The task would be considered as trivial until you try. USB/audio bridges, if my memory serves well, were available at the end of 90th from Ti, however, I met almost a military-grade-secret approach if trying to get the application info for USB bridges today, and I was very surprised.
I was interested in a compact low power bridge for a portable DAC, I start to google it and found pretty much nothing. Ok, next I googled for "USB-C 3.5mm jack teardown" and noticed bridges from Cirrus Logic, Conexant and Realtek. All these companies had no such parts officially i.e. they hide all info about USB bridges.. I did contact CL office in HK to get CS46L41-CWZR pdf, they requested my company info and forget about me. After a couple of weeks, I asked again and they apologized about forgot my request, and said - CL will not give you any info about that product, any other chip - you are welcome but not CS46L41-CWZR. Intriguing turn, right? I see CS46L41-CWZR for $5 in Arrow, Digikey, can buy that but have no idea how to use it.
I tried to get some info from Realtek www, I got an email address of my local Shenzhen Realtek agent and ask him about ALC4042/4050. He gave me pdfs the same day, however, the brand new ALC4042/4050 chip has preprogrammed FirmWare with switched off I2S outputs. I asked the agent, could he please turn I2S on? He said - sorry, no time for that complex work which will take 3 months, please, ask another agent I'll give you the contact. Ok, I've asked another "agent" and he said the same - it will take 3 months, we have no time. Well, I'm Russian, right, so I offered him a bribe i.e. cash pay for the FW with turned on I2S port. The guy found the time instantly and asked $7000 for the FW for ALC4050 with I2S is On. Furthermore, he'll not give me the FW file and even programming tool (windows EXE app for programming by USB) but he can program for me all 5000pcs ALC4050 for extra pay, of course, money upfront. I know mainland-chinese very well and asked to show me the ALC4050 sample with I2S/DSD working. The "agent" disagree to prove me he's qualification, and asked me to pay first. At the same time he said a couple of things which makes me believe if he's not really a specialist, he said - Android can not play native DSD just because no way. The bridge I finally use does native DSD256 on Android. Also, the "agent" claims ALC4050 doesn't support 88.2, 176.4 and 352kHz Fs, so I have doubts about how ALC4050 may support DoP DSD in that case??
Finally, the guy called me many times and asked any money I can pay him, I said about we made the decision to go with Comtrue bridge CT7601 + ES9038Q2M because they provide the source code and free Win driver as well. "Realtek agent" said: could I purchase that project, many our customers need that? I do not reply anymore if he calls )) I have no idea who was that moron but I met him because of realtek www, hence due to moronic Realtek management.
Ok, the txt becomes too long, better I'll show you a short chart of bridges I tested:
1) CMEDIA. Doesn't looks active, never reply to my emails, only resend that to their local agents in SHZ. Local agents are ignorant as usual in mainland-china, any tech question will take months of email ping-pong. Also, agents are crazy greedy, they asked me $5 for CM6642 bridge, which I found for $2 finally. The chip(6x5mm QFN) is quite handy just 4pcs 0402 external components required, single power rail 5V, 20mA at 24/44.1. The chip contains OTP for the FW, and CMEDIA gave me win exe app to program IC by USB(BTW, the DLL used with the app was made by Realtek!). However, CM6642 contains the design defect, it has no CRC validation for audio packets, hence, any dust in the USB-C connector may cause a loud noise. CMEDIA product manager said that they can't fix that defect by FW, hence, only the new silicon version may help. Actually, most USB audio bridges(but not XMOS) made on 8051 free core and state machine, hard-logic for the fast USB operations. The FW(8051 program code) may correct some functions but not all.
Pros: compact, low power, no external oscillator required(PLL from USB's 48MHz), single power rail. It doesn't need driver at all.
Cons: SPDIF output only with 24/192 limit. Near to zero support, design defective chip. A quite bad idea to go with cmedia in 2020..
