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HOLO Audio MAY DAC


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That's what I thought. I hope the +5V coming from the source is used only for the hand-shake / initialisation.

 

But, how would they separate the grounds (laptop ground -  MAY DAC ground, using the isolator IC's, and still be able to power up the whole USB interface with the internal power supply. This would mix the grounds and make isolator chip redundant. 

 

It would be good to know exactly how it's done.

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  • 2 weeks later...

I have been listening to DDDAC with WaveIO USB interface for 3-4 years. This was a DIY project that turned into a brilliant sounding, true NOS DAC. Extremely straight-forward with a lot of very low noise regulation (even the isolator chip on WaveIO board had its own, dedicated very low noise regulator). Many improvements over the original design had been made. The output from 33ohm I/V resistors was then taken straight to Aleph J clone (only 2 gains stages, last one working in a single-ended pure class-A config) - without a single coupling capacitor in the whole signal chain. Just wonderful.... with one minor annoyance -> DDDAC being a true NOS DAC (digital filters on DAC IC's disabled), suffered from the high frequencies roll-off + it had a fair bit of distortions (especially with higher sample rate material being fed to it). So, I was delighted to see a discrete, true ladder R-2R design that also measured exceptionally well. And I pulled the trigger and ordered May DAC.

 

Well, what I've been looking for I managed to find in this DAC. It's an amazing blend of natural sound, plenty of details, and support of various file formats to allow people to obtain the sound that best suits their taste and the rest of their system. Outstanding! It is obvious that someone with great experience, true love and dedication for High-End HiFi, spent a lot of time and invested a great amount of knowledge to create May. 

 

I found the best results with true NOS, no overselling neither in hardware (May) NOR in JRiver that I use. Very close to analogue sound; very faithful to how the instruments should sound. Great dynamics (black background). Very quiet -> my Aleph J with 240Kohm input impedance picks up the tiniest amount of noise coming from the source - and this thing (May) is exceptionally quiet. And the total absence of distortions.... finally!

 

What also helps is a minimal amount of noise coming from the PC - so, the CPU's that can be downclocked to 400MHz or 800MHz, low noise linear power supply, an OS that installs a bare minimum of applications.... all help. It is somewhat a different approach to oversampling to the max that May can support... but oversampling may work for others - that is completely fine and understandable. 

 

 

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2 hours ago, lpost said:

Here's what Tim said in reply to my question about the 5V line.

 

'USB port needs 5V for handshake. So I just say these is zero advantage to make a cable without this 5V connection. Our usb module is isolated and does not use the 5V for anything other than the handshake. It’s self powered and ultra low noise voltage regulators. No worries. Hope you don’t bother with the usb non standard cable as it will only create issues with connections snd give no other advantages'

Yes, I understand the above, thanks. 

 

The question is: do you believe that the 5V rail sitting in parallel with + and - USB data can influence USB data transfer in any way, or it can not... I like to disable the 5V DC coming out of the laptop, once the handshake is done.... even though the USB interface inside the May DAC has its own low voltage regulator(s).

 

It's not what the laptop +5V DC does to the USB interface inside the May DAC; it's what it could potentially do to + and - USB data integrity (especially at those high transfer rates when oversampling; DSD256 for example)... along the full run of the USB cable. This is taking it to the Exterme... it doesn't have to be done, of course.

 

Now, few of you may say: "+5V DC coming from the laptop can not do too much harm because there's no current running along that 5V DC wire, once the handshake is done!" ....but, without knowing the exact schematics and what type of IC's are involved during that hand-shake, I decide to turn OFF the 5V DC coming from the laptop once it's not needed any more.

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  • 3 weeks later...

I ordered my May DAC L2 from Wildism Audio HK. Jo was exceptionally friendly and quick in his replies; he was replying to my emails pretty much straight away as I was clicking on "send" button.

 

But the mazing thing happened when I ordered the DAC (from Hong Kong), and then received it in Sydney... after 4-5 working days. Stunning. Jo also found time to check the unit and confirm it was working correctly before he shipped it.

 

 

 

 

 

 

 

 

 

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  • 2 weeks later...

I have spent a lot of time experimenting as well. The most relaxed, detailed and natural sound I get is with LSN15 shaper, upsampled to 1.536Mhz, using poly-sync-lp filter and bit-depth of 20bits. It is an exceptionally enjoyable experience. Moving from 768KHz to 1.536MHz is like going from standard crystal oscillators to low phase noise ones (NDK SD to SDA). The bass frequencies are also fuller, better defined and fully integrated. Nothing sticks out; everything sounds just right. 

