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Ideas wanted -- USB DAC product
Ideas wanted -- USB DAC product
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Old 10th December 2017, 07:45 AM   #21
MarcelvdG is offline MarcelvdG  Netherlands
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Quote:
Originally Posted by blueskull View Post
1. THD+N: <=-120dB
2. DR: >=140dB (32-bit input)
140 dB? Reed relay shorting the outputs when you detect an all zeros input signal?
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Old 10th December 2017, 08:53 AM   #22
MarcelvdG is offline MarcelvdG  Netherlands
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Features that could be useful when you use digital filtering:

1. Selectable filter characteristics:
1A. Apodizing filter for people worried about pre-ringing
1B. Steep filter with a stop band starting at fs/2 for people who like anti-imaging filters to really prevent imaging
1C. Compromise filter with low latency for professional and video applications

2. Headroom
Most filters with 0 dB passband gain for stationary sine waves have overshoots on signals that are not stationary or not sinusoidal, such as music. Many digital recordings go all the way up to 0 dBFS, so you need to keep some headroom yourself if you want to prevent clipping or overflowing.

Suggestion 2 goes at the expense of the SINAD and DR numbers you get when you measure with stationary sine waves, so please ignore suggestion 2 if you are really only after getting impressive measured performance without caring what it sounds like with music.
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Old 10th December 2017, 09:19 AM   #23
MarcelvdG is offline MarcelvdG  Netherlands
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Quote:
Originally Posted by MarcelvdG View Post
140 dB? Reed relay shorting the outputs when you detect an all zeros input signal?
Dynamic range is usually measured with a -60 dBFS signal, so this was a stupid remark.
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Old 10th December 2017, 09:31 AM   #24
Markw4 is offline Markw4  United States
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Intersample over distortion immunity.
Audio Application Notes tagged "Inter-Sample Overs" - Benchmark Media Systems, Inc.
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Old 10th December 2017, 10:16 AM   #25
MarcelvdG is offline MarcelvdG  Netherlands
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Fascinating articles, I didn't realize you need headroom for stationary sine waves as well as for music!

Still, my comment that providing headroom goes at the expense of measured SINAD and DR values remains true, as these are usually measured at 0 dBFS and lower.
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Old 10th December 2017, 11:32 AM   #26
pcan is offline pcan  Italy
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Ideas wanted -- USB DAC product
The target price listed by the original poster is above my current budget, but on a multi-purpose DAC I will also expect a network connection with support for some open streaming protocol. This is useful for multi-room and to control the playback from the smartphone. I currently use the former Logitec Squeezebox protocol, now open sourced and with a good third-party app. It would also be useful to support USB-C charging mode on the USB port, when using the Android smartphone as FLAC source with a USB-C cable connection. On my current setup with a conventional USB DAC, I am forced to use a powered USB-C hub to avoid the battery drain and to get a standard USB2 connector, and it is unpractical.
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Old 10th December 2017, 12:26 PM   #27
Markw4 is offline Markw4  United States
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Quote:
Originally Posted by pcan View Post
The target price listed by the original poster is above my current budget, but on a multi-purpose DAC I will also expect a network connection with support for some open streaming protocol. This is useful for multi-room and to control the playback from the smartphone. I currently use the former Logitec Squeezebox protocol, now open sourced and with a good third-party app. It would also be useful to support USB-C charging mode on the USB port, when using the Android smartphone as FLAC source with a USB-C cable connection. On my current setup with a conventional USB DAC, I am forced to use a powered USB-C hub to avoid the battery drain and to get a standard USB2 connector, and it is unpractical.
Lots of software drivers to be written, then?

Given the price of a Benchmark Media DAC-3 is a bit over $2k, would you be wiling to pay a full $3k for the same technical performance in order to pay for costs of ethernet streaming support and a few other goodies?

Some mastering rooms are starting to try the new Crane Song DACs, and as you can see like Benchmark they don't have all the connectivity features either:
SOLARIS
It's up to the user to provide an interface box near to the DAC location if most of those features are wanted. Just sayin'.

Last edited by Markw4; 10th December 2017 at 12:34 PM.
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Old 10th December 2017, 03:00 PM   #28
pcan is offline pcan  Italy
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Ideas wanted -- USB DAC product
The cost of the ethernet streaming support may be almost zero, if GPL code is used on a low cost standard microcontroller. If proprietary/licensed code is used and/or a fancy microcontroller without mainstream support, then the cost may be significant and I agree that it will not be justified in this context.
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Old 10th December 2017, 08:49 PM   #29
blueskull is offline blueskull  China
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Quote:
Originally Posted by chris719 View Post
What standard do you plan to use over Ethernet?

Hi. I'm not planning to use any existing standards at this moment. I would implement my own protocol and rush the product out as fast as I can, then I will consider adding industry standard protocols in the future.

For my own protocol, I will provide a Windows player software, an FB2K output plugin, an ASIO output plugin and player software for OSX, iOS and Android.

I've been working on Windows KS and Linux ALSA drivers, and I would say that's not easy, so I will not try to tap into kernel mixer at this moment, but I may do that in the future.
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Old 10th December 2017, 08:52 PM   #30
blueskull is offline blueskull  China
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Quote:
Originally Posted by MarcelvdG View Post
For home equipment, support for DSD with 2.8224 MHz and 5.6448 MHz sample rate would be nice. Despite its disadvantages, DSD is quite popular. I don't know if any studios use 2.8224 MHz or 5.6448 MHz noise shaped PCM (a.k.a. DSD wide).
I can support DSD over USB/Ethernet. Since my design is a multi-bit sigma delta design, it can be reduced to single bit operation, which effectively makes it native DSD-ready. My design can output bit-perfect DSD.
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