Doepfer

There seems to be indeed a small negative offset of one semitone at the transpose input (1/12V = 0.083V, 1.922V+0.083=2.005 which
would be the correct value). But as the A-156 is able to process only positive voltages at the inputs and outputs the lowest
semitone is missing. I took a look at the schematics (from 1997 :-). The transpose CV is attenuated by a trimming potentiometer
(P3), buffered (TL062/IC4) and then connected to the ADC input of the processor. As the TL062 is used only for this task I suppose
that it produces a small negative offset. I'd to replace the TL062 (or return the module if it's still under warranty for repair to
the dealer where you purchased it). Another source of error could be the ADC input of the processor.

Best wishes
Dieter Doepfer


> -----Ursprüngliche Nachricht-----
> Von: Doepfer_a100@yahoogroups.com [mailto:Doepfer_a100@yahoogroups.com]
> Gesendet: Donnerstag, 12. März 2015 17:37
> An: Doepfer_a100@yahoogroups.com
> Betreff: Re: [Doepfer_a100] A-156 Dual Quantizer Transpose issue
>
>
>
>
> I did some further measurements:
>
> I used the upper quantizer for this.
>
> CV In: 2.000 V gives CV Out: 1.922 V
>
> Then with Transpose In
>
> 1.001 V gives CV Out: 2.836 V
> 2.003 V gives CV Out: 3.834 V
> 3.000 V gives CV Out: 4.828 V
>
> Strange.
>
> Karel.