Author Topic: USB DAC  (Read 5877 times)

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Offline gnifTopic starter

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USB DAC
« on: September 21, 2017, 04:23:59 am »
Hi Everyone,

I am looking for some imput on an affordable decent quality USB DAC that implements a standard interface that would be well supported under both Windows and Linux. I intend to drive my own analogue preamp from it, so a simple line out device would suit. I would also like it to have the ability to handle a line input for recording. Note that I am NOT looking for audiophoolery devices, just a basic interface that works well for the price with decent SNR.

Suggestions very welcome :)
 

Offline ruairi

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Re: USB DAC
« Reply #1 on: September 21, 2017, 04:35:46 am »
Check out the ODAC - https://www.jdslabs.com/products/39/odac-objectivedac/

I haven't actually heard one but reviews are very good and the design is solid.  I may actually be ordering one this week so if you are not in a rush I will let you know how it fares.

It has quite an interesting backstory and development that makes for some good educational reading - http://nwavguy.blogspot.com
 
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Offline gnifTopic starter

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Re: USB DAC
« Reply #2 on: September 21, 2017, 04:52:53 am »
Check out the ODAC - https://www.jdslabs.com/products/39/odac-objectivedac/

I haven't actually heard one but reviews are very good and the design is solid.  I may actually be ordering one this week so if you are not in a rush I will let you know how it fares.

It has quite an interesting backstory and development that makes for some good educational reading - http://nwavguy.blogspot.com

I am in no rush, I will await your feedback on this, the price is in my budget also :).

If you are looking for a no bullshit, decent audiophile but no audiophool ADC/DAC combo, consider something from Apogee or ESI. Both are not HiFi makers, instead, they are pro audio makers. The ESI stuffs use proprietary driver, while most Apogee stuffs use USB Audio Class 1.0/2.0.

Thanks but the cost of these devices is prohibative, I also do not require or want any of the pre-amp or conditioning they have as I am already running through my own diy HiFi. I also want a device that 'just works', I swap between operating systems continually for work and need the device to just work.

I have moved all my audio conditioning external and in the analogue domain so that when I switch operating systems my audio experience is the same without having to mess around with any software EQ, etc.
 

Offline stmdude

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Re: USB DAC
« Reply #3 on: September 21, 2017, 05:05:03 am »
I've used the TI PCM2705C for a USB DAC build. It's specs are nothing to write home about, but it's a massive upgrade from any integrated soundcard in your laptop or desktop.

I've used it successfully in Windows 7/10, Linux and OSX. It also works out-of-the-box with OpenELEC to get decent sound out of a RaspberryPI.

Now, the 2705C doesn't have line-in, but the 2704 (and some others) do. Haven't tried that, but I don't see why it wouldn't work fine.

Typical specs:
16bit, various samplerates up to 48KHz
THD = 0.025% (When bus-powered, selfpowered is 0.006%)
SNR = 98dB

Yep, definitely not audiophoolery, but still gives very nice HQ audio for its price.
 
 
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Offline gnifTopic starter

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Re: USB DAC
« Reply #4 on: September 21, 2017, 05:28:26 am »
I've used the TI PCM2705C for a USB DAC build. It's specs are nothing to write home about, but it's a massive upgrade from any integrated soundcard in your laptop or desktop.

I've used it successfully in Windows 7/10, Linux and OSX. It also works out-of-the-box with OpenELEC to get decent sound out of a RaspberryPI.

Now, the 2705C doesn't have line-in, but the 2704 (and some others) do. Haven't tried that, but I don't see why it wouldn't work fine.

Typical specs:
16bit, various samplerates up to 48KHz
THD = 0.025% (When bus-powered, selfpowered is 0.006%)
SNR = 98dB

Yep, definitely not audiophoolery, but still gives very nice HQ audio for its price.

Thanks, yes, I had already moved to a better card some time ago (Asus Xonar DX) but I am sick of getting hiqh pitch inteference from the 4x HDMI interfaces under certain conditions. I know I can run audio transformers to isolate everything but I figure if I just move to USB I won't have to mess around so much.
 

