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Hello and VCO tuning question

2014-10-30 by sj230962@gmail.com

Hi to everyone - nice to be part of this group. Haven't had a chance to participate much in this area since I stopped organising the Hampshire Jam events in the UK, as I've moved to Malaysia where I live and work nowadays - and Malaysia isn't a hotbed of analogue synth aficionados.

I've had my Doepfer system since 2000 and am still amazed at how each time I start patching time seems to stand still (or so my wife says!).

I'm not especially technical, so please bear with any schoolboy errors in terminology.

Anyway - question re: VCO calibration and tuning.

I have 4x A-110 VCOs and all of them over the past 14 years have drifted away from their factory-pristine state. Having read the service notes, I decided to tackle the immediate issues I have with the range switches [SW1] and main tuning [P1].

1. I set [SW1] to 0= middle, and [P1] to 5 =middle to start with. I then checked the range of [SW1] by turning +/- 2 octaves and tried to calibrate with [P5] - the range potentiometer. Whilst the tracking was a little off +/- 1 octave from 0 (ie 20-40 cents), by +-2 octaves the offset had increased to over 100 cents. How can I adjust [P5] so that the range steps are equal...? I didn't seem to find any setting that gave even close to a 1 octave per switch movement.

2. Dumbass question, but should the VCOs be producing C with [P1] at 0 = fully anticlockwise, or at 5=middle position ? My 4 VCO's all seem to tune closer to A at [P1] = 5 = middle position.

Appreciate any advice or education on this.

Thanks,

Steve Jenkins

Re: [Doepfer_a100] Hello and VCO tuning question

2014-10-30 by Florian Anwander

Hello

Am 30.10.2014 04:54, schrieb sj230962@gmail.com [Doepfer_a100]:
> 1. I set [SW1] to 0= middle, and [P1] to 5 =middle to start with.   I
> then checked the range of [SW1] by turning +/- 2 octaves and tried to
> calibrate with [P5] - the range potentiometer.  Whilst the tracking was
> a little off +/- 1 octave from 0 (ie 20-40 cents), by +-2 octaves the
> offset had increased to over 100 cents.  How can I adjust [P5] so that
> the range steps are equal...?  I didn't seem to find any setting that
> gave even close to a 1 octave per switch movement.
You first have to be sure that the general octave tracking is perfect. 
(trimmers P7 and P8). This has to be done usinge your MIDI/CV-interface 
or your standard CV-keyboard. Do touch P1, P6, and the octave switch 
while doing these adjustments.

Unless this octave tracking works perfect for all four VCOs you should 
not start with the range adjustment of the octave switch.

After you verified that this general octave tracking is good, you can 
adjust the tracking for the switch with P5. This may come close to 
perfect, but not really perfect.
The reason therefor is: Unfortunately the tracking of the octave switch 
depends not only on P5, but also on the relation between the resistors 
R1(+R1'), R2, R3(+R3'). Their outcoming resistance of their combination 
has to have an exact relation of 1:2:4. It is unimportant whether the 
individual resistors are exactly 150k. But it is very important, that 
these resistors are truely equal within each other.



> 2. Dumbass question, but should the VCOs be producing C with [P1] at 0
>   = fully anticlockwise, or at 5=middle position ?   My 4 VCO's all seem
> to tune closer to A at [P1] = 5 = middle position.
Simply adjust it with P6

Florian


PS:
 > Malaysia isn't a hotbed of analogue synth aficionados.
I once had the opportunity to buy a Jupiter 8 from Malaysia - 
unfortunately I was not successful. But from the communication with the 
seller it seemed, there are is a vivid music scene.

Re: [Doepfer_a100] Hello and VCO tuning question

2014-10-30 by Florian Anwander

Argh ... awful typo:
 > Do touch P1, P6, and the octave switch while doing these adjustments.
This must read: "Do NOT touch P1, P6,...."



