Doepfer

In a message dated 4/25/2008 7:43:49 PM Pacific Standard Time,  
prscrptn@yahoo.com writes:

the  Digital Random Voltages necessary and how are they  used?





hello,
necessary ? well................. that depends on your interests - for me,  
the a-149/2 is indispensible for producing random gates to be used for various  
purposes.
best,
dave
 



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--- In Doepfer_a100@yahoogroups.com, davevosh@... wrote:

  
 In a message dated 4/25/2008 7:43:49 PM Pacific Standard Time,  
 prscrptn@... writes:
 
Are the  Digital Random Voltages necessary and how are they used?
 
 
 
 
 
hello,
necessary ? well................. that depends on your interests - 
for me,  
the a-149/2 is indispensible for producing random gates to be used 
for various  
purposes.
best,
dave
  
 

I understand that they are stored random voltages, but do they always 
send the same random events? Does each output send a differnt random 
voltage? Are the events of the A-149-2 dependant on the settings on 
the A-149-1? Can the same patterns be obtained by just using the  A-
149-1? I am planning on picking up the A-149-1 but I was told that 
the A-149-2 was not necessary. I guess what I am asking is would you 
be happy with the A-149-1 with out the A-149-2???

Thanks!

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

> I understand that they are stored random voltages, but do they
> always send the same random events? Does each output send a
> differnt random voltage?
The A-149-2 outputs are binary:
"The outputs are controlled by the "Quantized Random Voltages" section 
of the assigned A-149-1 and correspond to the 8 digital outputs of the 
shift register that is used to generate the Quantized Random Voltages"
A-149-1 and especially A-149-2 are distintively pseudo-random:
http://launch.groups.yahoo.com/group/Doepfer_a100/message/13422

> Are the events of the A-149-2 dependant on the settings on 
> the A-149-1?
I don't remember anymore. I don't think so.

> Can the same patterns be obtained by just using the  A-149-1?
Not the binary outputs.
 
> I am planning on picking up the A-149-1 but I was told that
> the A-149-2 was not necessary. I guess what I am asking is
> would you be happy with the A-149-1 with out the A-149-2???
Possibly. I didn't like A-149-2.

Jari Jokinen

With regards to the VCAs (130-131) and Mixers offered by Doepfer, are these circuits all a Gain of 1? 

Or is there indeed the possibility of gain?

Thanx,

Tony

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

as far as i know the actual vca's (a130, a131) have a bit of gain.
the older cem-based vca's and all the mixers (a138x) don't offer
amplification.

best wishes

ingo



--- In Doepfer_a100@yahoogroups.com, Anthony Rolando 
<goldenechos@...> wrote:
>
> 
> With regards to the VCAs (130-131) and Mixers offered by Doepfer, 
are these circuits all a Gain of 1? 
> 
> Or is there indeed the possibility of gain?
> 
> Thanx,
> 
> Tony
> 
> _________________________________________________________________
> In a rush? Get real-time answers with Windows Live Messenger.
> http://www.windowslive.com/messenger/overview.html?
ocid=TXT_TAGLM_WL_Refresh_realtime_042008

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

> I am planning on picking up the A-149-1 but I was told that
> the A-149-2 was not necessary. I guess what I am asking is
> would you be happy with the A-149-1 with out the A-149-2???


that depends on your application.
if you need random gates (for firing envelopes, retriggering
lfo's, operating switches or sequencers) you will find uses
for the a149/2, as the a149/1 cannot produce gate signals.
if you want to modulate vco's, vcf's or vca's directly,
then you will probably be happy with the a149/1 alone.

to speak for myself, i find the a149/2 really useful,
but as said, it depends on the application.

best wishes

ingo

Thanx, that confirms what I thought I was hearing. I have an older CEM based VCA. Def. no gain. I t would be nice to have in a VCA.... might need to get a new VCA.

