Who makes and where to buy USB Audio chips? - Page 1
Forum section: electronics / projects

author: eV1Te
author_rank: Regular Contributor
timestamp: December 09, 2018, 12:36:23 pm
content: I'm planning on making a USB Audio DAC/Amplifier. First project will be to drive headphones because it is simpler/cheaper than making a large power amp.The main purpose is to learn more about USB interfacing, connectors, impedance matched traces etc. without having to write my own windows drivers and firmwares. I am also in the need for a headphone amp and haven't found anyone I like on the market that doesn't cost more than $1000.But I am having problems finding USB audio ICs that will interface with a PC (using default drivers in Windows) and output serial data.It seems the most common serial protocol is I2S (not I2C), and many DACs support this format, hence USB to I2S is probably what I am looking for, alternatively if the chip has its own DAC with good quality.But feel free to suggest alternative methods if you like!Here is what I have found so far:Texas Instruments have PCM29XX and PCM27XX series chips that do exactly this, but they are all limited to 48 kHz sampling rate and 16 bit resolution, they also run S/PDIF which is also a bit limiting when selecting DACs (unless you use built-in one)http://www.ti.com/audio-ic/converters/usb/products.htmlSilicon Labs make the CP2615, but it is also limited to max 48 kHz.https://www.silabs.com/products/interface/digital-audio-bridges/usb-audio-bridges/device.cp2615Cirrus Logic makes a lot of Audio Interfaces, Codec, and DAC chips etc. but I have not found any USB chips on their website:https://www.cirrus.com/solutions/playback/hifi/C-Media makes good USB Audio chips (ex. CM6631A)! But I you cant buy them from Digikey, Mouser, etc, and documentation is also a bit lack:https://www.cmedia.com.tw/products/USB20_HIGH_SPEEDRealtek have chips in most computers, but I have also not found any sources for these or any documentation for that matter, perhaps you need to sign contract with them?!Does anyone have any other ideas for good solutions for USB to Audio ICs?

author: HB9EVI
author_rank: Frequent Contributor
timestamp: December 09, 2018, 02:49:26 pm
content: If it's a low profile DIY project; why do you not start with the PCM29xx; they are doing a good job; I know today everybody wants glamorous numbers like 24bit and 384kbit sampling rate; but most of the last 35 years we were living good just with the classical 16bit @ 44,1 or 48kbit.And nobody forces you to invest 1000 bucks in an headphone amp; has to be from pure unobitanium to justify that price. A good amp you can build yourself for a few bucks.

author: Hydron
author_rank: Super Contributor
timestamp: December 09, 2018, 03:24:56 pm
content: I'd agree with the above comment - 16bit/48k is enough for _all_ audio use if implemented well.However this may be of interest - I had a look at using the "audio widget" design for my own dac/amp a few years back:https://www.henryaudio.com/open-source.php/https://code.google.com/archive/p/sdr-widget/(getting a job and not having enough free time prevailed and I ended up just buying and tweaking a commercial dac/amp).

author: Buriedcode
author_rank: Super Contributor
timestamp: December 09, 2018, 04:44:22 pm
content: You could build a headphone amp for about $10 (not including enclosure). There are plenty of decent high current opamps that do the job well. Also Elliot Sound Products has a few projects:http://sound.whsites.net/project24.htmUltimately, people tend to build to a price point, not to measurable "quality".As for USB audio, it really depends on the price point. Many devices including the PCM29xx series, the C-media CM108, and Akm AK4571 all use a PLL to derive the sampling clock from the USB clock. Some think they can hear the jitter introduced by this (most can't) so there are other devices that use USB asynchronous transport, where the sampling clock and USB clock are effectively separate. In theory this should have much less jitter, but I doubt many could actually hear the difference. Also, I don't think Apple products support this yet.Also, you can roll your own with a reasonably sized USB microcontroller with an I2S port. I built a prototype with a PIC24 and a WM8759 - sounded fine to me! (at least compared to my soundcard).As with all things audio, there's plenty of woo, and misleading information about it. It all depends on what the requirements are... power consumption for portability, number of channels, S/PDIF IO etc.. Arbitrarily imposing specs like "must be 24-bit" or "96kHz minimum" is all well and good, but it can make life a lot harder, so best to make sure its actually needed.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: December 09, 2018, 05:07:20 pm
content: To tell the truth, as a radioamateur and a home musician, I make use of high sample rates only for the first;for the use of a 0Hz down mixing I/Q SDR, it's good to have a codec with a sample rate of 192kHz to get almost 100kHz spectrum on the screen; for audio on the other side: my best Shure condenser reaches 20kHz, so 48kHz is just doing fine.Personally I also don't hear the difference between 16bit and 24bit sampling depth

