Review and Measurements and miniDSP 2x4 HD DSP and DAC

[mdsimon2]

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.

Why go through all that with exporting a sine wave? Just send a 0 dBFS sine directly from REW.

Do you have any boost applied? I have seen no issues with 0 dBFS test signals to the DDRC. If you need to attenuate to get a clean signal that implies you are applying boost.

EDIT: Or it be could be that you are summing L + R in the mixer which will also require 6 dB of attenuation to get a clean signal.

Michael

 

[GimeDsp]

Why go through all that with exporting a sine wave? Just send a 0 dBFS sine directly from REW.

Do you have any boost applied? I have seen no issues with 0 dBFS test signals to the DDRC. If you need to attenuate to get a clean signal that implies you are applying boost.

EDIT: Or it be could be that you are summing L + R in the mixer which will also require 6 dB of attenuation to get a clean signal.

Michael

REW output for sine wave is DBFS rms and goes up to -3dbfs.

 

[mdsimon2]

REW output for sine wave is DBFS rms and goes up to -3dbfs.

Under Preferences -> View there is an option called "Full scale sine rms is 0 dBFS", if you select that you will be able to output 0 dBFS.

Michael

 

[GimeDsp]

Under Preferences -> View there is an option called "Full scale sine rms is 0 dBFS", if you select that you will be able to output 0 dBFS.

Michael

Thanks! I got to work now but will retest when I get back.

 

[mdsimon2]

Thanks! I got to work now but will retest when I get back.

Curious what your results ended up looking like and what was the reason for distortion above -6 dBFS?

For reference here is what I get from my DDRC-24 at 0 dBFS measured from a MOTU M4.

Michael

 

[mdsimon2]

And lots of monitors have hiss.

The above measurement I posted is hardly stellar and is dominated by noise, using the ADC only hurts noise performance further. How bad that hiss is will largely depend on the gain of the amplifier and the sensitivity of the tweeter. You can pad the tweeter using passive components or use a line level attenuator to help improve performance. I imagine that most monitors with better hiss performance use lower gain amplifiers and/or padding on the tweeter rather than using substantially better performing DSP / DACs.

I did some exploration on audibility of hiss vs SNR at 2 V in the thread below which you may find interesting.

https://www.audiosciencereview.com/...-topping-performance.24768/page-2#post-849537

From a price vs performance perspective not much touches the 2X4HD TBH. Next step up is something like a RPi4 running CamillaDSP with a MOTU M4 but that is more expensive, has limited input options (no TOSLINK input), no master volume control (can be implemented in CamillaDSP), is a much larger form factor and is nowhere near as user friendly. On the plus side you get greatly improved processing power, better THD+N performance, much better ADC and balanced outputs.

Michael

 

[Night&Day]

Curious what your results ended up looking like and what was the reason for distortion above -6 dBFS?

For reference here is what I get from my DDRC-24 at 0 dBFS measured from a MOTU M4.

View attachment 156320

Michael

Would there be any change in noise if 12 dB gain was added to the outputs? My active speakers have some very low noise in the tweeter but there's no noticeable change if I disconnect the miniDSP.

 

[mdsimon2]

When you say 12 dB gain added to the output are you saying boost in DSP? Or are you saying a downstream preamplifier adding 12 dB gain?

If there is no noticeable change when you disconnect the miniDSP to me that says your amplifier has more noise than the miniDSP. Curious what tweeter and amplifier you are using?

Michael

 

[Plcamp]

I did some exploration on audibility of hiss vs SNR at 2 V in the thread below which you may find interesting.

https://www.audiosciencereview.com/...-topping-performance.24768/page-2#post-849537

That is interesting. I battled 2x4HD noise with some success but surely not as good as my DAC.

I never measured 2x4hd noise, but could hear audible hiss at 1m on 95 dB efficient speakers.

After I replaced the provided wall wart power supply with an old linear supply from a ZIP drive, I could no longer hear that hiss. I suspect the hiss involved noise coming from a nearby plasma tv.

I also got audible noise when using pc to USB input, which I could somewhat reduce with ferrite clamps on the USB cable.

My E30 DAC is just…quiet.

 

[Night&Day]

When you say 12 dB gain added to the output are you saying boost in DSP? Or are you saying a downstream preamplifier adding 12 dB gain?

If there is no noticeable change when you disconnect the miniDSP to me that says your amplifier has more noise than the miniDSP. Curious what tweeter and amplifier you are using?

Michael

I meant boosting 12 dB on the DDRC-24. The speakers are active monitors with the amps placed inside the box. The noise isn't very audible and gone in less than two feet.

 

[mdsimon2]

I meant boosting 12 dB on the DDRC-24. The speakers are active monitors with the amps placed inside the box. The noise isn't very audible and gone in less than two feet.

Ah gotcha, in that case not surprising that the DDRC noise is not noticeable as active monitors often have quiet a bit of noise in the base case. If they would have been discrete components it would have been interesting to know the amplifier gain and tweeter sensitivity as a reference point for others.

12 dB boost in the DDRC will not affect noise but you should always be careful when boosting in DSP. If your output signal goes above 0 dB you will clip the DSP (and Dirac can also add up to 10 dB of boost). I assume you are using the DDRC as volume control? Out of curiosity why are you adding 12 dB of gain?

Michael

 

[Night&Day]

I own the DDRC-24 "basic" ie 2x4 HD and it's connected to the balanced inputs on the monitors. Using the consumer setting -10 dB on the monitors adds a lot of noise and the sound quality suffers. Boosting the gain on the outputs on the 2x4 HD 12 dB and adjusting the monitors to the +4 dB setting lowers the noise and improves sound quality. I don't boost but only lowers peaks in the DSP, mainly in the bass.

