AW: AW: [sdiy] AD/DA schematics? quantizers,etc

[Dan Snazelle]

ok this is interesting.

right now i have the bits hooked up like this

a1-d2
a2-d2
a3-d3
a4-d4
a5-d5
a6-d6
a7-d7
a8-d8

it seems you are saying that there may be a different config i need to find

also...i do NOT know if i am running this at the correct sample rate

i have had NOTHING but trouble finding a clock that is both stable and will go high enough


i am finding 2 things...that for driving this with AUDIO i need a very high clock (neither of my  vcos go anywhere near high enough)
and that for the quantizer i get some results with my vcos but would probrably get better with a clock rate specified in the datasheet


anybody have schematics for a really high freq clock? maybe even a a voltage controlled one?

or do i just need to switch the cap of a vco to a really low one like a 50pf?

anyway...this has been a great learning experience. 

even if it only sounds like a sample and hold at this point, it IS in tune when i move my offset pots correctly.


anyway...i am sure i will be writing more later !

thanks



>
>> Von: synth-diy-bounces at dropmix.xs4all.nl
>> [mailto:synth-diy-bounces at dropmix.xs4all.nl]Im Auftrag von Dan Snazelle
>> Gesendet: Freitag, 15. Mai 2009 17:38
>> An: jerryge at cableone.net; sdiy
>> Betreff: RE: AW: [sdiy] AD/DA schematics? quantizers,etc
>>
>> ok
>>
>> in the current setup, the quantatizing (sp?) seems to be working
>> better BUT and this is a big BUT....
>> When DRIVING a VCO....it is sounding more like a sample and hold
>> than a quantizer.
>>
>> and what i mean by this is that if i feed in a very low freq
>> sawtooth what i get out of the vco sounds like a series of notes
>> with steps in between very very similar to a sample and hold fed
>> by a white noise and fed into a vco
>>
>
> 1st thing that comes to my mind is: you wired the input bits of DAC in the
> wrong order.
>
> if wired correctly you should see a staircase as result of your sawtooth.
> the datasheet should give you a table that shows the combination of the bits
> resulting in what output voltages.
> i.e. 0100000 for 0.04V and 01111111 for 9.96V (7 bits used, 10Vref). so what
> would 01001100 be? you should verify that.
>
> hope i did not misunderstood the whole issue!?
>
> cheers,
> matthias
> ___
> www.fonitronik.de
>
>
>
>>
>>
>> is this due to what fonik was mentioning? he noted that he needed
>> to put latches on the output of the DAC so that there was a
>> smooth flow between notes
>>
>>
>> or maybe i have done something wrong again
>>
>>
>> all in all it is a cool sounding effect but not quite the sound i
>> had been going for.
>>
>>
>> i do not know even how to setup a latch on the out...what would
>> control it?
>>
>> the clock? a bit from the A to D?
>>
>> thanks
>
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