Minidsp Flex Review (Audio DSP)

[Hipster Doofus]

Wonderful review…and so much fun to see the bar rise before our eyes.

.ahhh and I almost pulled the trigger as I am looking for a parametric to tame my Tekton Set speakers.

But no MQA.

And since I only stream tidal nowadays.

I was thinking of roon but this system is in the room without Ethernet. And roon makes my feeble head spin, Will roon work in all 3 of my rooms and let me equalize differently for each of my 3 sets of speakers without lots of new equipment.

thank you

 

[CEAV]

I've been following this site for some time now, and I plan to buy the Flex. Thanks for the review. It seems like an excellent unit to blend 1-2 subs in with an excellent DAC and excellent room correction. I plan to add a streamer and use the optical input for a TV.

Has anyone used the Elac EA101EQ-G? I've been using it for a few years. I'm curious to see how it measures (I assume not amazingly well) but it works for my purposes. It has a ton of digital inputs and provides gentle room EQ and the ability to blend a subwoofer in is great.

One feature of the Elac that I think is really useful for these 2.1-2.2 channel preamps/amps is the ability to decide Dolby audio. I've noticed that when I feed the Elac a source that is Dolby it really helps clean up the dialogue and presents the movie mix at a much better level when compared to 2 channel PCM only.

I wonder if anyone else has experienced this. I think it'd be awesome if this unit cold decode Dolby too. Not sure how much that more limited license would cost the company.

Thanks again for review and the commentary. My plan is a PA5 hooked up to this with one subwoofer to start.

 

[rvsixer]

There are two versions of this device, one with TRS input/output and one with RCA.

Three versions. Balanced, unbalanced, and digital. Better differentiated by connection type (not connector type as all versions have RCA connectors, etc.).

 

[Blake Klondike]

This is a review and detailed measurement of the Minidsp Flex audio signal processor. It was sent to me by the company and costs US $475 for unbalanced and $550 for balanced that I tested.

View attachment 185804
Flex borrows the interface from SHD and puts it in a compact package. Seeing how I really liked that interface with nice volume control, this is a very good move.

Back panel shows why this product is so useful:

View attachment 185805

Not only do you have a suite of digital input but also analog. More importantly, you can rote any input to any output and apply crossover, parametric EQ filters and compression. The software interface is mostly intuitive except for channel routing which required a bit of looking around.

The supplied remote control allows you to eliminate any need for a preamplifier and drive a power amp directly.

Minidsp Flex DAC Measurements
I alternated between Coax S/PDIF input and USB although performance is the same in both. Here is our dashboard:
View attachment 185806

OK, I was not ready for this. A multifunction device with DSP that has a SINAD (relative sum of distortion and noise) to rival and outperform many dedicated DACs?


View attachment 185807

Among its own category which is a mix of DSP and AV receivers and processors it sets a new high bar:


View attachment 185808

First of its kind to land in the blue "excellent" category!

Above was with the volume at -0.5 dB. There is a bit more performance if you set it to 0:

View attachment 185809

Dynamic range is very respectable for this class:

View attachment 185810

There is something holding IMD distortion back though:

View attachment 185811

This causes the same limiting in multitone:

View attachment 185812

JItter test shows some interference but they are at such ridiculously low level that bother the eye far more than any ear could ever detect them:

View attachment 185813

DAC filter is the typical default "lazy" ones in DAC chips:

View attachment 185814

This hurts THD+N versus frequency a bit but the outcome is still good:
View attachment 185815

Linearity is excellent:
View attachment 185816

Minidsp Flex Analog Input Measurements
Some people have an analog only path (e.g. for turntables) and would still want to implement active speakers and/or equalization for room modes. Let's see how we do here:


View attachment 185817

I am amazed once again! End to end performance this good? Remember this is the performance of ADC and DAC combined. And we still manage to have distortion at < -110 dB (18+ bits).

Dynamic range suffers a bit naturally but still, quite good:

View attachment 185818

I was relieved to see wide and flat response:

View attachment 185819

So unlike many AV products that resample everything to 48 kHz, here we have end to end sample rate of 96 kHz (my guess). Bandwidth is in excess of 35 kHz.

Crosstalk was superb:
View attachment 185820

This is better than countless stand-alone preamps!

