i checked the MPU 101 and it's putting out solid 1 v/oct, i'll start at 1 volt and attempt adjustment of the octaves from there...where should i set the VCO high end trim when adjusting the octaves, and to what degree will it affect the octave adjustment in other words, if the high end adjustment is out (and it is at this point), will it be impossible to adjust the octaves


----- Original Message ----
From: " hardware@... " < hardware@... >
To: Doepfer_a100@yahoogroups.com
Sent: Thursday, January 10, 2008 3:24:31 AM
Subject: AW: 1 A110 calibration help needed

> i have two A100 oscs that are at least ten years old i beilieve,
> and they aren't tracking correctly... i read over the info from
> here: http://www.doepfer de/a110_tec. htm and i've attempted
> adjust the tracking, but i'm not doing to well...i understand
> what the basic idea is, but i'm not too sure on the best
> procedure... i've adjusted the tracking on two SCI Pro One synths
> before and got pretty close, but the SCI repair docs were more
> specific on the exact procedure...
>
> i'm using a Roland MPU 101 to provide cv, and i'm tuning by ear
> to a digital synth, single raw waveform, no modulation.. .i'm
> tuning to a lower octave, raising an octave and adjusting the vo
> scale and high trim and checking differnent octaves, etc, but i'm
> not getting the tracking any better..if anyone thinks they could
> give me some tips, i'd very much appreiciate the
> help...unfortunatel y there arn't any techs in my area (Chicaago,
> USA), so i'm kind of on my own here...
>
> thanks,
> rg

First of all you have to adjust the scale trimming potentiometer until the
scale is OK (independend of the absolute pitch). I'd recommend to apply
control voltages 0, +1.00, +2.00, +3.00 V ... to CV1 of the VCO and adjust
the scale trimming potentiometer until exact octave jumps appear. The
measuring instrument for that is the human ear. If the scale is adjusted the
offset trimming potentiometer is adjusted to the desired absolute pitch
(i.e. the pitch in the center position of the tune knob).
The CV could come e.g. from a correctly (!) adjusted CV source. Pay
attention that the CV source is not misadjusted (the MPU-101 in your case).
We had already users who tried to adjust the scale of the VCOs until they
discovered that the CV source (e.g. A-190, midi-to-cv interface, sequencer
...) was the reason for the wrong tracking. So first of all make sure that
the CV source is OK.

Best wishes
Dieter Doepfer




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