Doepfer

I think that the only "real" ring modulator among the bunch is the 
CGS unit. I will explain my own limited understanding of this, if 
anybody cares. (If somebody with more technical knowledge sees a 
mistake, please correct me)

The term "ring modulator" refers to a a certain way of 
acheiving "four quadrant multiplication." It is called "ring" 
modulation because the circuit uses four diodes arranged in what 
looks like a ring in the circuit diagram.  The only unit that 
actually uses this circuit is the CGS.

The term "Four quadrant multiplication" just means a kind of 
amplitude modulation where a negative control voltage will invert the 
carrier signal.  Here's an explanation of the this term: A regular 
VCA is a "two quadrant multiplier." The control voltage "multiplies" 
the signal at the input.  So, a zero signal gives no output because 0 
times anything equals zero.  The input signal can be positive or 
negative, but the multiplier signal can only be positive, a negative 
control voltage has no effect.  So there are two "quadrants."  
positive control and positive input or positive control and negative 
input.

So, "Four quadrant multiplier" just means that the control voltage 
can be negative.  When a negative multiplies a positive, it gives a 
negative, so a negative signal inverts the input.  This is what 
all "ring modulators" do, regardless of whether they actually use the 
diode ring circuit or not.  (However, different circuits clearly add 
various kinds of additional artifacts, judging by the different 
sounds Ingo got.)

So, changing "ring" modulation to amplitude modulation in a four 
quadrant multiplier (Like the A-133) just means changing the control 
signal from bipolar to all positive.  This can be done by adding a 
positive offset voltage to a bipolar control voltage. 

Of course, this is really just tech-trivia since it doesn't help 
anybody to figure out what sounds you will get by doing this. Only 
way to figure that out is by doing what we all do: plug wires and 
turn knobs. 