2) XMOS. All app info is opened, well documented. Good support forum, easy to start, easy to modify a custom FW(I spent a couple of days).
Cons: Expensive chips(XU208 PCM 32/384 DSD256 near to $10), no free Win driver. Huge power consumption, 24/44.1 about 110mA, just a lot of surrounding parts. absolutely not suitable for a portable purpose.
3) Realtek ALC4050, it is a combo, the same as CM6642 i.e. DAC+HPA + ADC, supplied with I2S port Off. 6x6mm QFN, single-rail power 5V, a few surrounding parts(5pcs 0402 caps and 1 res) needed to work as USB/I2S bridge. 32/384 DSD256. Core 1.2V, 18mA 24/44.1 consumption. Very low cost, $1.3-1.5. 64kB flash for the FW onboard. Widely used in the new PC motherboards and USB-C/3.5mm jack adapters.
Cons: Zero support, even to get I2S On is impossible(I can On/Off anything in CT7601 source code during a couple of minutes!). In the case if Realtek will offer its source code, it would be the most advanced USB/audio bridge for a portable purpose!
4) Savitech.
Cons: The most secret and most archaic tech at the same time.
Requires NDA to get FW USB programming app, I'm not kidding! )) It is so stupid when you can simply read the FW from the 24C256 where is FW located )) Their www was updated last time 2016, they never reply to your emails. I was sure if savitech simply bankrupt. All chips are 2011, requires 1.8V and 3.3V rails with terrible current, so you need to use buck convertor like with XMOS to make 1.8V >100mA. Even reset is an external RCD circuit, and when I used the Power_good output of my buck convertor, savitech asked to return back their resistor-capacitor-diode circuit! Oh yeah, savitech will ask you for the schematic for the review! )) $5 for the SA9302/9312 32/384 DSD256(to be honest, I didn't see works DSD256 ever with that ICs, only 128). Need wait months to get your "custom" FW, where you actually can not ask for any serious customization at all just product name and LED behavior. Not easy to buy, also needed to fill the form, why you want to buy savitech ICs etc. I see no reason to consider savitech as a USB/audio bridge supplier.
5) Comtrue CT7601CR, actually it is not an ideal bridge as well but they give you the source code(8051 keil project) and free win driver too! All pdfs you can download right now. You don't need a host MCU because all that you need could be implemented by modifying the source code. The chip itself is more technic vs savitech(1.2V core, less current, no stupid external RCD reset etc) but not such advanced as ALC4050 yet. They have different ICs in different packaging, named almost the same CT7601. I use 6x6 QFN 32/384 DSD256(DSD256 really works with Mac, Win, Android) $4.5. 1.8v and 3.3V rails required + one Xtall and few 0402 caps + SPI flash for the FW. Another CT7601PR in the pin2pin same case supports 32/768 and DSD512, as I know $6.5, and cheaper one CT7601SR 32/192 DSD128 $2.5. We asked Comtrue for the HID in/out which wasn't implemented, and they agreed to implement that if we'll give them the app to test HID functions with. Alive people, what can I say.
Cons: so far impossible to buy even in mainland-china. I've ordered 1KU and may offer it on my E1DA Aliexpress store.
6) Cirrus Logic CS46L41, seems needed only 5V as well, very low 24/44.1 current(almost the same current for PCM 384k and DSD128), about the same ALC4050 if not less. Requires external serial flash for the FW. 3x3 BGA case makes PCB noticeable more expensive due to .2mm vias. Also, needed one 22MHz oscillator.
Usually, CL offers two options for the cases so I guess CS46L41 QFN does exist too. About $5/pcs.
Cons: no application data available.
