Doepfer

hello group,

after yesterday evening's failed attempt to tune the doepfer to the
band, i went searching for the cause this morning, and found it to be
the a170 slew limiter, which won't give out the same voltage as it
receives. this applies to both sections of the a170. moreover, the
tune control on the a110 osc won't go far enough to make up the
difference. and an octave is no longer an octave anyway, so making up
the difference wouldn't help.

i assume that this problem is one of design, since both a170s show
this behaviour. but what are the experiences of other group members?
does someone know of a eurorack slew limiter that tracks accurately?
or does everyone peer over the brass players' shoulder to read a Bb
part :) ?

cheers,

stu

Is the tuning accurate when the pitch CV is not patched through the slew
limiter?
I don't use an a170 so I don't know if it's by design, but you may be able
to make up for it by amplifying the CV with an A133 polarizer, or some
mixer/amplifier with <1 gain.

On Fri, Jun 20, 2008 at 5:26 AM, Stu Grimshaw <grimshaw@stugrimshaw.com>
wrote:

>   hello group,
>
> after yesterday evening's failed attempt to tune the doepfer to the
> band, i went searching for the cause this morning, and found it to be
> the a170 slew limiter, which won't give out the same voltage as it
> receives. this applies to both sections of the a170. moreover, the
> tune control on the a110 osc won't go far enough to make up the
> difference. and an octave is no longer an octave anyway, so making up
> the difference wouldn't help.
>
> i assume that this problem is one of design, since both a170s show
> this behaviour. but what are the experiences of other group members?
> does someone know of a eurorack slew limiter that tracks accurately?
> or does everyone peer over the brass players' shoulder to read a Bb
> part :) ?
>
> cheers,
>
> stu
>
>  
>


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

I mean >1 gain.

On Fri, Jun 20, 2008 at 6:16 AM, Monroe Eskew <monroe.eskew@gmail.com>
wrote:

> Is the tuning accurate when the pitch CV is not patched through the slew
> limiter?
> I don't use an a170 so I don't know if it's by design, but you may be able
> to make up for it by amplifying the CV with an A133 polarizer, or some
> mixer/amplifier with <1 gain.
>
>
> On Fri, Jun 20, 2008 at 5:26 AM, Stu Grimshaw <grimshaw@stugrimshaw.com>
> wrote:
>
>>   hello group,
>>
>> after yesterday evening's failed attempt to tune the doepfer to the
>> band, i went searching for the cause this morning, and found it to be
>> the a170 slew limiter, which won't give out the same voltage as it
>> receives. this applies to both sections of the a170. moreover, the
>> tune control on the a110 osc won't go far enough to make up the
>> difference. and an octave is no longer an octave anyway, so making up
>> the difference wouldn't help.
>>
>> i assume that this problem is one of design, since both a170s show
>> this behaviour. but what are the experiences of other group members?
>> does someone know of a eurorack slew limiter that tracks accurately?
>> or does everyone peer over the brass players' shoulder to read a Bb
>> part :) ?
>>
>> cheers,
>>
>> stu
>>
>>  
>>
>
>


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

> hello group,
>
> after yesterday evening's failed attempt to tune the doepfer to the
> band, i went searching for the cause this morning, and found it to be
> the a170 slew limiter, which won't give out the same voltage as it
> receives. this applies to both sections of the a170. moreover, the
> tune control on the a110 osc won't go far enough to make up the
> difference. and an octave is no longer an octave anyway, so making up
> the difference wouldn't help.
>
> i assume that this problem is one of design, since both a170s show
> this behaviour. but what are the experiences of other group members?
> does someone know of a eurorack slew limiter that tracks accurately?
> or does everyone peer over the brass players' shoulder to read a Bb
> part :) ?
>
> cheers,
>
> stu

If you have an A-185-1 or A-185-2 available please check if the tuning is
correct if you insert the A-185-1/2 buffer between the output of the A-170
and the A-110. In general the lower section of the A-170 cannot be used for
VCO CV applications as mentioned on page 4 of the user's manual.

Best wishes
Dieter Doepfer

Hi Stuart,

do you connect the A170 out direct to the A110 CV1-in?
Does it work fine with another VCO (A111)?
Maybe you should try to insert in this path a A-185-1 Buss-Access or 
precision adder:

A170 -> A185-1/2 -> A110.

