Modding the DirectStream DAC MKI

The dimensions of the slot sets the lower bound on the frequencies that can pass straight thru. http://cdn.lairdtech.com/home/brandworld/files/EMI%20Rule-of-Thumb%20for%20Calculating%20Aperture%20Size%20Technical%20Note%20Download.pdf

I can’t help as much as to what interference frequencies are worst for the DS. For the TSS we intend to use a wire mesh and try some different sizes.

My DS and DS Jr have been open on the top for their whole lives so I wouldn’t worry too much about dust (unless when you dust the top you accidentally shovel that dust into the slots.)

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Wow, I didn’t know such calculation exits!

My slots would be matching the middle one of the examples on your linked site, like those I used for my replacement of the original chrome decorative preamp cover on top of the main casework.

My DS is now also open for several months, but it’s enough now, I think I give the laser cut a try :wink:

Mine has a block with a brass screw that adjusts vith a mall flat screw driver that tweaks votage up and down. That might be another optimization point. I recall a DS post by Ted that talked battery power and voltage affect on the sound. Seemed you might be able to push it up a half volt or so for maybe better faster sound.

After a month of receiving the transformers I decided to do the upgrade on my DSD. Desoldering and soldering went without difficulty. After I put it all back together and went to test it my left channel sounds a significantly lower volume than the right. I tested this with different amplifiers and speakers to make sure It wasnt something else. I also connected other components to my BHK preamp that dont use the DAC and my balance is good with them. It all goes down to the modified DSD. Any ideas what could be happening here? Could I have gotten a defective transformer? Thanks in advance!

You didn’t explicitly state that the balance control on the DS was even. Otherwise all I can think of is that one of the new solder joints is cold. If any are not shiny they probably need to be resoldered.

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The balance setting on the DSD is correct. To actually get an equal volume I have to reset it to 80 on the left and 60 on the right. Will check the solder joints again. Thanks for your quick response and help.

Checked all the solder connections. Touched them up and are all shiny and look very secure. The problem persists. Left channel volume continues to be much lower than the right. I can even them out with the DSD balance function but something is definitely not right. Any other possible causes that you could think of? Could a defective transformer do this? Thank you again and sorry to bother you.

Maybe desolder and swap the transformers?.

There’s always the chance of a defective transformer, but it doesn’t seem like the most probable item. Check the transformer wire connections to the transformer leads, if the leads got too hot during soldering that could have been a problem. (Not really likely, but it’s worth checking.)

Can you engage the 20dB attenuator and note the levels? Then disengage it and check the levels again.

With the Preamp set at 100 and the DSD at 80 I get the following readings:
Attenuator off: Right=84-92dB Left=77-84dB
Attenuator on: Right=68-82dB Left=61-68dB
Thanks again

Did you switch cabling for test? Just in case something went wrong with your signal,cabling…

I thought there was a chance that the attenuator relay might be having a problem, but that’s not it. I’m out of ideas at this point. I’ll think about it.

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I would check the transformer windings with an ohm meter first. Maybe you can do this in circuit?? Ted may know if any relays would short out the transformer windings when powered off.

Definitely the output windings is shorted when powered off.

Sounds like the transformers need to be pulled and tested. 116 Ohms (each winding)

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Did switch cabling and it did not change anything…

One more thing to check is make sure that no solder bridged past the round solder pads. There are traces real close the them. Check with good light and a magnifying glass. Check carefully on the channel that is attenuated.

Maybe Ted knows if hurting the multilayer board when soldering too hot/long could have caused this. But you’ll only know for sure after switching the transformers.

Any damage from too much heat should be visible by eye on the outer layers. Checking the pads for solder whiskers to the local traces is a good idea.

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I would only de-solder and remove the one that is attenuated and check it with an ohm meter only after close inspection of the solder pads to make sure there is no solder bridging to the traces that are close by.