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Amp Camp Pre+Headphone Amp - ACP+
Amp Camp Pre+Headphone Amp - ACP+
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Old 31st January 2020, 05:04 PM   #211
kacernator is offline kacernator  Czech Republic
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Default PCB missing capacitor correction

Hi,

I have little error on my PCB, there is missing 220pF cap on input mosfet.
Here is corrected PCB.
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File Type: zip ACP Headphone PCB.zip (214.4 KB, 47 views)
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Old 31st January 2020, 06:40 PM   #212
ergo is offline ergo  Estonia
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I've designed an alternate PCB for this nice project.
It's a 160*80mm one sided PCB.

If there is interest and Mr.Pass is ok with it then I can post Gerbers too. One proto has been built and the one mistake I had with traces is fixed in this snapshot... (on real thing the fix is hidden under the board )

PS. I left in an option to cut the GND trace and have a dual polarity supply instead to avoid the output cap... have not tried it myself yet though.
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File Type: png ACP+_PCB_EE.png (184.2 KB, 438 views)
File Type: png ACP+_PCB_EE_proto.png (783.4 KB, 430 views)
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Old 9th February 2020, 04:55 AM   #213
hirscwi is offline hirscwi  United States
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Amp Camp Pre+Headphone Amp - ACP+
Do I have to worry about counterfeit J113s? Or is most any source on eBay or Amazon likely to be legitimate?

My apologies for a dumb question.

Thanks.
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Old 9th February 2020, 09:12 AM   #214
2 picoDumbs is offline 2 picoDumbs  Australia
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Amp Camp Pre+Headphone Amp - ACP+
Please buy all your components from Mouser, Digikey, RS Components, Farnell, a diyaudio member or an ebay seller that is confirmed to be legitimate by another diyaudio member.

For things like J113, J112 etc just buy them from Digikey or Mouser.
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Old 9th February 2020, 01:33 PM   #215
hirscwi is offline hirscwi  United States
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Amp Camp Pre+Headphone Amp - ACP+
Thank you. I normally buy all my parts from Mouser or DigiKey. I thought they didn't have the J113 but I was looking for "2SJ113". Your suggestion prompted me to look for "J113" and of course found it. Thanks for your guidance!

I'm trying to learn PCB layout and this will be a good project for me.

I appreciate everything I learn from this forum and hope that I can contribute back.
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Old 22nd February 2020, 09:39 PM   #216
SRMcGee is offline SRMcGee  United States
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Amp Camp Pre+Headphone Amp - ACP+
Folks:

I was one of the fortunate souls who had the opportunity to build an ACP+ at BA19. I've been preoccupied with other projects the last few months but am now installing the board in a chassis and have built a simple linear supply to power it. I used a Hammond 229B34 transformer, wired to provide 17 VAC, but its secondaries are measuring 22.3 VAC unloaded. I'm getting about 28.75 VDC at the caps (again, unloaded). Before I connect the power supply to the ACP+, I gotta ask: should I be concerned?

FYI: the wall wart provided for the ACP+ at BA19 was 24 VDC. I understood acceptable voltages were in the 18 to 24 VDC range.

Regards,
Scott
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Last edited by SRMcGee; 22nd February 2020 at 10:08 PM.
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Old 22nd February 2020, 10:11 PM   #217
Ben Mah is online now Ben Mah  Canada
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Amp Camp Pre+Headphone Amp - ACP+
What type of linear supply? C, CRC, CLC?

You can always load test it first. The current draw is 0.3A or so. I measured mine and it was 0.33A. You can assemble some resistors for a total of 24V/.33A=73R +/-, and 24V x .33A = 7.9W minimum but use 20W total to keep temperature down.

The loaded output voltage will come down, but a test is good for peace of mind.

If the voltage is high, you can always reduce it with the R in a CRC filter.
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Old 22nd February 2020, 11:05 PM   #218
6L6 is offline 6L6  United States
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Amp Camp Pre+Headphone Amp - ACP+
I'd try it and see what the voltage is under load. Will most likely be fine. Ben's suggestion is great if you need to lose a little voltage, or just use a 7824 before the input if you really want it spot on.
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Old 22nd February 2020, 11:28 PM   #219
SRMcGee is offline SRMcGee  United States
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Ben Mah:

CLC. The power supply consists of the 229B34 followed by four MUR820 diodes and then 8100 uF in caps, a Hammond 155B inductor (6 mH, 0.3R) and another 5400 uF in caps.

Your idea was excellent. If I knew enough to be embarrassed for not having thought of it myself, I'd kick myself. Fortunately, I don't know enough and am grateful for the guidance. With a 75R load, the voltage dropped to 22.6 VDC, which is exactly what I had hoped for.

Sounds great! I'll take some photos and post on the pictures thread.

Thank you!

Regards,
Scott
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also, Everyone has a plan, till they get punched in the mouth. (Mike Tyson)
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Old 22nd February 2020, 11:32 PM   #220
6L6 is offline 6L6  United States
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Fantastic!!

Post photos here as well, would love to see it!!
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