Review and Measurements and miniDSP 2x4 HD DSP and DAC

[Plcamp]

2x4hd specs say (default setting) 2v rms in gives 2v rms out...unless you set the input sensitivity (internal) switch to 4v rms input.

Regardless, the output is 2v rms at 560 ohms and can drive a power amp fully, and can therefore be used as a preamp. Used it that way for years.

I never used analogue inputs, always toslink or USB audio.

I always followed the rule of “no net DSP boost” to assure

 

[mattf]

Unfortunately, I do not have any of those around. Any links to something I can buy today with similar characteristics?

It's been a while since you posted, but I'm running a MiniDSP 2x4 HD with this wart from iFi: https://www.amazon.com/gp/product/B01LZD8SHJ/ref=ppx_yo_dt_b_asin_title_o01_s00

It's even half the price I paid 1 year ago. I *think* it sounds better, but I can't prove it because it's difficult to A/B this thing when it has to reboot between power switch changes. I also put a USB isolator from HifimeDIY between my streamer (a Raspberry Pi) and the MiniDSP. I think these two "hacks" help the analog side of the MiniDSP a lot. And finally, on the digital side, I pre-convert all audio to 24/96 in the Pi, which has the horsepower to do it. There is a link earlier in this thread to another thread (here: https://www.audiosciencereview.com/forum/index.php?threads/measurements-of-minidsp-2x4hd.2459/page-3) that describes the onboard resampling/upsampling as poor.

FYI

 

[milosz]

I have run some measurements and no power supply- from the cheapest wall-wart to my sophisticated lab supply - has made any difference in measurement of my minidsp.

I do sometimes use USB isolators to break ground loops, though. You don't need any instrumentation (generally) to hear when your PC or pi streamer is coupling the high harmonics of the AC line into your audio chain. In some cases this is being carried along the shield of the USB cable, sometimes by the ground pin of the USB interconnect. In such cases one could put the offending PC or whatever on an AC power isolation transformer (kind of an expensive way to break a ground loop) or use a galvanically isolating USB coupling.

 

[Juhazi]

My Minidsp 4x10HD's original transformer started to overheat and I replaced it with some leftover laptop unit. To my surprise noise in right channel speaker disappered. Obviously the faulty unit radiated noise to the amplifier box of the right side active diy speaker nearby. Amps are B&O ICEpower units.

I have had no noise or hum problems with my three 2x4HD units, be source analog or USB. Best to use those shielded subwoofer-RCA cables anyway.

 

[jgazal]

I would like to use two 2x4 units as stereo active crossovers and to manage multiple subwoofers.

If I use a toslink splitter with short optical fibers, which configuration is better?

unit A running both channels
output 1 HF right
output 2 HF left
output 3 LF right
output 4 LF left

unit B running all subwoofers
output 1 SW x
output 2 SW y
output 3 SW z

or

unit A running right channel plus subwoofers
output 1 HF right
output 2 LF right
output 3 SW x
output 4 SW y

unit B running left channel plus subwoofer
output 1 HF left
output 2 LF left
output 3 SW z

 

[milosz]

Hmmm. I think the first option with the LF & HF for both channels on one DSP unit and the other DSP unit handling subwoofers would be better.

I think there could be very slight timing differences between the two MiniDSP's ( maybe? ) and with one unit handling all the "main channel" audio you could be assured that imaging wouldn't be impacted by any such differences between the two MiniDSP's, and any overall differences that might show up would only show up between "main channel" audio (LF+HF to your biamped speakers) and "subwoofer channel" - and I think using the MiniDSP delay settings you would be able to compensate for anything that would be perceptible between LF+HF and sub channels.

But in reality you might find that there is little or no audible difference between the two options. MAybe the two MiniDSP's will operate close enough together in the time domain that you can't hear any artifact.

 

[Plcamp]

I would like to use two 2x4 units as stereo active crossovers and to manage multiple subwoofers.

If I use a toslink splitter with short optical fibers, which configuration is better?

unit A running both channels
output 1 HF right
output 2 HF left
output 3 LF right
output 4 LF left

unit B running all subwoofers
output 1 SW x
output 2 SW y
output 3 SW z

or

unit A running right channel plus subwoofers
output 1 HF right
output 2 LF right
output 3 SW x
output 4 SW y

unit B running left channel plus subwoofer
output 1 HF left
output 2 LF left
output 3 SW z

If you do this, how do you control the output volume? Do you have a method to control volume of the optical in?

