Doepfer

I programmed a patch with my beautifully tuned VCOs, tonight.  When I decided to use the A155 through a 156 to drive it, I noticed a significant voltage drop and I had to apply a voltage from the 176 to bring it back in tune with my other synth.  Why should this be?

I have also noticed that running the CV from the quantizer through either the dual or the VC Slew also caused a voltage droop, regardless of how low the slew setting is.  

  Can anyone explain why this might be happening.

> I programmed a patch with my beautifully tuned VCOs, tonight.
> When I decided to use the A155 through a 156 to drive it, I
> noticed a significant voltage drop and I had to apply a voltage
> from the 176 to bring it back in tune with my other synth.  Why
> should this be?
>
> I have also noticed that running the CV from the quantizer
> through either the dual or the VC Slew also caused a voltage
> droop, regardless of how low the slew setting is.
>
>   Can anyone explain why this might be happening.

I'd recommend to use one of the buffer modules A-185-1 or A-1185-2 if
several VCOs are controlled by the same CV source. These modules do not load
the source and include a buffer that is strong enough to drive several VCOs
without voltage drop.

Best wishes
Dieter Doepfer

stuadh

see the threads about slew limiters and changing the output resistor 
to keep tracking accurate over several octaves.

sean

>I programmed a patch with my beautifully tuned VCOs, tonight. When I 
>decided to use the A155 through a 156 to drive it, I noticed a 
>significant voltage drop and I had to apply a voltage from the 176 
>to bring it back in tune with my other synth. Why should this be?
>
>I have also noticed that running the CV from the quantizer through 
>either the dual or the VC Slew also caused a voltage droop, 
>regardless of how low the slew setting is.
>
>Can anyone explain why this might be happening.
>
>
>


[Non-text portions of this message have been removed]

Thanks,

  I have an MX 224 (Analogue Solutions) in the chain after the Quantizer and/or VC Slew.  It is clearly happening inside the VC Slews.

--- In Doepfer_a100@yahoogroups.com, <yahoo@...> wrote:

>
> > I programmed a patch with my beautifully tuned VCOs, tonight.
> > When I decided to use the A155 through a 156 to drive it, I
> > noticed a significant voltage drop and I had to apply a voltage
> > from the 176 to bring it back in tune with my other synth.  Why
> > should this be?
> >
> > I have also noticed that running the CV from the quantizer
> > through either the dual or the VC Slew also caused a voltage
> > droop, regardless of how low the slew setting is.
> >
> >   Can anyone explain why this might be happening.
> 
> I'd recommend to use one of the buffer modules A-185-1 or A-1185-2 if
> several VCOs are controlled by the same CV source. These modules do not load
> the source and include a buffer that is strong enough to drive several VCOs
> without voltage drop.
> 
> Best wishes
> Dieter Doepfer
>

Have you checked how much current all your modules are consuming? 
Maybe it's too close to the quoted maximum for the power supply. In 
my experience with the old style 650mA G6 cases anything near 600mA 
and things start to go a bit wobbly.

>Thanks,
>
>I have an MX 224 (Analogue Solutions) in the chain after the 
>Quantizer and/or VC Slew. It is clearly happening inside the VC 
>Slews.
>
>--- In 
><mailto:Doepfer_a100%40yahoogroups.com>Doepfer_a100@yahoogroups.com, 
><yahoo@...> wrote:
>>
>>  > I programmed a patch with my beautifully tuned VCOs, tonight.
>>  > When I decided to use the A155 through a 156 to drive it, I
>>  > noticed a significant voltage drop and I had to apply a voltage
>>  > from the 176 to bring it back in tune with my other synth. Why
>>  > should this be?
>>  >
>>  > I have also noticed that running the CV from the quantizer
>>  > through either the dual or the VC Slew also caused a voltage
>>  > droop, regardless of how low the slew setting is.
>>  >
>>  > Can anyone explain why this might be happening.
>>
>>  I'd recommend to use one of the buffer modules A-185-1 or A-1185-2 if
>>  several VCOs are controlled by the same CV source. These modules do not load
>>  the source and include a buffer that is strong enough to drive several VCOs
>>  without voltage drop.
>>
>>  Best wishes
>>  Dieter Doepfer
>>
>
>
>


[Non-text portions of this message have been removed]

Cheers,

  I'm using a homebrew case with a 3.4A power supply.  Current load (approx) is 1.5A, so loads of space there.

Yours Aye

Stuadh

--- In Doepfer_a100@yahoogroups.com, Sean Williams <sean@...> wrote:

>
> Have you checked how much current all your modules are consuming? 
> Maybe it's too close to the quoted maximum for the power supply. In 
> my experience with the old style 650mA G6 cases anything near 600mA 
> and things start to go a bit wobbly.
> 
> >Thanks,
> >
> >I have an MX 224 (Analogue Solutions) in the chain after the 
> >Quantizer and/or VC Slew. It is clearly happening inside the VC 
> >Slews.
> >
> >--- In 
> ><mailto:Doepfer_a100%40yahoogroups.com>Doepfer_a100@yahoogroups.com, 
> ><yahoo@> wrote:
> >>
> >>  > I programmed a patch with my beautifully tuned VCOs, tonight.
> >>  > When I decided to use the A155 through a 156 to drive it, I
> >>  > noticed a significant voltage drop and I had to apply a voltage
> >>  > from the 176 to bring it back in tune with my other synth. Why
> >>  > should this be?
> >>  >
> >>  > I have also noticed that running the CV from the quantizer
> >>  > through either the dual or the VC Slew also caused a voltage
> >>  > droop, regardless of how low the slew setting is.
> >>  >
> >>  > Can anyone explain why this might be happening.
> >>
> >>  I'd recommend to use one of the buffer modules A-185-1 or A-1185-2 if
> >>  several VCOs are controlled by the same CV source. These modules do not load
> >>  the source and include a buffer that is strong enough to drive several VCOs
> >>  without voltage drop.
> >>
> >>  Best wishes
> >>  Dieter Doepfer
> >>
> >
> >
> >
> 
> 
> [Non-text portions of this message have been removed]
>

> I'd recommend to use one of the buffer modules A-185-1 or A-1185-2 if
> several VCOs are controlled by the same CV source. These modules do not load
> the source and include a buffer that is strong enough to drive several VCOs
> without voltage drop.
> 
> Dieter Doepfer

this voltage drop occurs with just one vco after one of the slew limiters. 

since this keeps coming up, i think a note on the slew limiter pages that additional modules are necessary would only be fair. 90% of people who buy a slew limiter are expecting it to be suitable for portamento.

solving the problem would be even better :)

cheers,

stu

> this voltage drop occurs with just one vco after one of the slew
> limiters.
>
> since this keeps coming up, i think a note on the slew limiter
> pages that additional modules are necessary would only be fair.
> 90% of people who buy a slew limiter are expecting it to be
> suitable for portamento.
>
> solving the problem would be even better :)
>
> cheers,
>
> stu

Stu,

you are right. We should add a corresponding note to the slew limiter
manuals. For the A-170 the design has been changed already and the new
version of A-170 includes buffers at the outputs (same as A-185-1/2). So far
only a few modules of the new version have been delivered as they are
manufactured since May 2009. They can be identified by the addition "Version
2" on the pcb silk screen (near the upper LED pair). For the A-171 the
revision is on our to-do list.

Best wishes
Dieter Doepfer