New Tube Porn!! - Page 2

G · 26th May 2004, 10:34 PM

Quote:

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 · 26th May 2004, 11:59 PM

Quote:

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

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

Quote:

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.

Quote:

Thank you very much for the compliments.

You deserve them. Thanks for the photos.

Best,

George Ferguson

G · 27th May 2004, 01:46 AM

Quote:

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 · 27th May 2004, 02:03 AM

Congrats!

Why does biasing the filaments above ground reduce the hum?

Best,

George Ferguson

Layberinthius · 27th May 2004, 05:07 AM

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 · 27th May 2004, 01:19 PM

Quote:

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 · 27th May 2004, 05:52 PM

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

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27th May 2004, 02:03 AM	#14
DrDeville diyAudio Member Join Date: Mar 2004 Location: Tucson AZ / Saugatuck MI	Congrats! Why does biasing the filaments above ground reduce the hum? Best, George Ferguson

27th May 2004, 05:07 AM	#15
Layberinthius diyAudio Member Join Date: Jan 2004 Location: nowhere	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.

27th May 2004, 05:52 PM	#17
DrDeville diyAudio Member Join Date: Mar 2004 Location: Tucson AZ / Saugatuck MI	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

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