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Old 7th December 2002, 03:50 AM   #1
Jean is offline Jean  United States
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Default My p3a amplifier project, pics.

Here are a couple pictures (sorry for bad quality).

Click the image to open in full size.

Click the image to open in full size.

Not on the same level as some other designs, but this one is my first one
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Old 7th December 2002, 03:58 AM   #2
ststone is offline ststone  United States
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It looks like a SCIFI project (must be the light and your effort to design your amp)
I love it...
Luv the front, looks real good
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Old 7th December 2002, 05:25 AM   #3
Jean is offline Jean  United States
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Thanks uncle Jun
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Old 7th December 2002, 05:37 AM   #4
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Nice work! And how does it sound?
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Old 7th December 2002, 10:33 AM   #5
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Very nice looking case. If it sounds as good as it looks you'll be in audio nirvanah.

It is a little hard to make out on the photos but it looks like you have 3 wires from psu to each amp board. I cannot see the zobel network on the speaker terminals so I assume they are on the amp boards themselves.

To get the best sound it is important to avoid shared ground issues. Normally this requires at least two ground lines back to the supply star point from each amp board. One for the input ground (and the phono connector on the back panel must be insulated from the case metalwork) and one for the zobel ground. Any local psu decoupling should be separately grounded too.

When you have finished the construction completely I would recommend you bind the psu lines to each board tightly together with cable ties to reduce their loop inductance. Also tie lines from transformer to rectifiers to reduce RF noise. In general, keep all the wiring tidy and compact.

Let us know how it sounds,
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Old 7th December 2002, 04:18 PM   #6
Jean is offline Jean  United States
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BAM,

You are correct, there 3 wires going to each board and they are "tied" together with heat shrink tube just to keep them together. Zobel network is on the amplifier board, and its hard to see but its there.

There is ground wire going to each board from the capacitor board, then speaker binding post ground wire connects also to the capacitor board, its hard to see but the black wires going from the back of the case around the transformer are the ones I am talking about. The rca connectors are insulated from the case, you are correct, and you can see I used shielded rca cables that go directly to the board and its signal ground.

I will have to do some minor work, get the wiring all cleaned up and get the AC plug installed in the back panel.

It sounds very good on everything that I listen to. Well thats not true, its easier now to see how some recordings aren't recorded as good as others. So I had to really dig through my records to find well recorded songs. I played Eagles - Hotel California, some Pink Floyd, Queen, Eric Clapton and Stevie wonder, Diana Krall and some demo cds and it sounds great. Now that the hum and noise is virtually 100% gone (I am not sure how much is still present if I get a Oscope but its not detectable to my ears), it sounds very clean and I pushed it to the max and it still stays put. Bass is nice and clean, drums on the hotel california track sound very very real. Voices from recordings like Andrea Bocelli , Sarah Brightman, and Diana Krall sound very clean and lifelike even when I max the volume control out

My source is really cheap, its a jvc cd changer almost 6 years old so its not really very high end. I have another one on order, I have a spare DVD player that I want to try once I find a good DTS audio recording to see if it sounds any better.

Overall I am very satisfied with it, now I am adding two more channels and doing some upgrades to my speakers.

Thanks for the comments and suggestions, really appreciate it!
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Old 7th December 2002, 10:53 PM   #7
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Looks good, what size is your transformer? Now I can't wait to finish my p3a, just waiting for the transformer and some other odds n ends.
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Old 8th December 2002, 12:00 AM   #8
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Hi Jean.

Amp looks great, well done, but I assume you are going to put a fuse on the input to the transformer, rather than connecting it directly like you are at the moment?
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Old 8th December 2002, 12:16 AM   #9
Jean is offline Jean  United States
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KenP, 500va 25-0-25 Avel Lindberg .

Pinkmouse, of course I just need to "cut" the rear panel for the fuse holder and AC female plug.
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Old 8th December 2002, 12:30 AM   #10
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Just checking

Had my Health and Safety hat on for a moment

Did you use Rod's boards, or did you roll your own?
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