 

[milosz]

I assume your MiniDSP units have provision for volume control. The MiniDSP's I've use allow you to use a 10k pot between Vcc and ground with the pot's wiper providing a variable DC voltage to the MiniDSP which controls the level of the output. These can be ganged together. So you can have as many MiniDSP's as you like controlled by a single easy to use volume control.

 

[Plcamp]

I assume your MiniDSP units have provision for volume control. The MiniDSP's I've use allow you to use a 10k pot between Vcc and ground with the pot's wiper providing a variable DC voltage to the MiniDSP which controls the level of the output. These can be ganged together. So you can have as many MiniDSP's as you like controlled by a single easy to use volume control.

I have seen no such provision on minidsp 2x4 HD.

 

[jgazal]

If you do this, how do you control the output volume? Do you have a method to control volume of the optical in?

I was thinking of using the IR remote control. At least, according to the manual, once “configuration is complete, the computer is not required and can be disconnected. An infrared remote can be used to control volume, mute, preset selection, and input selection”.
There is a risk of changing volume of one unit only if the IR of the other unit does not receive the signal, I guess. Both unit will be side by side.

 

[Plcamp]

I was thinking to use the IR remote control. At least, according to the manual, once “configuration is complete, the computer is not required and can be disconnected. An infrared remote can be used to control volume, mute, preset selection, and input selection”.

You are counting on both units receiving IR commands identically…I suspect volume would imbalance most time you tried to use it.
This limitation made me conclude with two 2*4’s you or forced to use the analogue in, and control volume from the feeding preamp.

 

[jgazal]

Perhaps I should leave the crossover unit variable and the subwoofer unit at a fixed level. I would need more bass at lower level anyway. But that indeed hinders volume control.
I could use the variable analog output from my tv instead as @Plcamp suggested.

 

[Plcamp]

Perhaps I should leave the crossover unit variable and the subwoofer unit at a fixed level. I would need more bass at lower level anyway. But that indeed hinders volume control.
I could use the variable analog output from my tv instead as @Plcamp suggested.

TV Analog is poor audio quality on my 65” Bravia 900F (would like to see an ASR review of tv DAC quality)…so watch out for that.
I really don’t see a usable dual 2*4 absent of limitations too annoying to consider. I was hoping minidsp might come out with an SH DAC quality 2*8 just for folks like me who enjoy playing with crossovers. So far, no.

 

[Chromatischism]

I was thinking of using the IR remote control. At least, according to the manual, once “configuration is complete, the computer is not required and can be disconnected. An infrared remote can be used to control volume, mute, preset selection, and input selection”.
There is a risk of changing volume of one unit only if the IR of the other unit does not receive the signal, I guess. Both unit will be side by side.

Use an IR repeater system with the sticky flashers on the MiniDSP units and they won't miss.

 

[Plcamp]

Use an IR repeater system with the sticky flashers on the MiniDSP units and they won't miss.

There’s a good idea! Also allows them to be hidden.

 

[milosz]

I have seen no such provision on minidsp 2x4 HD.

You are right I was thinking of the earlier MiniDSP 2x4 products.

 

[Kevmoso]

Is there any reason to think the 10x10HD would perform any better than this 2x4HD tested?

 

[DWPress]

Is there any reason to think the 10x10HD would perform any better than this 2x4HD tested?

There was a thorough review of the 4x10 at DIYGeezer but the site is down. I found it through the internet archive though and it can be viewed here:
https://web.archive.org/web/20180411215137/http://diygeezer.com/minidsp-4x10-hd-review/

 

[rvsixer]

Is there any reason to think the 10x10HD would perform any better than this 2x4HD tested?

Likely:
https://neurochrome.com/pages/minidsp-4x10hd

 

[GimeDsp]

I just measured my ddrc-24 and I am not sure if I did it right. here is what I did:

1. Export 1k sine wave from REW at -10dbfs rms
2. In Audacity normalize to -0.1dbfs peak
3. send out full signal to zoom h6 set gain to get -15dbfs signal
4. view in REW RTA spectrum

when doing it this way the MiniDSP will not show a clean signal until I lower the signal coming out of it to -6dbfs exactly.

I plugged in my sankrit 6th DAC to test and it could output the full signal up to -0.1dbfs with no issue
Will post a screengrab later.