200e

well, i have a couple of thoughts:

- maybe you answered this already (sorry), but are you sending a voltage
directly from the 225 (if so, is it the internal bus or the external cv
out?) or are you passing it through a 210 or 256? my guess is the latter but
i don't remember it mentioned...

- i just tested a 225 connected (with a patch cord) to the pitch cv of a 261
and was able to observe some jitter at certain frequencies close to the bit
transitions of the A->D converter. these jitters, at the largest, spanned
less than 0.2 cents, and were only visible on an oscilliscope. i could not
audibly detect them even by mixing the 261 output against an accurate test
oscillator and observing the beating patterns, which normally is a good way
to reveal the audible magnitude of such effects.

- using the internal bus ameliorated even these inaudible jitters. i am sure
that they were caused by a normal level of interference noise in the
patchcord or elsewhere.

- passing the cv through a 210, however, produced larger jitters that i
could audibly detect, again mostly at certain frequencies close to the bit
transition points. this is a result of more numerous and less accurate A->D
conversions in the 210, and it is certainly a problem.

- we should be able to fix this problem with a filter in the software, as
we've already done in the 259 (to fix the jitter jim aiken noticed in his
review), the 261 (because we had learned from the 259), and other modules
where e.g. noisy potentiometers posed a problem.

- there will always be some small loss of informational resolution when
doing lots of A->D->A conversions, but it needn't interfere with one's
listening experience or prevent you from using any kind of fine microtonal
pitch divisions, and the values certainly needn't leap around at random.

so anyway expect a significant improvement in the next 210 and 256 firmware
update. thanks for noticing, sorry for the annoyance...

and welcome to the digital world...

eb



On 6/11/06, cuari7 <cuari7@comcast.net> wrote:
>
>   Hi, guys.
>
> I hadn't checked this thread in a week! Thanx for all the responses.
>
>
> >>>ezra.buchla" <ezra.buchla@...> wrote:
> >
> > the answer to this probably lies in yr definition of 'jitter'. what
> > exactly are you noticing?<<<<
>
> Hi, Ezra. What I meant by "jitter" is basically a nervous, constant,
> erratic change in pitch when playing a sustained note (almost like
> you're modulating the pitch of the oscillator with a random source).
> I could describe it as the buzzing of a mosquito. This seemed to be
> a more obvious problem with the 259e, and Jim Aikin pointed it out
> in his review of it on Keyboard magazine. Putting the voltage
> through a 255 does NOT fix the problem. Bummer, because This keeps
> me from getting any satisfactory use of the 225e as a MIDI-CV
> converter (I play the 200e exclusively with my TKB). Another thing
> I've noticed is that passing the TKB voltages through the 210e or
> the 256e will have the same effect! It's like the voltages
> get "tainted" by these devices.
>
> Any suggestions?
>
> cuari7
>
>  
>


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