MDAC First Listen (Part 00101001)

[JohnW]

From what I understand, miniDSP has several hardware solutions for different kinds of room correction including Dirac Live, AcourateDRC, Python Open Room Correction (PORC) and rePhase.

It would be interesting to know which DSP solution they have in mind for the Fusion DAC.

Also some technical data would be nice:
-processing power,
-supported audio bit depth
-supported FIR filters
-data path to FPGA modulator (full bit depth or not?)

I have used Audiovero Acourate with J River MC's 64bit convolution engine before and the results can be quite remarkable. Especially for people like me with no dedicated listening room.

To support 192KHz at full resolution the MDAC2 features a pair of Analogue devices SHARK DSP processors. The plan is to be able to offer Dirac Live at 192KHz.

There will be no hardware datapath restriction between the DSP's and FPGA so its just a matter of the DSP software procession. We plan to offer the full 32bits when available.

 

[JohnW]

John, some (more) questions for you please:

1. Could we do away with the need for USB cable power for handshake with Fusion DAC? We could then use a data-only USB cable without requiring isolation, unless I'm wrong (highly likely).

The FDAC features an internally isolated USB port.

2. XLR and single-ended ADC inputs in Fusion DAC please. OK, this is not a question

I'll try to include an RCA ADC input, BUT its always better to use a RCA to balanced cable as this offers a semi-balanced system.

3. Regarding the Fusion DAC phono module features:

MM/MC

Yes

selectable capacitance/resistance

What are the most typical combinations?

variable analogue gain (hardware)

Only the MC / MM Gain selection & 20dB analogue gain step attenuator.

channel trim

Yes, in software

mono switch

Yes, in Software

software RIAA

Yes via the miniDSP framework

 

[JohnW]

No experience whatsoever, as I understand John's ideas miniDSP will be integrated into the Fusion DAC. I thought that miniDSP contributed with HW to be integrated with the Fusion DAC & Dirac as a SW vendor could be an option to integrate at some stage.

Yes, the FDAC will offer Dirac Room Correction option via the miniDSP website.

 

[JohnW]

I agree, some more data on the miniDSP implementation for the Fdac would be nice, which I'm sure will come in due course. I plan to see what the Fdac can offer on this....I believe JohnW said it would only be for Treble and Bass sloping.....So I plan to add a Dirac type system later perhaps.

The initial PFM crowd funded units (first 250pcs) will be initially released with Phase 1 software - this is basic functionality (but full hardware) we will offer software updates in rapid succession as we build up towards the more complete Phase 2 software.

Phase one is very basic UI, Master unit "Only" operation, DAC in standard ESS mode (no external modulator etc), No advanced clock etc.

We will add the more advanced features as soon as we have developed the software / firmware, the initial software will just feature "Treble and Bass sloping" DSP software but miniDSP will open there full portfolio of DSP software over time - I'm not aware of any hardware limitations of the FDAC platform (with its dual DSP processors) - I believe we will be able to offer the entire miniDSP library if desired - although this is not my decision to make.

 

[jadidih101]

John, Glad you are home safely. Trying to send you a PM but your mailbox is full.

 

[JohnW]

John, Glad you are home safely. Trying to send you a PM but your mailbox is full.

Send to Renata's Email or mine

 

[Stunsworth]

All this sounds very good. I'm getting excited about this product.

Hope the luggage arrives before too long.

 

[jadidih101]

Send to Renata's Email or mine

Thanks John. Sent it to Renata's. Nothing too urgent. It is about my faulty MDAC PS unit. I have been without my MDAC for a couple of weeks now and I am beginning to show withdrawal symptoms

Cheers.

 

[fusion5]

Yes, forgive me, so far I've only concentrated on the Analogue stage, and essentially this is completed, so now we have sat down and really thought out the Digital PCB - and fixed its Spec.

The recent tie-up with miniDSP has allow us to add HDMI & include there DSP expertise to complete the "package"

Sounds great so far

How many digital inputs do we get?

 

[iansr]

John
Re the "internally isolated USB port", does that mean that a device like that Regen USB hub is very unlikely to produce any SQ improvement with the FDAC?

 

[timola]

We will add the more advanced features as soon as we have developed the software / firmware, the initial software will just feature "Treble and Bass sloping" DSP software but miniDSP will open there full portfolio of DSP software over time - I'm not aware of any hardware limitations of the FDAC platform (with its dual DSP processors) - I believe we will be able to offer the entire miniDSP library if desired - although this is not my decision to make.

Wow John...that's brilliant! The miniDSP Dirac hardware and software is several hundred dollars worth! (I think about $600.00US for their Dirac solution). Seems miniDSP are definitely giving this project some really valuable features at a seriously low cost price. For me the value for money of the FDAC unit has just increased again! I'm very excited by the possibilities going forward too, FDAC is definitely going to be a must have HiFi front end. Future Software releases will keep everyone busy and listening.

 

[JohnW]

Sounds great so far

How many digital inputs do we get?