THD+N vs frequency again shows no frequency dependence:

View attachment 185821

IMD performance is again limited by DAC performance:
View attachment 185822

EDIT: Post review question was raised about performance of channels 3 and 4. Here is that dashboard:

View attachment 186032

As you see, performance is just as excellent as channels 1 and 2.

Another question was performance drop when using RCA input to TRS balanced adapter:

View attachment 186033

This is definitely the case. That said, highest distortion component is at -96 dB which is the same as 16 bit audio dynamic range. This is well above what analog sources such as LP can achieve. So I would not worry about it if this is the configuration.

Conclusions
What a nice combination of functionality, usability and performance! As with many DAC companies, it is clearly Minidsp has put strong focus on chasing away sources of noise and distortion. Yes, there is some work left to do with intermodulation distortion but other than that, measurement after measurement put a smile on my face. All AV processor and receiver companies lose any excuses they have for not providing this level of performance seeing how the Flex also implements various signal processing modules.

It is my pleasure to highly recommend Minidsp Flex audio signal processor, DAC and ADC. You made my day!

Very cool! Does this do room correction, as well?

 

[eardiggler]

In case you don't realise, there is different performance data quoted for each on the miniDSP website:

miniDSP Flex

Pocket size processor with flexible Input/Output configuration, Audiophile converters, 400MHz Sharc DSP processor, BT connectivity, DSP toolbox for subwoofer and multiway crossover, Dirac Live optional upgrade

www.minidsp.com

The unbalanced version does take a small hit as expected. Looks like crosstalk takes the biggest hit. The rest of the numbers are pretty close? I ended up ordering the unbalanced version since most of my components are unbalanced. I'm going to use an RCA switcher for my Phono Pre and CD player.

 

[anotherhobby]

Very cool! Does this do room correction, as well?

Yes, if you purchase the additional $200 Dirac license. I did and I am very pleased with the results.

 

[voodooless]

Yes, if you purchase the additional $200 Dirac license. I did and I am very pleased with the results.

You don’t need to buy Dirac to do room correction. You can still do IIR EQ’s or FIR correct (or both) with the base model. It’s just a lot more effort.

 

[sweetchaos]

From MiniDSP website:

STOCK UPDATE (14 Feb 2022): The Flex balanced is unfortunately now out of stock. A new batch is expected by end of March 2022. All orders will be in backlog for and shipped chronologically. Thanks again for your patience!

Ahhh...the ASR effect.

 

[rdenney]

Looking at the spec sheet on the web page, I see that the unbalanced version has a “maximum” (not “rated”) output of 2 VRMS, showing unity gain with the input. Where is the preamp part? This seems insufficient to drive a Buckeye NC502MP (25.5 dB gain) to full power (input sensitivity 2.35 VRMS, balanced, assuming 4-ohm speakers). My analog preamp has a rated output about that, and a max output of a dozen or so VRMS, but that is unbalanced.

But MiniDSP recommends using the unbalanced version if the sources are single-ended, even if the amp has balanced inputs.

I must be missing some point.

Rick “would like to a version with unbalanced inputs and balanced outs, with at least some gain” Denney

 

[NTK]

Looking at the spec sheet on the web page, I see that the unbalanced version has a “maximum” (not “rated”) output of 2 VRMS, showing unity gain with the input. Where is the preamp part? This seems insufficient to drive a Buckeye NC502MP (25.5 dB gain) to full power (input sensitivity 2.35 VRMS, balanced, assuming 4-ohm speakers). My analog preamp has a rated output about that, and a max output of a dozen or so VRMS, but that is unbalanced.

But MiniDSP recommends using the unbalanced version if the sources are single-ended, even if the amp has balanced inputs.

I must be missing some point.

Rick “would like to a version with unbalanced inputs and balanced outs, with at least some gain” Denney

If you don't mind a very small performance degradation and some DIY, you can build yourself some single-ended to differential or differential to single ended converters.

