JohnW
pfm member
The last of the Capacitors should arrive tomorrow... hopefully...
MDAC First Listen (part XXVI)
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The last of the Capacitors should arrive tomorrow... hopefully...
Thank you!
JohnW
pfm member
bsandovalb
Member
Hi John, sent you a PM some days ago with some questions regarding the mdac2 pcb board... Would appreciate if you can reply when you have time, thanks!
JohnW
pfm member
Paymant via PayPal (Credit card)
Total cost (+shipping) is targeted at £450 to £500, the first 3 instalments of £100 each of which are spread over the development cycle - with the last £150 to £200 covering the production costs (After testing of the prototype unit).
I like to target the first units being shipped around Christmas (so we can gift ourselves
) - but its fair to expect sometime between Christmas and February 2014 ...Postage via registered airmail, its a small package / PCB which can be shipped as a "service replacement part" if your unit has had issues
....Ignoring the DSD256, DXD 768fs support & AV bypass / Balanced Headphone output, dual ESS9018 DAC (16 DAC's in total) - I'm expecting a significant improvement in SQ - I'll also personally listen to each PCB and approve MDAC2's Sound quality.
I personally leave my MDAC powered on all the time, if your planning to upgrade to MDAC2 you don't have to worry about service life of your current PCB.
JohnW
pfm member
Sorry, I've never heard of the eclipse a502 power amp...
darrenyeats
pfm Member
It's not like physical windows, which we call transparent if you can generally see through them.
"Transparent" in audio is more analogous to a glass pane that is so see-through that you can't tell if it's really there or if there is just an empty frame, under certain viewing conditions. If there were such a piece of glass, then replacing it with a "better" piece of glass would have no discernible effect, under these certain viewing conditions, and we'd call it "transparent".
So it is relative, in that it depends on the viewing (listening) conditions. But it is absolute, in that under certain viewing (listening) conditions, an item can achieve absolute transparency.
Darren
Steven Toy
Accuphase newbie
Transparency in audio is a theoretical notion.
darrenyeats
pfm Member
Under certain listening conditions, it is a real thing that is achieved every day somewhere.
People tend to drop the "certain listening conditions" qualifier and that causes aggro. Of course "transparent" depends on the recording, the rest-of-system, the room, and perhaps even the listener.
For example, people have failed to detect an ADA loop in some particular tests that have been carried out, these are documented. So we can be confident in the context of these tests the ADA loop was transparent. Of course, it might be possible to detect a modern ADA loop under certain OTHER conditions (I mean that sincerely). However, this hasn't been demonstrated in any of the controlled tests I have heard about so far using music. It is possible to hear differences with "corner case" test-tones apparently ... we are back to context.
Darren
JemHayward
pfm Member
Hi John,I like to target the first units being shipped around Christmas (so we can gift ourselves
I'm also interested in the MDAC MK2 upgrade but I would like to clarify some questions on which I was unable to find answers here:
1. Will I need to send back the old MDAC mainboard after upgrade or not?
2. Will the MDAC MK2 upgrade incorporate the stepped attenuator (like was planned for MPAX) or not?
3. Please explain how will operate the digital volume control in case of DSD?
4. What kind of USB chip are you going to use in the MDAC MK2: XMOS or VIA VT1731?
5. Are you going to use in the MDAC MK2 design a digital isolator (like ADuM1401) in order to provide galvanic isolation from PC?
6. If I understood correctly the MDAC MK2 will use the same external power supply as original MDAC. There are any news regarding fate of the MPAX in connection with the MDAC MK2 project?
Thanks in advance!
Nick
Hi Nick, here are the answers you seek:
1. We would prefer to take ownership of the original mainboard after the swap. It will be of no use to the owner after all, but we can harvest certain components out of it and put them back in use.
