[sdiy] Chris Synths polysynth

[Roman Sowa]

But it's like putting the world upside down. This is actually quad DAC 
in classic meaning of the word "DAC" but instead of being fed by binary 
word like its normal brothers, it contains PWM-to-digital decoders. Must 
be pretty expensive knowing Linear's price policy (or rather Analog 
Devices now). BTW, was it yesterday when hostile takeover of Maxim by AD 
was officialy finalized?

Roman

W dniu 2021-10-22 o 17:53, Oren Leavitt via Synth-diy pisze:
> Specialty DAC chips for PWM to analog conversion do exist, such as the 
> LTC2645 series. Though these seem to be in short supply at moment..
>
> https://www.analog.com/media/en/technical-documentation/data-sheets/ltc2645.pdf 
>
>
> - Oren
>
>
> On 10/22/21 5:15 AM, Vladimir Pantelic via Synth-diy wrote:
>> Arturia uses a dual PWM scheme in all of the their Keystep and 
>> Beatstep products, basically following the circuit laid out here:
>>
>> http://www.openmusiclabs.com/learning/digital/pwm-dac/dual-pwm-circuits/index.html 
>>
>>
>> it works nicely, BUT also introduces a >4ms slew on all CV outputs, 
>> no biggie if driving an analog synth and it gets hidden in the 
>> attack, but a real nuisance if it gets sampled by a digital module...
>>
>>
>> On 10/21/21 11:34 AM, Tom Wiltshire wrote:
>>> Here’s the correction:
>>>
>>> Imagine you have a DAC with 4-bit resolution. If we use one with a 
>>> step-between-values of 1V, and then add the output of another with a 
>>> step-between-values of 1/16th of a volt, we can make an 8-bit DAC. 
>>> That’s basically what you do with the PWM. The process is helped by 
>>> the very good linearity of digital-counter-based PWM as a method of 
>>> producing a voltage.
>>>
>>> I’ve used a 3-bit PWM scaled to produce 1V per step and a 4-bit PWM 
>>> scaled to produce 83mV per step to produce Pitch CVs. It worked very 
>>> well and produced good CVs across the 8 octaves. The reduced bit 
>>> depth of each PWM DAC means that the output frequency can be higher 
>>> without the PWM clock frequency having to be super-high, and this 
>>> improves the effect of filtering and the responsiveness of the CV to 
>>> changes.
>>>
>>>> On 21 Oct 2021, at 09:54, cheater cheater via Synth-diy 
>>>> <synth-diy at synth-diy.org> wrote:
>>>>
>>>> Correct me if I'm wrong, but I think summing two PWMs will just add 1
>>>> bit of depth.
>>>
>>>
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>>
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