Epilogue: Why many of those companies hide USB bridges from a public domain? I guess we should blame.. Apple inc. When they did delete 3.5mm jack from their iPhone, they created a huge niche for USB/3.5mm jack adapters. Now a lot of Chinese phones goes the same way and the niche reached a few hundred million adapters/year. Suddenly, tiny Taiwanese companies as savitech(I guess it is just a few people, 1-2 is enough to debug FPGA and order the silicon) either not too big US company as CL got the chance to make a big money until big players wake up like Ti, ST, On, NXP, AD. BTW, I've found on AD engineering forum info that AD testing their own high-performance USB audio bridge, hence, I'm right about why that topic so much hermetic today.
I was interested in a compact low power bridge for a portable DAC, I start to google it and found pretty much nothing. Ok, next I googled for "USB-C 3.5mm jack teardown" and noticed bridges from Cirrus Logic, Conexant and Realtek. All these companies had no such parts officially i.e. they hide all info about USB bridges.. I did contact CL office in HK to get CS46L41-CWZR pdf, they requested my company info and forget about me. After a couple of weeks, I asked again and they apologized about forgot my request, and said - CL will not give you any info about that product, any other chip - you are welcome but not CS46L41-CWZR. Intriguing turn, right? I see CS46L41-CWZR for $5 in Arrow, Digikey, can buy that but have no idea how to use it.
I tried to get some info from Realtek www, I got an email address of my local Shenzhen Realtek agent and ask him about ALC4042/4050. He gave me pdfs the same day, however, the brand new ALC4042/4050 chip has preprogrammed FirmWare with switched off I2S outputs. I asked the agent, could he please turn I2S on? He said - sorry, no time for that complex work which will take 3 months, please, ask another agent I'll give you the contact. Ok, I've asked another "agent" and he said the same - it will take 3 months, we have no time. Well, I'm Russian, right, so I offered him a bribe i.e. cash pay for the FW with turned on I2S port. The guy found the time instantly and asked $7000 for the FW for ALC4050 with I2S is On. Furthermore, he'll not give me the FW file and even programming tool (windows EXE app for programming by USB) but he can program for me all 5000pcs ALC4050 for extra pay, of course, money upfront. I know mainland-chinese very well and asked to show me the ALC4050 sample with I2S/DSD working. The "agent" disagree to prove me he's qualification, and asked me to pay first. At the same time he said a couple of things which makes me believe if he's not really a specialist, he said - Android can not play native DSD just because no way. The bridge I finally use does native DSD256 on Android. Also, the "agent" claims ALC4050 doesn't support 88.2, 176.4 and 352kHz Fs, so I have doubts about how ALC4050 may support DoP DSD in that case??
Finally, the guy called me many times and asked any money I can pay him, I said about we made the decision to go with Comtrue bridge CT7601 + ES9038Q2M because they provide the source code and free Win driver as well. "Realtek agent" said: could I purchase that project, many our customers need that? I do not reply anymore if he calls )) I have no idea who was that moron but I met him because of realtek www, hence due to moronic Realtek management.
Ok, the txt becomes too long, better I'll show you a short chart of bridges I tested:
1) CMEDIA. Doesn't looks active, never reply to my emails, only resend that to their local agents in SHZ. Local agents are ignorant as usual in mainland-china, any tech question will take months of email ping-pong. Also, agents are crazy greedy, they asked me $5 for CM6642 bridge, which I found for $2 finally. The chip(6x5mm QFN) is quite handy just 4pcs 0402 external components required, single power rail 5V, 20mA at 24/44.1. The chip contains OTP for the FW, and CMEDIA gave me win exe app to program IC by USB(BTW, the DLL used with the app was made by Realtek!). However, CM6642 contains the design defect, it has no CRC validation for audio packets, hence, any dust in the USB-C connector may cause a loud noise. CMEDIA product manager said that they can't fix that defect by FW, hence, only the new silicon version may help. Actually, most USB audio bridges(but not XMOS) made on 8051 free core and state machine, hard-logic for the fast USB operations. The FW(8051 program code) may correct some functions but not all.
Pros: compact, low power, no external oscillator required(PLL from USB's 48MHz), single power rail. It doesn't need driver at all.
