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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: Re: Things that dump a lot of trash to ground.... posted by GBLPS on April 6, 2007 at 11:53:01:
Hi
I have about the same experience...
Going from dead quiet KT88 P-P stage, to a 300B SE stage, I ended up with about 6-8mV 100Hz hum from my +100dB/W speaker teminals (measured with DVM).
(100Hz = fullbridged recified 50Hz mains (Sweden))
I asked around.
And the problem seems to be in the DHT tube nature, sins the cathode is the heater (filament).
Very low ripple at the cathode/filament is amplifyed to audiable levels, and absolutelly zero hum is very hard to reach.
I´ll changed the 7805 filament regulators, which had to hi dropout levels to better Linear devices.
This lowered the hum to 3-4mV 100Hz ripple, which was just about audiable when listening very close to the speakers (changing records).
Regards
Pix
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- Re: Things that dump a lot of trash to ground.... - ahlgren11@telia.com 08:16:37 04/07/07 (0)
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