SparkFun THAT 1646 OutSmarts Breakout - BOB-14003 - SparkFun Electronics

The THAT 1646 OutSmarts Breakout Board offers an easy solution to adding a balanced audio output to your circuits. The THAT OutSmarts technology has been d

www.sparkfun.com

SparkFun THAT 1206 InGenius Breakout - BOB-14002 - SparkFun Electronics

The SparkFun THAT 1206 InGenius Breakout Board offers an easy solution to adding a balanced audio input to your circuits. The THAT InGenius technology has

www.sparkfun.com

 

[tvrgeek]

Well, they got me. Moving to the dark side for my build.
Sold out right now of course and I need to get another amplifier and refurb it.

 

[Ultrasonic]

Looking at the spec sheet on the web page, I see that the unbalanced version has a “maximum” (not “rated”) output of 2 VRMS, showing unity gain with the input. Where is the preamp part? This seems insufficient to drive a Buckeye NC502MP (25.5 dB gain) to full power (input sensitivity 2.35 VRMS, balanced, assuming 4-ohm speakers). My analog preamp has a rated output about that, and a max output of a dozen or so VRMS, but that is unbalanced.

But MiniDSP recommends using the unbalanced version if the sources are single-ended, even if the amp has balanced inputs.

I must be missing some point.

Rick “would like to a version with unbalanced inputs and balanced outs, with at least some gain” Denney

What you're discovering here is what most digital 'pre-amps' do. They don't actually amplify signals in the way traditional analogue pre-amps are capable of, but rather act just like DACs with variable outputs, with the peak levels being traditional line levels like DACs without variable volume or CD players. Yes these peak levels can vary between devices but you get the idea.

Generally these peak levels still exceed what people actually need in most systems but obviously this will depend on the amp, speakers, room and desired listening volume.

 

[rdenney]

Thanks—yes, it really seems no better than a passive volume control, and considering the amps on the market with input sensitivity higher than 2 VRMS, seems like a significant limitation.

It’s sort-of a deal-killer for me, or at least moves this back to the same role now filled by my Yamaha YDP2006 parametric equalizer, which sits in a processor loop. But as a tool for managing subwoofers, I’m thinking not if it won’t drive my NC502MP amp to full power. I paid for that power and don’t want to lose it—I have already proven to myself that I can make the clipping indicators flash without over driving my speakers, even from a CD player source.

That Yamaha will take up to 20 VRMS input and spit it back out at unity gain without clipping, so it can go downstream of my active preamp. But it’s a stereo PEQ—2x2–so I could only use it for the mains and any subs I’d buy would have to have their own PEQ to manage their side of the crossover.

But I don’t want to put the Yamaha downstream of the preamp, because it has a hiss at -90 dB or so and I want to keep that upstream from the volume control.

The MiniDSP in the processor loop, though, can use its volume control for enough attenuation to avoid clipping boosted frequencies, I suppose, but that’s all. But I would not be able to do bass management with it in that configuration.

I still feel like I’m missing something.

Rick “the Yamaha is digital but for PEQ only” Denney

 

[amirm]

Will roon work in all 3 of my rooms and let me equalize differently for each of my 3 sets of speakers without lots of new equipment.

Yes. You can apply EQ in software in Roon with each room/DAC getting its own EQ profile.

 

[waynel]

Looking at the spec sheet on the web page, I see that the unbalanced version has a “maximum” (not “rated”) output of 2 VRMS, showing unity gain with the input. Where is the preamp part? This seems insufficient to drive a Buckeye NC502MP (25.5 dB gain) to full power (input sensitivity 2.35 VRMS, balanced, assuming 4-ohm speakers). My analog preamp has a rated output about that, and a max output of a dozen or so VRMS, but that is unbalanced.

But MiniDSP recommends using the unbalanced version if the sources are single-ended, even if the amp has balanced inputs.

I must be missing some point.

Rick “would like to a version with unbalanced inputs and balanced outs, with at least some gain” Denney

With hypex amps you should go with the balanced version and either deal with the non noticeable degradation from an unbalanced source or use an unbalanced to balanced converter. What’s so special about your analog source?

Unbalance to balance converter?

I want to have very long cable (15meter) for subwoofer but pre only has RCA output, and subwoofer has XLR input. I believe it's best to use XLR for long run, so I am looking for a unbalance to balance device, if possible have voltage gain would be best. Is there such device available? Thanks.

www.audiosciencereview.com

 

[rdenney]

MiniDSP reports a 15dB reduction in SINAD when using an unbalanced source into the balanced version, and they recommend the unbalanced version for unbalanced sources. I figure they do that for a reason.

