JohnW
pfm member
Before we can even discuss the DAC - the ADC itself is not a 1 Bit modulator - rather 6bits so it does not output a pure unfiltered DSD stream, the "DSD" output is generated after conversion by a 1Bit "Re"modulator...
MDAC First Listen (part 00100011)
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Before we can even discuss the DAC - the ADC itself is not a 1 Bit modulator - rather 6bits so it does not output a pure unfiltered DSD stream, the "DSD" output is generated after conversion by a 1Bit "Re"modulator...
JohnW
pfm member
I'm so looking forward to designing the VFET amps - it will seem like a walk in the park after working on the MDAC2 design these past 3 years...
BTW, the VFET amps despite using Tube front end will be ultra linear
JohnW
pfm member
Well the Arda is 6Bits but I guess your asking about "Full" data widths...
adamdea
You are not a sound quality evaluation device
I meant non-delta-sigma dacs operating at 44-200khz sampling rate. I thought from ChrisPa's post that he was talking about the sort of Anti alias filter that that sort of ADC would require.
Anyway can you help with this bit John- will the M-dac2 have any analog filter before the ADC?
JohnW
pfm member
The MDAC2 L3 ADC have a max sampling rate of 7MHz per modulator with 2 modulators per channel combined resulting in 14MHz as the highest sample rate mode.
As the ADC also has to support lower sampling rate of 64Fs for DSD64 the analogue filter should filter "everything" above 1.411MHz - although I'll design a much softer low order analogue filter - Ill target a -3dB point at around 100KHz.
iansr
pfm Member
I'm so looking forward to designing the VFET amps - it will seem like a walk in the park after working on the MDAC2 design these past 3 years...
BTW, the VFET amps despite using Tube front end will be ultra linear
I'd expect nothing less from you John
I actually want the reproduction device to be as neutral as possible.
Then give me EQ controls for adding DSP based distortion, so I can decide what I like, even when not truthful.
But, that's just me
It's binary
There are only two states of mdac listen
Not heard it = 0
Heard it = 1
"First" is the state with the value one
Obvious!
misterdog
Not the canine kind
JohnW
pfm member
Mike - indeed
obviously you have some knowledge in this area Back in early late nighties when I worked on early FPGA based modulator designs I still recall how when we changed from a second order to third order modulator the third order sounded worst then the 2nd order despite its better simulated results. The 3rd order lost the "Dynamic" realism of the simpler 2nd order Mod. much in the same way I have a problem with PCM verses DSD.
ESS has a decent video lecture on the net where they discuss the care they have taken with there modulator design to "Constrain" the State variables during transient changes - very interesting as this closely follows what we discovered.
One of our solution is to use cascaded 1st order modulators (AKA a MASH type structure) where each modulator loop is therefore inherently "Bounded" between changes of state....
Also we would like to try "predictive" modulators...
JohnW
pfm member
PhilCTTE
Senior mumbler
Got the Auralic Aries up and running with my MDAC and very sweet it is ....
Coax/Optical/USB dig outputs. Still very early days only a few nights listening.
Will try and do an A/B of interfaces and source (NetBook) and give some feedback soon.
The lightning ds control app is nice. Simple to use which is key.
Running a minim server on my Qnap nas. Only problem I have at this stage is I havent been able to re-build the database index of new cd's I've added. Will spend an evening to sort this hopefully.
Its much more of a hifi component than a computer which is what I was after.
I,ve removed the usb isolator and so far not a hiccup in any playback.
Coax/Optical/USB dig outputs. Still very early days only a few nights listening.
Will try and do an A/B of interfaces and source (NetBook) and give some feedback soon.
The lightning ds control app is nice. Simple to use which is key.
Running a minim server on my Qnap nas. Only problem I have at this stage is I havent been able to re-build the database index of new cd's I've added. Will spend an evening to sort this hopefully.
Its much more of a hifi component than a computer which is what I was after.
I,ve removed the usb isolator and so far not a hiccup in any playback.
Nice, keep us posted.
As an interim solution I've bought a Squeezebox Classic (never used) to be used with ickStream API and stream Wimp/Tidal HiFi through the MDAC.
adamdea
You are not a sound quality evaluation device
If we are running the M-dac 2 at 9 bits and 14Mhz, do we need any more than a second order modulator. I'm too knackered to work this out but surely with even a first order modulator, the noise level in the audible range must be pretty low.Mike - indeed
Back in early late nighties when I worked on early FPGA based modulator designs I still recall how when we changed from a second order to third order modulator the third order sounded worst then the 2nd order despite its better simulated results. The 3rd order lost the "Dynamic" realism of the simpler 2nd order Mod. much in the same way I have a problem with PCM verses DSD.
ESS has a decent video lecture on the net where they discuss the care they have taken with there modulator design to "Constrain" the State variables during transient changes - very interesting as this closely follows what we discovered.
One of our solution is to use cascaded 1st order modulators (AKA a MASH type structure) where each modulator loop is therefore inherently "Bounded" between changes of state....
Also we would like to try "predictive" modulators...
JohnW
pfm member
Well that's what we will play with - certainly I can see a version of firmware with selectable Noise shaper order - maybe we will release the initial Beta version labelled A,B,C,D etc. for Blind listening...
adamdea
You are not a sound quality evaluation device
It's an interesting question as to whether given the increase in resolution available from using 2 DAC chips, and from running them in your special mode (IIRC), you might want to trade a little bit of snr against some other benefit from less aggressive noise shaping.
Apart from that, can you confirm whether the initial release M-dac 2 will be using the native ESS noise shaping (with all of bespoke fun and games to come) or whether the inital release (maybe the l2) will be starting off with some sort of custom noise shaping to be refined later on?
I thought that was answered by John's comment that, when first released the fpga won't do anything.
So I've understood that stuff like noise shaping will come later
JohnW
pfm member
Adam,
I'll be happy when the MDAC2's up and running with the ESS in "Native Mode" - the FPGA based noise shaping will be released much later - for such major advance "Pay For" functional upgrade there will be a small fee to help cover the development costs - there might be 6 months to a year development involved.
I has been suggested by other's in earlier posts that any "Pay for" Firmware upgrades can be downloaded for free with say a "spoiler tone" or some such every 5 to 10 minutes, this will allow owners to listen and decide if they wish to purchase the "Unrestricted" option.
The "Pay for options" are for those options that take a significant amount of development resources - not for simple features such as EQ etc.
The aim is not to make money from the "Advanced" upgrades, but just to help cover development costs - if it takes Dominik 6 months to a year to develop a feature - then I need to cover these costs somehow, we might just add a simple "Donate" button to remove the "Spoiler" - then the owner can pay what they feel is far.
It just depends where we will be financially one year down the road.
I'll be happy when the MDAC2's up and running with the ESS in "Native Mode" - the FPGA based noise shaping will be released much later - for such major advance "Pay For" functional upgrade there will be a small fee to help cover the development costs - there might be 6 months to a year development involved.
I has been suggested by other's in earlier posts that any "Pay for" Firmware upgrades can be downloaded for free with say a "spoiler tone" or some such every 5 to 10 minutes, this will allow owners to listen and decide if they wish to purchase the "Unrestricted" option.
The "Pay for options" are for those options that take a significant amount of development resources - not for simple features such as EQ etc.
The aim is not to make money from the "Advanced" upgrades, but just to help cover development costs - if it takes Dominik 6 months to a year to develop a feature - then I need to cover these costs somehow, we might just add a simple "Donate" button to remove the "Spoiler" - then the owner can pay what they feel is far.
It just depends where we will be financially one year down the road.
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