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Ideas wanted -- USB DAC product
Ideas wanted -- USB DAC product
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Old 8th December 2017, 06:25 AM   #1
blueskull is offline blueskull  China
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Default Ideas wanted -- USB DAC product

Hi all,

I'm working on a USB DAC, targeting ultra high end market, with specs comparable with Hugo 2 or ES9038-based solutions.

Like Hugo 2, I will also be using custom made DAC technology, based on DSP, FPGA and some other proprietary secret sauce.

Price will be in $2000~$3000 range, targeting Hugo 2 and Sony ZH1ES. Performance will be the top, tentative specs are:

1. THD+N: <=-120dB
2. DR: >=140dB (32-bit input)
3. Output driving: >=250mW @ 32~600 Ohms, sine wave
4. Input power: external power brick, DAC has internal low leakage isolation, eliminating ground loop and Y-capacitor leakage even without grounding.

Here comes the questions:

1. What kind of inputs are expected? USB is a must, Ethernet, IMHO, is a must for modern devices. Should I support WiFi/Bluetooth?

Keep in mind that we are a startup, and we don't have money to license proprietary technologies like aptX HD or LDAC. So if we implement BT, it will be plain SBC.

2. What sample rates are expected? 44.1/48/96/192 are baseline, should we add in support for 384 or even 768? Are 88.2/176.4 even being used?

3. What kind of outputs are expected? Currently we support XLR balanced output for line out, and TRS switchable single ended/balanced headphone output. Both share the same DAC, but the HPA also has a gain controller in between that can be bypassed if line out level doesn't have to be kept independent from HPA level. Any other ideas?

Thanks for reading the long text, and we hope to hear from your suggestions as both a DIYer and a buyer.
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Old 8th December 2017, 06:46 AM   #2
TNT is offline TNT  Sweden
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Old 8th December 2017, 07:02 AM   #3
phofman is offline phofman  Czech Republic
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USB DAC with ethernet + wifi? That requires adding a computer with OS (in any form), way of controlling the playback software, configuration etc. That makes it a very different product. Are you sure you understand what technology is required for each of your points?
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Old 9th December 2017, 06:58 AM   #4
blueskull is offline blueskull  China
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Quote:
Originally Posted by phofman View Post
USB DAC with ethernet + wifi? That requires adding a computer with OS (in any form), way of controlling the playback software, configuration etc. That makes it a very different product. Are you sure you understand what technology is required for each of your points?
The feature is there, regardless you are using it or not. USB2.0 is great, but that doesn't address a few questions:

1. How to synchronize multiple devices in a studio setup? You can hook up 10 devices to a same PC, but that's it. You can't synchronize devices across different PCs. With Ethernet, you can have an IEEE1588 time server to sync all devices to exactly the same sample rate in a studio.

2. How to run long cables across a large studio or live scene? USB can't be run for too long before it generates bit error. USB audio class spec has no error correction implemented -- a bad USB packet is to be discarded, and no re-transmission is issued. With Ethernet, I can implement a protocol with re-transmission. You can argue that I can also implement a USB protocol with re-transmission, but then I will have to rewrite audio driver from scratch. Ethernet medium is intrinsically designed for long distance transmission, up to hundreds of miles, with optical fiber cable.

3. How to stream audio from multiple devices? In a home setup, how to stream audio from your phone/laptop/tablet to the DAC while not having to force them to connect to the DAC with a physical wire that has to be reconnected all the time? Also, the evil Apple has the MFi thing -- if I want to stream from Apple device, I need to be MFi certified, which I can't. With Ethernet, I can write a client app that bypasses OS audio driver, and itself handles audio file reading, decoding and Ethernet transmission to my DAC.

4. Bluetooth is a bit useless -- you don't listen SBC audio through a $3000 device. I consider it because I plan to use ESP32 as main app processor, and it has BT built in, so I don't want to waste this capability. That's it. There's no reason why I just have to support it. Actually, for $4.5, just as the Ethernet controller plus audio buffer manager, it already is worth every cent, WiFi and BT are considered free by me.

------------------------------------

My device already has USB and AES3 (coax, XLR and optical) supported, so Ethernet and WiFi/BT are additional features to be considered.

As for whether I can make it or not, I guess that's a different question. I will consider to drop features if I see some features are so hard to do and don't provide much added value, but until then, I want to have a complete wish list. After all it's Christmas season.

-------------------------------------

I know this is going to be a tough project, but I would like to take on it.

