Minidsp 2x4 noise floor

[CabinetMakerRyan]

Is that 12v wall wort something you had on hand or did you buy something specific like a high quality class 2 adapter?

 

[Davey]

The tracking issue can be mitigated by using a multi-gang linear pot instead (Bourns PTD904-1015K-B103) and slightly modifying it (credit Rod Elliott). Unless you pay serious money, the standard "log" pot you buy from electronics shops is not log at all, but is comprised of two linear sections, each with a different resistance gradient, resulting in a pronounced 'discontinuity' as the control is rotated. Instead, take a linear pot, and connect a 1% tolerance resistor (10 to 15% of the pot’s value) across its wiper and end terminals. This will achieve a far more logarithmic curve than a standard log pot—a good approximation to true log pot operation is obtained over at least a 25 dB range. Treat all sections of a multi-gang pot the same way.

I still find the tracking issue exists even with linear pots like that. Four sections adds further variables.

The tapering fix is fine, but a higher value control should be selected than the 10k mentioned. (100k preferrably.)
If using a 10k linear pot with an attached 1k resistor, you will have a 1k pot since the lowish output voltage of the miniDSP 2x4 means it will be near maximum setting most of the time.
The miniDSP 2x4 has a 560 ohm output resistance, so you're incurring a nearly 4db signal loss just be attaching the pot. 🙂

Dave.

 

[dotneck335]

Wow---I had no idea that the miniDSP's output impedance was that high!! If that is indeed the case, then you are absolutely right---100K would be a much better choice.

 

[gpapag]

What are you guys using to power the miniDSP? It has a large input range. USB power was very noisy for me so I'm using a 12V adapter. I used a battery once and the noise was very low but that was not a convenient option.

You may like to see some useful details (1st attachment of this post)
http://www.diyaudio.com/forums/minidsp/238892-my-stack-5.html#post3742216

George