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Review and Measurements and miniDSP 2x4 HD DSP and DAC

Ruhled

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Just FYI my 2x4HD is dead silent on 105db horns. Okay maybe a little hiss if my ear is literally right in the horn but certainly nothing from a meter or more. I keep reading about how noisy it is but it just isn't so. I have no attenuation before the compression drivers either. Don't let rumors of noise issues hold you back from exploring a 2x4HD. If someone has excessive noise it's something else. I've tried several other active solutions before landing here and it's by far the quietest I've experienced in my system.
 

muad

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Just FYI my 2x4HD is dead silent on 105db horns. Okay maybe a little hiss if my ear is literally right in the horn but certainly nothing from a meter or more. I keep reading about how noisy it is but it just isn't so. I have no attenuation before the compression drivers either. Don't let rumors of noise issues hold you back from exploring a 2x4HD. If someone has excessive noise it's something else. I've tried several other active solutions before landing here and it's by far the quietest I've experienced in my system.
Thanks for this... I have been on the fence for years now over the mixed reaction to amir's review. Some people love it and other claim its complete garbage... I do find in audiophilia some peoples neuroses tends toward exaggeration.

I really don't want to spend minidsp flex level of money. But this thread has made me hesitate on the 2x4HD
 

Chromatischism

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Just FYI my 2x4HD is dead silent on 105db horns. Okay maybe a little hiss if my ear is literally right in the horn but certainly nothing from a meter or more. I keep reading about how noisy it is but it just isn't so. I have no attenuation before the compression drivers either. Don't let rumors of noise issues hold you back from exploring a 2x4HD. If someone has excessive noise it's something else. I've tried several other active solutions before landing here and it's by far the quietest I've experienced in my system.
Do you have a quiet room?
 

mdsimon2

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Whether or not the noise is unacceptable depends on a lot of factors. Many people use the 2X4HD without issue but some find the hiss unacceptable, especially those listening nearfield with high gain amplifiers. Objectively the 2X4HD has high noise compared to even middle of the road stand-alone DACs, if you want to see how this manifests itself after a 26 dB amplifier take a look at this thread -> https://www.audiosciencereview.com/...a-with-topping-performance.24768/post-1009248.

Maybe try out there 2X4HD and if it works for you great, if it doesn’t add a low cost high performance USB DAC like a Topping D10, you can still use the 2X4HD as a TOSLINK input but route the signal to the D10 via CamillaDSP. Other options would be Hifiberry digital input HATs like the Digi+ I/O or the DAC+DSP with a USB DAC and CamillaDSP. I’ve tried both of these out and they seem to work fine although the Digi+ I/O doesn’t have an ASRC so you will need to feed it a constant sample rate and the DAC+ DSP is a bit of a pain to setup, the 2X4HD is much more plug and play and comparison.

Michael
 

Yutaka IIDA

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This is a brief review and measurements of miniDSP 2x4 HD Processor and USB DAC. I purchased this online and seems like the price as of this writing is USD $207 as of this writing. This is a USB DAC with Toslink optical input and analog/digital in, four channel digital signal processor (DSP).

The DSP features can be used to implement everything from active speaker crossovers to full room correction/equalization. While the former functionality is easy enough to implement, the latter is up to you to program. This is a "raw" platform with no intelligence of its own. If you want room equalization, you have to figure out how to program its individual parametric filters or FIR parameters.

The unit comes in a shiny aluminum case that feels decent and has just enough weight to not get dragged too badly by the myriad of connections you would have to hang from it:


Above, I have the USB cable on the right, then Toslink and a couple of "monster cable" RCA interconnects. As you can see, my fat Toslink cable and USB barely fit next to each other.

There is an IR input which I did not test (no remote came with it). But it is super handy to have to switch between settings (e.g. overall room/target curve for your room EQ). So kudos for thinking about implementing this.

What I don't like one bit is that the hardware does not come with software that is essential and mandatory for its operation. Instead you have to go to their website and navigate to redeem a coupon to download that software/USB drivers (if needed). I am assuming they have done this to keep their brother Asian manufacturers from cloning the hardware and benefiting from software that is harder for them to implement. Be that as it may, they turned their problem into ours.

To wit, when I plugged the unit and installed the drivers, even though Windows would detect it as a sound card, I could not get any output from it. Turns out you have to install the "plug-in" package and then select the input to be USB. By default the input is the analog input! This cost me many hours of frustration when I first got the unit.