author: coppice
author_rank: Super Contributor
timestamp: December 09, 2018, 05:18:29 pm
content: Quote from: HB9EVI on December 09, 2018, 05:07:20 pmFor distributed audio 24 bits shouldn't offer much over well dithered 16 bit. The big benefit of 24 bits is during recording. You need to get everything just right with 16 bits. With the really low noise floors you can achieve these days you can set levels in a fairly relaxed way with 24 bits, and have no fear of clipping. When you've recorded everything, the final mix down to dithered 16 bits should produce a very satisfactory result.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: December 09, 2018, 05:53:49 pm
content: sure, we're talking about a fairly larger headroom in dynamics; makes perfect sense for mastering aso.I just don't understand why people fill their limited flash space on their portable devices with large 24bit flac files; so there is another misunderstanding about the use of digital media - like so oftenafter all, the analog side is often more prone to signal degeneration; what are 192k/24bit helping in a noisy environment?

author: diyaudio
author_rank: Frequent Contributor
timestamp: December 09, 2018, 06:30:14 pm
content: Look at XMOS, XU208https://www.xmos.com/developer/download/private/XU208-256-TQ64-Datasheet%281.16%29.pdf

author: NiHaoMike
author_rank: Super Contributor
timestamp: December 09, 2018, 10:58:00 pm
content: If you're OK with using S/PDIF instead of USB, I have a design for an open hardware DAC/amp. If you're hard set on USB, you can take the design and replace the S/PDIF chip with a USB one.https://github.com/NiHaoMike/OpenDAC-HDAt one point, gamers disliked USB audio for its higher latency. They don't seem so against it now so I think USB 2.0 has substantially improved things.Quote from: HB9EVI on December 09, 2018, 05:53:49 pmEven 128GB SD cards are so cheap nowadays there's not so much reason not to.

author: josip
author_rank: Regular Contributor
timestamp: December 10, 2018, 12:39:38 pm
content: I used PCM2707 for this, as USB / I2S interface for external DAC, even integrated one is not bad at all. It is plug&play for Win, without need to install anything.Not bad advice to beginner is to start with it, and pair it with (best buy DAC chip) TDA1543 on higher supply (around 8.5V) in NOS with passive I/V. TDA1543 is old horse and there are plenty information online, and combinations for driving headphones.

author: eV1Te
author_rank: Regular Contributor
timestamp: December 10, 2018, 04:22:40 pm
content: Thanks a lot for all the input (and some critique regarding my request to have higher than 16 bit and 48 kHz)As I see it, the downside with 16 bit DAC is that when you change the volume on the computer you will effectively reduce the number of bits used. Since sound is logarithmic you will easily end up using less than 12 bits at normal listening levels if you leave enough headroom to be able to drive high-impedance headphones. With a 24 bit DAC or a PGA (programmable gain amplifier linked to the volume control from the USB) you don't have to play at maximum volume to get at least 16 bits.The benefit of using more than 48 kHz would not be hearable of course, but useful for measuring frequency response of headphones/speakers further down the road. Not a priority.It seems that the PCM2707C is good choice if one wants I2S to a separate DAC, or another one PCM series with built in DAC. However no PGA as far as I can see, so you would need analog gain control via potentiometer and always run it on max volume in Windows.I also found that it is important that the part name ends with "C", this is the newer versions that are supported in Vista and hopefully Win10 and forward, the other ones without the "C" are for XP and older due to driver compatibility etc.Another better alternative is the AK4571 (thanks Buriedcode) due to built-in PGA it allows for volume control without loosing bits, AK also seems to have a lot more documentation and evaluation board circuit diagrams to learn from.It can also be run without any external roms (unless you want to customize the vendor and product name that pops-up in Windows). Making it ideal for low profile project like this.Some of the more high end options with 24 bit and 96+ kHz support, such as the XMOS series (built-in 32 bit, 8-core CPU, and more...) and even C-media chips (built-in microprocessor that require external ROMs) are probably a bit overkill for a hobby project like this. But definitely needed if you are building a 7.1 surround sound receiver with a bunch of DSP effects

