D1 I/V Stage Finished. - diyAudio
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Old 14th March 2004, 11:31 AM   #1
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Default D1 I/V Stage Finished.

After a long time I almost have my boards ready.
I am using till now an Upsampling DAC from Elektor magazine but I want to replace the analog stage because it has opamps with something better.

I made a stereo version of the D1 I/V stage on one board direct for tweaking CD Players and DACs.

My Dac has 2 PCM 1704 and 4 opamps for the I/V and filter stages.

I will be posting pictures later on.
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Old 14th March 2004, 12:14 PM   #2
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This the PSU.

I use here 4x 11DQ10 Schottky diodes. MKP Wima across them and Panasonic FC caps. The ICs arenīt on the PCB yet.
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Old 14th March 2004, 12:18 PM   #3
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This is the actual stage with two stages on one PCB. You could actually use it for balanced signal also.

I use the signals singel ended so use only one board.
The Mosfets are missing from the PCB but all other parts are on it.

Silver Mica CAPs for the filter part. Audyn 4,7uF in series with the output. Welwyn 1% low noise resistors. Panasonic FC electrolytics.
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Old 15th March 2004, 10:16 PM   #4
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Quote:
Originally posted by promitheus

The Mosfets are missing from the PCB but all other parts are on it.
I was wondering where those FETs were. Need to read the text before I look at the pretty pictures.

I was looking to do something very similar myself to an old Denon player, D1 output + 1704, balanced out. Do you have your DAC board documented anywhere?

Keep us informed.

Rob
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Old 15th March 2004, 10:20 PM   #5
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I will be posting more info soon.
Gerber files an so on.

The Mosfets are missing because I donīt have the heatsinks yet. Or maybe I will use them without heatsinks. I donīt know yet.

The I/O stage is exactly the same from Nelson Passīs D1 DAC.
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Old 16th March 2004, 04:48 AM   #6
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What transformer are you using?
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Old 16th March 2004, 08:17 AM   #7
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I will be using a small toroid 2 x 30 V / 30VA.
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Old 18th March 2004, 09:01 AM   #8
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So itīs finished at last. I could only test one channel for the moment because I have to make some changes on the DAC board.

I took the opamps off but I have to desolder a few resistors and capacitors or they will effect the signal.

Setting the DC voltage of the input isnīt so easy and stable as I thought but it stays in the range +/- 10 mV.
Does anybody know how much this should be max. ?

It doesnīt effect the sound though which I can say is super super clear.

I also made a few corrections on the PSU after burning 2 diodes in the bridge. Thatīs what happens when you try to test it 2:00 clock at night.
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Old 18th March 2004, 09:03 AM   #9
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I am also waiting to get to bypass caps MKP which are missing there in the middle.
I thought it would be good to parallel them with the electrolytics. The Panasonic FCs that are lying there.
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Old 18th March 2004, 09:07 AM   #10
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The inputs are at the top of the picture and you can see in the top corners the 2 small trimmers. With these you set DC offset at the input to 0V.

I use the PCM 1704 which has a current output like many DACs and the voltage there must be at 0 Volts.

The outputs are at the bottom where the 2 Audyn Caps are.
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