And why on earth do they call standard desktop app that controls it, a "plug-in?" That too threw me off thinking it is a plug-in to some other software so I kept search for the desktop software. Their website hides that software anyway unless you go through the coupon redemption process even after you logged in and used that.

All in all, made me quite grumpy to get it working. But once there, this thing is not bad! :) Lots and lots of flexibility with two analog channels in, and four out. The software itself uses Adobe AIR cross platform solution so should run wherever AIR runs. I remember vaguely though that AIR is discontinued and if so, wonder what the future holds for using this device with that app.

In this review I am only focused on the device's performance as a DAC and ADC-DAC combo. I did not attempt to use or measure the performance of its myriad of filters and functionality. I will do so in the future. So let's get into measurements and see how it did. If you are not familiar with my tests, I suggest reading my tutorial on audio measurements here: https://www.audiosciencereview.com/forum/index.php?threads/understanding-audio-measurements.2351/.

Measurements
For this testing, I tested three inputs: USB, Toslink and Analog. Let's start with frequency response test of Toslink using 44.1 kHz sampling:

View attachment 12215

Channel matching is not perfect although this is a highly amplified graph. The roll off for high frequencies is quite early at 18.7 kHz. There is also some roll off below 20 Hz but not significant.

Here is the response using analog input:

View attachment 12216

We get slightly more bandwidth to 20.7 kHz and that is it. I am unclear why there is extra bandwidth here since the same DAC is used in both cases. Maybe they both run at 48 kHz and again, the bandwidth is cut off too early. I have not found a way to change or monitor the internal sampling rate. If someone knows how, please comment.

Let's now look at jitter and noise spectrum:

View attachment 12217

I have overlapped both USB and Toslink on top of each other (red/cyan). Performance is identical in both and a step from high-performance DACs like Topping D50. It fits in the class of $30 USB DACs. Nothing horrific though. Just not as clean with 10 dB higher noise and visible jitter components.

Let's compare DAC linearity (ability to reproduce the output voltage representing the input digital PCM samples). Ideal graph would be a line. I tested this using both Toslink digital input and analog input (note, the test conditions vary some):

View attachment 12219

Numerically using my 0.1 dB deviation criteria, the analog input seems to do better by one bit. But its output goes pretty nuts after that, going off the chart at the extreme of -120 dB. Either way, it is average to below average performance and certainly not competitive with well executed desktop DACs.

-90 dB sine wave shows similar situation:

View attachment 12220

Sine wave is recognizable but there is fair amount of noise.

Digging into the spectrum of a 1 kHz tone (itself filtered) with respect to noise and distortion using Toslink input we get:

View attachment 12221

We see quite a bit more noise and distortion than our class leading dedicated DACs. Running the same test where my analyzer generates the analog output to drive the analog input of the miniDSP 2x4 HD we get:

View attachment 12222

Not surprisingly, the analog input underperforms digital, causing higher noise floor and more harmonic distortion. This confirms yet again that you want to use the USB input, not analog.

Let's look at intermodulation distortion using Toslink input:

View attachment 12223

As expected, the miniDSP significantly underperforms our reference DACs such as the Topping D50.

Similar story exists for THD+N versus level:

Conclusions
As a core audio platform, the miniDSP 2x4HD has OK performance. It has no glaring faults but also doesn't match the best-in-class products either. Seeing how this functionality is part of the larger DSP platform and that component can add noise of its own, this is to be expected. Personally I wish there was a plus version that had better execution on DAC side.

As it is, you would be compromising some performance to gain the benefits of its equalization. That technology if well implement, can make significant improvements to sound reproduction in your room so in balance you will come out way ahead.
I guess this measurement was done with version 1 board (using AKM AD/DA chip). Is there any comparison or full measurement result with version2 (BB PCM3168A chip)? I have bought MiniDSP 2x4HD from MiniDSP recently , it has BB chip and version2( "v2 printed").
A friend of mine said it looked SN is 6dB or around better in SPDIF but worse in USB input.
 

Mxman

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I emailed mini DSP and asked if there's a feature that boosted voltage and they just referenced the 12db boost. Is there any chance the voltage gets bumper up but doesn't distort?

I would love to use a xlr converter and use a xlr in class d amp on it....

Thoughts?
 

mdsimon2

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I emailed mini DSP and asked if there's a feature that boosted voltage and they just referenced the 12db boost. Is there any chance the voltage gets bumper up but doesn't distort?

