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Old 23rd February 2013, 03:10 PM   #1551
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I may when time comes. Too far in the hole to worry about now. I may not do it and just keep it as part of SE rig. It is the killing of the sweetness that I am not excited about, as that is the reason for it in the first place.
I do have question. I think 6v6 pre has about 15dB of gain. I should only need 10 more, max for Altec rig, correct.
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Old 23rd February 2013, 03:14 PM   #1552
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and the question is ?
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Old 1st March 2013, 04:32 PM   #1553
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removed C3 from the game just from curiosity
for the quiet nights I`m thinkinig to use a switch and a 2x10cm wire to interrupt C3R24 network.would there be any sound degrading or possible oscillation apearance? from the wire/switch part

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Old 1st March 2013, 06:50 PM   #1554
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instead of switching out/in of C3 , proper SE operation can be with switch across R20-R23 group

that way - there is no more CCS modulation and these resistors are no more in series with speaker output
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Old 1st March 2013, 07:07 PM   #1555
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and C3 remains connected?
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Old 1st March 2013, 07:17 PM   #1556
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yup
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Old 1st March 2013, 07:23 PM   #1557
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wil try
btw managed to mount that timmer, you gave me the schematic for , in the tube preamp and works nice, now I turn on confidently my amps
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Old 1st March 2013, 07:28 PM   #1558
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Old 5th March 2013, 12:05 AM   #1559
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Quote:
Originally Posted by sakellogg View Post
r27 as a pot to jack up the bias. more bias makes it sound better. but adds heat.
OK! My plain A-J boards check out, which is a relief! I tested a SE signal into each side of each board using a junk speaker and first impressions are favorable. One side measured 8.73 V across R8 rather than 8.3... That board seems to have a bit more gain and a little less control than the one that measures 8.3... Thoughts?

So, I'm planning to remove R27 and install multi-turn trimmer pots. Question: does increasing the resistance at R27 increase or decrease the bias?

TIA,

Frank

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Old 5th March 2013, 04:53 PM   #1560
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Answer to my own question: I don't have much thermal headroom to raise the bias anyway, so the R27 pots are sitting at 64k. With that amount of current, the temperature rise is ~32 degrees above ambient with silent airflow, 27 degrees with the fan 'barely noticeable', and 24-25 degrees with the fan at full speed of 1200rpm. If you are curious, images are the air tunnel, the front panel fan control with thermal readout, and the profile of the air exhaust. The power supplies have 75 degree thermal cutoff switches on the heatsinks.

Cheers,

Frank
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