Modding the DirectStream DAC

Shielding the display as well as placing absorber and shielding over the noisy digital chips ted identified all help immensely. Even wrapping the Edcor transformers. Dimmed display does little to quiet it.

I’m just responding to a comment about rfi possibly being introduced by putting a lpsu inside the dac. I originally did an external lpsu but I moved it inside later on. I created a box of absorber sheet around the entire analogue board (as well a strategically placed little bits). Also my dac display was shielded when I bought it.

None of that pesky rfi is allowed inside.

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Is there a photo or diagram of the chips Ted identified?

I have a post in here that I gathered up all of Ted’s recommendations. They were locational description’s describing devices. They were easy to find. I believe @jazznut took photos. I didn’t.but performed all the mods.

Haven’t you said an opposite before? Or Am I mistaken?

My earliest statement didn’t take into account the fact that the FPGA needs the clock from the analog card to boot. That overrides other considerations. I corrected myself a little later on the thread.

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Thanks for the clarification.

^^^This is what I was after. I can hear a subtle but noticeable difference when I turn the displays off but wondered what else might still be present. Thanks.

I’m still in Paul McGowan and Ted Smith, for ds users; I believe that by changing the screen and the processor behind it, they will produce an intermediate solution that will support new software. MK2
@Paul @tedsmith

Guys, awesome work and info going on here :slight_smile: Love the thread- Thanks!

My high end audio buddy loves the DS DAC as well (after borrowing mine) and bought one for himself last week.

@Ted please- I’m working on designing a different output stage (filter) for the DAC and may I ask please- what freq actually comes out the high speed switches (and into the transformer)? The PS Audio site says everything is converted up to 20x DSD internally, but I need to know what comes out finally for D2A.

I understand that will likely be generally frowned on here, and that’s ok. I’ll try it, just how I be :slight_smile:

Thanks! Turbo

Quad rate is what comes out of the FPGA: 44100*64 * 4 = 11.2896MHz.

OK got it, thank you chief digital dude.

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I bought my DSD a couple of years ago and never considered modding it until now. It would take me quite a while to read though nearly 2000 replies and I’m wondering if there’s a consensus as to what to modify on the DSD to make it sound even better.

Output transformers on he analog stage, linear power su-ply for the analog stage, 3M shielding for back of screen and 3M shielding on internal chips (not sure on these specifically)

@Ted PS- what do you use for the output impedance from the switches please?

Thanks, T

There are four switches in parallel per channel. Each is balanced and has 75 ohms on each leg. Net is 37.5 Ohms into the transformers. Watch out, the common mode voltage isn’t what you expect (i.e. there’s more than one reason for the transformers.) Don’t take any power from the analog or digital boards.

Ok, thanks Ted!

T

@Ted, can you share how the single ended outs are derived from the differential transformer outs?

Thanks, T

The standard way. The transformer output center tap is grounded. Balanced is across the whole output winding, unbalanced is from one end to ground.

Also shield output transformers completely wrapped.

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