MDAC First Listen (part XXIX)

[Mikas]

I agree - its a complicated and uncommon interface... nothing wrong with USB for Audio.... Every PC has a USB port...

I find it odd that the Hifi industry in general doesn't appreciate the added value of having a 'smart' ip based DAC.

There are discussions around Transport problems. Unreliable streaming, cable length, timing, electric interference, etc.

If you build an IP DAC, you will be able to completely control the quality of the bit streaming.

Personally, and to be completely honest about it, I think it's very easy to find reliable enough transports at very low costs. But then again, we can have full Ethernet support devices costing less than €50, so I really have some trouble to understand why this isn't a more common option.

From the user end side, it's hard to understand why should we have to assure reliable bit transmission over the length of a song, when we could just copy it in a couple of seconds and let the DAC then take care of the streaming/transport.

Michael

 

[AndyU]

So I think it comes down to a couple of things:
1) is there a completely universal streaming protocol which everyone uses is well understood and which supports all features hifi boxes need? For example many DLNA implementations don't do gapless properly? How many really support highres and DSD? [Squeezeboxes have their own protocol etc.]
2) do you want your dac designer to spend lots of time integrating the software and supporting it (and do they want to do it)?

It's easy if you know how. Slimdevices did it years ago. Linn can do it. Naim can do it. Cambridge Audio (ffs!) can do it. Auralic will soon do it. Gapless streaming is a done deal, if you know what you're doing.

 

[arthur]

Arthur my amps are either my Cyrus class AB or WAD class A no class D in my system.

Its just the way digital preamps work when run at low volume setting they throw away detail and dynamics but when run at high volume settings the sound is better the higher the setting.

In my system with 250 watts into 4ohm and 90 db speakers the volume setting on my M-dac when fed direct with the onboard pre was down in the 50 db to 40 db range on the m-dac display.

When I then run the M-dac through my Passion - Audio Synthesis passive and run the M-dac +3 and use the passive to attenuate the volume im getting optimal M-dac sound full detail full dynamics full volts and current.

Better still to my ears is to disable the M-dacs preamp and attenuate the volume with a analogue preamp.

Cheers John, I understand the notion of not using the dac at such tiny levels, but I had assumed that anything over about -30db would be ok though.


The reason I asked was because Rune uses digital amps and I'm under the impression that these benefit from the removal of RF noise quite markedly.

I also have a pair of class D amps driving the bass driver in my Adams, so I'm keen to eliminate any stray rf.

I might have to try a pre-amp...just in case.

 

[john dolan]

Cheers John, I understand the notion of not using the dac at such tiny levels, but I had assumed that anything over about -30db would be ok though.


The reason I asked was because Rune uses digital amps and I'm under the impression that these benefit from the removal of RF noise quite markedly.

I also have a pair of class D amps driving the bass driver in my Adams, so I'm keen to eliminate any stray rf.

I might have to try a pre-amp...just in case.

Well as JW just posted

Listening at -35dB to 40dB is an awful lot of attenuation, -40dB is x100 Attenuation!!! or you can look at it as a x100 increase in RF level relative to your audio signal... "amplifying" RF levels is never wanted in an Analogue system - forget by x100...

RF is also involved here so yeah give a passive a try m8 see how you go.

 

[arthur]

Listening at -35dB to 40dB is an awful lot of attenuation, -40dB is x100 Attenuation!!! or you can look at it as a x100 increase in RF level relative to your audio signal... "amplifying" RF levels is never wanted in an Analogue system - forget by x100...

Care has been taken with the design of the MDAC2's Analogue stage to provide passive RF attenuation before it reaches the Active gain stage... TDAC with its Tube front end will be more tolerant of unwanted RF modulation (Tubes behaviour more linear then semiconductor devices in the presences of RF energy).

A design defect of the ESS modulator stress the RF rejection performance of the Analogue stage - we will resolve this issue once we release the MDAC2 firmware upgrades (via software) that implements our own FPGA modulator design. So MDAC2 performance will progressively improve further as we introduce later "Software" upgrades.

Thanks John.

My usual listening with your attenuators is about -30 to -25 dB. Which I assume isn't too bad. It sounds mighty fine indeed.

But as I have the classD amps I was just wondering if using say a passive pre with the M-dac whacked up to +3dB might be the best idea to decrease any rf to the tiniest amount possible.

Having said that, for all I know Adam may well have a built in solution to any rf issues. They are hardly amateurs.