2. No attenuator in analog domain.
3. Volume control in DSD works identically as with PCM. This does not apply just to M-DAC, but in the most general sense. DSD is nothing but a 1 bit PCM at 2822.4 kHz sampling rate with a noise shaping applied. Just like CD is a 16 bit PCM at 44.1 kHz with a noise shaping applied (most albums produced in the past decade or two anyway). Both achieve higher dynamic range within audio band than what their bit depth would imply were it not for the noise shaping of their quantization error. To change a volume equates to multiplication with a constant. This creates a resulting sample with a bit depth equal to the original sample + the multiplication constant bit depths. In case of CD and a 32 bit constant the resulting sample would have 48 bit resolution (16+32), whereas with DSD the same multiplication would result in 33 bit resolution (1+32). In the end, the resulting samples have to be converted to a fewer bits again. And since nobody likes to introduce quantization error caused by truncation, instead a noise shaping is used to push the error out of the audio band of interest. If the volume control worked at the source sampling frequency, the CD version would have a very limited frequency band in which to push the noise, but on the other hand, the noise would be at the 16 bit LSB level which is indeed very low. In case of DSD the sampling frequency offers up vast amounts of super-sonic band in which to push the quantization error, however on the other hand the quantization noise itself is of extreme magnitude. The process is the same, the constellation is different, but the physical reality still applies when it comes to channel capacity being a function of both bit depth (channel SNR) and sampling rate (channel bandwidth).
If somebody tells you they are mixing or adjusting level "in DSD" what they are saying is that the black box takes DSD on it's input and spits out DSD from it's output, but if you look inside the black box you will find intermediate PCM values all over the place, not least in every integrator of a noise shaping loop aka sigma delta modulator. In case of M-DAC 2 the DSD input format is 1 bit 2,822.4 kHz and the output format is 9 bit 86,000.0 kHz.
The secret that makes DSD preferable over PCM is the high sampling rate, thanks to which digital filters can be eliminated from the ADC-DAC chain. The fact that DSD has only 1 bit resolution is the direct result of a tradeof between bit depth and sample rate. DSD went all in on sampling rate with it's available data rate budget. Other possibilities resulting in the same datarate would have been 2 bit 1411.2 kHz or 4 bit 705.6 kHz or 8 bit 352.8 kHz or 16 bit 176.4 kHz or 32 bit 88.2 kHz or 64 bit 44.1 kHz. Not all of them would make sense though.
4. Neither of them or any other 3rd party solution. We have our own implementation running on a general purpose ARM processor.
5. No, we prefer not to generate masses of RF radiation right inside the sensitive DAC chassis if we can help it. The correct solution to isolating audio source and a DAC is a bidirectional fiber optic link which is present on current M-DAC and will be on M-DAC 2 as well. Later we will make a dedicated transport component supporting this connection. Ultimate solution to the isolation problem. Both galvanic and RF, while keeping the DAC as a clock master.
6. M-DAC 2 being a mainboard swap for original M-DAC will keep on utilizing much of the original M-DAC chassis and accessories including the outboard transformer unit. The internal power supplies are significantly upgraded on the new mainboard though.
Have a nice day,
Dominik
fred sonnen
pfm Member
1. Thats new, but make sence.
6. that was my expectation. with the mdac2 is the MPAX obsolete.
JohnW
pfm member
At this time, we would only ask for the PCB to be returned if we cannot meet the GBP150 build cost - at which stage we could start to harvest the more expensive items from the original PCB's to keep to costs on target - however I'd rather not need to entertain this option ATM...
eddie pugh
pfm Member
John
I like the idea of the MDAC MK2 but how does this work if I want an MDAC MK 2 but don't at the moment have a MDAC. Do I have to go out and splash £600 on an MDAC only to throw the board away 6 months down the line.
Does the OLED display come attached to the new board.
Did that idea of retrieving MDAC casework from Audiolab come to anything?
eddie
I like the idea of the MDAC MK2 but how does this work if I want an MDAC MK 2 but don't at the moment have a MDAC. Do I have to go out and splash £600 on an MDAC only to throw the board away 6 months down the line.
Does the OLED display come attached to the new board.
Did that idea of retrieving MDAC casework from Audiolab come to anything?
eddie
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