Tony


> To: Doepfer_a100@yahoogroups.com
> From: synaptic_music@yahoo.com
> Date: Sun, 27 Apr 2008 11:10:34 +0000
> Subject: [Doepfer_a100] Re: mixer and VCA Gain question
> 
> 
> as far as i know the actual vca's (a130, a131) have a bit of gain.
> the older cem-based vca's and all the mixers (a138x) don't offer
> amplification.
> 
> best wishes
> 
> ingo
> 
> 
> 
> --- In Doepfer_a100@yahoogroups.com, Anthony Rolando 
> <goldenechos@...> wrote:
> >
> > 
> > With regards to the VCAs (130-131) and Mixers offered by Doepfer, 
> are these circuits all a Gain of 1? 
> > 
> > Or is there indeed the possibility of gain?
> > 
> > Thanx,
> > 
> > Tony
> > 
> > _________________________________________________________________
> > In a rush? Get real-time answers with Windows Live Messenger.
> > http://www.windowslive.com/messenger/overview.html?
> ocid=TXT_TAGLM_WL_Refresh_realtime_042008
> > 
> > [Non-text portions of this message have been removed]
> >
> 
> 
> 
> ------------------------------------
> 
> Yahoo! Groups Links
> 
> 
> 

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> > Are the events of the A-149-2 dependant on the settings on the A-149-1?

Yes, as the A-149-2 outputs are nothing but the shift register outputs of
the Quantized Random Voltages section of the A-149-1. The random CV of the
A-149-1 is generated by adding the shift register ouputs with different
weighting resistors.

Best wishes
Dieter Doepfer

> With regards to the VCAs (130-131) and Mixers offered by Doepfer,
> are these circuits all a Gain of 1?
>
> Or is there indeed the possibility of gain?
>
> Thanx,
>
> Tony

By default the max. gain is 1. But the VCAs can be modified so that they
amplify (one resistor has to be changed: R17 for both A-130 and A-131). But
with typical A-100 signal levels (e.g. from a VCO) you will reach clipping
very soon as the maximum output swing is about +/-10V with the 12V power
supply of the A-100.

Best regards
Dieter Doepfer

Do you mean, that the *knob* settings of A-149-1 affect A-149-2?

Jari Jokinen 

--- In Doepfer_a100@yahoogroups.com, <hardware@...> wrote:
>
> > > Are the events of the A-149-2 dependant on the settings on the 
A-149-1?
> 
> Yes, as the A-149-2 outputs are nothing but the shift register 
outputs of
> the Quantized Random Voltages section of the A-149-1. The random CV 
of the
> A-149-1 is generated by adding the shift register ouputs with 
different

> weighting resistors.
> 
> Best wishes
> Dieter Doepfer
>

Certainly. The higher N setting on the A-149-1, the greater the
variability of combinations on the 149-2. You might think of the eight
outputs on the 149-2 as the bits of a digital random number, and the
knobs of the A-149-1 determine the range of values displayed.

Doug

--- In Doepfer_a100@yahoogroups.com, "jalmari3" <jari.jokinen@...> wrote:

>
> Do you mean, that the *knob* settings of A-149-1 affect A-149-2?
> 
> Jari Jokinen 
> 
> --- In Doepfer_a100@yahoogroups.com, <hardware@> wrote:
> >
> > > > Are the events of the A-149-2 dependant on the settings on the 
> A-149-1?
> > 
> > Yes, as the A-149-2 outputs are nothing but the shift register 
> outputs of
> > the Quantized Random Voltages section of the A-149-1. The random CV 
> of the
> > A-149-1 is generated by adding the shift register ouputs with 
> different
> > weighting resistors.
> > 
> > Best wishes
> > Dieter Doepfer
> >
>

OK. By the way, I am just curious: I don't have those modules 
anymore, so I can't test, but some time ago I wrote this:
http://launch.groups.yahoo.com/group/Doepfer_a100/message/13422
"A-149-1 knobs don't affect A-149-2. Outputs 1 to 7 are "echoes" of
output 8. In this order:
8 => 7 => 5 => 4 => 2 => 1 => 3 => 6
For example, output 5 is two clock cycles behind output 8."

