Minidsp Flex Review (Audio DSP)

[Pdxwayne]

Parasound A21 has a gain of 29 dB which is going to be rather noisy with the 2X4HD. Lower gain will definitely help. Here are some residual noise calculations ignoring amplifier noise for the 2X4HD and the Flex with amplifiers of various gain, as you can see the Flex is a lot better but you can also do a lot better by using a lower gain amplifier.

View attachment 186413

Why would you use a DAC upstream of your 2X4HD? That is only going to add noise from the ADC and likely cause you to lose even more SNR due to less than perfect gain staging. If for some reason you did use an upstream DAC you would want it to be such that it was at maximum volume without clipping the 2X4HD input and then do volume control in the 2X4HD.

Michael

About using a Gustard dac before 2x4hd...it was because I want to stream Tidal and get mqa decoding.....

Maybe I should just forget about mqa and simply go direct from my node2i digital out to 2x4hd to amp (lower the amp gain). I will use node2i for volume control in this case. If still not satisfied with the noise, I will try flex.

Thanks!

 

[PeteL]

Parasound A21 has a gain of 29 dB which is going to be rather noisy with the 2X4HD. Lower gain will definitely help. Here are some residual noise calculations ignoring amplifier noise for the 2X4HD and the Flex with amplifiers of various gain, as you can see the Flex is a lot better but you can also do a lot better by using a lower gain amplifier.

View attachment 186413

Why would you use a DAC upstream of your 2X4HD? That is only going to add noise from the ADC and likely cause you to lose even more SNR due to less than perfect gain staging. If for some reason you did use an upstream DAC you would want it to be such that it was at maximum volume without clipping the 2X4HD input and then do volume control in the 2X4HD.

Michael

I just purchased a 2X4 HD, for sub integration mainly and some DRC. I didn't finish setting up, I will revert back on audible Hiss, hoping not because they have a final sales, no return policy. and yes I have 29 dB power amps, and a low gain preamp on the front. The 2X4 HD is very insufficient for me to be used as the sole preamp. I do have a Dac upstream, maybe I can potentially remove it but I need the analog in anyway for my analog sources, I have more digital sources than the 2X4 HD can handle and I also like to be able to control the volume of everything with the same remote control. Hoping I did not do a poor choice for my system, hiss free is totally a must in my book.

Edit: So far no audible hiss for me with just setting it up with a basic crossover so I guess I'll be OK. I did not do any DRC yet but It shouldn't make a major difference. My ears may be less sensitive to that than other tough.

 

[Tangband]

This may be because you've never experienced a subwoofer properly integrated by means of a device like the Flex .

It was using a miniDSP 2x4 HD that made me realise my natural 'audiophile' scepticism over using subwoofers for music was misplaced.

Yes its very hard to get perfect integration with an analog active crossover. Impossible with passive, if crossing at 80 Hz.

 

[mac]

This might just be the ideal LXmini crossover.

 

[withoutsuit]

I have my eye on the flex since it announcement in the newsletter last year. If there would only be a version with (at least) one digital (optical) and analog output together in one device Would be the perfect replacement for my DDRC24. There is only the large SHD :/

 

[Hayabusa]

The SHD doesn’t have FIR, how did you do RIAA?

I used this bi-quad:

b0=1
b1=-0.7555521
b2=-0.1646257113
a1=1.7327655
a2=-0.7345534436

This is for 96kHz

 

[Hayabusa]

I believe miniDSP meant what is written, which is consistent with your suggestion of it being a way to monitor the four output channels. I think this is possible. (There are indeed only two input channels i.e. stereo.)

With my SHD I've used similar functionality as a way to quickly see what the applied Dirac Live filters look like, but this was via REW which only makes use out output channels 1 and 2. I've not tried to see if it is possible to access outputs 3 and 4 as well via USB.

I could record the 4 channels via USB

 

[Ultrasonic]

I have my eye on the flex since it announcement in the newsletter last year. If there would only be a version with (at least) one digital (optical) and analog output together in one device Would be the perfect replacement for my DDRC24. There is only the large SHD :/

Neither the SHD or SHD Studio has a Toslink output, so the provision of one on the digital Flex model is actually a differentiating feature. No analogue output though of course.

