[sdiy] Can't find 1-bit ADCs
tom at electricdruid.net
Fri Jun 10 16:23:01 CEST 2022
Ok, so you need 16-channel ADC with a digital output, and a matching 16-channel DAC to convert back at the other end.
I was once on holiday in Greece with an Engineer from Soundcraft who spent his time designing stuff like you describe - his big thing was digital links from the stage to the front-of-house desk, and he was running large numbers of channels at 24-bit/96KHz quality down gigabit ethernet cable or similar, iirc.
My advice is to forget about "1 bit" because I don't think that's going to take you anywhere useful as a search term. While in theory the latency is small and the sample rate is high for the basic 1-bit convertors we've been talking about, in practice you need to average many samples to get the equivalent of a single 16-bit or 24-bit sample anyway, so you lose that advantage. You might as well look for 16-bit or 24-bit multichannel convertors and then select one that has a low latency and a reasonable price.
> On 10 Jun 2022, at 14:40, cheater cheater <cheater00social at gmail.com> wrote:
> that's kinda what I want, but different.
> I'm looking for a high audio quality and good DC precision (12 bits
> usable or better) ADC that will output 1-bit bitstream output. I would
> prefer it to "full width" output (eg 16 or 24 bits) because I would
> prefer sub-1-sample delay - I'm basically making a "digital audio
> snake" where the output of the ADC goes pretty much directly to a DAC.
> If the chip does 4, 8, or 16 channels, that's even better (because
> it's hopefully cheaper and smaller and lower power).
> A comparator isn't great, you'd have to run your own sawtooth
> oscillator, etc, kind of annoying, and definitely not good for audio
> quality. Won't /somebody/ please think of the golden ears... But no,
> seriously, looking for good audio quality.
> On Fri, Jun 10, 2022 at 3:04 PM Tom Wiltshire <tom at electricdruid.net> wrote:
>> It also depends a bit what you're going to do with the output. If you *actually want* a simple bitstream of the data, then the comparator is probably the way to go. There are some very retro eurorack delays done like this: 1-bit ADC, fed to pile of old RAM chips, out to an integrator. Example:
>> Otherwise, if you want some more modern data format at the output (I2S or SPI or whatever) then who really cares how that is achieved? That'd be up to the ADC designers, and I'm happy to let them be the experts in that field!
>>> On 10 Jun 2022, at 13:48, Steve via Synth-diy <synth-diy at synth-diy.org> wrote:
>>> they were being a bit mean to you ;)
>>> I suppose no one advertises delta-sigma ADCs (which is I guess what's
>>> talked about?) as having "1 bit",
>>> but by the number of bits their data register has, and that won't be 1,
>>> as the things are supposed to take the burden off of you, to make
>>> something useful out of a signal sampled that way. You typically
>>> wouldn't want to implement that in software, I'm pretty sure. (from my
>>> superficial understanding of the topic. I've only ever used those things
>>> as black box)
>>> cheater cheater via Synth-diy:
>>>> I'm talking about actual ADCs meant for audio :)
>>>> On Fri, Jun 10, 2022 at 12:17 PM Mike Bryant <mbryant at futurehorizons.com> wrote:
>>>>> Far better to use the LM361. Runs orders of magnitude faster and both edges have same speed so much more accuracy driving the feedback loop.
>>>>> -----Original Message-----
>>>>> From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of Neil Johnson via Synth-diy
>>>>> Sent: 10 June 2022 09:56
>>>>> To: cheater cheater
>>>>> Cc: synth-diy
>>>>> Subject: Re: [sdiy] Can't find 1-bit ADCs
>>>>> cheater cheater wrote:
>>>>>> I'm having a bit of trouble finding 1-bit ADCs. The kind that runs at
>>>>>> something like 1.5 MHz-ish or higher to sample audio. Mouser only
>>>>>> starts listing ADCs at 4.5 bit depth and google isn't helpful. How do
>>>>>> I find them? Can someone suggest any devices?
>>>>> LM311. Classic 1-bit ADC. Works up to ~3 MHz.
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