[sdiy] Can't find 1-bit ADCs
brianw at audiobanshee.com
Sat Jun 11 01:21:29 CEST 2022
If you want good DC precision, then you should specifically stay away from delta-sigma converters - it doesn't matter whether they're intended for audio.
The two bit values in delta-sigma are +1 and -1 ... there literally is no code for DC (i.e. ±0)
There are plenty of multi-bit ADC that work at hundreds of MegaHertz that will have great DC precision.
Even the best ADC chips are using multi-bit front ends and converting to 1-bit internally, just to avoid the noise of true 1-bit ADC.
Granted, if you want multi-bit ADC conversion with a serial interface, then that's easy, too. SPI or I2S will be required, since I2C doesn't clock fast enough for Megahertz conversion rates.
On Jun 10, 2022, at 6:40 AM, cheater cheater> 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 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 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)
>>>> 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: Neil Johnson
>>>>> Sent: 10 June 2022 09:56
>>>>> 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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