 

[rvsixer]

I have my eye on the flex since it announcement in the newsletter last year. If there would only be a version with (at least) one digital (optical) and analog output together in one device Would be the perfect replacement for my DDRC24. There is only the large SHD :/

The DDRC24 does not have digital output, so Flex can be a comparable solution as is? In any case, there are very small DAC's you can add to Flex to have both analog and toslink out if space is at a premium.

 

[Toxmarz]

There are two versions of this device, one with TRS input/output and one with RCA. They say themselves there is a performance hit if using TRS to RCA adapters and to buy the RCA version if that's what equipment you have. In your test of RCA performance it seems that was using adapters. I wonder what the performance of the RCA version might be without using adapters.

 

[testp]

There are two versions of this device, one with TRS input/output and one with RCA. They say themselves there is a performance hit if using TRS to RCA adapters and to buy the RCA version if that's what equipment you have. In your test of RCA performance it seems that was using adapters. I wonder what the performance of the RCA version might be without using adapters.

i think the RCA version would take very little hit on performance either from input or output..
TRS version took small hit from one end and bigger hit from the other, someone will specify better

 

[Vince2]

This does help…. Another question,

Is it possible to route the analog input to a digital RIAA equalizer and be rid of old school phono equalizers?

Sure, just do an online search for the peq filters that approximate the riaa curve. Seen it somewhere on the diy forum

 

[Dj7675]

You have a choice of either having Dirac Live functionality or sticking to the cheaper Flex without Dirac Live and having manually adjustable FIR filter capability. You can't have both.



I'd suggest more the opposite personally. I've used the PEQ filters on other miniDSPs to apply speaker correction based on quasi-anechoic measurements, whilst I'd view Dirac Live as principally software to adjust the in-room response. Yes it does its impulse correction thing as well, although I find it impossible to judge its value since you can't choose to turn this aspect on/off in isolation.

Personally I like the results of using Dirac Live just in the low-bass region rather than over the full frequency range. Others like the latter but I would encourage anyone to experiment with both to see what they enjoy most.

I am doing this as well (using Dirac on the low bass region and PEQ for speaker correction). When applying PEQ speaker correction, are you basing PEQs off of on axis, PIR, or other?

 

[Tangband]

This might just be the ideal LXmini crossover.

Yes .
Using a Computer with TIDAL/Apple lossless + minidsp flex + two Aiyima a07+ LX mini or Directiva = highend sound below the price of 2000 dollars .

One can also buy a good passive loudspeaker with twin terminals and rip off the passive crossovers and go active …. A JBL 530 comes to mind .

 

[Glasvegas]

They say themselves there is a performance hit if using TRS to RCA adapters.

I thought this was only on the input. Did they also say this about the output?

 

[Hayabusa]

Sure, just do an online search for the peq filters that approximate the riaa curve. Seen it somewhere on the diy forum

I just answered this a few posts back...

 

[rbachl]

I thought this was only on the input. Did they also say this about the output?

The advise from miniDSP is for the output, see TRS to RCA

 

[Ultrasonic]

There are two versions of this device, one with TRS input/output and one with RCA. They say themselves there is a performance hit if using TRS to RCA adapters and to buy the RCA version if that's what equipment you have. In your test of RCA performance it seems that was using adapters. I wonder what the performance of the RCA version might be without using adapters.

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

 

[Ultrasonic]

I am doing this as well (using Dirac on the low bass region and PEQ for speaker correction). When applying PEQ speaker correction, are you basing PEQs off of on axis, PIR, or other?

What I have experimented with was to try to improve the on-axis response but from listening I was never convinced I'd made things 'better' and am not currently applying this. The measurement setup I could manage in my garden was far from ideal though and I know this is a complicated subject, probably best discussed in another thread.

The point though is that the Flex gives users the possibility of applying speaker corrections in this way, including those that may be recommended for specific models based on high-quality data shared here.

 

[Multicore]

Rats. I was going to order this yesterday but got side tracked. Anyone here want to sell be one?