Offline stmdude

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Re: USB DAC
« Reply #5 on: September 21, 2017, 05:39:27 am »
Thanks, yes, I had already moved to a better card some time ago (Asus Xonar DX) but I am sick of getting hiqh pitch inteference from the 4x HDMI interfaces under certain conditions. I know I can run audio transformers to isolate everything but I figure if I just move to USB I won't have to mess around so much.

Ah, I see where you're coming from then.

Yep, internal soundcards (even the after-market ones) are very hit-and-miss due to the amount of interference inside the computer case.

I've also got an Asus Xonar U7 which might fit your bill. I've had it working in Linux, but I'm not certain if I ran it in USB 2.0 mode or 1.1 mode. (The card/box has a switch underneath it to switch between audio class 1.1 and 2.0, which is a neat feature)
The jog-wheel is a regular USB HID device, and work fine in Linux as well.
 

Offline ruairi

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Re: USB DAC
« Reply #6 on: September 21, 2017, 06:54:55 am »
If you are looking for a no bullshit, decent audiophile but no audiophool ADC/DAC combo, consider something from Apogee or ESI. Both are not HiFi makers, instead, they are pro audio makers. The ESI stuffs use proprietary driver, while most Apogee stuffs use USB Audio Class 1.0/2.0.

In the interests of full disclosure I should say that I do some repair work for a competitor of Apogee but I would disagree with your recommendation.  I own a lot of DACs from Prism Sound, Cranesong, Benchmark, Avid and a bunch more.  Having spent way too much time comparing DACs in proper level matched comparisons in acoustically treated mastering rooms Apogee would be near the bottom of my list.

I've never heard ESI.
« Last Edit: September 21, 2017, 07:07:02 am by ruairi »
 

Offline ruairi

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Re: USB DAC
« Reply #7 on: September 21, 2017, 08:40:12 am »
Having spent way too much time comparing DACs in proper level matched comparisons in acoustically treated mastering rooms Apogee would be near the bottom of my list.

I've never heard ESI.

Apogee is also the cheapest among real (I mean, not Behringer or similar cheap so called pro brands) professional gears. And their products are targeting musicians with professional musical talent but knows nothing about recording or electronics, so they really "just work". But in terms of standard compliant, they are not the best. My Apogee Groove hogs power after USB suspend or even power down, as long as VBUS is there, it hogs power. It also occasionally fails to wake up upon USB wakeup, and usually a cold replug is needed to get it to work -- it enumerates, but no audio output.

ESI is a relatively small company, specialized in sound cards. They released 24/192 interface with phantom power back in ~2007 or earlier. Generally, I think ESI products are the kind of really no BS, no bells and whistles, and just work ones. Specs are not bad for pro gears, but no where comparable to high end HiFi gears. Price is competitive, comparable with same level Creative consumer cards. Driver is proprietary, but robust, at least when I had my Maya44.

My comments about the Apogee were all about sound, they just don't sound very good in the main.  Apogee have long been excellent at marketing.  I've heard them many times and have recorded with various models too.

I've seen mention of the ESI cards before, thanks for the info. 
 

Offline grifftech

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Offline gnifTopic starter

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Re: USB DAC
« Reply #9 on: September 22, 2017, 12:17:29 am »
 

Offline BrianHG

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Re: USB DAC
« Reply #10 on: September 22, 2017, 12:41:38 am »
If you do not want PC interference, why not use optical audio or SPDIF out of your motherboard and use an off the shelf DAC interface.  These 2 interfaces separate from your PC's power supply completely...  (Just pass the SPDIF through any cheap data link transformer...)  Seeing how your on this site, and today, 10 PCBs for 5$, you can build a top notch DAC to your exact spec which will never have any power connection to your PC unlike USB dacs which will still share a ground and be powered from the PC.
 

Offline gnifTopic starter

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Re: USB DAC
« Reply #11 on: September 22, 2017, 12:51:29 am »
If you do not want PC interference, why not use optical audio or SPDIF out of your motherboard and use an off the shelf DAC interface.  These 2 interfaces separate from your PC's power supply completely...  (Just pass the SPDIF through any cheap data link transformer...)  Seeing how your on this site, and today, 10 PCBs for 5$, you can build a top notch DAC to your exact spec which will never have any power connection to your PC unlike USB dacs which will still share a ground and be powered from the PC.