author: tooki
author_rank: Super Contributor
timestamp: December 10, 2018, 08:03:16 pm
content: Quote from: eV1Te on December 09, 2018, 12:36:23 pmThe reason for the 16bit/48KHz limit is that that is the limit of driverless USB audio in Windows, up until a recent update to Windows 10. Specifically, it's the limit of USB Audio Class 1.0, which is limited to USB full-speed (12Mbps). USB Audio Class 2.0 lifts this limit and supports USB high-speed (480Mbps), but Windows didn't include a USB Audio Class 2.0 driver until just now. (A downloadable driver is/was available for earlier versions of Windows.)Quote from: eV1Te on December 10, 2018, 04:22:40 pmWhere'd you get that idea? The volume control on the computer sends volume control signals to the USB audio device. It doesn't do it by bit-crushing the bitstream!Quote from: eV1Te on December 10, 2018, 04:22:40 pmSection 9.5.1.2 of the datasheet says:QuoteSo clearly it's being done somewhere in the DAC's output stages. (App notes for some related chip models expressly mention that this changes the gain of the DAC.)Quote from: eV1Te on December 10, 2018, 04:22:40 pmWell, not so much drivercompatibilityas such, but rather oddities in how Windows uses audio devices, and the Windows logo program demanding very specific behaviors.Quote from: eV1Te on December 10, 2018, 04:22:40 pmThe TI chips have external ROM interfaces, but don't require a ROM unless you want to customize the strings.

author: cdev
author_rank: Super Contributor
timestamp: December 10, 2018, 08:47:08 pm
content: There may be some useful info for you on the Linux kernel documentation web site.Even though you plan to use Windows.The location of the docs varies according to kernel versions. Here is an example, not the newest one.https://www.kernel.org/doc/html/v4.14/sound/cards/index.html

author: Buriedcode
author_rank: Super Contributor
timestamp: December 10, 2018, 09:28:06 pm
content: I like threads like this. Good honest Q&A without turning into a pissing contest about who has golden ears. "USB audio" has also had a rocky road, mostly down to driver implementation, and whilst it has worked for well over a decade, its probably only recently that multichannel audio has been possible without custom drivers, interfaces.It's a good antidote to the questionable advice/facts on certain audio forumsGiven how cheap some of these devices are, I would buy a few off-the-shelf products, even the dirt cheap USB "dongles" that use the CM108, for testing (they're about $2). If you have the equipment to measure noise floor, and frequency response it could prove helpful in deciding what makes a difference in the design. Bit depth might be meaningless if the last 6MSB's are noise, or it could be the PLL introduces notifiable jitter. Best to see how these things affect the output before getting a finally PCB made and parts ordered.

author: eV1Te
author_rank: Regular Contributor
timestamp: December 10, 2018, 10:06:40 pm
content: Quote from: tooki on December 10, 2018, 08:03:16 pmThat is interesting information and explains a lot. Most audio DAC chips (without USB) supports 24 bit 96 or 192 kHz, hence why I was surprised why no USB chips did, now I know whyFor example among TIs DACs they are almost all 96+ kHz and 24+ bits (but in the USB section they are all 16 bit 48 kHz):http://www.ti.com/audio-ic/converters/dac/products.htmlQuote from: tooki on December 10, 2018, 08:03:16 pmThe reason I assumed the PCM27XX and PCM29XX "crushed the bitstream" was because the datasheet didn't mention anything about programmable analog gain of the DAC, even the block diagram shows signal going directly from the DAC to the output without any analog section. I also found some information on the internet claiming that you did lose resolution in many chips while adjusting volume on the computer side, hence why they recommended a 24 bit DAC or one with a PGA (making it sound as if it was not standard).I now understand that this information might have been incorrect, hence I am thankful for this information.Could you perhaps answer another question for me:If I use a USB to I2S interface, such as the PCM2707 and connect it to a separate DAC with I2S input. Would the volume information from the computer go via the I2S serial bus to the separate DAC in some way, or is that information lost and the DAC would output full volume all the time?I guess what I am asking is if the I2S serial protocol supports metadata such as volume information while retaining the full bit-resolution of the audio signal, i.e. no bit crushing?

