Wishes Upcoming PSA DirectStream MKII

I’m sorry, I don’t understand the “fat” transformer reference.

The DS Mk II has the Edcor XS4400 quadfiler audio transformers.
It has custom taller, but not as fat toriodal AC power transformers.
It also has higher bandwidth AES3 and S/PDIF pulse transformers.

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Hi Ted, maybe it is interesting to the forum to share an overview picture of the insides of the MKII showing the digital board, analog board and the power transformer (and perhaps some other components outside the 2 board like filtering caps)?

Here is my current debugging the analog board setup with the digital board upside down giving access to the analog board which is on the bottom (see pictures in links below):


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Very nice layout. It seems that you applied implicit EMI/RFI shielding by using board layout. Is that assumption correct?

And good to see there is plenty of room installing a line output 1:1 transformer of once own choice…

I definitely used space to separate things that need to not interfere with each other. Keeping power supplies away from the outputs, paying attention to the location of components on the digital board vs the analog board, spacing higher frequency traces away from critical traces, using ground fill to help isolate each critical trace… Also, things like being able to power down circuits that aren’t in use (e.g. network upgrade path, USB, I2S…) will help to lower hash in the box.

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Very nice. Thank you for the pictures and explanations. So maybe not enough room to fit an AirLens in there. And maybe not something to be desired. Ditto fitting the MKII into a smaller case itself.

We definitely want to keep streaming hardware out of the DAC box… Anything that can connect to Ethernet requires a fast processor which equates to noise, and certainly Ethernet packet arrival is asynchronous to anything else in the box which also leads to non-white noise. And, yes, extra spacing is good.

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Ted, is it correct that toroidal transformers radiate axiallly? I wonder here and there how they are placed, especially in power amps.

How seriously do you estimate the radiation inside an all in one chassis? Does an aluminum cover protect from the main effects axially?

Yes, toroidal transformers radiate axially. When mounted on the back wall they radiate directly into the audio transformers, not good. The magnetic field falls off quickly radially, so not so much of a problem when mounted on the bottom of the chassis. Even so, in the DS we found that we needed to rotate the power transformer carefully to lower the amount of interference in the (far) audio transformer.

A magnetic field isn’t affected nearly as much by aluminum as steel. That’s one reason to be careful when sticking audio components, if the power transformer in one ends up in a bad place on the unit above or below you can get hum, etc. in your system.

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Thanks Ted! So what would be recommended to put between the toroidal and the audio transformers to improve things?

Regarding stacking components, that’s what I always thought to be honest. I not only wondered about audiophiles doing this all around, but also Paul often mentioned there’s no problem doing it. Many even seem to put power plants on top of racks or inbetween.

From experiments with active HF protection I know how much impact even a normally radiating component, placed alone, has when placed alone between speakers.

All of the different shielding we tried between the AC transformer and the audio transformers when working on the DS made things worse: muffled, rolled off… This happened whether we shielded close to the AC transformer (which does make the most sense) or we shielded the audio output transformers. The people who build the audio transformers probably have already shielded them well and it’s not simple to do better than they can.

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Very interesting!

In the past I made similar mixed experience with mu metal shielding. And in the DS with shielding the audio transformers (removed meanwhile).

So given the DS I with external PSU for the analog board, the only meaningful measure would be to also put the remaining transformer outside the chassis.

Which is why I wondered why some, building a separate PSU for the analog board, put it inside the chassis, too.

Does this mean, aluminum covers for transformers don’t protect at all and are used only for cosmetic reasons? Or they protect less and are a compromise between no shielding and metal shielding?

Aluminum is paramagnetic (Paramagnetism - Wikipedia) and hence reacts quite differently to magnetism than diamagnetic things like steel.

I suspect that the covers you are referring to aren’t pure aluminum. But I’m no expert on shielding.

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Today is a good day to learn…and I still have to get a good part of the latter.

What I was referring to was just what’s usually applied, as e.g. in your picture of the DS II transformer cover.

So I understand, those aluminum covers are used for a better suited shielding than steel would be, but they don’t fully isolate.

P.S. I corrected “metal” to “steel” in the above post, confused it.

The DS Mk II transformers (the XS4400) are shielded by tin plated copper tape (Copper Shielding (edcorusa.com))

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I meant the power transformer.

I don’t know that the power transformer in the Mk II is shielded:

The blueish circumferential wrap feels like paper or foil and is very thin. I’m not sure it’s an active part of the design of the transformer. There is no shielding specified in the request for quote or the returned spec.

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My mistake, I didn’t look close enough and thought this is it.

I was wondering what you saw that I didn’t :slight_smile: That’s a probe for programming and debugging the control processor.

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