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Old 3rd February 2008, 12:21 AM   #1
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Default Pass D1V3 DAC - build thread

Hope this isn't considered too marginally Pass for the PL forums...

I'm curious to see how others are progressing with Spencer's "NP D1 clone with enhancement" see here. It seems like quite a few boards have been sold to members but there hasn't be much said about build progress.

I received my pcb and bags of parts from Spencer early in the week and was very impressed with the quality of the board. The parts supplied look to be good industrial quality - Panasonic FC caps, S&M (siemens??) film caps, Linear Tech reg's, etc etc, and everything came neatly bagged and labeled.

The board is very densely packed in places, and is a bit daunting when you come to locate the correct location for many of the resistors and caps. I've had to resort on a number of occasions to searching the schematic pdf to locate the context of a part number before I could find it's position on the board.

I've managed a few soldering sessions and have roughly got to midway through step 3 in Spencer's suggested build sequence - surface mount regulators, resistors, diodes, jumper pins, and ic sockets, plus 75% of the 0.1uf film caps are mounted on the board. I've also soldered a surface mount cs8412 onto one of Spencer's 8414 adapter boards.

A nice, no-bs guide to smd soldering techniques can be found at http://www.infidigm.net/articles/solder/

I'll try to get some pics of my efforts so far posted tomorrow.


cheers
Paul
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Old 3rd February 2008, 01:41 AM   #2
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I was following Spencer's thread with great interest even knowing I couldn't tackle it with my lousy eyesight. It is a quite daunting project. I did try his I/V boards in a player with PCM63s and they are very impressive, totally transparent, no grain at all.
I don't believe he's making a dime on anything he's selling.

Best, Bill
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Old 5th February 2008, 09:01 AM   #3
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Still no pics, but have had a couple of good soldering sessions over the past fews - vastly improved by an extractor fan. well really just a portable fan blowing away from the work surface

I've completed the first 17 stages in the suggested build and test sequence. I'm now at the stage of testing and adjusting the JFET I/V power regulators. The 50VA 18V + 18V transformer I'm using - left over from an old DIY modular synth PSU - is putting out a little over 27V+/- at the designated test points. This slightly higher than the maximum of 25V+/- indicated in the original build thread. I suspect this isn't a real issue as the earliest board revisions used higher voltage secondaries, and the main side effect is higher dissipation in the regs.

A quick check of the reg output test points shows everything is operating ok with voltages ranging between 18.0V and 18.4V prior to adjusting the pots.

I curious if anyone has used Visaton MKP crossover caps for coupling. I've seen a comment in the archives that they are far better than the Wima MKP. They are certainly far easier and cheaper to find here in Australia. Any experiences?
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Old 5th February 2008, 08:30 PM   #4
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Default Board overview

Board stuffed to analog power supply testing stage.
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File Type: jpg board.jpg (87.4 KB, 6036 views)
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Old 5th February 2008, 08:33 PM   #5
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Default JFET I/V close up

Close up of a partially stuffed section. This is the most densely packed area of the board.
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Old 5th February 2008, 08:51 PM   #6
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I can't see the gold.
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Old 5th February 2008, 09:20 PM   #7
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The pics are a bit low res I guess... the pads are definitely gold plated, and the "bling" white solder masking is very thin and scratches off pretty easily to show gold underneath. Personally I'd have preferred blue or green solder mask and tinned pads.

Attached is a pic of the unused xo clock section showing some pcb bling. When compared to the D1 or Tent Labs dac clocks the xo clock section on the board seems to be missing some essential circuitry to allow the xo clock timing to be adjusted vs the recovered clock. This lack apparently results in clicking on the output when using xo clock. I'm not sure how feasible it will be to implement a piggyback board to get the xo clock working correctly.
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Old 5th February 2008, 09:39 PM   #8
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We used to use clear mask over gold, that way you don't hide
the bling.
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Old 5th February 2008, 09:49 PM   #9
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no point in bling if you can't flaunt it

thinking about the xo clock in the shower, it occurred to me that the main issue is tapping the clock signal across to the xo pinout. I guess I'd need to use mini-coax for the jumper to maintain signal integrity?
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Old 8th February 2008, 04:17 PM   #10
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I met with one of the top engineers at AKM when he was in Silicon Valley a couple of months ago. He said that their testing proved that an inverted white mask (all white with trasparency for text) reduced noise.

-David
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