The Spec's call for 6 BNC Flexible I/O's who's function can be defined "on the fly" but I need to insure I can squeeze all the I/O onto the rear panel, if space becomes short then I'll have to drop a BNC or Two...

 

[JohnW]

John
Re the "internally isolated USB port", does that mean that a device like that Regen USB hub is very unlikely to produce any SQ improvement with the FDAC?

Ian,

In a perfect world the Regen should make no difference but I suspect as there is not 100% perfect screening between digital domains I'd not be surprised if the Regen still effects the sound quality - although hopefully by a much smaller margin.

 

[Clerenlas]

John

I'm pleased that the phono module is now so firmly on the agenda. Where does it fit into the DSP development pattern you've outlined? I.e. when might we expect it to be available?

John

 

[adamdea]

Ian,

In a perfect world the Regen should make no difference but I suspect as there is not 100% perfect screening between digital domains I'd not be surprised if the Regen still effects the sound quality - although hopefully by a much smaller margin.

Quite difficult to finally eradicate a problem which might well not exist, and certainly can't be demonstrated to exist. Difficult design brief.
This months sterophile contains an interesting report on the audio quest jitterbug. John Atkinson fails to identify any consistent measurable effect but thinks it makes his Mac mini /laptop combo sound better.
Now assuming John Atkinson is responding only to vibrating air molecules- how would you change the device to make the jitterbug redundant? It already has no consistent measurable effect and strangely appears to work with all the dacs he used. Whereas the much greater measurable effect of using battery or mains power made no sonic difference.

How to solve such an elusive problem?

 

[sq225917]

Either it does nothing or hes not measuring the right things.

 

[adamdea]

Either it does nothing or hes not measuring the right things.

Possibly- the problem lies with specifying the problem. How do you filter out something you can't identify?

 

[JohnW]

Quite difficult to finally eradicate a problem which might well not exist, and certainly can't be demonstrated to exist. Difficult design brief.
This months sterophile contains an interesting report on the audio quest jitterbug. John Atkinson fails to identify any consistent measurable effect but thinks it makes his Mac mini /laptop combo sound better.
Now assuming John Atkinson is responding only to vibrating air molecules- how would you change the device to make the jitterbug redundant? It already has no consistent measurable effect and strangely appears to work with all the dacs he used. Whereas the much greater measurable effect of using battery or mains power made no sonic difference.

How to solve such an elusive problem?

If correctly implemented, the Regen should isolate the DAC from the Host PC USB Jitter - although its not designed to be "Jitter less" its easy to believe it will have a cleaner lower jitter eye pattern on its output ports then the PC native USB port.

Before I left for HK, there was a discussion that someone would send me a unit and I'd measure the ReGens Eye pattern.

 

[rtrt]

What are the most typical combinations?

Hi John,

I don't know about typical combinations, as my limited observation is that most, (though not all) phono stages offer little to no adjustment.

Speaking for myself as a MM owner only, i'd like to see MM capacitance ajustability between 50pF to 250pF. MM Resistance I'd like to see adjustable between 30k to 75k

Context of these values as follows;

My turntable/arm cabling of just over 120pF - I believe this is not untypical.

My 2 current cartridges;

• Goldring 1040 (old version of the 1042) which is specified for 150-200pF and 47k, but I've seen it suggested that it's better balanced with slightly higher resistance of somewhere just over 50k
  
• Shure M97xe which is apparently significantly more balanced sounding at c370pF and 75k.

My reason for suggesting flexibility below the 'standard' 47k resistance, even though those cartridges don't need it, is that Ive seen reviews of another good MM, the Ortofon 2M black which iirc suggested the low 30k's for resistance was ideal.

For comparison my current stage is c53k resistance and I think 220pF from looking at a circuit diagram.

If it becomes a challenge then a lower capacitance and a higher resistance, at least allow the use of external plugs, to vary capacitance up and resistance down as far as I remember.

 

[adamdea]

G

If correctly implemented, the Regen should isolate the DAC from the Host PC USB Jitter - although its not designed to be "Jitter less" its easy to believe it will have a cleaner lower jitter eye pattern on its output ports then the PC native USB port.

Before I left for HK, there was a discussion that someone would send me a unit and I'd measure the ReGens Eye pattern.

Yes. I seem to remember there was talk of someone sending you a unit. How do you measure USB jitter- is it a variation in the timing of the packets of data sent in 8 kHz bursts? If so, Is it jitter within a burst ie in the individual bits or a variation in the overall 8khz bursts? Sorry if this is a dumb question.

Where would we look to find the problem in the dac caused by this jitter?
If I understand it correctly the theory is that the jitter could possibly cause little electrical glitches which might somehow pollute the conversion clock and/or output stage.
Given the galvanic isolation between the USB receiver and the dac and the further (optical?) isolation between the digital and analog power supplies in the MDac2 then isn't one entitled to wonder how this rather indirect and (afaik) never actually demonstrated effect could be expected to change the sound of a Mdac2. Of course isolation is never complete , but how do we even know what we are aiming to isolate