 

There's a caveat to the above....  I get much better sound (more natural and relaxed) with my laptop - battery powered, compared to NUC11 powered with a low noise linear power supply. The difference is striking. I noticed that many manufacturers are moving towards "zero noise" supper capacitors based power supplies, which they also use to do upsampling inside the DAC unit itself. 

 

I was just about to give up on digital and go back to analog (turntable and reel-to-reel)... and then along came the May DAC and the HQ Player.

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Asynchronous USB looks to be the perfect solution; you configure your PC for bit-perfect output and the DAC takes care of the timing totally independent of the timing of the PC.

 

But there are posts on the Internet claiming that even in the case of an async USB DAC what is happening upstream is still affecting sound quality. Sending a signal to a DAC is done using a 100% analogue waveform/carier. The digital packets are superimposed on this, still analogue, waveform. But can software affect this wave? Is it done in bursts or is it throttled? The burst might induce periodic jitter, the throttle a constant jitter. 

 

Asynchronous USB is theoretically meant to make the USB receiving device immune to the PC, but..... it isn't immune. I can clearly hear the difference in sound when I use various laptops/desktops/NUC11.  I found the lower the switching frequency of the CPU and the lower the switching voltage of the CPU (the switching voltages in general... on the motherboard) - the more pleasing and analogue sound I hear.

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4 hours ago, Miska said:

 

Asynchronous USB Audio Class transfer sends data every 125 µs (8 kHz rate  you can see sometimes leaking to DAC analog output).

 

How much data is sent on this block is controlled by two things; 1) audio format (sample rate, number of bits and number of channels), 2) asynchronous feedback from the DAC.

 

This data ends up in memory buffer at DAC which is then playing it out from there based on it's master clock. If the buffer level is dropping, it tells the computer "send me more", if the buffer level is increasing, it tells the computer "send me less".

 

44.1k base rates are not multiple of the USB clock, so the amount of data per transfer block varies all the time. While 48k base rates are multiple of USB clock and the amount of data per transfer block is more constant with less variation. But generally USB Audio Class is packet based transfer where the packet interval is constant but the amount of data per packet varies.

 

Then there are some DACs that use something else than USB Audio Class and use so called bulk transfer, and they operate in totally different manner. But these also require custom drivers to operate. exaSound DACs are example of such.

 

 

Thank you.

 

Even though I was aware of the above, you worded it so nicely that it truly helps understand what an a-sync data transfer between PC and USB interface card means.

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6 hours ago, lpost said:

Looks like I'll probably part with my AMD server with linear supplies since a bog standard Intel PC from 2017 equals or beats it in SQ and plays 1.5M/20bits without issue to the May. Saves power too! The USB input on the May is something special to not hear any difference between these two classes of computers/power supplies.

 

...just remembered that HQ Player caters for an on-the-fly phase inversion.... try that as well.

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  • 2 weeks later...

Well, to start:

 

- you would not have a detrimental effect of contact resistance X 2  (RCA's / XLR's) on sound quality

- same applies to one interconnect cable (which you would not have to use).... each cable will have specific capacitance, inductance, resistance and the cable material (copper, silver) would also provide their own coloration

- one less HiFi unit to pollute the power outlet

Now, here comes the pre-amp in itself:

- switches / potentiometers.... still only contacts / wipers / relays, all causing sound degradation

- resistors, capacitors, PCB traces... same as above

- internal hook-up wiring, PCB design => additional capacitance , inductance, resistance

- active elements (transistors / valves); each gain stage will introduce a bandwidth limiting, phase shifts (that will not be the same for the full frequency spectrum, even audio spectrum)... 

 

 

 

 

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Oooh, I forgot another important factor:

 

the volume pot should be preceded by a gain (gain of 1) stage of some sort (valve/transistor) to ensure high input impedance for the source

....and....

be followed by a buffer stage (another gain stage), that will ensure a very low output impedance for the amp.

 

Of course, the above is a good practice; however, it can be omitted... but then you'll have a varying output impedance, as seen by the amplifier (both, undesirable scenario and very high output impedance -> at most of the volume settings)

...and...

a non-perfect input impedance, seen by the source. 

 

... those gain stages, that should be used if the volume pot is to be implemented correctly, will require... a power supply, low noise of course,...

 

Summary: measuring a volume pot in isolation does not mean anything.... we have to consider its performance within a contexts of actually controlling the volume in real life situation. And that real life situation includes all of the above elements that will provide sound coloration and will defenetly have a detrimental effect on overall sound reproduction. 

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