Minidsp Flex Review (Audio DSP)

[antcollinet]

Errr, surely the relevant point is that USB connectivity is available on the Flex?

(Yes it's available on many other miniDSP products too.)

The implication in the answer given to me, is that it would be on this one also. (Ie this is a standard feature on mini dsp units)

 

[Ultrasonic]

The implication in the answer given to me, is that it would be on this one also. (Ie this is a standard feature on mini dsp units)

We don't need to be speculating though. This is a real product that some have even already bought, not some proposed future release.

 

[antcollinet]

It is, I have tried it and it works.

How much dynamic range are you losing? According to the measurement, DR is 20bits on the ouput. Let's be really generous, and assume analogue input can give the same 20 bits. Accepting a 4V input for balanced?

4mV is -60db - losing 10 bits. So you are only getting 10 bits of DR just amping up with DSP. 11 bits with unbalanced (if the unbalanced can achieve the same DR as the balanced - also a generous assumption).

Even given the limitations of vinyl, 10 bits (best case) doesn't seem enough to me.

 

[Ultrasonic]

It is, I have tried it and it works.

Without an obvious noise floor issue?

 

[antcollinet]

We don't need to be speculating though. This is a real product that some have even already bought, not some proposed future release.

Anyone is welcome to give better informed answer than I am able to.

 

[Hayabusa]

Without an obvious noise floor issue?

[edit] Noise floor was above below vinyl noise floor.

 

[Ultrasonic]

Anyone is welcome to give better informed answer than I have.

The USB capability is stated in the miniDSP product specification (and others have already answered the question above):

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]

Noise floor was above vinyl noise floor.

Which would seem a good reason not to do what you've suggested then?

 

[antcollinet]

The USB capability is stated in the miniDSP product specification (and others have already answered the question above):

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

Fair enough - missed that

So it is:

USB audio recording feature (4xCH processed output via USB audio to record inputs, e.g. Vinyl)

Do they mean 4 channel input here. I thought there were only stereo analogue inputs. Or do they mean you can record the result of the DSP/crossover/routing. If so that's sort of neat.

 

[Hayabusa]

Which would seem a good reason not to do what you've suggested then?

typo!
Noise floor as BELOW vinyl noise...

I know it sounds implausible. But realise that the RIAA correction reduces the total gain needed at higher frequencies..

 

[antcollinet]

typo!
Noise floor as BELOW vinyl noise...

I know it sounds implausible. But realise that the RIAA correction reduces the total gain needed at higher frequencies..

But isn't vinyl noise higher at the lower end of the spectrum? And so RIAA will make this even worse. (Or is that only AFTER RIAA correction, so uncorrected playback has flat noise spectrum?)

But in any case the RIAA Correction means you are losing even more dynamic range below 1KHz. Up to another 3 bits at 20Hz.

 

[abdo123]

How much dynamic range are you losing? According to the measurement, DR is 20bits on the ouput. Let's be really generous, and assume analogue input can give the same 20 bits. Accepting a 4V input for balanced?

4mV is -60db - losing 10 bits. So you are only getting 10 bits of DR just amping up with DSP. 11 bits with unbalanced (if the unbalanced can achieve the same DR as the balanced - also a generous assumption).

Even given the limitations of vinyl, 10 bits (best case) doesn't seem enough to me.

Keep in mind that even the BEST phono stages here on the forum are 25 dB noisier than the Flex's Analogue input. So you're more or less back where you started.

 

[antcollinet]

Keep in mind that even the BEST phono stages here on the forum are 25 dB noisier than the Flex's Analogue input. So you're more or less back where you started.

I don't think you are, because you are losing 60dB by doing the amplification in the digital realm inside the flex. You effectively amplify the Flex Ain noise as well as the signal - by far more than 25dB.

 

[abdo123]

I don't think you are, because you are losing 60dB by doing the amplification in the digital realm inside the flex. You effectively amplify the Flex Ain noise as well as the signal - by far more than 25dB.

no that's not how 32bit floating point processing works, no dynamic range is lost when amplifying, whatever you had before within the limits of the Flex's ADC remains till the output stage.

Nothing clips unless something goes above 0dBFS at the very end of the chain.

 

[Jas0_0]

RIAA is useless unless they also provide a 40+ dB analogue gain - which is not possible in DSP.

RIAA on Flex input also not useless if you sort the gain/impedance before the signal reaches the Flex, e.g. using a mic preamp

 

[Hayabusa]

But isn't vinyl noise higher at the lower end of the spectrum? And so RIAA will make this even worse. (Or is that only AFTER RIAA correction, so uncorrected playback has flat noise spectrum?)

But in any case the RIAA Correction means you are losing even more dynamic range below 1KHz. Up to another 3 bits at 20Hz.

I have tested this with the SHD, I will try to make recording of result to verify again...

 

[Hayabusa]

I have tested this with the SHD, I will try to make recording of result to verify again...

A sample with the minDSPSHD as phono preamp.
With a few seconds pre and post needle drop...

 

[abdo123]

A sample with the minDSPSHD as phono preamp.
With a few seconds pre and post needle drop...

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

 

[Stephen]

Ok, but you cant do dsp crossover the way you use your behringer, with digital out to a dac . I suppose you have loudspeakers with analog crossovers and use the Behringer dsp as a roomcorrection and eq ?

You can have much better results with a real, active dsp crossover .Thats next level. The minidsp flex can do both: dsp roomcorrection, eq + digital crossover.

My loudspeakers are passivs, so yes: the embedded filters does the job (and rather well...). In HIFI I hate to use subs, in home theater it's another story.

 

[Ultrasonic]

My loudspeakers are passivs, so yes: the embedded filters does the job (and rather well...). In HIFI I hate to use subs, in home theater it's another story.

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.