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MDAC First Listen (Part 00101001)

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John,

I have made payments for 1 USB detox development + MDAC2 fourth installment.

So USB Detox +1 :)

Cheers
 
clivem2 said:
John,

When you test the Regen can I suggest you tried with the solid connector and with a cable? I'll be interesting to know whether its proximity to the DAC shows to be relevant in your tests.
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Clive,

I'd be very surprised if I where able to measure any difference between the "Direct connection" and via Cable.

I'm sure its possible to hear a difference, but experience shows its hard to correlate measurement with listening experience at this level.

I'm sure I might measure differences with signal risetime - maybe a slightly different RF pattern (or levels) but how does this relate to sound... Audio's so hard to quantify...
 
Seems to be a real challenge measuring these type of devices that operate on the digital transmission part.

See John Atkinson's review of the Audioquest Jitterbug
- - > http://www.stereophile.com/content/...noise-filter-measurements#PDzGZjjUDwMM5Sgg.97

and yes, have a JB installed in my system as of today, my only excuse is that this is one of my hobbies and I'm a sucker for new technology/devices of all sorts. Not yet formed any opinion of impact

/Cheers
Lars
 
The point in doing measurements on these devices is to accumulate enough datapoints whereby one can discount certain areas from further investigation &/or focus on certain areas which hint at possible correlations to SQ differences. There is no more expectation than a hint can be ascertained at this stage.

So far we have two sets of measurements on the JB (HF&N & Stereophile) - none on the Regen. Both JB measurements seem to indicate a reduction in jitter for the JB when used with the Dragonfly but not with other USB audio devices.

There are two mechanisms in operation in both the Regen & JB which need to be separated & their effects measured independently - the cleaning/regeneration of the Vbus & the cleaning/regeneration of the signal lines. Not separating the measurements for each of these two mechanisms can only lead to confusion, I believe.
 
jkeny said:
The point in doing measurements on these devices is to accumulate enough datapoints whereby one can discount certain areas from further investigation &/or focus on certain areas which hint at possible correlations to SQ differences. There is no more expectation than a hint can be ascertained at this stage.
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Yes indeed - I'm going to start by looking at USB Packet jitter (and Eye pattern) + RF levels, these should be easily measurable - but its not easy to equate these result with sound quality.

One problem that I face is that lowest jitter might not be the best sound quality - as its the spectrum of the jitter that's important.

I believe it was Michael (Fusion) who pointed me to a CA thread where the designer of the Regen inserted resistors in the Ground connection of the USB lead and this resulted in "much improved Bass".

My first thought was that once the impedance of the Earth connection was increased Earth leakage currents found the next easiest route which was through the USB Data Lines themselves - thus superimposing higher Mains related harmonics on the Jitter spectrum - "Mains Hum" if added in small doses adds "bass weight". I've seen this effect before - it even sounded better, but it’s not technically correct.

The problem with looking at an interface in isolation is that striving for the best "individual" result might not be the best option when the whole system is considered.

I've found that in many instances when the system is non linear (when we cannot have Zero interface jitter) then its better to add "noise" to the Clock to "Bury" any discrete spurie components. Our hearing is sensitive to "discrete" components but not so much to random noise.

For example – a gentle air-conditioning blowing in the background does not disturb me as it produces purely ‘White noise” but if the bearings in the fan are warn then the fan can rattle & rub which produces discrete tones / noise, this noise is no longer clean “White Noise” and becomes “noticed” by our brain and rather irritating.

The same happens with the Phase noise spectrum, we know the USB devices are not designed for low noise and produce complex noise spectrum (even as a second order effect in the system) – I find its better to bury these discrete components under noise….

While the “total” integrated jitter level result is worst – atleast the phase noise plots no longer have a complex spectrum of spurie components, sure everythings “buried” by the higher noise floor :p

This is the reason I’m adding the Spread spectrum mode – I was even toying with the idea of using a tube based clock oscillator, to use the inherent noise of the Tube to produce a “nice” noise spectrum – its “Clean” noise…

The problem is that I need to balance my credibility with what I believe people are prepared to accept. I believe a Tube base oscillator would be better because its noise would bury (Mask) a whole spectrum of discrete noise components unavoidable in the USB interface, but it would be a leap too far for many….

I do respect Adamdea’s point of view on such matters, but I believe that there is a good reason why an idea like this is not so crazy… in a perfect world Zero jitter would be best, but with the USB interface so much is beyond my control – it’s better to bury the unavoidable discrete components with noise.