I would love to use a xlr converter and use a xlr in class d amp on it....

Thoughts?

Max output level is 2 V. If the output level from the DSP exceeds 0 dBFS (depends on source level, volume position, channel summing and DSP boost) you will get clipping.

What is the input sensitivity of your amplifier? 2 V is good for the vast majority of amplifiers.

Michael
 

df00

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I've been using the 2x4HD for a few years. Your noise level will depend on how you are using it. I only use it for EQ and DAC operation. When in the tape monitor loop of my Bryston B60, I don't hear any noise at all because I have the main volume after the minidsp. The 2x4HD is a godsend for owners of old anolog systems with a tape loop. Connected to a Marantz 2230 you get awesome EQ, DAC, partial remote input switching and remote volume (assuming you leave the volume up on the receiver).

On the other hand, if you don't have a tape loop, or want to use the active crossovers, you then need to wire it directly to your amp, and yes, you may hear some noise. For me, using a Bryston 3B connected to JBL 4430s I did not have any noise problems. Only if I put my ear to the horn would I hear any hiss. Like Ruhled said, nothing noticable from a few feet away. Use decent cables.

The Flex looks interesting. If I ever go that route, I would toss my preamp as I only need one analog and one digital input.
 

Wirrunna

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I have been running two miniDSP 2X4HD to tri-amp my Klipschorns, one for each speaker. The miniDSP 2X4HD perform EQ for each driver, Delay for driver time alignment and FIR filters that define the crossovers and provide phase flattening for each driver.

For each speaker the miniDSP feeds RCA to RCA to an Audiophonics MPA-S125NC Hypex N-Core stereo amp and using an RCA to TRS cable feeds one side of a Topping PA5 amp. The K-Horn bass bin is stock at about 104db/W at 1M while the Mid and Hi use a B&C DCX464 co-ax and an Eliptrac horn at about 110db/W.

Pre-amp duties are performed by a NAD C725BEE Receiver fed from a RPi Allo Boss2 streamer.

Noise. The vol ctl on the preamp has no affect on the miniDSP hiss.
With sensitive drivers and horns the miniDSP noise was too loud. I first tried a 7db L-Pad on the mid and hi drivers which reduced the hiss to being able to be heard a meter and a half from the mid/hi horn mouth. I then added a Passive Preamplifier Audio Volume Controller for the Audiophonics amps. This vol ctl was set by turning it to full and then backing off until the hiss was only just heard.

Initially I used the NAD power amp for the Bass and the N-Core amps for mid and hi. Swapping the NAD amp to Mid improved the sound, the bass was tighter on the N-Core amp and the miniDSP hiss was slightly reduced to just hearing it about half a meter from the horn mouth.

Topping PA5. After reading the review I ordered one of these that took a month to arrive. After cabling it in, RCA out from mDSP to TRS into the PA5 to drive the mids I listened with no signal - only the faintest hiss at max vol on the Topping PA5 ! I ran a REW sweep and adjusted the gain in the miniDSP, ran another sweep to confirm, cheked again for mDSP hiss , still very feint. Played some music and it sounded fine. I removed the L-Pad on the mid, this time I turned the Topping PA5 from full (4 o'clock) to where the hiss is just heard at the horn mouth which is about 2 o'clock on the vol ctl, and re did the gain on the mDSP.

I then removed the L-Pad on the Hi driver of the DCX464, redid gains in the mDSP and checked for hiss, none from the Hi.

Topping PA3s. Somewhat confused as to why the PA5 caused such a reduction in hiss from the mDSP I tried out a Topping PA3s, first with RCA to RCA cable and then with RCA to TRS cable. The PA3s hissed like a cut snake. With nothing else connected to the mDSP or with the input from the NAD and the other outputs the PA3s hissed.

I can't explain it, but as soon as the PA5 was connected the hiss was gone.
 
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Miercoles2022

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Wirunna, can you describe a little more about your audio chain with two minidsp 2x4HD and stereo 3-way crossovers?

Do I have this correct? You use two of the Hypex amps?
  • Allo streamer analog out --> NAD pre
  • NAD pre out (RCA splitter?)
    • MiniDSP 2x4HD #1 analog in --> Analog out
      • Hypex NC stereo amp #1 --> bass bin #1 and high #1
      • Topping PA5 --> Mid #1
    • MiniDSP 2x4HD #2 analog in --> Analog out
      • Hypex NC stereo amp #2 --> bass bin #2 and high #2
      • Topping PA5 --> Mid #2
Has anyone used two 2x4HDs via an optical toslink splitter and then analog out to amplifiers for 3+way crossovers? Would a split toslink signal be synced between two 2x4HDs?
 