K  

--- In Doepfer_a100@yahoogroups.com, "selfoscillate" 
<synaptic_music@y...> wrote:
>
> 
> hello ingo (the not self-oscillating :-)),
> 
> afaik the a133 is not really a ring modulator, but like a vca,
> it can be used to achieve similar effects.
> i'll record a sample using the a133, but i cannot
> do this before weekend i guess. i still have some troubles
> with my recording card. one time it works, the next time it
> doesn't. computers can be a pain in the ....
> 
> best wishes
> 
> ingo
> 
> 
> 
> --- In Doepfer_a100@yahoogroups.com, "ilanode" <techmeier@w...> 
wrote:
> >
> > Is the A133 really capable of both amplitude and ring modulation? 
> > There's no info referring to this on the Doepfer HP. Anyhow, 
Ingo, 
> > if you don't mind I'd like to hear some examples of amp/ring 
> > modulation with the A133. Regards, Ingo
> > 
> > 
> > --- In Doepfer_a100@yahoogroups.com, "selfoscillate" 
> > <synaptic_music@y...> wrote:
> > >
> > > 
> > > hello,
> > > 
> > > i tried the a133 too, but i haven't recorded it, because i
> > > wanted to compare only dedicated ring modulators.
> > > you are right, the a133 can also be used to generate
> > > ring modulator effects. damn, i should have recorded
> > > that module too.
> > > 
> > > best wishes
> > > 
> > > ingo
> > > 
> > >  
> > > 
> > > --- In Doepfer_a100@yahoogroups.com, "okiikahuna" 
> > <okiikahuna@y...> 
> > > wrote:
> > > >
> > > > --- In Doepfer_a100@yahoogroups.com, "ilanode" 
<techmeier@w...> 
> > > wrote:
> > > > 
> > > > I think you guys might have missed Doepfer's "other" ring 
> > modulator 
> > > > in your otherwise exhaustive comparison.  The A-133 Polarizer 
> is 
> > > just 
> > > > a 4 quadrant multiplier and seems to make a fine balanced 
> > > modulator.  
> > > > Just adjust the carrier for the least amount of leakage with 
no 
> > cv 
> > > > applied, then put the modulator signal into the CV jack. You 
> can 
> > > vary 
> > > > it continuously between balanced modulation and ampitude 
> > modulation 
> > > > by turning the knob or applying an offset.  To me, the sound 
> > seems 
> > > > most similar to the unmodded A-114, which raises lots of 
> > > interesting 
> > > > questions about the effect of DC v. AC coupling, since the A-
> 133 
> > is 
> > > > clearly DC.
> > > > 
> > > > Although it has been a few years since I have played with 
one, 
> I 
> > > have 
> > > > very fond memories of the sound of the Buchla 100 series ring 
> > > > modulator.  Does anybody know what was in this circuit?  Was 
> > there 
> > > > anything special about it?
> > > > 
> > > > K
> > > > 
> > > > > --- In Doepfer_a100@yahoogroups.com, denis goekdag <q-
> > art@g...> 
> > > > > wrote:
> > > > > >
> > > > > > it's really easy to assemble one or two cgs ringmods from 
> > the 
> > > > > assembled 
> > > > > > boards you can buy, just take an 8 hp blindplate, drill 6 
> > 8.2mm 
> > > > > holes 
> > > > > > for the s6 sockets, hot-glue the two cgs boards to the 
> plate 
> > > (the 
> > > > > > transformer's "casing" allow this quite smoothly), wire 
the 
> > > > > sockets, 
> > > > > > done. 
> > > > > Yes, probably the most simple DIY project around. The most 
> > > > > complicated part is to get in touch with Ken of CGS at 
least 
> > he 
> > > has 
> > > > > never replied to my mails. > :( Ingo
> > > > > 
> > > > > > Am 15.11.2005 um 18:09 schrieb Zoran Bosnjak:
> > > > > > 
> > > > > > 
> > > > > > > Ingo,
> > > > > > >
> > > > > > > thank you so much for the example! I like the CGS ring 
> > module 
> > > > > the 
> > > > > > > most. What
> > > > > > > a pity it is not offered assembled. I still have to get 
> > the 
> > > > > soldering 
> > > > > > > lesson
> > > > > > > #1 before trying to figure it out myself... (Does 
anybody 
> > > offer 
> > > > > basic
> > > > > > > electronics course in Montreal?)
> > > > > > >
> > > > > > > Regards,
> > > > > > >
> > > > > > > Zoran
> > > > > > >
> > > > > > >
> > > > > > >> From: "selfoscillate" <synaptic_music@y...>
> > > > > > >> Reply-To: Doepfer_a100@yahoogroups.com
> > > > > > >> To: Doepfer_a100@yahoogroups.com
> > > > > > >> Subject: [Doepfer_a100] Re: comparing ring modulators
> > > > > > >> Date: Tue, 15 Nov 2005 10:38:39 -0000
> > > > > > >>
> > > > > > >> --- In Doepfer_a100@yahoogroups.com, "ilanode" 
> > > > <techmeier@w...> 
> > > > > wrote:
> > > > > > >>>
> > > > > > >>> --- In Doepfer_a100@yahoogroups.com, "selfoscillate"
> > > > > > >>> <synaptic_music@y...> wrote:
> > > > > > >>>>
> > > > > > >>>>
> > > > > > >>>> hello antonio,
> > > > > > >>>>
> > > > > > >>>> the missing lows in #5 are probably because the
> > > > > > >>>> cgs real ring is a passive device, the output
> > > > > > >>>> loudness is weak on this module.
> > > > > > >>>
> > > > > > >>> Just want to add that the RRM is known to load the 
VCOs 
> > and 
> > > > > thus
> > > > > > >>> affecting their performance. The results would be 
> > different 
> > > > if 
> > > > > the
> > > > > > >>> inputs of the RRM were buffered. One could add an Op 
> Amp 
> > to 
> > > > > each
> > > > > > >>> input or (if I'm not mistaken) 2 Analogue Solutions' 
> > MX224
> > > > > > >>> Mixer/Buffer Modules. Obviously the latter is not 
very 
> > > > > economical.
> > > > > > >>> Regards, Ingo
> > > > > > >>
> > > > > > >>
> > > > > > >> i usually use those mx224 buffers in front of the cgs 
> > real 
> > > > ring,
> > > > > > >> but i didn't in my example, because i wanted to show 
the
> > > > > > >> significant differences of the loudness.
> > > > > > >> anyway, if you use those buffers, the output level of
> > > > > > >> the cgs real ring is still much lower than on the other
> > > > > > >> ring modulators.
> > > > > > >>
> > > > > > >> best wishes
> > > > > > >>
> > > > > > >> ingo
> > > > > > >>
> > > > > > >>
> > > > > > >>
> > > > > > >>
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