Putting it between my preamp and my amp means having to bypass the line preamp, because the input of the MiniDSP can’t take more than 2 VRMS on its inputs. That isn’t necessarily a problem.

Like I said, I’m trying to figure out how the gain structure would work given that it provides no headroom on the analog line level inputs. My sources provide a range of peak outputs from 2 VRMS down to 400 mVRMS, as was typical of analog source equipment of the past. That’s why preamps had active amplification (and why they were called preamps, for that matter). I’d need the line stage preamp for some sources except the CD players (not all of which have digital outputs), but would defeat it for the full 2-V sources when playing loudly.

None of my sources have balanced outs. I could put a balanced converter on the preamp output into the miniDSP, though at some cost I do not yet understand.

My main issue is I’m not understanding what they are saying in their specs completely, but am taking them at their word that I don’t want to feed an unbalanced signal into their balanced model.

My sources are not special (though I don’t understand the question or the motive behind it) but my DSP-based PEQ is already within 15 dB of the performance of this unit. I’d like the integration with REW, the ability to manage a couple of sub outputs, and the greater flexibility, but not if it means I’m giving up something I paid money to have (abundance of power being one of those things).

Rick “gain structures used to be easy” Denney

 

[waynel]

MiniDSP reports a 15dB reduction in SINAD when using an unbalanced source into the balanced version, and they recommend the unbalanced version for unbalanced sources. I figure they do that for a reason.

Putting it between my preamp and my amp means having to bypass the line preamp, because the input of the MiniDSP can’t take more than 2 VRMS on its inputs. That isn’t necessarily a problem.

Like I said, I’m trying to figure out how the gain structure would work given that it provides no headroom on the analog line level inputs. My sources provide a range of peak outputs from 2 VRMS down to 400 mVRMS, as was typical of analog source equipment of the past. That’s why preamps had active amplification (and why they were called preamps, for that matter). I’d need the line stage preamp for some sources except the CD players (not all of which have digital outputs), but would defeat it for the full 2-V sources when playing loudly.

None of my sources have balanced outs. I could put a balanced converter on the preamp output into the miniDSP, though at some cost I do not yet understand.

My main issue is I’m not understanding what they are saying in their specs completely, but am taking them at their word that I don’t want to feed an unbalanced signal into their balanced model.

My sources are not special (though I don’t understand the question or the motive behind it) but my DSP-based PEQ is already within 15 dB of the performance of this unit. I’d like the integration with REW, the ability to manage a couple of sub outputs, and the greater flexibility, but not if it means I’m giving up something I paid money to have (abundance of power being one of those things).

Rick “gain structures used to be easy” Denney

By special I mean : what analog source are you using that has SINAD better than 90dB? In that case you may want to use one of the unbalanced to balanced converters linked in my prior post.
Balanced output to the amps trumps analog in degradation.

 

[voodooless]

If like @abdo123 mentioned, you can up the gain by 40dB, and still hear no noise coming out, I think you should be fine with a wide variety of input sensitivities. You could just make presets with various input gain settings.

 

[Hayabusa]

Looking at the spec sheet on the web page, I see that the unbalanced version has a “maximum” (not “rated”) output of 2 VRMS, showing unity gain with the input. Where is the preamp part? This seems insufficient to drive a Buckeye NC502MP (25.5 dB gain) to full power (input sensitivity 2.35 VRMS, balanced, assuming 4-ohm speakers). My analog preamp has a rated output about that, and a max output of a dozen or so VRMS, but that is unbalanced.

But MiniDSP recommends using the unbalanced version if the sources are single-ended, even if the amp has balanced inputs.

I must be missing some point.

Rick “would like to a version with unbalanced inputs and balanced outs, with at least some gain” Denney

Indeed you would need the balanced one to fully use the Buckeye.
About gain: digitally you can make enough gain!
Its a digital pre-amp.

 

[Hayabusa]

MiniDSP reports a 15dB reduction in SINAD when using an unbalanced source into the balanced version, and they recommend the unbalanced version for unbalanced sources. I figure they do that for a reason.

Thats unusual.. How is this 'reported'? I would expect 6dB max.