Any measurements on the MiniDSP

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This is not really relevant to the OP, but since I have your attention:

I have the 2/4 miniDSP in a box. It is now revB. The difference between the revA and the revB being the position of a jumper switch. RevA has 0.9v input, revB has 2.0v input. Output remains 0.9v.

My question is: If I feed the miniDSP with SPDIF, either 44.1 or 48k and either 16 or 24bits, it will directly convert that to floating point and proceed. Correct? Also, what happens if I feed the miniDSP 88.2 or 96K?

The point of order here is my computer does not have SPDIF out, so I am contemplating the purchase of a USB-SPDIF converter to avoid the DAC>ADC conversion.

Thanks.
Bob

Both the 2x4 and 2x2/4x10 boards have an internal sampling rate that is fixed by the plug in that you use. 2x4s only offer 48kHz IIRC and the 4x10 and other have both 48kHz and 96kHz plug ins depending on what the plug in does.

To supply an SPDIF signal to a MiniDSP board you need an SPDIF receiver and a sampling rate converter that converts the incoming SPDIF signal into I2S at the correct rate. MiniDSP offers the DigiFP board for the 4x10 and the MiniDIGI for other applications.

All rates must be converted up or down to the internal rate. It therefore doesn't make much sense to use a higher rate from your source, just use whatever rate that the MiniDSP is operating at.
 
It can get a little confusing. :) The earlier 2x4 units were not jumper-configurable with regard to the input pad, so you had to order either RevA (0.9 volt input) or RevB (2.0 volt input) and you were locked in. I think they quickly realized the problem with this configuration and dispensed with the two versions and started offering just one that had a jumper onboard that could be configured either way.
The "in a box" units were available either way as well. :)

Indeed! I bought a revA and immediately saturated it. The biggest problem is getting into the box was trying to remove the tiny Phillips screws. The heads would strip before the screw could be removed. Anyway, I did get in and swap the jumper. I now have a revB.

S/PDIF inputs/outputs are not directly supported without adding some more hardware.

I guess that you are right. There is no reasonable way around the DAC>ADC conversion. At least the miniDSP ADC>DAC pair seems to be quite good.

Thanks for your help.
Bob
 
Why does everyone keep saying the output is 0.9 volts when documentation suggests its 2.0volts

Everyone is NOT saying that. :) There are still two different versions of the 2x4 unit available and since the unbalanced output unit was available earlier I suspect there's many more of those is field use.

Please take a look at the model comparison.

miniDSP Kits | MiniDSP

Dave.
 
However, it will improve the signal to noise.

Yeah, it will, but enough to warrant all the extra work/circuitry you'll need to fabricate? I suspect your S/N ratio will not be improved nearly as much as you think it will. And unless you're going to make it remote-controllable, probably pretty inconvenient as well.

Multi-channel volume controls make perfect sense with gadgets like the (unmodified) DCX2496 which operate at voltage levels not suitable for domestic applications. In that aspect the miniDSP units are at least a step in the right direction, but still with some tradeoffs that need to be understood.

I built an SSM2018-based VCA volume control for my DCX2496 about ten years ago. Certainly a valid solution and it worked well, but I ultimately decided to modify the DCX itself and abandon the VCA volume control.

Cheers,

Dave.
 
You may be correct. As I mentioned, however, this is an experimental system and I want to find out whether that's the case. I am bi-amping and I want to try some room EQ; the MiniDSP seems like a good way to play.
I built an SSM2018-based VCA a while back, with mediocre results - very prone to noise pickup on the control line. After reading Rod's article I can see where I might have done better.
If I decide that I need analog volume control after the DSP in my final arrangement, I may end up using another solution, perhaps controlled by a micro.
 
Measurement footnote: in the course of other testing, I eyeballed square waves emanating from my Apple MacBook headphone jack using REW. Looks about the same as the miniDSP 2x4. And output from an iMac (a kind of external USB sound card) is worse. Sine waves from the headphone jack and iMac are pretty flat to 10 Hz.

B.
 
Very educational to actually measure how many volts are going into your speakers, not to mention finding out what the various components are using. My pre-amp is rated 1.0vrms output but puts out a clean 5vrms.

You know why amps with power output displays often have a "x .1" display option? It is because those amps are never called on to go over a tenth of their power and the pretty display would never budge otherwise.

Do you know how many acoustic watts a jet airliner puts out? Might be a whole lot less than your amp is rated for multiplied by the efficiency of your speakers.

Ben
 
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