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Doepfer

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Message

Re: a155 graphic vco (or turning dc into ac)

2004-10-18 by selfoscillate

hello bakis,

yes, it won't give you the same accuracy as when you
use modules with ac-coupling, but it should work  :-)

best wishes

ingo




--- In Doepfer_a100@yahoogroups.com, Bakis Sirros 
<synth_freak_2000@y...> wrote:
> hello ingo,
> many thanks!
> i also have another idea: if you add, to the bottom
> a155 row output, a -3.2 volts offset(an a176 cv source
> passed thru an a133 vc polarizer), you will then have
> an AC output alternating between -3.2 and +3.2 volts, 
> of course, depending on the settings of the bottom
> a155 row knobs (scale knob setting to 10).
> so, in detail, for every bottom a155 row knob, the
> setting "0" leads to -3.2volts, the setting "5" leads
> to 0volts,the setting "10" leads to +3.2.
> and this give us an AC output, if you set 4 knobs to
> positive and four knobs to negative volts, in a
> symmetrical way.
> otherwise, you will have a wierd waveform with more
> than 50% of the wave above and less than 50% of the
> wave below zero(or vice versa).
> 
> bakis.
> 
> 
> 
> 
> 
> 
> --- selfoscillate <synaptic_music@y...> wrote:
> 
> > 
> > 
> > hello list,
> > 
> > last weekend i made some tests with the a155,
> > using it as a graphic vco. bakis told me, that
> > i should post the results here, maybe they are
> > of interest for anybody.
> > 
> > as all of you may know, the a155 is dc-coupled
> > and outputs only positive voltages. so if you use
> > the a155 as a graphic vco, the audio waveform will
> > be positive as well and not alternating around
> > zero as usual. not a big deal, as there is no real
> > audible difference between dc and ac, but if you
> > use the waveform in the middle of a patch, the
> > differences can be huge, for example when using
> > the a155 output as a modulator for exponential fm
> > with an a110 or a111 vco. so sometimes you may
> > want to transform the dc voltage of the a155
> > into an ac voltage in certain cases.
> > 
> > here is a list of a100 modules which do this:
> > 
> > all vcf's without exception
> > a109 vca part
> > a114 ringmod
> > a119 external input
> > a125 phaser
> > a126 frequency shifter
> > a128 fixed filter bank
> > the old a130 and a131 vca's (with cem chips)
> > a135 vc mixer
> > 
> > 
> > now the modules where the a155 output remains dc:
> > 
> > the new a131 vca (with ca3080 chips)
> > a132 vca
> > a133 polarizer
> > a138a, a138b, a138c mixers
> > a170, a171 slew limiters
> > 
> > 
> > sorry if some modules are missing, but i couldn't
> > test them all during the weekend.
> > 
> > i hope this info is of use for anyone  :-)
> > 
> > 
> > best wishes
> > 
> > ingo
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> 
> 
> =====
> Bakis Siros
> Parallel Worlds / Polariton
> Athens-Greece
> [Doepfer_a100] group owner
> http://www.shimarecords.co.uk
> http://www.ward12.com
> 
> 
> 		
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