Maybe the Detox should be renamed “White Washer” :D

I might be sitting up there with the “crazies” with a tube based Detox :D – but hey sometimes I have to put the measurements aside and just listen to the Music :D
 
Great points, John. My own feelings about what's going on that effect the SQ are along the lines your outlined i.e fixed noise Vs modulating noise - I believe that both devices work in some way to reducing the amount of modulation of low level noise, not necessarily the absolute level of the noise (be that noise in the audible range or RF noise that folds back into the audible range or causes the analogue stage of the DAC to cause the same effect).

How to measure this dynamic noise modulation is the question?
 
LarsS said:
I have a JB installed in my system as of today, my only excuse is that this is one of my hobbies and I'm a sucker for new technology/devices of all sorts. Not yet formed any opinion of impact.
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LarS,

I'm sure its correct to say we are all keen to hear about your experiences with the JB (Jitter Buster) :)

Its should really be called a USB filter then a Jitter Buster - as it can only reduce jitter on USB powered DAC's which have poor PSRR (Power Supply Rejection Ratio) by cleaning up the 5V PSU rail.
 
John, my reasons for being interested in measuring differing cables/connectors with Regen is as JK has described - to try to find something that at least hints at a correlation with what we hear - yes clutching at straws. Also is there something that demonstrates whether it's better the Detox should be placed very close to the DAC input?

As JK also suggests....I find Regen beneficial but I can't decouple my usb card being powered by my linear PS into the Regen vs the regen and filtering function.
 
clivem2 said:
John, my reasons for being interested in measuring differing cables/connectors with Regen is as JK has described - to try to find something that at least hints at a correlation with what we hear - yes clutching at straws. Also is there something that demonstrates whether it's better the Detox should be placed very close to the DAC input?
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Yes, I hear you :) lets see what I discover, it will take time for me to buildup a picture of what's pertinent / relevant :)
 
I know there are some MDAC (or future FDAC) owners with electrostatic speakers around here. Is the SQ really that good? I've spoken with the designer of ESL components today and I'm almost convinced to start another DIY project :rolleyes:
 
fusion5 said:
I've spoken with the designer of ESL components today and I'm almost convinced to start another DIY project :rolleyes:
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In case you talked to the creator of Silberstatic speakers - do go ahead. Best sound of show for me at Highed Munich 2015. But probably any other ESL implementation will be a way forward for your system as well.

Cheers,
Achim
 
I wonder if you can help me please?

I would like to use/try the minDSP DDRC-22D Dirac Live® correction DSP http://www.minidsp.com/dirac-series/ddrc-22d

I think it's the best one out there? But I can't see how/where to connect it into my MDAC system...what connectors/cables types should I use?

I'm using USB from a laptop to the MDAC and the phono/RCAs out to my Linn Aktiv crossover...(I use the MDAC as a preamp.... with 6xLK280 monoblocks driving Briks).

I had a look at the back panel of the DDRC-22D but I can't see how I would connect it between the PC and the MDAC.

Also there is an 8-channel version: http://www.minidsp.com/products/dirac-series/ddrc-88a Could this replace my Aktiv crossover, if so how would I connect it?

Or should I just wait for the FDAC? I haven't purchased a DSP yet and I know the FDAC will have something, but will the FDAC DSP be as good or fully featured as this Dirac?

My apologies for so many questions, but it's a rolling snowball sort of issue for me.

Many thanks:)

The Detox I'm guessing, will just be inline between the PC and the MDAC/FDAC.
 
Hi Tim,

I have a ddrc-22d in front of me, and if your using a PC via USB as your audio source then there is no simple way to use with the MDAC.

If your using a SPDIF source then:-

The SPDIF signal from the source is connected to SPDIF input on the ddrc-22d

The SPDIF Digital output from ddrc-22d should be connected to the SPDIF input on the MDAC.

If you would like to stream audio from your PC via USB to the ddrc-22d / MDAC then you need an USB to SPDIF converter as the ddrc-22d does not have an USB Audio input (Its USB port is for control only).

I'd not recommend playing with the 8 Channel unit with your active speakers as without the correct digital crossover design you could send the wrong signals (incorrect frequency range) to the various drivers and damage your speakers.

With the support of miniDSP software then the FDAC's internal DSP's will be fully featured - the FDAC's internal DSP engine is not hardware limited.
 
John

Am I right that the XLR and RCA analogue output can be use in parallel?
If you are redesigning the FDAC analogue pcb anyway and using the FWC is there enough space in the back for a second RCA analogue output?

regards
F.S.
 
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