[sdiy] Digital oscillator problem

[Neil Johnson]

Hi Tom,

> The problem is noise coming in on the ADC channels. 

[snip]
 
> I've thought about trying to apply some digital filtering to the CV  
> inputs, but I'm not sure how that would work. The ADC is running  
> using a DMA channel in the background, so I don't know exactly how  
> often it samples. My oscillators are producing samples at 50KHz.

There are two things here which need further understanding on your part: exactly how often your ADCs are sampled, and what exactly the noise looks like.  Is it white noise?  If not, what is its spectral makeup - are there any strong 50kHz components?

Depending on the outcome of further investigation you *might* improve the situation by locking your ADC sampling to your output sample clock.  This would reduce, to some extent, any 50Khz (and harmonics)-related noise.

If there is no such connection, this won't help.

Neil

--
http://www.njohnson.co.uk

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