I have considered this but have decided not to for several reasons:

1) It wont 'just work', espesially under some configurations I run such as Linux + ALSA. I know first hand how terrible ALSA is with dealing with optical links (I wrote the audio code in Kodi that does all that mess).
2) I already have several USB isolators for keeping my DSO from grounding out through it, might as well use one for this ;)
3) I'd like to plug it into my laptop from time to time which has no optical or even coaxial support.
 

Offline BrianHG

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Re: USB DAC
« Reply #12 on: September 22, 2017, 01:21:23 am »
2) I already have several USB isolators for keeping my DSO from grounding out through it, might as well use one for this ;)

Warning, for Audio Class 2.0, your will need high speed USB support, otherwise, you'll be stuck at 48KHz, 16bit stereo...

Are you looking for an IC like this?
https://www.cmedia.com.tw/products/USB20_HIGH_SPEED/CM6632A
https://www.cmedia.com.tw/products/USB20_HIGH_SPEED/CM6631A
At 7$, plus you can interface it with an I2S DACs and ADC of your choice, you will have what you want.
(I personally would just insert an opto data isolator on the I2S lines, something like a SI8065AA an forego an external usb isolator, power the analog side from an AC output transformer making a nice isolated dual supply...)

Damn, now I'm tempted to build one...  I just need to find the right DAC & I would like the option of +4dbu or even +6db output.

 

Offline gnifTopic starter

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Re: USB DAC
« Reply #13 on: September 22, 2017, 01:39:48 am »
2) I already have several USB isolators for keeping my DSO from grounding out through it, might as well use one for this ;)

Warning, for Audio Class 2.0, your will need high speed USB support, otherwise, you'll be stuck at 48KHz, 16bit stereo...

Hrmm, that blows that idea out of the water :(

Are you looking for an IC like this?
https://www.cmedia.com.tw/products/USB20_HIGH_SPEED/CM6632A
https://www.cmedia.com.tw/products/USB20_HIGH_SPEED/CM6631A
At 7$, plus you can interface it with an I2S DACs and ADC of your choice, you will have what you want.
(I personally would just insert an opto data isolator on the I2S lines, something like a SI8065AA an forego an external usb isolator, power the analog side from an AC output transformer making a nice isolated dual supply...)

I would be but that is beyond my current EE abilities, or time that I have available to learn to build it :). That has capture too which would be ideal.

Damn, now I'm tempted to build one...  I just need to find the right DAC & I would like the option of +4dbu or even +6db output.

Make two :P
 

Offline Buriedcode

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Re: USB DAC
« Reply #14 on: September 22, 2017, 02:27:33 am »
Most of the cheap USB soundcard dongles use the CM108 from C-media.  Surprisingly OK quality. On board PLL ADC's/DAC's, on parr with the ancient PCM2704, but for a fraction of the price.

Almost all USB DAC's will be asynchronous, and be limited to 16-bit @48kHz.  The newer USB audio 2.0 spec can have higher bit depth and 96kHz sample rate, but its overkill for playback.  Whilst synchronous transport sorts out the any jitter, I don't think the difference is particularly noticeable.

As you're after >16-bit @48kHz I can only assume the application isn't audio listening, so what is it for?
 

Offline gnifTopic starter

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Re: USB DAC
« Reply #15 on: September 22, 2017, 02:29:09 am »
Most of the cheap USB soundcard dongles use the CM108 from C-media.  Surprisingly OK quality. On board PLL ADC's/DAC's, on parr with the ancient PCM2704, but for a fraction of the price.

Almost all USB DAC's will be asynchronous, and be limited to 16-bit @48kHz.  The newer USB audio 2.0 spec can have higher bit depth and 96kHz sample rate, but its overkill for playback.  Whilst synchronous transport sorts out the any jitter, I don't think the difference is particularly noticeable.

As you're after >16-bit @48kHz I can only assume the application isn't audio listening, so what is it for?