 

[arthur]

Well as JW just posted

Listening at -35dB to 40dB is an awful lot of attenuation, -40dB is x100 Attenuation!!! or you can look at it as a x100 increase in RF level relative to your audio signal... "amplifying" RF levels is never wanted in an Analogue system - forget by x100...

RF is also involved here so yeah give a passive a try m8 see how you go.

I'll be trying to borrow one I think, they are expensive. But I'll happily get one if I prefer the sound I get with it.

 

[Adrian]

It's easy if you know how. Slimdevices did it years ago. Linn can do it.

Yes I know

 

[JohnW]

Hi John et al.

As I'm a little late to the "party" - how should I proceed if I want to test the coming MDAC2 out?
j
1) Buy / pay for both a salvaged MDAC + installments 1+2 on the LakeWest MDAC2 website?

2) or...?

Best wishes,
Peter

Peter,

Thank you for your interest in our MDAC2 project - I'd just caution you not to trust my development times - more realistically we are looking at around June when the first MDAC2 PCB will be shipped.

Hopefully the delay will not be too much of a deterrent - if you still wish to proceed then "Option 1" is the way to go.

 

[JohnW]

Thanks John.

My usual listening with your attenuators is about -30 to -25 dB. Which I assume isn't too bad. It sounds mighty fine indeed.

But as I have the classD amps I was just wondering if using say a passive pre with the M-dac whacked up to +3dB might be the best idea to decrease any rf to the tiniest amount possible.

Having said that, for all I know Adam may well have a built in solution to any rf issues. They are hardly amateurs.

Arthur - Don't you have some -20dB Attenuators I made for you? (or did they negativity effect the sound too much)?

 

[JohnW]

I find it odd that the Hifi industry in general doesn't appreciate the added value of having a 'smart' ip based DAC.

There are discussions around Transport problems. Unreliable streaming, cable length, timing, electric interference, etc.

If you build an IP DAC, you will be able to completely control the quality of the bit streaming.

Personally, and to be completely honest about it, I think it's very easy to find reliable enough transports at very low costs. But then again, we can have full Ethernet support devices costing less than €50, so I really have some trouble to understand why this isn't a more common option.

From the user end side, it's hard to understand why should we have to assure reliable bit transmission over the length of a song, when we could just copy it in a couple of seconds and let the DAC then take care of the streaming/transport.

Michael

Michael,

The issue is one of developmental resources - not just the initial product developmental but then the endless support required afterwards.

Also the DAC should be consider primary an Analogue device - for the very best performance you need to isolate heavy digital processing and non related clocks (Ethernet requires multiple clock frequencies for the PHY and other layers of processing) - these all radiate RF energy which is near impossible to isolate within a confined enclosure that houses the critical analogue stage.

My expertises is in Analogue design and conversion, I'm not a "Computer engineer". Leave the analogue to analogue experts - and leave the digital streaming hardware to the "computer" experts.

 

[Rosewind]

Peter,

Thank you for your interest in our MDAC2 project - I'd just caution you not to trust my development times - more realistically we are looking at around June when the first MDAC2 PCB will be shipped.

Hopefully the delay will not be too much of a deterrent - if you still wish to proceed then "Option 1" is the way to go.

Thanks John, much appreciated. I'll jump on the roller-coaster.

Best wishes,
Peter

 

[Rosewind]

Hi all.

Just some more info please:

Toy or Fusion upgrafes? Where do they fit in the picture when ordering the MDAC2?

Thanks,
Peter

EDIT: Just paid installments 1+2 and for a "salvaged" Black MDAC

 

[arthur]

Arthur - Don't you have some -20dB Attenuators I made for you? (or did they negativity effect the sound too much)?

I do john.

They make it possible to listen at between -30 and -25 dB.

I was simply wondering, because of the digital amps I have, if it would be better again to use the MDac right down to 0 dB with a preamp?

Just messing about until I get the MDac 2 sorted

 

[JohnW]

This evening I just could not resist building up a Tube Analogue stage for the "TDAC" …

As it’s a crude “rats nest build” on the lab bench, its not the full circuit I have in mind for the TDAC – but atleast it gives an idea of what’s possible in performance terms using long life subminiature tubes.

