[sdiy] Consider this DAC

[Simon Brouwer]

Antti Huovilainen schreef:
> On Sat, 13 Mar 2010, Paul Perry wrote:
>
>> The thing about a DC cou[[led DAC that gives 16 bit accuracy...
>> that's going to be at least 4 bits better than the drift and noise floor
>> of the rest of your system.
>> Unless you are a very good analog engineer (certainly, far better 
>> than I.)
>
> Surely achieving < 1mV (for max 5V signal) noise floor and drift can't 
> be quite that hard?
1mV out of 5V only corresponds to about 12 bits accuracy... at 5V full 
scale 1 LSB of a 16-bit DAC is 0.076 mV.
>
> Plus of course there's the thing where you want higher resolution than 
> accuracy to avoid stepping even if you don't particularly care if your 
> filter cutoff is off by a 2 cents.
Then it is far cheaper to get a 16 bit DAC with only the 1-LSB DNL and 
much worse INL.
For example TI DAC8411IDCKT which costs 6.62 EUR in single quantity 
(Farnell) and has max. +- 12 LSB max INL.

IMO that should even be accurate enough for any control voltage 
including VCO pitch. According to 
http://en.wikipedia.org/wiki/Cent_%28music%29 humans are only able to 
distinguish 5 to 6 cents in pitch difference at best. Let's take 2.5 
cents as acceptable pitch error (other pitches in the composition might 
be 2.5 cents off in the *other* direction).
Then, assuming a range of 10 octaves, that would amount to 1/4800 of 
full scale. 12 LSB error in the 16-bit DAC corresponds to 1/5461 of full 
scale.

-- 
Vriendelijke groet, 
Simon Brouwer.