Doepfer

Thanks in advance and best regards,

Karel.

1 volt should transpose by an octave, unless you have the output cv going into an attenuator or amp before the VCO.

Neil

Sent from my iPhone

> On 12 Mar 2015, at 05:07, karelvanbezooijen@yahoo.com [Doepfer_a100] <Doepfer_a100@yahoogroups.com> wrote:
> 
> My A-156 Dual Quantizer doesn't respond correctly to transpose voltages. When I apply 1 volt it does transpose from C3 to D3. With 2 volt it transposes to D4 etc. So it's still 1 V/Oct. At the bottom of the pcb is P3 (according to A156_adjustment.pdf). Do I only have to adjust this trimpot to correct the issue? 
> 
> 
> 
> Thanks in advance and best regards,
> 
> 
> 
> Karel.
> 
>

That is very odd, what is the output voltage of the Quantizer?

Sent from my iPhone

> On 12 Mar 2015, at 10:59, karelvanbezooijen@yahoo.com [Doepfer_a100] <Doepfer_a100@yahoogroups.com> wrote:
> 
> Thanks for your reply Neil.
> 
> I agree that its 1V/Oct. The problem is that it looks like there is an 'offset' of minus one semitone. If that is possible anyway. Maybe Dieter can confirm or deny this?
> 
> The CV Out of the A-156 goes directly to my VCO. I've measured the input signal for the Transpose CV with a multimeter and it's exactly 1.00, 2.00 and 3.00 volt resp. 
> 
> For the time being I've made a workaround by feeding the CV Out of the quantizer and Transpose signal from my keyboard to a mixer before it enters the vco.
> 
> Best regards,
> 
> Karel.
> 
>

That doesn't sound right for sure!

Sent from my iPhone

> On 12 Mar 2015, at 16:36, karelvanbezooijen@yahoo.com [Doepfer_a100] <Doepfer_a100@yahoogroups.com> wrote:
> 
> 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.
> 
>

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.

> Dieter,
>
> Thanks for your explanation. I don't have a TL062 around at the moment (only TL072 and TL082) but I'll order some (they
> cost only €0,25). If replacing doesn't help I'll have to send it for repair.
>
> Best regards,
>
> Karel.

TL082 should work too. If you have a multimeter available you may also measure the output voltage at pin 7 of the TL062/082. It
should read 0V (or a small positive voltage) when 0V are applied at the transpose CV input. In any case no (small) negative voltage
should appear.

Best wishes
Dieter Doepfer

> I guess I am wrong about the PIC. It's the TLC5620 that should be replaced isn't it.
>
> Best regards, Karel.

I don't think so. As far as I can see the ADC of the transpose input ignores the lower values. So far I had no time to try it out
with an A-156 from our stock as I'm busy because of the preparations for the Musikmesse in Frankfurt. For the time beeing a simple
patch should solve the problem: add a resistor in the 330k range between the juncture of R9/D3 and +12V. From theory this should add
about 1/12 V to the incoming transpose voltage (provided that I did not make a mistake in my calculation for the resistor value).

Best wishes
Dieter Doepfer

> This is what I did: http://www.pulsepsycle.nl/wp-content/uploads/doepfer_a156.jpg
>  http://www.pulsepsycle.nl/wp-content/uploads/doepf...
> View on www.pulsepsycle.nl Preview by Yahoo
>
>
>
>
>
> Now when I apply 1 volt to the upper Quantizer CV In it reads 1.006 volt at the CV Out instead of 0.924 volt so that's all right.
> But after adding another 2 volt at Transpose CV In reads 2.918 volt so that's not right. Without the 330K resistor it
> then reads 2.836 volt.
>
> I didn't solder anything yet. Just used clamps and cables to test.
>
> Best regards,
>
> Karel.

It should be possible to correct this by adjusting P3 (that's the spindle trimmer at the lower edge of the pcb, next to the TL062).
It is used to adjust the input scale of the transpose input.

Best wishes
Dieter Doepfer

> I think I'm going insane! I've soldered the 330K resistor this time.
>
> Again the upper Quantizer is used.
>
> CV In = 1.000 volt, CV Out 0.923 volt. But sometimes (very sometimes, rare is better) it reads 1.006 volt again.
> At that moment only when I unplug the CV In it reads 0.85 volt.
>
> Next.
>
> CV In = 0 volt
> Transpose CV IN = 1.000 volt, CV Out = 1.006 volt.
> Transpose CV IN = 2.002 volt, CV Out = 2.002 volt.
> I can reproduce this over and over.
>
> So, this time the transpose function is OK, but the CV In isn't.
>
> During the tests I've adjusted P3 so probably it isn't in the original setting anymore.
>
> Best regards,
> Karel.

The CV In scales are adjusted by means of the 3 trimming potentiometers P1 (CV1 In), P2 (CV2 In) and P3 (Transpose In). The
difference between 1.006 and 0.923V is 0,083V which is exactly one semitone (1/12V). After the re-adjustment of P1 the CV output
should read stable 1.006V without toggling. But it's better to adjust for a higher CV difference (e.g. 0/4.00V or 0/5.00V).

Best wishes
Dieter Doepfer