Wirrunna

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Miercoles2022, you have the audio chain correct. There is no need for an RCA splitter, the two NAD pre out RCA (Left and Right) feed the two MiniDSP 2x4HD units just as you have described.

May I cut and paste your description to my post ?
 
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ah-ra

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I know it's an old thread, but I think I can add a bit of my experience with this unit here....I have it as DDRC-24 (basically a 2x4HD with dirac live). It's implemented in my system between a Marantz NR1710 which I am using as pre-amp and a Marantz PM8006 which I now only use as power amp.

I use it as DSP and X-over between my Main Speakers (I use two different sets, a fullrange speaker and some Canton Vento 2-way speakers) and two SVS-subs. I've read of course Amir's review of it's DAC-performance, but I can say that the improvement it brings to the whole set up (after I figured out, how it works and how to use Dirac) is just stunning. I made some stupid mistakes in set-up and in the whole measuring process in the beginning, but after some days of playing around and the implementing of a house-curve (derived from the known Harman curve) I'm really really happy. I verified the results with some measurements in REW as well.

I can't understand any discussion about noise coming from this unit through the speakers. There is very(!) little hiss from the speakers and you can only hear it with your ears very (!) close to the speakers. I do not use the internal DAC of the miniDSP, but I can just say, that the mediocre test results as DAC simply do not seem matter in my usecase. Actually I can't think of any other unit (especially at this price pint) that brings such an improvement to the overall sonic experience of my system. Bass response in my small room improved tremendously, but then there is also a better overall balance in sound and soundstage.

By the way, I used the standard 2x4 before, which also was a great device, but the 2x4 HD or in my case the DDRC-24 just takes my system at least one step further. I know I don't have a high end system by audiophiles standards, but I have heard quite a lot of those and I can say I'm quite happy....
 

PeteL

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I do not use the internal DAC of the miniDSP, but I can just say, that the mediocre test results as DAC simply do not seem matter in my usecase.
There are no digital outputs, how can you possibli not use the internal DAC?
 

Ruhled

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The 2x4hd supports external i2s dacs, but only via an internal connector on the pcb. So not too practical for those who want to avoid a bit of diy work but possible nonetheless.
 

ah-ra

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There are no digital outputs, how can you possibli not use the internal DAC?
What I meant was that I don't use it as DAC. Of course you are using the AD/DA circuits when you're using it as DSP as well.
 

srslee

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I have a couple leftover pieces remaining that I'm looking to incorporate into a bedroom setup. They include the SMSL Sanskrit 10th MK II and MiniDSP DDRC-24. Could I do something like this? TV or RPi -> SMSL Sanskrit -> MiniDSP DDRC-24 -> Power Amp/Powered Subs. How much would the additional ADC/DAC affect the sound quality? Would this additional conversion render the well-measuring DAC in the Sanskrit useless? The main reason I want to use the SMSL Sanskrit in this chain is because it has a volume display, and again, just looking to cobble these pieces together if possible.
 

mdsimon2

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I have a couple leftover pieces remaining that I'm looking to incorporate into a bedroom setup. They include the SMSL Sanskrit 10th MK II and MiniDSP DDRC-24. Could I do something like this? TV or RPi -> SMSL Sanskrit -> MiniDSP DDRC-24 -> Power Amp/Powered Subs. How much would the additional ADC/DAC affect the sound quality? Would this additional conversion render the well-measuring DAC in the Sanskrit useless? The main reason I want to use the SMSL Sanskrit in this chain is because it has a volume display, and again, just looking to cobble these pieces together if possible.

In my experience using the DDRC-24 / 2X4HD ADC adds about 10 dB THD and 3 dB noise, resulting in about a 6 dB decrease in SINAD. In addition using an upstream device for volume control is not a good idea from a gain staging / SNR perspective. Of course if it sounds fine to you I'm not sure I would worry about it.

IMO I would get rid of the Sanskrit and DIY a simple 4X20 LCD display using minidsp-rs. I posted a simple Python script for the DDRC-24 here -> https://www.audiosciencereview.com/...-x-4-hds-usb-port-as-output.19976/post-880660. You can then use the RPi and your TV as source with the RPi powering the display and running the Python script.

Michael
 
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