Jari Jokinen

--- In Doepfer_a100@yahoogroups.com, "Doug" <dougc356@...> wrote:
>
> Certainly. The higher N setting on the A-149-1, the greater the
> variability of combinations on the 149-2. You might think of the 
eight
> outputs on the 149-2 as the bits of a digital random number, and the
> knobs of the A-149-1 determine the range of values displayed.
> 
> Doug
> 
> --- In Doepfer_a100@yahoogroups.com, "jalmari3" <jari.jokinen@> 
wrote:
> >
> > Do you mean, that the *knob* settings of A-149-1 affect A-149-2?
> > 
> > Jari Jokinen 
> > 
> > --- In Doepfer_a100@yahoogroups.com, <hardware@> wrote:
> > >
> > > > > Are the events of the A-149-2 dependant on the settings on 
the 
> > A-149-1?
> > > 
> > > Yes, as the A-149-2 outputs are nothing but the shift register 
> > outputs of
> > > the Quantized Random Voltages section of the A-149-1. The 
random CV 

> > of the
> > > A-149-1 is generated by adding the shift register ouputs with 
> > different
> > > weighting resistors.
> > > 
> > > Best wishes
> > > Dieter Doepfer
> > >
> >
>

What is the A-117 CV response like? Is it vaguely exponential? linear? 

Is this a Shift register based noise circuit where the CLOCK is under VC?

I am looking for something that has a sound similar to my SN-Voice Noise... any insight will be appreciated.

Tony
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Has anybody ever tried processing audio with the 166? What were the results? 



Tony
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Hi Tony,

> What is the A-117 CV response like? Is it vaguely exponential? 
linear? 
> 
> Is this a Shift register based noise circuit where the CLOCK is 
under VC?

Yes, the A-117 produces a simple shift register sequence, but no, it 
is not under voltage control. Thus there is no 'CV response' to talk 
of. 

With nothing plugged into the 'ext clc' socket, the register is 
clocked by an internal oscillator, which is controlled manually by 
the pot on the front. If you don't want to use this, then you can 
plug an external oscillator in, so if you want voltage control, use a 
VCO - the response then will by whatever the response of the VCO is.

For the internal oscillator, the rate pot is perhaps reverse from 
what you'd expect: low knob settings give a fast clock (max f on mine 
approx, 68kHz); turning clockwise to higher settings slows the clock 
down (min f on mine, approx 90Hz). The pot is actually a log pot 
(taper 'A'), and so the high frequency drops off rapidly from knob  
setting 0 to about setting 2 (where it is approx 3kHz), and then much 
more slowly down to the minimum at setting 10. (I did plot a very 
rough graph, but it doesn't really tell you much, but I could post it 
if you like..)

Tim

Thanx Tim, I should have looked more closely! Pretty obvious there is no CV but rather an ext. clock input.

Any idea how long is this sequence? Can you notice it repeat when using high frequency clocks?

Thanx dude,

tony

> To: Doepfer_a100@yahoogroups.com
> From: timothy@tstinchcombe.freeserve.co.uk
> Date: Sat, 3 May 2008 10:17:38 +0000
> Subject: [Doepfer_a100] Re: A-117 CV response question
> 
> Hi Tony,
> 
> > What is the A-117 CV response like? Is it vaguely exponential? 
> linear? 
> > 
> > Is this a Shift register based noise circuit where the CLOCK is 
> under VC?
> 
> Yes, the A-117 produces a simple shift register sequence, but no, it 
> is not under voltage control. Thus there is no 'CV response' to talk 
> of. 
> 
> With nothing plugged into the 'ext clc' socket, the register is 
> clocked by an internal oscillator, which is controlled manually by 
> the pot on the front. If you don't want to use this, then you can 
> plug an external oscillator in, so if you want voltage control, use a 
> VCO - the response then will by whatever the response of the VCO is.
> 
> For the internal oscillator, the rate pot is perhaps reverse from 
> what you'd expect: low knob settings give a fast clock (max f on mine 
> approx, 68kHz); turning clockwise to higher settings slows the clock 
> down (min f on mine, approx 90Hz). The pot is actually a log pot 
> (taper 'A'), and so the high frequency drops off rapidly from knob  
> setting 0 to about setting 2 (where it is approx 3kHz), and then much 
> more slowly down to the minimum at setting 10. (I did plot a very 
> rough graph, but it doesn't really tell you much, but I could post it 
> if you like..)
> 
> Tim
> 
> 
> ------------------------------------
> 
> Yahoo! Groups Links
> 
> 
> 

