Did you make the base yourself?

No. I'm not that good at finish carpentry. I had a cabinetmaker that lives nearby make the frame and one for my planned linestage also. Any competent cabinetmaker should be able to build you a frame with dovetail joints on the corners. The cost was only $20.

[DrDeville]

That is indeed "Tea for the Tillerman". Good eyes!!

That album is part of the music that is forever a part of my gestalt.

This amp has more hum than my first humble project does. Go figure huh?

Indeed. I doubt you're discouraged, and you shouldn't be. As you undoubtedly know, there's plenty of things you can do--resolder joints, adjust the wire paths, use coax for the filament wiring, switch to DC filament power, etc. You'll get rid of it.

Thank you very much for the compliments.

You deserve them. Thanks for the photos.

Best,

George Ferguson

[G]

Originally posted by DrDeville


use coax for the filament wiring

What a novel idea. Hadn't thought of that one. I solved the problem. I found that the 5687 I was using was microphonic. I also biased the filaments approximately 40v above ground. No more problem. You have to put your ear about 4 inches from the speakers to hear any hum or hiss. I can live with that.

[DrDeville]

Congrats!

Why does biasing the filaments above ground reduce the hum?

Best,

George Ferguson

[Layberinthius]

G, GREAT WORK!!

The attention to detail of layout is truly a class winner in my strive-but-never-get-there dream of a 'professional' look both underneath and above.

[G]

Originally posted by DrDeville
Congrats!

Why does biasing the filaments above ground reduce the hum?

Best,

George Ferguson

Try this thread. It will explain it better than I can.

http://www.diyaudio.com/forums/showt...p?postid=90211

[DrDeville]

Thanks Gavin,

To save others digging:

From Sir Bas Horneman, I gather that electrons emitted from the heater itself can travel to the cathode, causing hum. Raising the heater bias stops this effect.

But perhaps the major advantage is preventing filament-cathode arcing in designs where the cathode can swing high above ground.

Thanks again, and I hope I got that right!

Best,

George Ferguson