Am 30.10.2014 13:49, schrieb Florian Anwander fanwander@mnet-online.de 
[Doepfer_a100]:

Show quoted textHide quoted text

> Hello
>
> Am 30.10.2014 04:54, schrieb sj230962@gmail.com [Doepfer_a100]:
>> 1. I set [SW1] to 0= middle, and [P1] to 5 =middle to start with.   I
>> then checked the range of [SW1] by turning +/- 2 octaves and tried to
>> calibrate with [P5] - the range potentiometer.  Whilst the tracking was
>> a little off +/- 1 octave from 0 (ie 20-40 cents), by +-2 octaves the
>> offset had increased to over 100 cents.  How can I adjust [P5] so that
>> the range steps are equal...?  I didn't seem to find any setting that
>> gave even close to a 1 octave per switch movement.
> You first have to be sure that the general octave tracking is perfect.
> (trimmers P7 and P8). This has to be done using your MIDI/CV-interface
> or your standard CV-keyboard. Do touch P1, P6, and the octave switch
> while doing these adjustments.
>
> Unless this octave tracking works perfect for all four VCOs you should
> not start with the range adjustment of the octave switch.
>
> After you verified that this general octave tracking is good, you can
> adjust the tracking for the switch with P5. This may come close to
> perfect, but not really perfect.
> The reason therefor is: Unfortunately the tracking of the octave switch
> depends not only on P5, but also on the relation between the resistors
> R1(+R1'), R2, R3(+R3'). Their outcoming resistance of their combination
> has to have an exact relation of 1:2:4. It is unimportant whether the
> individual resistors are exactly 150k. But it is very important, that
> these resistors are truely equal within each other.
>
>
>
>> 2. Dumbass question, but should the VCOs be producing C with [P1] at 0
>>    = fully anticlockwise, or at 5=middle position ?   My 4 VCO's all seem
>> to tune closer to A at [P1] = 5 = middle position.
> Simply adjust it with P6
>
> Florian
>
>
> PS:
>   > Malaysia isn't a hotbed of analogue synth aficionados.
> I once had the opportunity to buy a Jupiter 8 from Malaysia -
> unfortunately I was not successful. But from the communication with the
> seller it seemed, there are is a vivid music scene.
>
>
>
>
> ------------------------------------
> Posted by: Florian Anwander <fanwander@mnet-online.de>
> ------------------------------------
>
>
> ------------------------------------
>
> Yahoo Groups Links
>
>
>

Re: [Doepfer_a100] Hello and VCO tuning question

2014-10-30 by Steve Jenkins

Thanks Florian. Very helpful 

On my drive home tonight I figured I ought to have started with the CV tracking - you have confirmed Tutsi suspicion 

I'll keep an eye out for any analog action here in KL - although after 7 years I've only bumped into a few like-minded souls. 

Cheers 
Steve

Out of office - sent from mobile device

Show quoted textHide quoted text

> On 30 Oct 2014, at 20:49, Florian Anwander fanwander@mnet-online.de [Doepfer_a100] <Doepfer_a100@yahoogroups.com> wrote:
> 
> Hello
> 
> Am 30.10.2014 04:54, schrieb sj230962@gmail.com [Doepfer_a100]:
> > 1. I set [SW1] to 0= middle, and [P1] to 5 =middle to start with. I
> > then checked the range of [SW1] by turning +/- 2 octaves and tried to
> > calibrate with [P5] - the range potentiometer. Whilst the tracking was
> > a little off +/- 1 octave from 0 (ie 20-40 cents), by +-2 octaves the
> > offset had increased to over 100 cents. How can I adjust [P5] so that
> > the range steps are equal...? I didn't seem to find any setting that
> > gave even close to a 1 octave per switch movement.
> You first have to be sure that the general octave tracking is perfect. 
> (trimmers P7 and P8). This has to be done usinge your MIDI/CV-interface 
> or your standard CV-keyboard. Do touch P1, P6, and the octave switch 
> while doing these adjustments.
> 
> Unless this octave tracking works perfect for all four VCOs you should 
> not start with the range adjustment of the octave switch.
> 
> After you verified that this general octave tracking is good, you can 
> adjust the tracking for the switch with P5. This may come close to 
> perfect, but not really perfect.
> The reason therefor is: Unfortunately the tracking of the octave switch 
> depends not only on P5, but also on the relation between the resistors 
> R1(+R1'), R2, R3(+R3'). Their outcoming resistance of their combination 
> has to have an exact relation of 1:2:4. It is unimportant whether the 
> individual resistors are exactly 150k. But it is very important, that 
> these resistors are truely equal within each other.
> 
> > 2. Dumbass question, but should the VCOs be producing C with [P1] at 0
> > = fully anticlockwise, or at 5=middle position ? My 4 VCO's all seem
> > to tune closer to A at [P1] = 5 = middle position.
> Simply adjust it with P6
> 
> Florian
> 
> PS:
> > Malaysia isn't a hotbed of analogue synth aficionados.
> I once had the opportunity to buy a Jupiter 8 from Malaysia - 
> unfortunately I was not successful. But from the communication with the 
> seller it seemed, there are is a vivid music scene.
> 
>