DIY Modding DAC

[Nearlymusical]

Been messing around this week with some mods that have been suprisingly simple and effective . The jist of it is that unused USB or I2S input on a DAC may be "shorted" out by a home made cannabilsed USB cable / HDMI cable (or plug)

I have both a spare USB input and I2S input on my PS Audio DAC, so since I had a spare printer USB cable I set to giving this a try.

I got all the information on how to do this from the PS Audio forum under the thread "Modding the Directstream DAC"

So for the USB shorting cable

1. Firstly cut off the USB B end off a couple of inches from the plug
2. This should reveal Black,White, Green, Red wires, and metal foil screen and mesh.
3. Strip the ends of the Black,White and Green cables and either twist or (preferably) solder them together.
4. The red wire - the USB voltage carrier - can be left as it is or preferably cut back - but needs to be out of electrical contact with the other elements of the shorted plug
5 Rewrap the foil sheld around the twisted Black white and green.
6 Use tape to insulate

Insert into unused USB Input.

To make an HDMI shorting plug - the easiest way I found was to purchase a plug from Amazon -



In order to make the short plug solder together pins 1 to 12. Leave 13 to 19 and 20 (earth) unmolested.
As an alternative to soldering it also possible to short 1 to 12 together by using conductive adhesive copper tape.( A new find for me)

In both the USB and HDMI short plugs ensuring good shielding is recommended - I found a layer of electrical tape followed by a layer of copper tape, then another layer of electrical tape does the trick for me .

The biggest effect of these Mods is on breadth and width of soundstage. I was quite astonished, and it prompted me to try these Mods also on the unsed inputs of my upstream DDC ( The Audio DG - DI 20) - shorting the USB input on this unit - took things to another level - same wide and deep soundstage but an improvement in tonality of instruments and more precise placement.

For me a Wow result

For more detail and pictures its worth a visit to PS audio. Their digital Guru Ted Smith is the man who suggested this.

[Nearlymusical]

Interesting. Is there any explanation as to WHY this works?

[Nearlymusical]

Good question
This is what Ted Smith siad in relation to the DS DAC

"Without something driving the input wires they may have voltages that keep fluctuating relative to each other so the hardware thinks bits are changing when it’s just input noise. Then the processor has to figure out that those bits don’t make sense and ignore them. This causes random hash on the USB’s power supply."

I was not expecting the same mod to work on the USB of my DDC - so there may be something that is more general - but I havnt seen this as a mod in other fora

[slinger]

That might also explain why plugging AQ Jitterbugs into unused USB ports on streaming units has a beneficial effect on the audio signal.

[Nearlymusical]

Good point - I had'nt made that link - although the Jitterbug is "shorting" an output.
This is more like a USB/HDMI version of those shorting plugs used on unused input phono's on a pre-amp ( e.g Russ Andrews Shorties )
Since I posted a PS forum member has also said this benefits the sound on unused inputs on Denafrips Terminator.
There may be more to this than just a PS - Audio thing.
Assuming anyone has an unused USB input on their DAC Its pretty simple and cheap to try - providing you dont mind canablising a USB printer cable . ( as a starter for ten as it were )
The unfortunate side effect is it set off my Upgraditis and so spent a few days in that loop of incessant tweaking and frustration, where part way through you start not to trust your ears anymore, did have to post in "boozing tonight" part way through.
I concluded that shorting both I2S and USB unused inputs on DAC and DDC had a combined very beneficial effect on my enjoyment of the music, they have stood the test of listening every day for a week now. So these mods stay