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MDAC First Listen (part 00110011)

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adamdea

adamdea

You are not a sound quality evaluation device
Discovery said:
While it's quiet, I noticed this recently...

Bryston, US manufacturer of exotic hifi equipment, recently introduced an entry-level digital player into their range. Surprisingly, they make no secret of the fact that it's based on a Raspberry Pi 2 and a HifiBerry S/PDIF output board.

Bryston certainly appear to take this hardware seriously: http://bryston.com/products/digital_audio/BDP-Pi.html
Click to expand...
I wonder what exactly they have changed beyond the price.
 
There is a nice box, a display and a power supply... plus a lifetime warranty.
The funny thing is that this isn't even based on the latest pi.

I'm also wondering what software this runs... but all of this should be for another thread.
 
Ian you have gain to burn via balanced outputs, why not just split the cable after the DAC. I use my mdac at minus 10db and about 1/10th of the volume of the bpbp.

What exactly is it you want to achieve?
 
iansr said:
I'd been given to understand that if I used 2 identical DACs that I would be OK and it never occurred to me that their outputs could be out of phase. Given this additional info do you still think there is a potential phase problem?
Click to expand...

Even with two identical DAC's there's nothing to guarantee the channels will be in-phase due to the internal PLL / ASRC locking arrangement - hence the Clock link on the FDAC.

Its not easy to lock two DAC's on the same PCB with internal ASRC...
 
sq225917 said:
Ian you have gain to burn via balanced outputs, why not just split the cable after the DAC. I use my mdac at minus 10db and about 1/10th of the volume of the bpbp.

What exactly is it you want to achieve?
Click to expand...

Simon
I've got 4 separate unique channels ( 2 per speaker) to convert from digital to analog, hence I need 2 x 2 channel DACs.
 
JohnW said:
Even with two identical DAC's there's nothing to guarantee the channels will be in-phase due to the internal PLL / ASRC locking arrangement - hence the Clock link on the FDAC.

Its not easy to lock two DAC's on the same PCB with internal ASRC...
Click to expand...

John
Ok - I'll send you a Skype message.
Cheers
Ian
 
JohnW said:
We had Phase issues with the MDAC2 prototypes that used one DAC per channel (and same Master clock) on SPDIF signals - we had to resort to a few tricks to force rapid Phase Locking between DAC's (and Audio Channels).
Click to expand...

What were the adverse effects of this?
(I'd have expected that the long term stability in each DAC, and therefore channel, was good rather than (say) sample to sample phase shifts. And therefore the effect should only have been like moving your head (very) slightly to one side.)
 
iansr said:
Simon
I've got 4 separate unique channels ( 2 per speaker) to convert from digital to analog, hence I need 2 x 2 channel DACs.
Click to expand...

Sounds like what you need is quad channel dsp and DAC in one clock locked device.
 
ChrisPa said:
What were the adverse effects of this?
(I'd have expected that the long term stability in each DAC, and therefore channel, was good rather than (say) sample to sample phase shifts. And therefore the effect should only have been like moving your head (very) slightly to one side.)
Click to expand...

Chris,

On an early MDAC2 development board we looked at 20KHz FS signwaves on a scope for each channel (via SPDIF inputs) and you could see during a lock event that the channels would be out of phase with each other - drifting between each other (not a fixed phase error) - sometimes taking minutes to "Snape" into phase lock.... thats with a Single Master Clock to both DAC's - so without too much thought its easy to imagine the situation with separate non Clock Locked DAC's...

The inter-channel locking Phase was VERY random... I recall early ASRC IC's used to have Sync pins to synchronise multi channel applications - the ESS devices dont have this feature.
 
Hi John

M-DAC arrived back today safe and sound. Listening to it right now, sounding great again through Sennheiser HD650! Thanks very much for your time and trouble.

Many thanks

mrflibble
 
I can send my sources to either the coax or optical inputs of the mdac. Is there any diffference in sq introduced by the mdac?
 
mrflibble said:
Hi John

M-DAC arrived back today safe and sound. Listening to it right now, sounding great again through Sennheiser HD650! Thanks very much for your time and trouble.

Many thanks

mrflibble
Click to expand...

I wanted to say that to you and Superior to give your unit a few days "run-in" period as you have a host of new Caps + extra organics, and to my ears they need to run-in...

IIRC, you have V0.90 installed - it be interesting to see if you hear any difference with later software versions.... I prefer V0.90 (as a side note, you have the Detox version of V0.90 installed - it has the 12MHz output option in the "SPDIF output menu").
 
Rjpcardoso said:
Johnw as it's been so quite here, let me tease you with this amp. We saw it at the show and thought it was the vfets :eek:

https://www.criterionaudio.com/product/boulder-2160/

The amp sounded veryyy good but I am sure the Vfets will be better!
Any developments on the projects recently?

Regards,
Ricardo
Click to expand...

Ricardo,

We are waiting for the 6 Axis CNC machines to arrive to sample the VFET chassis - I loosely hoping to arrange (collect) while I'm in China for Detox production.
 
brab said:
I can send my sources to either the coax or optical inputs of the mdac. Is there any diffference in sq introduced by the mdac?
Click to expand...

For sure there will be, so try both options and see which sounds better in your system.
 
Hi John

Are the 'MiniAmps' the 8200MB re-engineered? ...I'm a bit confused as to what these items are if not those?

Thanks
 
JohnW said:
I wanted to say that to you and Superior to give your unit a few days "run-in" period as you have a host of new Caps + extra organics, and to my ears they need to run-in...

IIRC, you have V0.90 installed - it be interesting to see if you hear any difference with later software versions.... I prefer V0.90 (as a side note, you have the Detox version of V0.90 installed - it has the 12MHz output option in the "SPDIF output menu").
Click to expand...

Thanks John :)

How many hours run-in do you recommend?

Out of interest, what are the extra capacitors for?

Cheers

mrflibble
 
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