ISO DDCs with USB Output, act in USB Host mode, work without a computer

[john61ct]

I thought one of the HiFiMe devices worked like this, turns out I was mistaken got bad info.

Not looking for an ADC or audio interface, or hybrid DAC / mixers etc, but if these do exist with this capability, please do post.

Technically the Wiim devices' USB output do qualify, but those are in effect just locked-down Linux computers and priced accordingly - similar boxen need not apply.

What I really want is cheap & cheerful, good SQ quality DDCs

S/PDIF inputs, either TOSlink or Coax (I2S, AES a plus)

2- channels is fine, more would be better.

TIA

 

[Roland68]

I thought one of the HiFiMe devices worked like this, turns out I was mistaken got bad info.

Not looking for an ADC or audio interface, or hybrid DAC / mixers etc, but if these do exist with this capability, please do post.

Technically the Wiim devices' USB output do qualify, put those are in effect just locked-down Linux computers and priced accordingly - similar boxen need not apply.

What I really want is cheap & cheerful, good SQ quality DDCs

S/PDIF inputs, either TOSlink or Coax (I2S, AES a plus)

2- channels is fine, more would be better.

TIA

What exactly do you want to do with it? Perhaps then we can help you solve your problem.

A device with a USB output is not usually a DDC. If you have an example of such a device, please post it.

A USB output that controls another device is always also a USB host, so in some way always a computer; it's technically impossible to do otherwise.

 

[john61ct]

There are lots of inexpensive USB host chips, MCU / SOC could implement this cheaply, but perhaps no one has yet seen a market need.

I understand USB output is more rare from DDCs than S/PDIF, lots of what I came across as "capture cards" are likely poor quality.

The exemplar TYPE of device would be PocketADC, but ofc completely different function.

I don't have a particular problem, nor am I seeking general advice. One use case is looking at different ways to get into playing with DSPi, but more importantly looking to increase my knowledge wrt any-to-any signal conversion.

Happy to just wait and see if someone who IS aware of such a gadget comes along, others can just ignore.

And if it does indeed turn out that what I'm asking for does not exist, so be it - a Raspberry Pi as host would be a reasonable cost, and give other DSP tool options to learn from hands-on.

 

[Roland68]

There are lots of inexpensive USB host chips, MCU / SOC could implement this cheaply, but perhaps no one has yet seen a market need.

I understand USB output is more rare from DDCs than S/PDIF, lots of what I came across as "capture cards" are likely poor quality.

The exemplar TYPE of device would be PocketADC, but ofc completely different function.

I don't have a particular problem, nor am I seeking general advice. One use case is looking at different ways to get into playing with DSPi, but more importantly looking to increase my knowledge wrt any-to-any signal conversion.

Happy to just wait and see if someone who IS aware of such a gadget comes along, others can just ignore.

And if it does indeed turn out that what I'm asking for does not exist, so be it - a Raspberry Pi as host would be a reasonable cost, and give other DSP tool options to learn from hands-on.

I think you're getting bogged down in this.
As I said, a DDC doesn't usually have a USB output, and what would be the point of that?

It doesn't make sense to output SPDIF data via a USB host, since every DAC, and other digital audio devices, also have SPDIF-based inputs (coaxial, Toslink, AES/EBU).

ADCs with a USB interface, and audio interfaces as well, are not host devices and don't have a USB host output.

Are you perhaps confusing this with the "USB to Host" interface?

A USB host is the device that initiates and controls the entire data transfer. Audio devices connected to a computer are not that.

USB host chips are either used in such host devices or are special ICs for data transfer and are also Android or Linux-based. But they are not suitable for audio.

That's why I'm asking for a concrete example or use case, since I can't think of one.

 

[john61ct]

That's all fine, I don't feel bogged down...

The concrete example I gave for now was DSPi

but really, delivering USB input to any device that requires that, without being forced to do so from a full general-purpose computer

upstream input being S/PDIF signals (either transport) - or analog by adding PocketADC.

 

[Roland68]

That's all fine, I don't feel bogged down...

The concrete example I gave for now was DSPi

but really, delivering USB input to any device that requires that, without being forced to do so from a full general-purpose computer

upstream input being S/PDIF signals (either transport) - or analog by adding PocketADC.

If you're referring to the DSPi based on the Raspberry Pi Zero, that's just a regular host USB output, no different from a PC or Mac, etc.
The Pi Zero is already a fully-fledged general-purpose computer.

I think you've gotten carried away with this idea.

I simply can't see any use case where you'd need to convert data from an SPDIF output back to USB. What would be the advantage? And for what purpose?
You still haven't mentioned a use case.

ADCs either output SPDIF or pass the data to a computer for processing via USB, e.g., a PC, Mac, or Pi Zero.
In my circle of acquaintances, some people use the PocketADC to connect their turntable to the DAC (coaxial or TOSLINK), thus eliminating the need for a preamplifier.
But in none of these cases is the ADC a USB host, or would it need to be.

 

[john61ct]

DSPi project runs on Pico platform RP2040 or RP2350

These are MCU, embedded system running on firmware, not a host running an OS like the Raspberry Pi which e.g. CamillaDSP runs on.

They work in device mode only, needing a USB host.

Thanks for your input, and feel free to just let the matter rest, I outlined my Plan B if it turns out no such device exists.

 

[john61ct]

related thread

S-PDIF to USB converter. Any suggestions?

I'm looking for an inexpensive converter that will take an S-PDIF input and deliver a USB output. There are any number of USB to S-PDIF output for under £$€20 , but I can't find a single one that provides an S-PDIF input. I want to make some measurements on a stand-alone ADC that takes in...

www.audiosciencereview.com

My current thinking may allow me to use USB output only at the top level source / digital preamp

only use S/PDIF as the digital output farther down the signal chain,

and avoid devices that have USB as their only digital input.

If still needed, an rPi host - as computer - is not too expensive, large or power thirsty.

Just a bit more DIY than would be ideal.

But if anyone does comes across a cheap and cheerful "DDC as USB host" as per my OP please do post !

 

[phofman]

A USB host must have drivers for connected USB devices. So the "DDC as USB host" would have to happen to support the connected USB device. The driver which supports by far most USB audio devices is .. the linux USB audio driver. Hence incorporation of a tiny linux computer is the way to go... and many manufacturers rightly do so.

 

[john61ct]

Thanks for that

Yes if I do need this functionality I plan at this point to use Raspberry Pi.

For the use case of getting into playing with DSPi, obviously their standard RP2040 / RP2350 Pico firmware implements Gadget Class (via TinyUSB?) to be automatically recognized by the Linux kernel without drivers.

 

[phofman]

The kernel does have a driver for that - the alsa usb audio driver. Since that Pico firmware uses the UAC1/2(?) standard, no other driver is necessary. But that USB audio driver is pretty complex (just as OSX or windows UAC2 drivers, with the difference that those do not contain the many quirks for the vast realm of non-standard devices and require vendor-specific drivers for these)