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

Hi Tony,
 
> Any idea how long is this sequence? Can you notice it repeat when 
using high frequency clocks?

Personally, no I can't, at least it is not obvious to me in the way 
that some sequences I've heard are. At high clock rates (say knob 
setting below about 3, so above a couple of kilohertz or so) it 
sounds pretty much like white noise, and so I find becomes harder to 
hear any 'structure' that one can latch onto and see if it repeats. 
And of course at slower rates, you have to listen for that much 
longer to see if the 'structure' one can hear *does* repeat.

The circuit uses all 18 stages available in the '4006 chip used 
(which has 2 blocks of 5 bits, and 2 blocks of 4 bits), but the way 
the feedback is accomplished, I doubt the sequence is 2^18 long: 2 
bits are XORed, then inverted (ensures some 1s injected which 
prevents the sequence being all 0s), then this is XORed to a third 
bit, which is then fed back. From memory I think this is likely to 
mean that the 'linear complexity' of the sequence will be less than 
18, which means it could be generated on a shorter shify register 
(assuming the tap-points were available). Alas it is some years since 
I studied such things, as otherwise I could probably have worked out 
the appropriate polynomial and *told* you how long the sequence is...!

Tim

> -----Ursprüngliche Nachricht-----
> Von: Doepfer_a100@yahoogroups.com
> [mailto:Doepfer_a100@yahoogroups.com]Im Auftrag von jalmari3
> Gesendet: Dienstag, 29. April 2008 21:18
> An: Doepfer_a100@yahoogroups.com
> Betreff: [Doepfer_a100] Re: A-149-2
>
>
> Do you mean, that the *knob* settings of A-149-1 affect A-149-2?
>
> Jari Jokinen

In any case the clock of the A-149-1 QRV section affects the A-149-2. I'm
not sure if the QRV knob setting and CV affects the A-149-2 too. This
depends if the A-149-2 are "pre" or "post" the gating function of the shift
register outputs. I'll have to ask Christian who wrote the firmware of the
A-149-1 if the gate outputs are affected of if the "raw" shift register
states are taken. A detailed description how the A-149-1 works can be found
on our website (A-149-1 info page).

Best wishes
Dieter Doepfer

> > Any idea how long is this sequence? Can you notice it repeat when 
> using high frequency clocks?

<<snip>>

> Alas it is some years since 
> I studied such things, as otherwise I could probably have worked out 
> the appropriate polynomial and *told* you how long the sequence is...!

Well, I just couldn't let it rest at that!

I'm now pretty sure the sequence is at least 2^19 = 524288 long, so at 
1kHz (approx knob setting 4), it will take nearly 9 minutes to repeat. 
(And at max rate/min setting, approx 68kHz, it will be about 8 seconds, 
but as I said before, at such speeds it is hard to pick up any sense 
of 'structure' to determine that it *is* repeating.)

My previous assertion that the inclusion of the inverter in the 
feedback loop would reduce the 'linear complexity', and hence the 
length of the sequence was in error - if I'm interpreting how to go 
between the hardware gates and the maths correctly, the inverter makes 
the feedback non-linear, by effectively cancelling the feedback from 
the the first tap. Thus the sum of two of the taps is now *multiplied* 
by the third, and this changes everything!