Remember this is only the result of a basic Single ended test (without the advantages of a fully balance output), and simplified test circuit…

THD at 1KHz @ 2Vrms 0.0002%

THD at 1KHz @ 1Vrms 0.00009%

Awtd Dynamic range 121.8dB (Single ended)

Even I’m impressed… especially for my first tube circuit in maybe 15 years

https://dl.dropboxusercontent.com/u/86116171/Tdac Proto.JPG

And FFT 1KHz 2Vrms

https://dl.dropboxusercontent.com/u/86116171/Tdac proto 1KHz 2Vrms.jpg

I get pretty upset when people make cheap swipes at Tube sound quality saying “Oh you just like the sound of Tube distortion” when with a simple but well designed Tube stage you can achieve 0.0002% THD at FULL level (I believe it’s a pretty unique circuit I’ve developed – hence why I was so keen to confirm the results of the computer simulations).…

I'm a happy little bunny tonight...

 

[JohnW]

Hi all.

Just some more info please:

Toy or Fusion upgrafes? Where do they fit in the picture when ordering the MDAC2?

Thanks,
Peter

EDIT: Just paid installments 1+2 and for a "salvaged" Black MDAC

Thank you for your payment(s) - Renata will send you a confirmation Email in the morning.

Well the Toy / Fusion are proposed upgrade options - we can only decide upon the exact variations once we have a completed design .. so at the very last stage, just before production. The final Payment (after the 3rd and last installment) basically covers the build cost of the PCB - at this stage you can order any options.

 

[zzzmonster]

This evening I just could not resist building up a Tube Analogue stage for the "TDAC" …

As it’s a crude “rats nest build” on the lab bench, its not the full circuit I have in mind for the TDAC – but atleast it gives an idea of what’s possible in performance terms using long life subminiature tubes.

Remember this is only the result of a basic Single ended test (without the advantages of a fully balance output), and simplified test circuit…

THD at 1KHz @ 2Vrms 0.0002%

THD at 1KHz @ 1Vrms 0.00009%

Awtd Dynamic range 121.8dB (Single ended)

Even I’m impressed… especially for my first tube circuit in maybe 15 years

https://dl.dropboxusercontent.com/u/86116171/Tdac Proto.JPG

And FFT 1KHz 2Vrms

https://dl.dropboxusercontent.com/u/86116171/Tdac proto 1KHz 2Vrms.jpg

I get pretty upset when people make cheap swipes at Tube sound quality saying “Oh you just like the sound of Tube distortion” when with a simple but well designed Tube stage you can achieve 0.0002% THD at FULL level (I believe it’s a pretty unique circuit I’ve developed – hence why I was so keen to confirm the results of the computer simulations).…

I'm a happy little bunny tonight...

Congrats John,

So will the TDAC be part of MDAC2, if yes, I will hop on this rollercoaster now

 

[JohnW]

Sadly not - the tube circuit requires higher PSU voltage rails then I'd hoped - its too messy to make it a common platform with the MDAC2 design - although it can follow very quickly after the MDAC2 launch.

I need a little time to consider how to proceed with the TDAC... I'm rather keen on the TDAC... (But bare in mind I've not listened to it yet)...

Not only was I keen to test the Tube circuit topology - but its been useful feedback to gain further confidence in the computer simulations as the design shares much in common with the MDAC2 analogue stage (Sans tube)... this and the results from the first version of the MDAC2 prototype analogue stage design has yielded a treasure trove of positive results confirming the validity of the past couple of years R&D since returning from China - I'll be very proud of the MDAC2 design once its completed!

 

[fusion5]

All this TDAC talk makes me hungry

Keep up the good work John!

 

[JohnW]

My khozmo preamp has arrived. It took exactly the week not to bad!

... and the conclusion is that it has made a big improvement over using the pre in the mdac. My normal listening levels would be 35-45 db.
Now the music sound more natural and dynamic.
The sound stage has improved and it sounds more natural. The base tighter and deeper and there are more high frequency details.
I had expected it to be bright sounding with the silver wiring, but not at all with my speakers and amps (dali epicon 8 and ncores)

Now I can finally listen at lower volume without the music sounding flat and unemotional which is a big plus.

Can't wait to hear the mdac2 in my system

Rune,

I'm very glad to hear your happy with your khozmo preamp, I'm amazed every time I look at the workmanship of the attenuator (I've got a sample on my lab bench)... Areks done an really amazing job!

I'm still pondering how to incorporate it into our designs... Maybe a hi-end reference unit...

 

[JohnW]

All this TDAC talk makes me hungry

Keep up the good work John!

Thank you

Worked though the night on the little tube stage - its nice to have such positive result after so much background development work over the past couple of years...