Any other suggestions?
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Old 9th December 2017, 08:51 AM   #5
planet10 is offline planet10  Canada
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Ideas wanted -- USB DAC product
Quote:
Originally Posted by blueskull View Post
1. What kind of inputs are expected?
I am aways looking for FireWire (or Thunderbolt now).

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Old 9th December 2017, 09:06 AM   #6
blueskull is offline blueskull  China
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Thanks for the input.

FW is long outdated, and the supporting chips are not being made anymore. Specialized chips for research and industrial purposes are too expensive, and usually require NDA to be signed.

Thunderbolt is a wonderful protocol, but again, I see no reason to use it. USB2.0 provides enough bandwidth for many, many channels of 32/768 audio, yet its latency is not too high. Sure, Thunderbolt has virtually no latency since it is just PCIe, but the extra overhead caused by USB is less than 1ms anyway.

Besides, Thunderbolt, which was promised by Intel as an open protocol, remains closed, and you need to sign an NDA and talk with an Intel representative before being able to access to their documents. Unlike USB, you can't just grab an interface chip and start working on it.
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Old 9th December 2017, 10:05 AM   #7
abraxalito is offline abraxalito  United Kingdom
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I must be missing something here but I can't see a price tag of $2-3k being at all credible as 'ultra high-end'. The ultra high-end price tags are at least 10X that. Ultra high-end means dCS, Aries Cerat, maybe AudioNote and certainly the top end of MSB's DACs.
In this stratospheric price range, DACs would not come with headphone amps built in, that would be too much of a compromise.
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Last edited by abraxalito; 9th December 2017 at 10:08 AM.
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Old 9th December 2017, 10:36 AM   #8
blueskull is offline blueskull  China
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Quote:
Originally Posted by abraxalito View Post
I must be missing something here but I can't see a price tag of $2-3k being at all credible as 'ultra high-end'. The ultra high-end price tags are at least 10X that. Ultra high-end means dCS, Aries Cerat, maybe AudioNote and certainly the top end of MSB's DACs.
In this stratospheric price range, DACs would not come with headphone amps built in, that would be too much of a compromise.
I'm an engineer with a PhD degree, not a dark artist. I care about specs, not how people interpret them.

For example, dcs and aries carat both have horrible specs. Only man among that list has some good figures.

I don't mind spending $20k on a top of the line audio analyzer or spending 500 hours to build one, but I only care about measured electrical data.

Bit I do like your last point -- to get rid of the headphone amp and let the user to figure out how to add their own.

I have to admit that hpa is a big compromise in my design. It causes quite some problems, and practically no one will listen to a high end dac without an amp.
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Old 9th December 2017, 10:46 AM   #9
abraxalito is offline abraxalito  United Kingdom
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Quote:
Originally Posted by blueskull View Post
I'm an engineer with a PhD degree, not a dark artist. I care about specs, not how people interpret them.

For example, dcs and aries carat both have horrible specs. Only man among that list has some good figures.
It seems to me that you're not quite up to speed on marketing in audio. 'Ultra high-end' is not a spec classification in the audio world, its a marketing term. If you're wanting to sell on specs alone, good luck in convincing the customer base that great specs are a guarantee of great sound. You'll need to spend more on marketing that proposition than on DAC R&D and fancy test gear I reckon.

Incidentally if you go over to MSB's website armed with your PhD you might notice their figures are fudged. The fact that this passes completely unnoticed by the consuming public might tell you something....

Quote:
I don't mind spending $20k on a top of the line audio analyzer or spending 500 hours to build one, but I only care about measured electrical data.
Seems to me you'll want to open up a completely new market, one of believers in specs over and above reviewers and dealers and related hangers-on.
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Old 9th December 2017, 04:11 PM   #10
planet10 is offline planet10  Canada
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Ideas wanted -- USB DAC product
Quote:
Originally Posted by blueskull View Post
FW is long outdated
Not at all, it is a subset of Thunderbolt.

Quote:
Thunderbolt is a wonderful protocol, but again, I see no reason to use it. USB2.0 provides enough bandwidth for many, many channels of 32/768 audio, yet its latency is not too high. Sure, Thunderbolt has virtually no latency since it is just PCIe, but the extra overhead caused by USB is less than 1ms anyway.
Right, Thunderbolt, if you use the Firewire subset is designed to deal with audio, putting audio over USB is still just a convience.

Thunderbolt is not just PCIe, that is one of the subsets supported, just like FireWire, USB3, DisplayPort. Intel would really like to see the death of USB but it has far too much use for it to die anytime soon.

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