There is however a nifty algorithm, the 'Berlekamp-Massey algorithm', 
which will find the minimum length (= the linear complexity) of a 
linear feedback shift register necessary to generate a given sequence. 
I ran this against another circuit (which I designed and hence I know 
what to expect), and it correctly identifies the feedback taps, so I 
was happy it was working OK, and when run against several 'captured' 
sequences from the A-117 (using my scope, most about 40 bits, the 
longest being 59), and it consistently returns the same taps, and gives 
the linear complexity as 19. I'm having some difficulty with the idea 
that a non-linear shift register of length 18 can produce a sequence 
from a linear one of length 19, but for now I have to trust that my 
computations are correct (at least they look pretty compelling!).

If Dieter is reading this and knows any more detail about where this 
circuit came from, I'd love to hear it!

Tim

> I'm now pretty sure the sequence is at least 2^19 = 524288 long, so 
at 
> 1kHz (approx knob setting 4), it will take nearly 9 minutes to 
repeat. 

With a little computational help from the kind people on the Synth DIY 
list, and some cajoling to get me to run some calcs myself, I can 
confirm that the sequence length is actually 262140 = 2^18-4. Kind of a 
strange number, but I'm working on shedding some light on it!

Tim

Tim,

I'd be willing to bet you a patch-cord that those minus 4 comes from a
miscalculation somewhere. It would be a lot easier to designing an
algorithm or a circuit with a cycle length of 2^18 straight than
2^18-4 as for the latter you would need to reset the bit pattern at a
specified point. With two 4 bit shift registers and two 5 bit ones you
might conceivably design one with a length of (2^4-1)^2 * (2^5-1)^2
but even this would be harder than designing one with an exact length
of 2^18 and there would be no good reason to do it (at least not for
the purpose in question)

/Silas

On Tue, May 6, 2008 at 11:20 PM, Tim Stinchcombe
<timothy@tstinchcombe.freeserve.co.uk> wrote:

>
>
>
>
>
>
> > I'm now pretty sure the sequence is at least 2^19 = 524288 long, so
>  at
>  > 1kHz (approx knob setting 4), it will take nearly 9 minutes to
>  repeat.
>
>  With a little computational help from the kind people on the Synth DIY
>  list, and some cajoling to get me to run some calcs myself, I can
>  confirm that the sequence length is actually 262140 = 2^18-4. Kind of a
>  strange number, but I'm working on shedding some light on it!
>
>  Tim
>
>

Hi Silas,

Well three of us have arrived at that figure independently, so I'm 
reasonably confident it is good. I have now also checked it against 
the 19-stage linear FSR equivalent, and that agrees too. Since I *do* 
have the polynomial for the 19-stage sequence, I'm working on how to 
derive the sequence length analytically, but it is taken a while to 
get back up to speed - it was about 10 years ago I last looked at all 
this stuff.

The circuit is very interesting, as whilst it is certainly not a 
linear FSR in the usual sense (I can't work out if it is non-linear 
or just 'inhomogeneous', but in either case, most of the established 
theory will probably not be applicable), it very capably produces a 
good long sequence, and does not need any special circuitry to kick-
start it into action (the inverter in the feedback loop sees to that).

So far I've tracked it down to 3 other places:

- Ken Stone's CGS Digital Noise (probably later than the A-117)
- A book by Ray Marston: 'Integrated Circuit and Waveform Generator 
Handbook' (1990)
- and the Transcendent 2000 (circa 1978?)

I suspect it is originally from some short paper published ages ago 
(perhaps in something like 'Electronics Letters') - I just wish I 
could track the exact reference down, and save me probably a deal of 
work!

