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-   -   USB DSD DAC and ADC by ElectrArt (https://www.diyaudio.com/forums/digital-source/177336-usb-dsd-dac-adc-electrart.html)

asaf23 12th September 2012 05:36 AM

Hi Bunpei,

Quote:

Originally Posted by Bunpei (https://www.diyaudio.com/forums/digital-source/177336-usb-dsd-dac-adc-electrart-post3161345.html#post3161345)

They say nothing about ASIO "genuine" DSD bitstream compatibility. They just say an ASIO driver on Windows supports up to PCM 192 kHz. DoP up to DSD128 is supported.

Yes, I2S/DSD digital output is available. I have connected it to TPA Buffalo II DAC.


Bunpei


Thank you very much for explanation.

With best regards,
Andrey

gentlevoice 12th September 2012 05:44 AM

@Gahlord: You might also find this card interesting:

USB Audio - RigiSystems AG

It supports all 24 bit & 32 bit sample frequencies up to 384 kHz (24 bits) and 352.4 kHz (32 bits) both in and out and at the same time with low latency (~6 ms). Additionally, it supports DSD up to 128fs also in and out. Possibly also DxD but I haven't been able to find out about this. Altogether up to 49 Mbps both ways at the same time for one card.

The documentation on their website is not consistent about the frequencies supported but I communicated with the most helpful designer about the specs. To ensure continuous A/D sampling he also recommends an Intel chipset based computer.

I'm interested in buying a card myself so just in case you or somebody else takes an interest in the card I'd appreciate being in on a buy, maybe set up a mutual buy.

Greetings,

Jesper

P.S.: Ok, so now I'm opening the bottle ... I may/might be mistaken about this but there might be a chance of customizing the card to accept DSD*512 both ways, i.e. in and out. It would require custom programming to do so which probably costs a bit (let's assume ~USD 6500) but if enough people is interested it could be "affordable". It would allow for DSD playback/recording at 22.579 and 24.576 MHz.... Any interest?

Bunpei 13th September 2012 03:16 PM

Quote:

Originally Posted by gentlevoice (https://www.diyaudio.com/forums/digital-source/177336-usb-dsd-dac-adc-electrart-post3161525.html#post3161525)
... I may/might be mistaken about this but there might be a chance of customizing the card to accept DSD*512 both ways, i.e. in and out.

Hi, Jesper,

How do you prepare an ADC (Delta-sigma modulator) for DSD512?
For DSD256, some are available. But for DSD512? I have no idea.

Bunpei

gentlevoice 14th September 2012 03:42 PM

1 Attachment(s)
Hi Bunpei,

Quote:

How do you prepare an ADC (Delta-sigma modulator) for DSD512?
For DSD256, some are available. But for DSD512? I have no idea.
Well, I don't know of any DSD512 converters either but I hope to either:

- make a discrete delta-sigma converter as part of a collaboration (preferred).

Or ...

- use the ADS1204 from Texas Instruments, although probably at 256fs.

http://www.ti.com/lit/ds/symlink/ads1204.pdf

The ADS1204 is not an audio chip as such but it's a "pure" second-order delta-sigma modulator that outputs a bitstream and allows for up to 16 MHz sampling frequency. I prefer lower order modulators as their frequency band cut-off slopes are less steep than the higher order modulators. If you look at this datasheet then please note that the data shown is for a sinc3 filter and it could be better with another filter (I would use no digital filter at all except when playing back where a second order analog filter would give an approximately 111 dB reduction of modulator noise at 50 kHz).

Also the second-order modulator can be implemented in a single modulator stage whereas higher orders need more stages (if I remember correctly). Thus, a simple, yet highly optimized circuitry could be possible with a second-order modulator - either a discrete circuitry as part of a collaboration or possibly within the ADS1204.

My sources for delta-sigma modulator designs are some but mostly:

Delta-sigma data converters: Theory, Design & Simulation, Steven R. Norsworthy & Richard Schreier. Goes a bit over my head but as far as I understand considered a very good book on ds-converters.


Uwe Beis: An Introduction to Delta Sigma Converters:

An Introduction to Delta Sigma Converters (see middle of the page for second order converters and for SNR for various order modulators)


Grimm Audio's white paper by Bruno Putzeys (of Hypex.nl) on some of their inspiration for building their AD-1 discrete DSD A/D converter:

http://www.grimmaudio.com/whitepaper...0converter.pdf

There's also other information on their website about jitter etc.


And then, not last nor least, Bruno Putzeys most kindly outlined for me a practical way of building a discrete A/D converter including what to look for in a comparator, operational amplifier, CMOS flip/flop and latch. I have attached this paper to this post ....


