Experience with this DIY DAC ?

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#2,685
Bill Fuss said:
but I do have a Squeezebox for internet stations. I haven't even opened the case of that yet.
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I wish you would. I would like to run I2S out of mine but I have no idea how to go about it. I was given the following info on another forum.

I2S can be tapped off the DUET fairly easily. Hooking it into a DAC is where the problems occur. It is not a good idea to run over I2S 6". Too much noise will enter into the lines. The signal lines need to be very short with no breaks. If you plan to put the DUET circuit board inside the case with the DAC, this could be done.

You would then have problems with noise generated by the Wi-Fi board and the internal switchers in the DUET Receiver.

I think John Swenson did end up running I2S out of his DUET into a custom DAC. After many months of trying to get the wiring dressed correctly and dealing with the noise pick-up, he concluded it was not really worth it. The SP/DIF as good, after simple mods.
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#2,686
Yeah, that's pretty much why I haven't fooled with it. The PS audio solution may be worth the effort though. I'll probably try it but have no immediate plans. SPDIF has so many inherent problems that getting it perfect takes a bit of test equipment. The signal bouncing back and forth in the line definitely affects the sound, but the resolution of the rest of the system (or lack thereof) could lessen the percieved imperfections. I'm speaking jibberish, ain't I, but you know what I mean.
 
#2,690
Hi guys:

I have the big gigaworks DAC and just received the 24/192 version with the PCM 1798 chip. Unfortunately, it arrived with the C23 cap dangling by one lead from the board. I'm a novice, so wondering if I can simply heat a drop of solder and reattach the cap. I'd hate to have to go through a return with this thing.

Thanks in advance for your advice.

Here is a link to the DAC on ebay: 2010 version 24bit/192khz DAC with fully assembled kits - eBay (item 160431534154 end time Jun-04-10 13:02:49 PDT)
 
#2,691
stc4life said:
No sound. But curiously, when I switched it off I had the it still hooked up and I heard a strange sort of sweep across the audio spectrum (from high to low). Maybe some caps discharging?

The transfo should be hooked up like below, correct?

+ from 4398 --> 1
- from 4398--> 4
RCA + --> 5
RCA - --> 8

EDCOR - XSM10K/10K

Maybe the + and - are mixed up, which I will check tonight. Would that matter?
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So I am totally stumped. I still cannot get any sound. I don't know what could be the problem 🙁

To recap: The only real mod is that I removed the caps after the 4398 and soldered leads from the top of the board to the transformers. Using 13k resistor and 680uf cap across the primaries and have the standard resistor and cap combo on the secondaries.

I am getting a fairly uniform voltage at the primaries and at the top of the 4398 board - they do not really seem to be jumping with the music, but are different for different tracks (usually between 1.5v-2.5v, which seems right). I am getting nothing at the secondaries and no sound. Also, no sound if I bypass the transformer entirely and hook it directly to the rca. I get a strange descending sweep of the spectrum when I power down, but otherwise no sound.

I am getting about 5v at pin 22, 4.5v at pin 27, and 3.30 at pin 7 on the 4398 board. I am getting 5v at the caps following each of the 317 regs. Another strange thing is that I am getting opposite voltage readings at the same points if I use the ground on the IEC or the ground on the board.

I am getting to my wits end... Anybody have any ideas or something else I should check? 😕😕😕
 
#2,692
The strange desending sweep is the dac screaming when you power down. That's why the muting relays are there. It really seems like your transformers are attached correctly but you have inadvertantly switched the dip switches near the dac chip. If you flip the two on the right to anything buy both openyou will get no sound. Check them carefully.

Sheldon
 
#2,694
stc4life said:
So I am totally stumped. I still cannot get any sound. I don't know what could be the problem 🙁

To recap: The only real mod is that I removed the caps after the 4398 and soldered leads from the top of the board to the transformers. Using 13k resistor and 680uf cap across the primaries and have the standard resistor and cap combo on the secondaries.

I am getting a fairly uniform voltage at the primaries and at the top of the 4398 board - they do not really seem to be jumping with the music, but are different for different tracks (usually between 1.5v-2.5v, which seems right). I am getting nothing at the secondaries and no sound. Also, no sound if I bypass the transformer entirely and hook it directly to the rca. I get a strange descending sweep of the spectrum when I power down, but otherwise no sound.

I am getting about 5v at pin 22, 4.5v at pin 27, and 3.30 at pin 7 on the 4398 board. I am getting 5v at the caps following each of the 317 regs. Another strange thing is that I am getting opposite voltage readings at the same points if I use the ground on the IEC or the ground on the board.

I am getting to my wits end... Anybody have any ideas or something else I should check? 😕😕😕
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Your voltage readings are confusing me. On the DC scale you should read zero across the primaries at all times. On the AC scale you should only get a reading when there is a signal present. Sorry to be this basic but it must be confirmed before proceeding.

The 13k R and cap is for the trafo filter, it should be on the secondary. Are you sure you have not damaged the traces when you removed the caps, they are very fragile.

Do you have the input jumpers set correctly.

Have you tried bypassing the upsampler board.

What is this standard cap and R on the secondary that you speak of.
 
#2,698
stokessd said:
The strange desending sweep is the dac screaming when you power down. That's why the muting relays are there. It really seems like your transformers are attached correctly but you have inadvertantly switched the dip switches near the dac chip. If you flip the two on the right to anything buy both openyou will get no sound. Check them carefully.

Sheldon
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Thanks. I kind of though that was the reason for the descending sweep. I have the switches set as: 1 up, 2 down, 3 down, 4 down. Is that not right? This is what I saw in all the pictures (I don't have a computer that can read the mini-CD I got with the DAC).
 
#2,699
Ryssen said:
Du you have opams still on the board?You could check if you get sound through them,then you´ll know if the DAC is allright.
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Thanks Ryssen. I actually removed the caps after the 4398, but I will try jumpering those connections if I still cannot get sound after trying some of the other tweaks suggested. I think the first change will be to switch the filters on the primaries and secondaries, which are wrong.
 
#2,700
Bill Fuss said:
Your voltage readings are confusing me. On the DC scale you should read zero across the primaries at all times. On the AC scale you should only get a reading when there is a signal present. Sorry to be this basic but it must be confirmed before proceeding.

The 13k R and cap is for the trafo filter, it should be on the secondary. Are you sure you have not damaged the traces when you removed the caps, they are very fragile.

Do you have the input jumpers set correctly.

Have you tried bypassing the upsampler board.

What is this standard cap and R on the secondary that you speak of.
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Hi Bill, thanks for the advice.

I should have said that I get 1.5-2.5vdc from either of the primary connection points at the trafo.

I definitely mixed up the filters at the trafo, so the first thing I will try is switch those. The traces where I removed the caps seems fine (I am getting the same vdc readings there as at the trafo primaries. But I soldered my leads from the top of the dac board, so I was assuming that they would not matter anymore.

I will double check the input jumpers. Are those the jumpers by the 13v input?

Bypassing the upsampling board is definitely on the list of things to try, I suppose this will let me eliminate that board as the culprit.

I had these messed up. I am going to try 510R on primaries with 0.001uF across. Then I will use a 13k resistor and 680pf cap across the secondaries.
 
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