Cons: SPDIF output only with 24/192 limit. Near to zero support, design defective chip. A quite bad idea to go with cmedia in 2020..
2) XMOS. All app info is opened, well documented. Good support forum, easy to start, easy to modify a custom FW(I spent a couple of days).
Cons: Expensive chips(XU208 PCM 32/384 DSD256 near to $10), no free Win driver. Huge power consumption, 24/44.1 about 110mA, just a lot of surrounding parts. absolutely not suitable for a portable purpose.
3) Realtek ALC4050, it is a combo, the same as CM6642 i.e. DAC+HPA + ADC, supplied with I2S port Off. 6x6mm QFN, single-rail power 5V, a few surrounding parts(5pcs 0402 caps and 1 res) needed to work as USB/I2S bridge. 32/384 DSD256. Core 1.2V, 18mA 24/44.1 consumption. Very low cost, $1.3-1.5. 64kB flash for the FW onboard. Widely used in the new PC motherboards and USB-C/3.5mm jack adapters.
Cons: Zero support, even to get I2S On is impossible(I can On/Off anything in CT7601 source code during a couple of minutes!). In the case if Realtek will offer its source code, it would be the most advanced USB/audio bridge for a portable purpose!
4) Savitech.
Cons: The most secret and most archaic tech at the same time.
Requires NDA to get FW USB programming app, I'm not kidding! )) It is so stupid when you can simply read the FW from the 24C256 where is FW located )) Their www was updated last time 2016, they never reply to your emails. I was sure if savitech simply bankrupt. All chips are 2011, requires 1.8V and 3.3V rails with terrible current, so you need to use buck convertor like with XMOS to make 1.8V >100mA. Even reset is an external RCD circuit, and when I used the Power_good output of my buck convertor, savitech asked to return back their resistor-capacitor-diode circuit! Oh yeah, savitech will ask you for the schematic for the review! )) $5 for the SA9302/9312 32/384 DSD256(to be honest, I didn't see works DSD256 ever with that ICs, only 128). Need wait months to get your "custom" FW, where you actually can not ask for any serious customization at all just product name and LED behavior. Not easy to buy, also needed to fill the form, why you want to buy savitech ICs etc. I see no reason to consider savitech as a USB/audio bridge supplier.
5) Comtrue CT7601CR, actually it is not an ideal bridge as well but they give you the source code(8051 keil project) and free win driver too! All pdfs you can download right now. You don't need a host MCU because all that you need could be implemented by modifying the source code. The chip itself is more technic vs savitech(1.2V core, less current, no stupid external RCD reset etc) but not such advanced as ALC4050 yet. They have different ICs in different packaging, named almost the same CT7601. I use 6x6 QFN 32/384 DSD256(DSD256 really works with Mac, Win, Android) $4.5. 1.8v and 3.3V rails required + one Xtall and few 0402 caps + SPI flash for the FW. Another CT7601PR in the pin2pin same case supports 32/768 and DSD512, as I know $6.5, and cheaper one CT7601SR 32/192 DSD128 $2.5. We asked Comtrue for the HID in/out which wasn't implemented, and they agreed to implement that if we'll give them the app to test HID functions with. Alive people, what can I say.
Cons: so far impossible to buy even in mainland-china. I've ordered 1KU and may offer it on my E1DA Aliexpress store.
6) Cirrus Logic CS46L41, seems needed only 5V as well, very low 24/44.1 current(almost the same current for PCM 384k and DSD128), about the same ALC4050 if not less. Requires external serial flash for the FW. 3x3 BGA case makes PCB noticeable more expensive due to .2mm vias. Also, needed one 22MHz oscillator.
Usually, CL offers two options for the cases so I guess CS46L41 QFN does exist too. About $5/pcs.
Cons: no application data available.
