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Old 20th February 2013, 11:27 PM   #761
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The requirement for the JFET is that it will conduct 5mA with a gate-source voltage in the -1V to -4V range. If Q4 is not in that range, you will not be able to set the output voltage with P1.

Be sure to verify the pin-out of any substitute part. The 2SK170 has the gate on the middle pin. Many 2N or MPF parts have the gate on the pin that would be the collector of a 2N3904, the leads will have to be twisted to connect to the PCB layout. Generally JFETs like these will work just fine with the Source and Drain interchanged.
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Old 24th February 2013, 01:17 AM   #762
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Built my first p2p. THANKS PAPA!
Nelson Pass Amp Camp | retrofit into a Orion 1200d (600@1 class d)

First, is my temperature ok?
Averaging 48c after 8 hours/ all day of use.
It gets hot. I can hold my hand on it. I would like it to run cooler.
~ 25c ambient +25c dissipation = <50c so I am ok?

15vac100va dual secondary antek transformer
33,000uf 50v nippon chem

18vdc full load PS
10.1vdc Q1
dead silent, no hum

current setup with amp:
Tang bang 926s 1 cuft @ 80 hz @ 4 ohms
audio gd nfb 12 dac via toslink
Sound blaster Recon 3d Pro
Foobar wasapi 16bit 44.1khz

made with many left overs. upgrades to come.

Tang Band W3-926SD 3" Poly Cone Neodymium Full Range Driver 264-815
33000uf/50V-Repeat Of A Sell Out


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Old 24th February 2013, 07:48 AM   #763
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Very nice, very nice. Please show more pictures of a finished amplifier.
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Old 28th February 2013, 11:32 PM   #764
bcmbob is offline bcmbob  United States
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Way, way back - 6L6 suggested a Peter Daniels Universal PS board as a match for the ACA. I finally go them stuffed and working yesterday. The sound quality is great and I perceive more and cleaner bass as well as improved dynamics.

Kudos Mr. Pass

The only glitch is a very warm transformer at max volume, which I haven't experienced over in the chip amp world. My first guess is the toroid isn't big enough but I'll take the advice of the experts.

Antek AN-0215 25VA 0.8Amp
ApexJr 18,000 uF 50V Caps
Arcol 5W 0.47 ohm resistors
Attached Images
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File Type: jpg AC2.jpg (712.6 KB, 597 views)
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File Type: jpg AC4.jpg (179.1 KB, 254 views)
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Old 28th February 2013, 11:41 PM   #765
N Brock is offline N Brock  United States
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Quote:
Originally Posted by bcmbob View Post

The only glitch is a very warm transformer at max volume, which I haven't experienced over in the chip amp world. My first guess is the toroid isn't big enough but I'll take the advice of the experts.

Antek AN-0215 25VA 0.8Amp
ApexJr 18,000 uF 50V Caps
Arcol 5W 0.47 ohm resistors
iirc, the psu should provide 2.2A per channel when running at 19 volts.

I see yours isn't quite 19v but it still seems undersized.

best,
N-Brock
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Old 28th February 2013, 11:42 PM   #766
6L6 is offline 6L6  United States
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25VA ???????? I'm surprised it hasn't melted the tape off it yet!!! That's seriously undersized, you need something closer to 150-200VA.

The laptop PSU used are probably 60-90W output, each. You will need 1 transformer that can supply both channels, so 150-200VA (VA are basically equal to W)

That aside, your build looks really nice, I wish I could come over and hear it!

Last edited by 6L6; 28th February 2013 at 11:45 PM.
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Old 28th February 2013, 11:43 PM   #767
bcmbob is offline bcmbob  United States
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The DC output is 20.1 on the nose from both power supplies.
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Old 28th February 2013, 11:45 PM   #768
bcmbob is offline bcmbob  United States
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Thanks to all of you. I'll buy a new trani. Does everything else look O.K.?
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Old 28th February 2013, 11:52 PM   #769
6L6 is offline 6L6  United States
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Yes, it looks great!
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Old 28th February 2013, 11:54 PM   #770
bcmbob is offline bcmbob  United States
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