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Old 26th June 2009, 02:53 PM   #1071
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Location: Albany , NY (smallbany)
I would leave the 22k/1K ratio. Using the LS attenuator would be best with an op-amp follower (no change to amp open/closed loop gain). When I do get all 4 of my amps going at once , I will use 4 of the LS's like this to safely attenuate/balance my F/R (maybe even remote controlled). I have a real clean +- 12v auxiliary supply .. why not use it ?
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Old 26th June 2009, 03:21 PM   #1072
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Default Re: Simple QC test?

Originally posted by danielwritesbac

Hey OS. I've got a question.
Did you try those big Mallory as output caps? Maybe that's workable instead of an NFB cap? Even if only temporarily done that way, I think it can illustrate if your NFB cap selection is good or not.

For instance, if the NFB cap is really nice, bypassing it in favor of using a speaker output cap instead (for DC protect job) won't make an improvement in the sound.

Otherwise. . . maybe there could be an interesting illustration of what the amp could sound like if the NFB cap was good?
What do you think of that?

Polarized caps as output caps will need a DC bias voltage to prevent the cap being reversed biased for half of the output waveform. At the currents that are involved here the cap could be damaged or fail without the bias.
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Old 26th June 2009, 04:04 PM   #1073
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by steve dunlap - Polarized caps as output caps will need a DC bias voltage to prevent the cap being reversed biased for half of the output waveform.
Good point ,steve! I think that is why I have been trying to dissuade DWB from trying this. BOOOM !!

Daniel , you will really like the way this sounds from 20hz-20khz !!
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Old 29th July 2009, 06:45 PM   #1074
Bhu108 is offline Bhu108  United States
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Default My old APT Holman amps ned a little help

thanks to everyone and specially Tom Holman for the commentary on this great Apt Holman amp. I am currently using them (pair) in Bridged mode, and just last week got a pair of Acoustat 3. one of my amp is about 50% less output than the other. so the balance on the pre amp at about 9:30 to get equal volume. the auto turn on feature on my Celestions and Baltic speaker required that you crank the volume up till you get the signal to go through and it sounded pretty rough for 20-30 seconds and sometime one amp would cut out requiring the cranking procedure again. Since driving the Acoustat 3 systems the auto turn on fires up almost every time but the one amp still has low output. Sound is pretty good on the Acoustats, okay it sounds amazing. Got any suggestions on the low output or where I could get these perked up for reasonable? I am not that savvy (yet) with electronics fixes and soldering irons
San Luis Obispo, CA
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Old 30th July 2013, 03:32 AM   #1075
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Default Schematics, etc. . .

It seems that a few files have gone missing over the years, so here's a "Frugalamp Care Pack" in zip format, attached.
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Tools, Models & Software for DIYClipNipper boostLM1875 TurboPowerful TDA7293 kitTDA7294 pt2pt ♦ My post has opinion.
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