It is for audio listening, but I also mess around with analogue audio and sometimes require the higher bitdepth and sample rate for SNR and THD measurements. Basically I use the PC as a poor mans signal generator :), all hobby level stuff so good enough for it.
« Last Edit: September 22, 2017, 02:31:02 am by gnif »
 

Offline BrianHG

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Re: USB DAC
« Reply #16 on: September 22, 2017, 02:36:20 am »
I'm willing to design it here, open source & proofed on EEVblog (in a new dedicated thread).  However, I will be designing the schematic and PCB in Protel 99se.  I know it's old, but I legitimately own it, know how to use it's in and outs, and, I'll provide all source files, gerbers, and documentation...  Everything will be 100% manual routed...

The PCB will have the USB interface with optional isolated DC-DC converter for the dac and analog section, or, an AC input with regulators.  It will be the choice of which components you stuff.  The I2S Data lines will be opto-isolated

There will be line level output on RCA, with maybe an optional balanced output, or, 8 channels out instead.  I don't know which yet.

Stereo input will  be there as well.

You will be able to set a fixed optional +Xdb gain resistor on the output as the output driver amp will have a +/-12v supply with the headroom.

If there are any additional takers, let me know now as it will help me decide whether to go or not....
If there are any special additional considerations, let me know as well.
 
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Offline gnifTopic starter

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Re: USB DAC
« Reply #17 on: September 22, 2017, 02:40:28 am »
I'm willing to design it here, open source & proofed on EEVblog (in a new dedicated thread).  However, I will be designing the schematic and PCB in Protel 99se.  I know it's old, but I legitimately own it, know how to use it's in and outs, and, I'll provide all source files, gerbers, and documentation...  Everything will be 100% manual routed...

The PCB will have the USB interface with optional isolated DC-DC converter for the dac and analog section, or, an AC input with regulators.  It will be the choice of which components you stuff.  The I2S Data lines will be opto-isolated

There will be line level output on RCA, with maybe an optional balanced output, or, 8 channels out instead.  I don't know which yet.

Stereo input will  be there as well.

You will be able to set a fixed optional +Xdb gain resistor on the output as the output driver amp will have a +/-12v supply with the headroom.

If there are any additional takers, let me know now as it will help me decide whether to go or not....
If there are any special additional considerations, let me know as well.

Sounds perfect! Link the thread here if you start one!
 

Offline WZOLL

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Re: USB DAC
« Reply #18 on: September 22, 2017, 03:05:32 am »
I used to have one of those c media sound cards when the headphone jack broke on my laptop. The SNR and quality was dreadful. I bought one of these as a replacement https://www.amazon.com/gp/product/B000KW2YEI/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1 . For 48 kHz, 16 bit converters and fantastic SNR and audio quality, it's decent value IMO. 
 

Offline BrianHG

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Re: USB DAC
« Reply #19 on: September 22, 2017, 03:21:57 am »
 

Offline NiHaoMike

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Re: USB DAC
« Reply #20 on: September 22, 2017, 03:26:29 am »
Maybe track down a reputable source for quality USB-C DACs or the chips used in them? I know at least the ones LeEco uses (appears to be SaviAudio from the USB IDs) are very good.
1) It wont 'just work', espesially under some configurations I run such as Linux + ALSA. I know first hand how terrible ALSA is with dealing with optical links (I wrote the audio code in Kodi that does all that mess).
I have never had any issue with PCM stereo over S/PDIF, at least not on the software side. What is problematic is surround over S/PDIF, in that there are multiple standards.
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Offline BrianHG

