Hey Guys,
I have a friend who is "not on the list" who is helping me with some tube based modules prototypes. He is much more technical than I as he worked at JPL back in the 60's when they were doing some interesting stuff (not that it's not interesting today) and has a good 30 years of experience on me. We have been talking about analog Vs. DSP for certain aspects of the modules we are thinking of making (don't want to say "what" just yet) so I FWD'd this thread to him and he had a question that I couldn't answer so I'm hoping one of you will be able to.
On Oct 1, 2007, at 5:01 PM, Paul Schreiber wrote:
b) In the past, the "missing link" in what I will call 'digital core'
modules is the lack of inexpensive, but accurate, ADC and DAC ICs. If you
want to control MOTM VCOs accurate to pitch, you need a minimum of 14 bits
with about +-2LSB of INL. A 12-bit converter just is not accurate enough
(you need uV of error, not mv). And, you need accurate, non-drifting voltage
references to drive these.
Such parts have been around 5 years or so, but just ∗recently∗ been at a
price point that makes them a "no brainer". The ADC used to be the limiting
part, but now the ADC technology has surpassed the DAC side. Analog Devices
is touting (but not yet delivering) a family of 16-bit parts priced where
the 14-bits are now (that is 8 ∗times∗ better accuracy). I have been closely
following ADC/DAC price/performance trends (like I like to follow USB thumb
drives. I predict 16GB at $39 Christmas 2008).
Chuck's response/Question:
"==== ALSO, I don't see the 16 bit ADC for VCO's..Paul S. mentioned. There is VCO stability--linearity--jitter--etc also... Why not use the DDO's that have microcycle resolution over a wide range- EVEN Freq or phase modulation !
-when driven by a proper instruction of a step-stored sequence word?? ( A MIDI variant.) Obviously, I need to know the problem better-- "
I will relay any responses to him and of course I'm just interested to know too.
Thanks!
Rob