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Old 27th December 2012, 11:18 AM   #681
bcmbob is offline bcmbob  United States
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Don't want to hijack the thread too deep into speakers, but there is an interesting design that should sound good with the ACA. I haven't had time to make the combination yet, but will do so soon.

Foam Core Board Horn.
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Old 27th December 2012, 01:43 PM   #682
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The kit or boards is sold out. Can someone point me to the final schematics and parts list for this amp. I am tempted to just purchase the parts and do it point to point. Thanks.
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Old 27th December 2012, 01:56 PM   #683
bcmbob is offline bcmbob  United States
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Amp Camp #1
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Old 27th December 2012, 02:04 PM   #684
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great. many thanks!
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Old 27th December 2012, 02:10 PM   #685
bcmbob is offline bcmbob  United States
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Old 27th December 2012, 02:47 PM   #686
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Quote:
Originally Posted by Loudthud View Post
You could just leave off R1 and R3 and that would cut the current in half. I suspect the distortion would increase because Q1 would be farther into it's non-linear zone and open loop gain would be reduced. The distortion will be low order, you might actually like the sound. I like listening to mine with the feedback disconnected. Just remove R12. My latest build (#6) has a pair of IRF520s. They have a flatter distortion at 1W graph.
Loudthud,

When you said just remove R12 for the no feedback, you meant to just put a piece of wire in place of R12 or just dont install it at all (for standard build.) Can i also remove R11. Thanks.

Last edited by xecluded; 27th December 2012 at 02:59 PM.
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Old 27th December 2012, 03:39 PM   #687
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Quote:
Originally Posted by xecluded View Post
Loudthud,

When you said just remove R12 for the no feedback, you meant to just put a piece of wire in place of R12 or just dont install it at all (for standard build.) Can i also remove R11. Thanks.
I meant don't install it. My ACAs are all built on proto board, I installed little computer style jumper blocks in series with R12 for quick changes. I left R11 in place just as a way to limit gate current of Q4 when the amp is overdriven. (I'm prone to doing that when using the ACA as a guitar amp.) You would replace R11 with a wire if you want to try that. It may lower noise and extend the high end slightly.
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Old 27th December 2012, 03:48 PM   #688
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Thanks Loudthud. I've sent you a pm.
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Old 27th December 2012, 05:47 PM   #689
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Quote:
I have built the ACA and I have found the sound a little "laid back".

The speaker impedance can affect the sound, but it might also be the absolute phase. The ACA simple design inverts the phase. To correct that Mr. Pass has the + terminal connect to the common in the design so that the phase will be inverted back to original. If you by chance have the - terminal connected to common, try reversing the polarity to the speakers. An inverted absolute phase tends to "truncate" the soundstage toward the middle and back. It might be a long shot, but worth mentioning. Some recordings are processed to end up with inverted phase and will sound better with reversed polarity. At least you will be able to recognize when this happens.
I use a separate P.S. to each channel and it sounds neutral to me into 8 ohm speakers.
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Old 27th December 2012, 06:47 PM   #690
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I have never before in my life DIY'ed a ClassA amplifier, but this little AMP_CAMP #1 amplifier attracted my ambition,
and I did a single-sided layout by myself and will etch and build it.

Click the image to open in full size.

http://www.abload.de/img/aca_1x4kit.png

There is only one wire (from bottom-VCC to SK170-VCC) to be inserted manually!
The size of the PCB is 73 x 46 mm.

I do not know, if I am allowed to show you my layout (I did not ask Mr. Nelson Pass for permisson), and I do not want to
compromise anybody's group-buy!

But here it is!

Best regards - Rudi_Ratlos
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File Type: pdf AMP CAMP#3.brd (1).pdf (11.1 KB, 269 views)
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