Florian

Stu Grimshaw wrote:

> hello group,
> 
> after yesterday evening's failed attempt to tune the doepfer to the
> band, i went searching for the cause this morning, and found it to be
> the a170 slew limiter, which won't give out the same voltage as it
> receives. this applies to both sections of the a170. moreover, the
> tune control on the a110 osc won't go far enough to make up the
> difference. and an octave is no longer an octave anyway, so making up
> the difference wouldn't help.
> 
> i assume that this problem is one of design, since both a170s show
> this behaviour. but what are the experiences of other group members?
> does someone know of a eurorack slew limiter that tracks accurately?
> or does everyone peer over the brass players' shoulder to read a Bb
> part :) ?
> 
> cheers,
> 
> stu
> 
> 
> ------------------------------------
> 
> Yahoo! Groups Links
> 
> 
>

> Hi Stuart,
> 
> do you connect the A170 out direct to the A110 CV1-in?
> Does it work fine with another VCO (A111)?
> Maybe you should try to insert in this path a A-185-1 Buss-Access or 
> precision adder:
> 
> A170 -> A185-1/2 -> A110.
> 
> Florian

Twice the same idea from bavaria :-)
Dieter

My Bananalogue VCS does slew limiting accurately.

hi,

thanks for the responses.

the vco's tracking seems to be fine, i connected the pitch cv to it
without the a170 and everything was accurate over several octaves.

the patch yesterday had the output of the slew limiter - the upper
section, by the way - going to two destinations. i reduced this to a
single connection to the vco's cv1 input. this removed some of the
voltage drop, so that i'm able to compensate with the tune offset (so
no more brass parts). however, each octave is about 20 cents flat -
not really a huge problem with one octave, but with three octaves i'm
more than a quarter tone flat.

i don't have the precision adder, so i can't try out that solution.

does noone else have this? i tried it with three a170's - i discovered
another one in the drums rack which i`d forgotten :) - and got the
same result. i'm not particularly sensitive about intonation, i like
it dirty, but  a quarter tone is, well, TOO dirty :)

stu

:(

On Fri, Jun 20, 2008 at 1:08 PM, jalmari3 <jari.jokinen@netikka.fi> wrote:

>   My Bananalogue VCS does slew limiting accurately.
>
>  
>


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

> no more brass parts). however, each octave is about 20 cents flat -
> not really a huge problem with one octave, but with three octaves 
i'm
> more than a quarter tone flat.
> 
> i don't have the precision adder, so i can't try out that solution.

This is probably simply caused by the 'protection' resistor in the A-
170 output: at 1k it is higher than those in other modules handling 
precise-CV-type signals, which are typically around 100ohms. A-100 
inputs are typically either 100k if no pot (like A-110 CV1 in), or a 
50k pot (like A-110 CV2 in); if feeding two inputs, it would be easy 
to get the input impedance down to around 50k, and then a 1V input to 
the A-170 would be seen as 50/51 of a volt at the output, or 0.98V, 
so 20mV too low. 1V/octave is 1/12V = 83mV per semitone, so 20mV is 
around 24 cents too low (which seems to tie in with your figures).

A simple solution would be to locate 'R2' on the PCB (above the 'A-
170' designation), and either replace it with a 100ohm, or simply 
solder a 100ohm in parallel with it (i.e. across its legs), and this 
will reduce the error by about a tenth, i.e. down to a few cents 
instead. (And that will still leave you with *some* protection 
against shorting the output, which is what it is there for I believe.)

Tim

problem solved. thanks tim. tracks accurately now over four octaves or
so, which is close enough for jazz.

dieter, am i increasing the risk of short circuit damage by reducing
R2 to 100 ohms? if not, could this be a worthwhile modification to the
circuit?

thanks all round,

stu

> hi,
>
> thanks for the responses.
>
> the vco's tracking seems to be fine, i connected the pitch cv to it
> without the a170 and everything was accurate over several octaves.
>
> the patch yesterday had the output of the slew limiter - the upper
> section, by the way - going to two destinations. i reduced this to a
> single connection to the vco's cv1 input. this removed some of the
> voltage drop, so that i'm able to compensate with the tune offset (so
> no more brass parts). however, each octave is about 20 cents flat -
> not really a huge problem with one octave, but with three octaves i'm
> more than a quarter tone flat.
>
> i don't have the precision adder, so i can't try out that solution.
>
> does noone else have this? i tried it with three a170's - i discovered
> another one in the drums rack which i`d forgotten :) - and got the
> same result. i'm not particularly sensitive about intonation, i like
> it dirty, but  a quarter tone is, well, TOO dirty :)
>
> stu

I'm quite sure that it's a problem with the output protection resistor in
the A-170. It's the 1k resistor R2 just above the printing "A-170" on the pc
board. The A-100 modules are designed in a way that they cannot be damaged
even with "wrong" patches (e.g. connecting two A-170 outputs). For this
nearly each output is protected by a 1k resistor. This resistor prevents
module damage even in case of patches that could destroy modules (especially
if two outputs are connected by mistake). You could short the 1k resistor R2
e.g. by a wire. I'm wuite sure the tuning problems will disappear then. But
the A-170 output is no longer 100% protected. As long as usual patches are
made this will not be a problem. But if you e.g. modify two A-170 in this
way and connect the outputs they will be damaged.

The better solution is the usage of the A-185-1 or A-185-2 as they have
special output circuits. But even shortening R2 will help as long as only
this single A-170 is modified in this way.

Best wishes
Dieter Doepfer