Epilogue: Why many of those companies hide USB bridges from a public domain? I guess we should blame.. Apple inc. When they did delete 3.5mm jack from their iPhone, they created a huge niche for USB/3.5mm jack adapters. Now a lot of Chinese phones goes the same way and the niche reached a few hundred million adapters/year. Suddenly, tiny Taiwanese companies as savitech(I guess it is just a few people, 1-2 is enough to debug FPGA and order the silicon) either not too big US company as CL got the chance to make a big money until big players wake up like Ti, ST, On, NXP, AD. BTW, I've found on AD engineering forum info that AD testing their own high-performance USB audio bridge, hence, I'm right about why that topic so much hermetic today.
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Very interesting info, thanks IVX. Just for the sake of completeness - its going to be expensive I'm sure as its aiming at the high end - there's this coming from Thesycon : U-HEAR – USB High-end Audio Receiver Firmware Solution
Schiit is using a PIC32 for their most recent USB bridge called 'Unison'. I wonder how much of the code they got from Microchip for that. They say they invested a couple of person years writing the code.
Schiit is using a PIC32 for their most recent USB bridge called 'Unison'. I wonder how much of the code they got from Microchip for that. They say they invested a couple of person years writing the code.
Thanks IVX, for sharing to us these information.
I believe it is all about supply and demand:
- USB DACs are already a niche;
- portable USB DACs are the niche of a niche;
- those 90s TI chips doesn't seem to be old, if we consider how old is I2S standard and how new is a bigger storage capacity of our phones (a few years ago, a few high res albums would have filled their whole storage);
- there is no future for portable USB bridges and if I were such a company, I would invest my money in a better wireless/bluetooth? solution.
- if we speak about the windows driver support for portable devices, we certainly are in a niche of a niche of a niche;
- if a such of solution will still appear, it will be offered probably by a big company, like AD, as you said.
I believe it is all about supply and demand:
- USB DACs are already a niche;
- portable USB DACs are the niche of a niche;
- those 90s TI chips doesn't seem to be old, if we consider how old is I2S standard and how new is a bigger storage capacity of our phones (a few years ago, a few high res albums would have filled their whole storage);
- there is no future for portable USB bridges and if I were such a company, I would invest my money in a better wireless/bluetooth? solution.
- if we speak about the windows driver support for portable devices, we certainly are in a niche of a niche of a niche;
- if a such of solution will still appear, it will be offered probably by a big company, like AD, as you said.
there is CP2615 from silabs, only audio 1.0, bi-directional, only 44.1kHz and 48kHz, almost no external components, asynchronous, integrated clock (not very good, jitter), cheap, customization software ... I have not tried if the I2S word is customizable (default seems to be 32/48 bits instead of standard 64 bits)
https://www.silabs.com/documents/public/data-sheets/cp2615-datasheet.pdf
https://www.silabs.com/documents/public/application-notes/an1044-cp2615-customization-user-guide.pdf
https://www.silabs.com/documents/public/data-sheets/cp2615-datasheet.pdf
https://www.silabs.com/documents/public/application-notes/an1044-cp2615-customization-user-guide.pdf
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Oh, hell, I missed the 3) part about the realtek ALC4050! Shortly, if realtek will open its source code ever, the chip would be very affordable for all. 32/384 + DSD256 <$1.5, 64KB flash onboard for the FW, single-rail power 5V, core voltage 1.2V but actually near to 1V. Very low idle power, and 18mA at 24/44.1. A few 0402 caps + 1 0402 resistor the all that you need for the USB/I2S operation. 6x6mm QFN case. Seems may work with/without external oscillator. In my opinion, it is better than CL bridge but no way to get FW, no source code, stupid support etc. Very pity!
Mainland-chinese agents, FAE, "engineers" etc in most cases very low educated accidentally hired farmers. The only chance to get something is direct realtek contact but they NEVER reply.
PS: realtek could delete ADC/DAC area from that chip to reduce QFN case to 24pins i.e. 3x3mm! And less price such USB bridge may beat all future products from big monsters like Ti, ST, On etc.