What I'd like to do is to build a delta-sigma modulator (a/d converter) of second order and preferably of a "single-ended" configuration, i.e. without a balanced or differential configuration (if possible but I guess differential cannot be avoided). As simple as possible and using the experience gathered from the sound of single-ended amplifiers - transistors or tubes.

As simple as possible also is the reason why I hesitate to use the Arda AT1201. It converts from a multibit to single-bit DSD signal and my guess would be that this is audible.

I believe a first order modulator would sound best but to get a reasonable SNR the second order modulator is more practically feasible. According to Uwe Beis a first order modulator at 512fs sampling rate would give about 80 dB SNR.

Second order modulator because, theoretically, it allows for about 108/122 dB SNR 256fs/512fs and also can be a fairly simple circuitry with not too steep cut-off slopes, as mentioned. Although theoretically the switched capacitor modulator is less sensitive to jitter I'd actually prefer to make it a continuous time configuration which is what I understand Grimm Audio has also done, although their modulator to my knowledge is a 5th order.

However, I don't know how to calculate the corner frequencies for the modulators so I am most interested in finding collaboration with someone/more people who can do that and could be interested in building such a modulator. If that is not possible I'll try out the ADS1204 at 256 fs and also at 512fs - to see if it works at these frequencies.

For your information I've also just bought the rigisystems USBPAL in/out card. As I understand from its designer it should work (more or less for sure) up to 256fs with one-bit signals both ways. This also means that I won't be buying the Amanero card for now as it "only" goes one way - but nevertheless looks very interesting.

Hope this may help clarify your question ;)

Greetings,

Jesper

Bunpei 16th September 2012 03:17 AM

What a long post of rich contents!

I understood your interest comprehensively. However, I failed to have a basic information on your backgrounds and skills.

The designer and builder of the USB Dual Audio board, ElectrArt, have two ARDA AT1201 chips and he might be developing his own DSD256 recorder now.
If he presented any progress for the recorder on his blog page, I will introduce it here.
(though I know you hate a multi-bit delta-sigma modulator)

andpa 23rd September 2012 12:30 PM

Quote:

Originally Posted by Bunpei (https://www.diyaudio.com/forums/digital-source/177336-usb-dsd-dac-adc-electrart-post3166660.html#post3166660)

The designer and builder of the USB Dual Audio board, ElectrArt, have two ARDA AT1201 chips and he might be developing his own DSD256 recorder now.
If he presented any progress for the recorder on his blog page, I will introduce it here.
(though I know you hate a multi-bit delta-sigma modulator)

Thank you for intresting information about DSD256 in Japan, I have read all you posts and try to read the ElectrArt blog. The device PCM2DSD256 excite me very much there. The process of transfering the PCM to DSD256 using software is complicated and long. If it will be possible to do on fly it will be the realy bomb! What do you think and knew about this device? What about plans of the ElectrArt to sell it?

Bunpei 24th September 2012 12:47 PM

Quote:

Originally Posted by andpa (https://www.diyaudio.com/forums/digital-source/177336-usb-dsd-dac-adc-electrart-post3175707.html#post3175707)
... The device PCM2DSD256 excite me very much there. The process of transfering the PCM to DSD256 using software is complicated and long. If it will be possible to do on fly it will be the realy bomb! What do you think and knew about this device? What about plans of the ElectrArt to sell it?

ElectrArt is developing his original hardware-based PCM2DSD256 converter.

The board on the right side is the PCM2DSD256 conversion board.
Input: S/PDIF, I2S PCM 44.1kHz/16bit, 48kHz/16bit - 176.4kHz/24bit, 192kHz/24bit
Output: DSD256(11.2896MHz, 12.288MHz; DSDL, DSDR, DSDCLK, MCLK( ~ 90.3168MHz, 98.304MHz)
He has built a S/PDIF decoder , a Digital FIR upsampler and a Delta-Sigma Modulator into one FPGA chip (Xylinx Spartan 6 or Altera Cyclone III)

He is expected to release the board as a finished board kit for DIY users. However, no finalized release plan is announced yet.

The board on the left side is his "DAC" board. It includes an Analog FIR and an Analog Filtering OP amp circuit (Stereo balanced analog output).

The combination runs as his proprietary "DAC".

Bunpei

andpa 24th September 2012 05:33 PM

Thank you Bunpei!
It seems very interesting device and I am intching to try it. Hope he will finish it soon. Are you planing to try it? Your opinion will be very important to me. Is it big differences of sound to the software conversion and to native PCM?
Andrey

qusp 24th September 2012 05:47 PM

the board on the left, as you would realize, is of interest to me =) its exactly the sort of thing i've been conceptualizing, seems i'm too late =) oh well less work for me hehe

Bunpei 26th September 2012 04:46 AM

ElectrArt's Analog FIR
 
His first design is this;


The prototype of filtering board appears at the upper left.


The prototype has evolved to the full balance board shown in the previous post.


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