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Re: USB DAC
« Reply #21 on: September 22, 2017, 11:14:57 am »
Before I begin, I would like to test out the CM6631A for compatibility, however, I can only test for windows 7.   Is anyone else interested enough to pick one of these CM6631A boards?
https://www.aliexpress.com/item/2017-NEW-CM6631A-USB-Digital-interface-32-24Bit-192k-USB-To-I2S-SPDIF-coaxial-Output-With/32822375930.html?spm=2114.search0104.3.50.l0QSr5&ws_ab_test=searchweb0_0,searchweb201602_4_10152_10065_10151_10130_10068_10344_10342_10343_10340_10341_10139_5550020_10307_10137_10060_10155_10154_10056_10055_10054_5470020_10059_10532_100031_10099_5460020_10338_10339_10103_10102_440_10052_10053_10107_10050_10142_10051_10325_5380020_10326_10084_10083_5370020_10080_10082_10081_10178_10110_10111_10112_10113_10114_143_10312_10313_10314_10078_10079_10073,searchweb201603_30,ppcSwitch_5&btsid=9554feed-9509-43a4-8ed3-db27711f35c6&algo_expid=d6ef9ad1-f2c3-4b7b-ad7a-bcc648ed3886-6&algo_pvid=d6ef9ad1-f2c3-4b7b-ad7a-bcc648ed3886

I know it has a cheap 30$ DAC for the analog section, but, it's basically the CM6631A with an I2S output port and SPDIF coax out for the digital side and it should be adequate for OS compatibility testing & checking for any audio artifacts due to poor USB audio buffering.

If anyone else is interested in testing for other OS since I just have Windows 7 Pro, let me know...
 

Offline Buriedcode

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Re: USB DAC
« Reply #22 on: September 23, 2017, 04:39:55 pm »
.....Almost all USB DAC's will be asynchronous, and be limited to 16-bit @48kHz.

I should correct this to isosynchronous  :palm: Asynchronous is where the DAC runs its own clock and provides feedback to the host rather than constantly adjusting to the hosts clock using a PLL (adds a bit of jitter).

I can't say I hear the difference between the two, but it is generally accepted that it improves performance since the sample clock isn't dithering.

If you're after designing your own, there is a PIC32 app note for USB audio and I2S, and a slight modification of the example project of 'USB speaker' allows for async operation. I believe the NV1 used this:
http://www.diyaudio.com/forums/digital-line-level/244123-usb-audio-pic32-processor-pcm1796.html

Whilst microchips framework is a bit of a nightmare, I vaguely remember having this up and running in an afternoon on a PIC24.  Never made measurements though (just didn't hear any artifacts).
 

Offline gnifTopic starter

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Re: USB DAC
« Reply #23 on: October 02, 2017, 09:06:55 am »
Before I begin, I would like to test out the CM6631A for compatibility, however, I can only test for windows 7.   Is anyone else interested enough to pick one of these CM6631A boards?
https://www.aliexpress.com/item/2017-NEW-CM6631A-USB-Digital-interface-32-24Bit-192k-USB-To-I2S-SPDIF-coaxial-Output-With/32822375930.html?spm=2114.search0104.3.50.l0QSr5&ws_ab_test=searchweb0_0,searchweb201602_4_10152_10065_10151_10130_10068_10344_10342_10343_10340_10341_10139_5550020_10307_10137_10060_10155_10154_10056_10055_10054_5470020_10059_10532_100031_10099_5460020_10338_10339_10103_10102_440_10052_10053_10107_10050_10142_10051_10325_5380020_10326_10084_10083_5370020_10080_10082_10081_10178_10110_10111_10112_10113_10114_143_10312_10313_10314_10078_10079_10073,searchweb201603_30,ppcSwitch_5&btsid=9554feed-9509-43a4-8ed3-db27711f35c6&algo_expid=d6ef9ad1-f2c3-4b7b-ad7a-bcc648ed3886-6&algo_pvid=d6ef9ad1-f2c3-4b7b-ad7a-bcc648ed3886

I know it has a cheap 30$ DAC for the analog section, but, it's basically the CM6631A with an I2S output port and SPDIF coax out for the digital side and it should be adequate for OS compatibility testing & checking for any audio artifacts due to poor USB audio buffering.

If anyone else is interested in testing for other OS since I just have Windows 7 Pro, let me know...

I am in, sorry about the delayed reply, I have been away the last week on break :). I can test under

  • Debian 6, 7, 8, 9
  • CentOS 6, 7
  • Windows 7
  • Raspian
  • Armbian

Edit: Unfortunately AilExpress doesn't like shipping to my area, it doesn't even list it as an option. If you can provide a comparable device on eBay I will go that way instead.
« Last Edit: October 02, 2017, 09:13:01 am by gnif »
 


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