PS: realtek could delete ADC/DAC area from that chip to reduce QFN case to 24pins i.e. 3x3mm! And less price such USB bridge may beat all future products from big monsters like Ti, ST, On etc.
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Hi,
About Microchip and PIC32:
For USB Audio 1.0 up to 24bit/96kHz PIC32MX270 can be used.
Small package SSOP or QFN, price about 3.5$ for single piece
For example used in DragonFly DAC,
https://www.audioquest.com/dacs/dragonfly/dragonfly-red
Feniks Audio Speakers ( Firmware designed by me)
Feniks Audio
I think that firmware can be transfered to much chiper PIC32MM064, about 1.5$
For USB Audio 2.0 up to 32bit/192khz (384 not tested) PIC32MZ0512EFE064 can be used.
Small package TQFP64 or QFN64, price about 8$ for single piece.
I am currently finishing work on bare metal firmware (without Microchip Harmony) for this chip.
I also started project with new LPC55 series from NXP.
Using your own firmware allows you to use uP as USB-I2S converter and main processor for control DAC.
Regards,
JarekC
About Microchip and PIC32:
For USB Audio 1.0 up to 24bit/96kHz PIC32MX270 can be used.
Small package SSOP or QFN, price about 3.5$ for single piece
For example used in DragonFly DAC,
https://www.audioquest.com/dacs/dragonfly/dragonfly-red
Feniks Audio Speakers ( Firmware designed by me)
Feniks Audio
I think that firmware can be transfered to much chiper PIC32MM064, about 1.5$
For USB Audio 2.0 up to 32bit/192khz (384 not tested) PIC32MZ0512EFE064 can be used.
Small package TQFP64 or QFN64, price about 8$ for single piece.
I am currently finishing work on bare metal firmware (without Microchip Harmony) for this chip.
I also started project with new LPC55 series from NXP.
Using your own firmware allows you to use uP as USB-I2S converter and main processor for control DAC.
Regards,
JarekC
But as you wrote:
Cons: so far impossible to buy even in mainland-china.
New LPC55 chips with build USB HS PHY and Ref Clk input for SPI cost about 2,8$/1000szt.
I like to have control over the firmware and have several places to buy.
The main problem with the MCU is that few of them have built-in USB HS PHY and a fast SPI port.
If this is met, they are usually in large packages,with many unnecessary peripherals and and unnecessary computing power
That's why ASICs wins.
Cons: so far impossible to buy even in mainland-china.
New LPC55 chips with build USB HS PHY and Ref Clk input for SPI cost about 2,8$/1000szt.
I like to have control over the firmware and have several places to buy.
The main problem with the MCU is that few of them have built-in USB HS PHY and a fast SPI port.
If this is met, they are usually in large packages,with many unnecessary peripherals and and unnecessary computing power
That's why ASICs wins.
Jarek, do you have a working USB-I2S code/example/harmony project for a PIC32xxx? Everything failed from my attempts.
I have working project UAC1.0 PIC32MX270, Harmony version
and UAC2.0 PIC32MZ2048EF with own USB stack without Harmony.
Unfortunately, I cannot make it public at this time because the projects were commercial.
I'm working on a open source version but it's not ready yet.
CM6635 might be the best choice for high performance and low BOM size.
I found it on Taobao, but unfortunately it costs as much as $14.10.
https://m.tb.cn/h.VgkPAIG?sm=cfa6d2
I don't know if the distributor will provide technical support to individuals.
I found it on Taobao, but unfortunately it costs as much as $14.10.
https://m.tb.cn/h.VgkPAIG?sm=cfa6d2
I don't know if the distributor will provide technical support to individuals.
Pantek, SHZ distributor of media, told me that 6635 still has problems and they didn't recommend me use it so far(it was last summer).
Here is the pdfs for 6635 CM6635.rar — Yandex.Disk
Here is the pdfs for 6635 CM6635.rar — Yandex.Disk