[sdiy] Niche ACM-1 how's this thing work?

Roman Sowa modular at go2.pl
Wed Mar 22 09:11:25 CET 2023


That's right not every DAC goes up with bandwidth to the same frequency, 
but I have yet to see a DAC that cannot reach even 20kHz. Usually it's 
in range of 100s of kHz up to several MHz, and all of that in low speed 
DACs.
For example out of 600 1-channel >=12-bit DACs in stock at mouser sorted 
by price, the cheapest ones offer from 50 to 500kHz with -3dB bandwidth.

Maybe there's one peculiar DAC having problems with AC at Vref (I can't 
see a reason why it should have) but why bother looking for it since $1 
part already does the job. And if I want better performance I can go 
straight to DAC7811, which is real multiplying DAC and even offers low 
glitch on code changes.

So yes, I will say ANY DAC

Roman

W dniu 2023-03-21 o 17:25, brianw pisze:
> Not every DAC has a flat, 20 kHz bandwidth response to signals applied to its Vref input. Hell, not even every op-amp guarantees flat audio response across the full range of inputs. Fortunately, for op-amps, we have over 10,000 different models to choose from. Not so much for DAC chips. So, you can't really use "any" DAC chip for this, without even mentioning the type of DAC.
> 
> Brian
> 
> On Mar 21, 2023, at 3:25 AM, Roman Sowa <modular at go2.pl> wrote:
>> You can make multiplying DAC out of 2 any DACs with external reference input. Both DACs must be controlled by the same SPI. The Vref of 1st DAC is driven with your input of interest, say mxer's channel audio, but with added voltage offset to midscale so the signal fits within DAC's ratings. The Vref of 2nd DAC takes only the offset itself. Then the output of 2nd DAC is reversed and added to the output of 1st DAC.
>> Despite the hassle and complexity it's still cheaper than "real" multiplying DAC.
>>
>> Roman
>>
>> W dniu 2023-03-20 o 23:29, Paul Perry via Synth-diy pisze:
>>> This reminds me that I can't seem to find any cheap available multiplying DACs. Any suggestions? Are they abandoned technology?
>>> paul perry Melbourne Australia
> 


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