 

[gasolin75]

Any cheaper alterantive to the mini dsp hd ?

 

[Kontrastimies]

My current setup includes Elac Air-x 403, Elac 2070 and Yamaha Wxc-50 and as the Yamaha preamp doesn’t have good settings to handle the bass integration to the mains, I’ve been looking for a solution to do it and while I’ve done acoustic treatment for my livingroom, I still have standing wave. So, on top of handling crossover etc. I’m looking to get room correction. Other than missing the bass control festures I’m happy with the Yamaha, so I was thinking would the ddrc-24 be a good choise for me or might there be a problem with hissing sound as the mains are active monitors?

Edit: The plan would be to connect the Yamaha to the Minidsp either with toslink or rca and the Minidsp to the 403’s with rca-xlr and to 2070 with rca-rca.

The other option is to change the Yamaha to Minidsp shd. Apparently the Studio is not an option for me as the 403/2070 doesn’t have digital inputs? How big of a difference there would be if I would go for the latter option?

 

[NappyRob]

I have two questions:

1. Can I put a EQ APO profile on the miniDSP?
2. Can I use the same profile without PC?

 

[NTK]

I have two questions:

1. Can I put a EQ APO profile on the miniDSP?
2. Can I use the same profile without PC?

1. Yes. The miniDSP 2x4HD allows you to program a maximum of 10 PEQ's.

2. Once the miniDSP is programmed with a computer, it will work without connected to one. It can also store 4 configurations and they are selectable using the remote control.

 

[beneix]

From a price vs performance perspective not much touches the 2X4HD TBH. Next step up is something like a RPi4 running CamillaDSP with a MOTU M4

Since the 2x4HD has Toslink in and USB I/O, could you not use it together with an RPi running CamillaDSP and just leverage the 2x4HD for input/output duties, not using its DSP processing? I am thinking of either taking a digital signal in via Toslink or an analogue via the 2x4HD's analogue inputs, processing it with CamillaDSP on the RPi and then taking the resulting output from the analogue outs of the 2x4HD. Compared to the Motu M4, this would offer the ability to take S/PDIF in - and be smaller and more unobtrusive.

 

[abdo123]

Since the 2x4HD has Toslink in and USB I/O, could you not use it together with an RPi running CamillaDSP and just leverage the 2x4HD for input/output duties, not using its DSP processing? I am thinking of either taking a digital signal in via Toslink or an analogue via the 2x4HD's analogue inputs, processing it with CamillaDSP on the RPi and then taking the resulting output from the analogue outs of the 2x4HD. Compared to the Motu M4, this would offer the ability to take S/PDIF in - and be smaller and more unobtrusive.

There is very little advantage in using CamillaDSP over the 2X4HD's processing. If you want SPDIF inputs then get something like the Motu Ultralite MK5.

Personally I would not trust my speakers with a CamillaDSP setup without at least passively attenuating the tweeter.

 

[mdsimon2]

There is very little advantage in using CamillaDSP over the 2X4HD's processing. If you want SPDIF inputs then get something like the Motu Ultralite MK5.

Personally I would not trust my speakers with a CamillaDSP setup without at least passively attenuating the tweeter.

I agree, I don’t see why you would use the 2X4HD by itself with CamillaDSP.

As has been documented here many times the 2X4HD has rather high residual noise so depending on your gain structure and speaker sensitivity it is likely you will have hiss. The other issue is that the 2X4HD does not present itself as a 4 channel DAC to CamillaDSP so you cannot apply individual output channel correction. The only potential advantage I see is applying long FIR filters in CamillaDSP upstream of the 2X4HD processing.

The 2X4HD does have some advantages in a CamillaDSP system upstream of another DAC as it has a TOSLINK input and a built in ASRC so you can run CamillaDSP at a constant 96 kHz sample rate.

I personally do not worry much about CamillaDSP volume control, if anything I find it safer than using a miniDSP without a display as it is very easy to setup CamillaDSP so that anytime it starts/restarts it will be at a low volume. In either case adding a display definitely gives some peace of mind that the volume is not inadvertently cranked up.

Michael

 

[beneix]

I agree, I don’t see why you would use the 2X4HD by itself with CamillaDSP.

As has been documented here many times the 2X4HD has rather high residual noise so depending on your gain structure and speaker sensitivity it is likely you will have hiss. The other issue is that the 2X4HD does not present itself as a 4 channel DAC to CamillaDSP so you cannot apply individual output channel correction. The only potential advantage I see is applying long FIR filters in CamillaDSP upstream of the 2X4HD processing.

The 2X4HD does have some advantages in a CamillaDSP system upstream of another DAC as it has a TOSLINK input and a built in ASRC so you can run CamillaDSP at a constant 96 kHz sample rate.

I personally do not worry much about CamillaDSP volume control, if anything I find it safer than using a miniDSP without a display as it is very easy to setup CamillaDSP so that anytime it starts/restarts it will be at a low volume. In either case adding a display definitely gives some peace of mind that the volume is not inadvertently cranked up.

Michael

Thanks for the input. I am just trying to find a reasonably priced total solution to take a digital 2-channel (no sub) signal, apply room correction and output this as an analogue 2-channel signal. If the 2x4HD has poor performance from a noise/hiss perspective, then I would be looking for something to combine with an RPi running CamillaDSP. Here, finding something that takes an S/PDIF input and sends it to the RPi, for this to be room corrected, and then something that takes the resulting digital signaland turns it into an analogue signal, is proving difficult. That's why I am trying to be creative.