author: BrianHG
author_rank: Super Contributor
timestamp: December 10, 2018, 10:37:42 pm
content: If you pass CD direct to the DAC and then have your analog volume pre-amp, the 16bit 44.1k is perfect. If you have windows master volume as your amplifier volume, especially with a 200watt / channel, or above, NO, the 16bit DACs will sound more and more muffled as you lower the system volume. It is clear and obvious as much of the time, I use a volume of 10% or less for background music. The only good fix is a 16 bit dac with a 50% to 100% system volume and an analog volume control, or, without a analog volume, get awindow's recognized24 bit dac. (Having windows operating in 16bit sound with a 24 bit DAC wont work..) And also, even with a high definition DAC in windows, sometimes the system still defaults down to 16bit 44.1khz or 16 bit 48khz sound. You need to set this in the speaker properties while disabling all sound enhancement features.As for sample rate, usually 48Khz is fine. You only need more if you are running a studio, or you have unusually superb high frequency response in you ears to the point where even 320k MP3s are a problem for you. Otherwise, there is something wrong with your PC's re-sampling algorithm or you DAC's oversampling circuitry.

author: BrianHG
author_rank: Super Contributor
timestamp: December 10, 2018, 10:50:28 pm
content: Here is a USB20. audio chipset:https://www.cmedia.com.tw/products/USB20_HIGH_SPEEDYou get I2S audio output and input serial bus. You need to buy your own DAC and optional ADC separately.Use a data grade 4 channel optoisolator between this IC's I2S out and your DAC if you want no ground loop connection to your PC at all.Just buy this board: (I don't exactly trust Aliexpress, but search there as many different revisions of CM6631 boards exist including those with 24/32 bit DACs and transformer isolated SPDIF RCA connectors)https://www.aliexpress.com/item/CM6631-IIS-digital-interface-compatible-with-Italy-Amanero-USB-192K-32BIT

author: BrianHG
author_rank: Super Contributor
timestamp: December 10, 2018, 11:06:11 pm
content: Complete board:https://www.aliexpress.com/item/Douk-Audio-CM6631A-AKM4490-USB-DAC-32BIT-384K-HiFi-Audio-Decoder-Board-Assembled

author: NiHaoMike
author_rank: Super Contributor
timestamp: December 11, 2018, 12:50:15 am
content: Quote from: eV1Te on December 10, 2018, 10:06:40 pmIt does not. DACs that have built in PGAs like the PCM1792A have a control interface like I2C.

author: bson
author_rank: Unknown
timestamp: December 11, 2018, 05:21:14 am
content: XMOS makes microcontrollers with everything needed to roll a single-chip USB 2 HS to I2S playback device. Then use it with your I2S DAC of choice.For example:https://www.digikey.com/product-detail/en/xmos/XU208-128-QF48-C10/880-1124-ND/6206218(https://www.xmos.com/developer/silicon/xcore200-usb)Small 48-pin QFN package.I believe they provide a complete toolchain as a free download, including a simulator. They're OTP devices, so development usually is done via JTAG and running code from SRAM, with a small bootloader in OTP ROM to help regain control of the prototype if you screw up.They don't have I2S per se, but they have FIFOs and serial shift registers (SERDES) as part of the GPIO structure that can be clocked externally, onto GPIO pins. Which is all you need to roll SPI, I2S, etc. (They may even have libraries and code you can drop in if you're lazy or just want to do some quick prototyping.)

author: cdev
author_rank: Super Contributor
timestamp: December 11, 2018, 02:42:28 pm
content: Do any of these (premade or kit) external USB audio devices support both very high S/N ratio 192 kbps 24 or 32 bit or higher input (and hifi output for regular use) so the USB audio device can be used as a high quality external 'sound card' with an SDR?More bits = more dynamic range.

author: SiliconWizard
author_rank: Super Contributor
timestamp: December 11, 2018, 02:45:04 pm
content: Quote from: cdev on December 11, 2018, 02:42:28 pmCertainly. You can pick on of those XMOS-based boards:https://www.diyinhk.com/shop/audio-kits/107-xmos-dsd-dxd-768khz-high-quality-usb-to-i2sdsd-pcb.html(There are others out there.)

author: BrianHG
author_rank: Super Contributor
timestamp: December 11, 2018, 04:21:28 pm
content: Quote from: cdev on December 11, 2018, 02:42:28 pmJust read the features sheets. I provided all the links:https://www.cmedia.com.tw/products/USB20_HIGH_SPEED/CM6631AThe chip does it, however, I'm not sure if the serial 'D-In' pin is wired. note that the MCLK BCLK and L/R clk pins may be the same is the IC operates in master mode.IO PCB and configuration tool:https://www.diyaudio.com/forums/digital-line-level/217764-cm6631-usb-audio-interface-46.html

