A wacky thing happened...A30 - diyAudio
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Old 11th February 2006, 10:25 PM   #1
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Default A wacky thing happened...A30

Tested my mini/a30 using direct output from the analog out of a compter CDP. Plays and sounds good but no real volume on either on the mini side or the a30 side.

No problem. Took it upstairs to the real stuff and connected it a preamp to get a little more gain.

Didn't play. Nothing on the Mini side or on the 30 side.

I fussed a little and it played for a couple seconds after a power cycle then went quiet. Then I noticed that it smoked a little RC circuit I placed on the GND connector of the PS boards. The RC thing was to put a brick on any loops, a' la Nuuk's GC site.

Back down stairs, clipped out the cooked RC... it was the R that burned and connected GND directly. Hooked back up to the comp CDP and everything was fine. Played, but not very loud. All channels fine. The 30 watt A30 channels only very slightly louder than the 10 watt Mini channels?????

I broke out the MOX active cross that I built and connected to the "buffer out". From recollection, this is just a tiny amount of gain. Plays louder but the 30 side still isn't much louder than the Mini side.

Anybody know what may be going on? Any ideas or should I go back to the "pre"?
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Old 11th February 2006, 10:30 PM   #2
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If your not running balanced inputs (or in other words, are you using RCA input); have you grounded your neg. input?
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Old 11th February 2006, 10:31 PM   #3
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YUP, bridged the - to GND.
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Old 11th February 2006, 11:22 PM   #4
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are both schematics same,regarding input sensitivity?
besides that 30W can't go much much louder than 10W......
what resistors you use for negative reaction in mini and what in A30 side?
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Old 11th February 2006, 11:27 PM   #5
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Yes, these are cookbooked from the Brian GT chipamp.com/aleph site.

Negative reaction??? ... are those the source resistors?

http://www.diyamps.com/aleph/docs/miniAleph-sch.pdf
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Old 11th February 2006, 11:35 PM   #6
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Quote:
Originally posted by chipco3434
Yes, these are cookbooked from the Brian GT chipamp.com/aleph site.

Negative reaction??? ... are those the source resistors?

http://www.diyamps.com/aleph/docs/miniAleph-sch.pdf

r15 (100K) and r10 (68k1) in that pdf
I see that in A30 , at least in Nelson's manual are the same.....


double check all resistors around LTP
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Old 12th February 2006, 04:06 AM   #7
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Quote:
Originally posted by choky
besides that 30W can't go much much louder than 10W......
Very true! In fact I have built a 30 and a mini here

I can confirm that there is not much difference. It's noticeable but not huge; as the math would suggest it is not huge. Perhaps your just having the same experience?

regards....
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Old 12th February 2006, 04:21 AM   #8
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I will try it again tomorrow with the pre... I don't think there's much coming out of the analog cdrom.

Wouldn't the A30 be NOTICABLY louder than the Mini? The A30 has considerably less output than my LM3875??????
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Old 12th February 2006, 04:28 AM   #9
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I don't know the exact numbers but the Aleph amps in general, being only 2 gain stages, have considerably less gain than a 'regular' amp. Therefore they require more "drive" than a 'regular' amp to approach the same output. I'm thinking you may not be giving either enough input and you haven't even reached the mini's potential ....maybe?

I'm guessing here : Aleph ~ 26dB gain <<>>Regular amp 30dB gain
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Old 12th February 2006, 04:51 AM   #10
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I'm not the only one...

http://www.diyaudio.com/forums/showt...ight=#post5373

So maybe it's right.

I would still like to know what cooked that GND RC network...

DC offset from the pre?
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