Tim

--- In Doepfer_a100@yahoogroups.com, "Silas Johansen" <sijodk@...> 
wrote:
>
> Tim,
> 
> I'd be willing to bet you a patch-cord that those minus 4 comes 
from a
> miscalculation somewhere. It would be a lot easier to designing an
> algorithm or a circuit with a cycle length of 2^18 straight than
> 2^18-4 as for the latter you would need to reset the bit pattern at 
a
> specified point. With two 4 bit shift registers and two 5 bit ones 
you
> might conceivably design one with a length of (2^4-1)^2 * (2^5-1)^2
> but even this would be harder than designing one with an exact 
length
> of 2^18 and there would be no good reason to do it (at least not for
> the purpose in question)
> 
> /Silas
> 
> On Tue, May 6, 2008 at 11:20 PM, Tim Stinchcombe
> <timothy@...> wrote:
> >
> >
> >
> >
> >
> >
> > > I'm now pretty sure the sequence is at least 2^19 = 524288 
long, so
> >  at
> >  > 1kHz (approx knob setting 4), it will take nearly 9 minutes to
> >  repeat.
> >
> >  With a little computational help from the kind people on the 
Synth DIY
> >  list, and some cajoling to get me to run some calcs myself, I can
> >  confirm that the sequence length is actually 262140 = 2^18-4. 
Kind of a

> >  strange number, but I'm working on shedding some light on it!
> >
> >  Tim
> >
> >
>

> Hi Silas,
>
> Well three of us have arrived at that figure independently, so I'm
> reasonably confident it is good. I have now also checked it against
> the 19-stage linear FSR equivalent, and that agrees too. Since I *do*
> have the polynomial for the 19-stage sequence, I'm working on how to
> derive the sequence length analytically, but it is taken a while to
> get back up to speed - it was about 10 years ago I last looked at all
> this stuff.
>
> The circuit is very interesting, as whilst it is certainly not a
> linear FSR in the usual sense (I can't work out if it is non-linear
> or just 'inhomogeneous', but in either case, most of the established
> theory will probably not be applicable), it very capably produces a
> good long sequence, and does not need any special circuitry to kick-
> start it into action (the inverter in the feedback loop sees to that).
>
> So far I've tracked it down to 3 other places:
>
> - Ken Stone's CGS Digital Noise (probably later than the A-117)
> - A book by Ray Marston: 'Integrated Circuit and Waveform Generator
> Handbook' (1990)
> - and the Transcendent 2000 (circa 1978?)
>
> I suspect it is originally from some short paper published ages ago
> (perhaps in something like 'Electronics Letters') - I just wish I
> could track the exact reference down, and save me probably a deal of
> work!
>
> Tim

Some other interesting places may be:

MM5837 data sheet (digital noise source)
Digital Noise Generator of the Formant Synthesizer (Book Elektor Verlag,
ISBN 3-921608-19-8, 1981, pages 24-25)
Digital Noise Generator published in the magazine Elektor about 1978/1979 (I
have to find out the exact issue if you are interested, it was the basic
circuit for the Formant digital noise)

Best wishes
Dieter Doepfer

Hi Dieter,

> MM5837 data sheet (digital noise source)
> Digital Noise Generator of the Formant Synthesizer (Book Elektor 
Verlag,
> ISBN 3-921608-19-8, 1981, pages 24-25)
> Digital Noise Generator published in the magazine Elektor about 
1978/1979

Thanks for those pointers - I found that book online, and through it 
discovered the circuit is used in quite a few others places: the ETI 
3800, 4600 & 5600, and it is also mentioned in Barry Klein's book 
too, though unfortunately none of these give any decent analytical 
treatment of it. However I finally managed to work through most of 
the theory myself, to the point where I could deduce the period as 
2^18-4, so agreeing with the brute-force calculation of the whole 
sequence. If anyone is that interested, I gave the bare-bones of it 
on the Synth DIY list, available in the archives here:

http://search.retrosynth.com/synth-diy/search/lookit.cgi?-v0805.169

Tim

> http://search.retrosynth.com/synth-diy/search/lookit.cgi?-v0805.169

Dammit! Don't you just hate being thwarted by technology? There's 
something 'dynamic' I don't understand about that link that 
gives 'internal server error' (well it does for me!), but if you then 
back arrow out, and forward arrow back in it may work...

Or else go to:

http://search.retrosynth.com/synth-diy/

and search on 'shift register sequence period', it's near the end of 
the thread, on 9th May.

Tim