author: Hydron
author_rank: Super Contributor
timestamp: December 11, 2018, 04:34:11 pm
content: Avoiding bit-crushing from SW volume controls or using the DAC for other non-audio purposes are both good reasons to go for >16-bit or >48kHz.Fully analogue (physically controlled rather than digitally) volume controls are horrible, expensive or a bit of both; very seldom neither (in my experience). It's for this reason that I ended up buying a USB DAC/amp that uses a reasonable 24-bit converter and a software (encoder knob) volume control - with the gain set sensibly so that it goes as loud as needed but not excessive (keeping the last few noisy bits inaudible in all circumstances) it works very well.This approach might run into issues when using both low-sensitivity (e.g. 600 ohm over-ear) and high-sensitivity (e.g. 16 ohm in-ear) head/earphones in the same setup (requiring a very large usable attenuation range) but DACs with rather large SNRs are readily available and it's not like analogue controls normally have huge usable ranges either.Finally note that if a SW volume control is done internally to the DAC then 16-bit could still be enough from USB though (the DAC itself will do the bit-crushing internally but with more internal bits to play with than it's externally fed).

author: bson
author_rank: Unknown
timestamp: December 12, 2018, 05:56:34 am
content: You can also buy a ready to use USB to I2S converter; I have a Gustard U12, an inexpensive box based on the XMOS xCORE controllers that will output LVDS I2S on an HDMI connector. This allows use of HDMI cables and connectors, although of course it's not HDMI signaling. This lets you focus on the DAC and analog end, and makes it easy to A/B compare etc. When you're happy with how it sounds you can then add a USB device controller as a separate project.

author: cv007
author_rank: Frequent Contributor
timestamp: December 13, 2018, 11:13:39 pm
content: I have been using a PCM2706 for quite a while as a headphone amp for quite a while (connected to an Onion Omega2 which streams mp3's)-https://photos.app.goo.gl/RPS3Y58nACGkvy6g7https://photos.app.goo.gl/XxBw8UcfH3Q2L5iM8https://photos.app.goo.gl/SM6cY1bLtb5Y6nWf7I also have one driving my tda8923 boards-https://photos.app.goo.gl/BiRxAkeJ7mQEmiuU8(although I recently blew them up when messing with the power supply voltage : ) )probably not a great circuit board layout as I just wanted something quick, but I'm very happy with the result. I probably do not have golden ears, but it sounds pretty good to me. The music sounds great, and when there is no music its dead silent. You don't need much to get it going and works on any os. I think it makes a good little project that you can easily get working, and if its not good enough you are not out much time and money, or you can hang a dac on it via i2s (which I intended to do, but have never done).Good test stream-holiday.stream.publicradio.org/holiday_cms.mp3

author: amlu
author_rank: Contributor
timestamp: December 16, 2018, 12:15:41 am
content: PCM 270* are good enough. 44.1, 48 khz sampling rate, same or more as humble cd audio, 98db SNR, you dont need any more fancy stuff unless if for some high end recording studio or broadcasting equipment.I got couple of cheapo china ones scattered around for every workstation, some hooked up to pro audio kit and cant really complain about them. big step up from whats built in any laptop or motherboad. Make your own nice board with nice capacitors and off you go.

author: Smokey
author_rank: Super Contributor
timestamp: December 10, 2022, 01:50:26 am
content: https://www.behringer.com/product.html?modelCode=P0BJZ> Audiophile 24-Bit/192 kHz resolution for professional audio qualityhttps://www.audiosciencereview.com/forum/index.php?threads/behringer-umc204-hd-audio-interface-review.9856/It looks like these guys are using one of these...https://www.cirrus.com/products/cs4271/And one of these...https://www.xmos.ai/download/XS1-U8A-64-FB96-Datasheet(1..pdfNOTE: The forum decides to turn URLs into smiley faces sometimes.... Google "XMOS 8U6C5"https://www.xmos.ai/software/usb-audio/driver-support/

author: magic
author_rank: Super Contributor
timestamp: December 10, 2022, 08:52:00 am
content: Your smiley link actually works fine if you click it

author: eliocor
author_rank: Unknown
timestamp: December 11, 2022, 01:38:25 am
content: SEVERAL years ago I used theUDA1321TIt did exactly what you are looking for.Somewhere and in some places (according to my inventory) I should have 500 pieces of this component: I do not remember to have thrown them away.Let me know if you are interested in

author: jonpaul
author_rank: Super Contributor
timestamp: December 11, 2022, 03:14:49 am
content: try AKM, wide line of digital audio ICSj