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Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

801 low power SE amp
801 low power SE amp
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Old 1st April 2006, 08:33 PM   #61
Sheldon is offline Sheldon  United States
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front:
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Old 1st April 2006, 08:35 PM   #62
Sheldon is offline Sheldon  United States
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Under the hood:
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Old 1st April 2006, 08:37 PM   #63
Sheldon is offline Sheldon  United States
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Response (white curve for amp, green is soundcard looped back) in RMAA. Down 1dB at 20khz:
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Old 1st April 2006, 08:39 PM   #64
Sheldon is offline Sheldon  United States
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THD at about 0.4w (almost full power). Some tubes give a 2nd harmonic a little lower than the third:
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Old 1st April 2006, 08:50 PM   #65
Sheldon is offline Sheldon  United States
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Like this:
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Old 1st April 2006, 08:51 PM   #66
Sheldon is offline Sheldon  United States
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and IMD:
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Old 1st April 2006, 09:12 PM   #67
AKSA is offline AKSA  Australia
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Lovely work, Sheldon!

Cheers,

Hugh
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Old 1st April 2006, 09:53 PM   #68
rdf is offline rdf  Canada
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Nice work! Two quick ones, is that Hammond iron and are those Russian telfons underneath? OK, three, how do you like both?
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Old 1st April 2006, 10:22 PM   #69
Sheldon is offline Sheldon  United States
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Thanks guys, I'm having fun. Next up, it's mirror image for the other channel (4 channels per side, two tube, two ss - at least for now).

Yes those are Russian teflons, but the iron is from Electra-print. The amps sound nice to me, but I have not compared different caps, etc.. Only so much time, and so many things I want to do. So I rely mostly on semi-informed guesswork - informed partly by reading here. I take my shot, and if it sounds good, I move on to the piece of the project. When I get this all done, I may try some fiddling with components.

Sheldon
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Old 30th June 2006, 10:27 PM   #70
Sheldon is offline Sheldon  United States
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Both amps finished for a bit now and sounding very nice. I was getting some left/right crosstalk, so I looked over my work and made two changes. On the amp schematic (one page back), the bias for the 801 is applied between the two 100k resistors in series to ground. In Steve's original schematic, there is a 2.2uf cap bypassing the lower resistor. I added this cap and it reduced the crosstalk, but didn't eliminate it. So I split the bias supply at the last RC (it has an (CRCRCRC), by adding a second parallel RC for the final section. That completely eliminated the crosstalk.

Sheldon
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