| Positron |
And this is only your second major project I believe?
Keep up the good work Gavin. You did a nice job. |
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| G |
| quote: | Originally posted by Positron
And this is only your second major project I believe?
Keep up the good work Gavin. You did a nice job. |
Thank you Steve. All of the agonizing over parts selection and color and cussing....etc, were worth it. Now if I can be as successful with my 5687 buffered linestage I will be a really happy tubehead.
:) :) |
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| Positron |
Wait till your next project, :devilr: :D ;)
Just kidding. It takes along time to do things. I just spent several MONTHS upgrading my preamp. You are doing just fine. |
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| Hesky |
That is some seriously thick copper!!
Lovely looking project :D
Hesky |
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| G |
| It's a custom metallic paint. Thanks. |
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| karma |
| very nice work;) now i need a cold shower:Popworm: |
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| mourip |
| Did you make the base yourself? |
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| DrDeville |
Very pretty!
Signal lines crossing at right angles... :checked:
AC lines crossing at right angles... :checked:
Is that "Tea for the Tillerman" I see in the first photo? :checked:
:D
Best,
George "Some Memories Are Forever" Ferguson |
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| G |
| quote: | Originally posted by DrDeville
Very pretty!
Signal lines crossing at right angles... :checked:
AC lines crossing at right angles... :checked:
Is that "Tea for the Tillerman" I see in the first photo? :checked:
:D
Best,
George "Some Memories Are Forever" Ferguson |
Hi DrDeville. That is indeed "Tea for the Tillerman". Good eyes!! I thought that I had done everything much better than I did with my first amp but you what? This amp has more hum than my first humble project does. Go figure huh? When I say hum I mean from the filament wiring. It is a very low level hum that you can only hear from about a foot away from the loudspeaker, which is 97 dB 1w/1m, so it don't take much. I'm going to run a voltage divider from the B+ to ground and bias the heaters up about 40 volts or so and see if that makes any difference. I'm also going to get a bright flashlight and see if I can spot any cold solder joints. The hum seems to subside somewhat after the amp fully warms up which tells me I have a bad joint (resistor?) somewhere. I may swap some tubes around also. Thank you very much for the compliments. Cheers. |
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| G |
| 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. |
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| DrDeville |
| 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. :D
Best,
George Ferguson |
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| G |
| quote: | Originally posted by DrDeville
use coax for the filament wiring
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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.
;) |
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| DrDeville |
Congrats! :up: :D
Why does biasing the filaments above ground reduce the hum? :scratch2:
Best,
George Ferguson |
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| 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. |
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| 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 |
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