Experience with this DIY DAC ?

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#1,301
Help!!!

I've got the DAC all set up w/ A-20's and optical input connected. When I turn it on there's buzzing and then clicking noises. I can only faintly hear music after a few seconds and the clicking continues and the buzzing. Sometimes the music stutters like it's trying to process it. Any ideas what's going on?!🙁
 
#1,303
jkeny said:
I also wanted to try to bias the transformer on the secondary side to 2.5V on the CT so I can avoid a DC blocking capacitor on the input of the Tripath amplifier which would have 2.5 V on each input lead if not for a blocking cap.

If I want to also try 1:2 configuration of the Transformer I need to turn it around and use the secondary connected to my DAC & the primary feeding the amp because it has 2 windings each with a center tap & I will be using one only with it's CT connected to bias.

Diagrams attached

Edit: Thanks Bill, cross posting happened. I have my Slagle trafo wired with 2K across the primary (I picked up this notion from somewhere?) & it sounds wonderful. There may well be a bit more HF on the Slagle trafo - this would be the Nickle core & bifilar winding of the Slagle, I presume & not the 2K Racross the Pri? I should take this out now & put a 1K in series on each primary leg as per the LL1517s
Click to expand...

So I bought some LL-1517 Lundahls and I'm ready to experiment 😀.

But would somebody give input on the best setup regarding resistor values.

It's going to be used with a shigaclone ->the CS4398 DAC in this thread with the LL-1517 Lundahl transformers as output (un-balanced) -> T-amp (no biascap mod, just plain use as normal).

Should I use 2x1K in series with the primaries like with the PCM chip or does someone have a better proposition? 🙂


Also I had to buy a few more Lundahls than I needed so if anyone is interested I have a few for sale. 1 pcs = £30 or $50 or 34 euro. Just pick the one cheapest for you.
 
#1,304
Bill Fuss said:
Sounds like you are on the wrong chip settings, which board do you have.
Click to expand...

Hi Bill, I've got the board w/ the usb:

I've got the daughterboard installed and chip settings are per the diagram. I've played w/ the chip settings and the other setting just give me hiss.

I've got 220Rs on each primaries w/ a .01uf cap between them and 1k on each secondary.
 

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#1,306
Bill Fuss said:
I suspect the problem is on the digital side, check that the jumpers are making good connections. Try a different source if you have one.
Have you made any other mods.
Click to expand...

I changed the source this morning, switching from my WDTV/HD optical out to my receiver's optical out. The music was still very faint but I didn't hear any of the stuttering. No clicking this time.

Strangely the buzzing is audible even when I turn the dac off. But disappears when I unplug the ac cord, so maybe the buzzing is grounding related?

No other mods were made
 
#1,307
Havoc08 said:
So I bought some LL-1517 Lundahls and I'm ready to experiment 😀.

But would somebody give input on the best setup regarding resistor values.

It's going to be used with a shigaclone ->the CS4398 DAC in this thread with the LL-1517 Lundahl transformers as output (un-balanced) -> T-amp (no biascap mod, just plain use as normal).

Should I use 2x1K in series with the primaries like with the PCM chip or does someone have a better proposition? 🙂


Also I had to buy a few more Lundahls than I needed so if anyone is interested I have a few for sale. 1 pcs = £30 or $50 or 34 euro. Just pick the one cheapest for you.
Click to expand...

I started with 270s on the primaries then tried 500 and 1k, I liked 500 the best, with a 500pf cap across the primaries. Secondaries straight to the output with a 1Kohm/.001uf RC filter across the jacks. Works for me, YMMV
 
#1,308
wushuliu said:
I changed the source this morning, switching from my WDTV/HD optical out to my receiver's optical out. The music was still very faint but I didn't hear any of the stuttering. No clicking this time.

Strangely the buzzing is audible even when I turn the dac off. But disappears when I unplug the ac cord, so maybe the buzzing is grounding related?

No other mods were made
Click to expand...

You have more than one problem I suspect. Can you take the time and make a detailed drawing of every single connection you have made. Part of it is a ground loop, but not everything.
 
#1,310
First off, on the a20s do you have 3 connected to 4, and 9 connected to 10. You won't get anything if you don't.
Is your chassis properly grounded.
Whats the switch for, and are you sure it is wired correctly.
The RCAs should be isolated from everything but the a20s and not wired together, possible ground loop.
 
#1,312
Bill Fuss said:
First off, on the a20s do you have 3 connected to 4, and 9 connected to 10. You won't get anything if you don't.
Is your chassis properly grounded.
Whats the switch for, and are you sure it is wired correctly.
The RCAs should be isolated from everything but the a20s and not wired together, possible ground loop.
Click to expand...

Yes, 3/4 and 9/10 are connected. Actually came that way. Chassis is plastic. I have the DAC board grounded to a screw in the chassis. I assume you mean the DPDT switch. It's a stand-in for a Grayhill rotary switch. I swapped the rotary for the dpdt in case that was the issue. However, I get the same results either way so yes, I believe it is wired correctly.

I'll check out the RCA isolation. The ground loop I'm sure I'll track down. The faint audio is where I'm stumped. I will clean the jumpers on the board and do some more investigating tonight. I'll also order some jumpers so I can pull of the daughterboard and see what happens if I skip the upsampling. As well as test the coaxial input.

thanks for your help.
 
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