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 Forum index » DIY Hardware and Software » Ken Stone designs - CGS
real ringmod
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fluxmonkey



Joined: Jun 24, 2005
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PostPosted: Mon Aug 11, 2008 9:39 am    Post subject: real ringmod Reply with quote  Mark this post and the followings unread

finished up a build last nite of a dual real-ringmodulator module. added buffers to the ins and outs using a pair of CGS70 mixer/inverter blocks, with bit of makeup gain (RGs at 180k instead of 100k). WOW, these things just rock! these are the real deal, like the Barron's used on Forbidden Planet.

i brought the ins/outs of the other 2 inverter sections to the front panel as well, always handy to have. all in 1/2 frac.

thanks ken!

b

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numbernone



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PostPosted: Mon Aug 11, 2008 1:31 pm    Post subject: Reply with quote  Mark this post and the followings unread

Brilliant, I have a pair of these too, with the old computer diodes... been wondering how to hook em up.
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ericcoleridge



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PostPosted: Mon Aug 11, 2008 2:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

I'd love to hear some samples of this ring-mod. I've read a lot of praise for it, and I've always wondered what it is that seperates it from a typical ring mod (1496 or 633 types, for instance). Do you have any recordings? Very Happy
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flies



Joined: May 20, 2008
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PostPosted: Tue Aug 12, 2008 2:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

there are some samples of this (other) passive ring mod available here http://www.analoguehaven.com/makenoise/moddemod
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jnuaury



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PostPosted: Wed Aug 13, 2008 12:40 am    Post subject: Reply with quote  Mark this post and the followings unread

and bridechamber is selling 2 tranformers and 4 matched diodes for $10 for the cgs ring mod

so you can do a nice cheap and easy ring mod on stripboard if you want
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ericcoleridge



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PostPosted: Wed Aug 13, 2008 2:32 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yeah, I also like the wave multiplier+real ring that they sell, thinking of trying one of those. But I already have a couple ring mods, and don't really need another. But I am curious to hear this one.
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Adam-V



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PostPosted: Wed Aug 13, 2008 7:23 pm    Post subject: Reply with quote  Mark this post and the followings unread

I wonder if you could replace the diodes with op-amps set up as ideal diodes?
I also wonder if it would be worth while?

Cheers,
Adam-V

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otherunicorn



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PostPosted: Fri Aug 15, 2008 3:13 am    Post subject: Reply with quote  Mark this post and the followings unread

Adam-V wrote:
I wonder if you could replace the diodes with op-amps set up as ideal diodes?
I also wonder if it would be worth while?

Cheers,
Adam-V


You would be defeating the purpose. Most "ring modulators" in synths are actually 4 quadrant multipliers, which on the whole are "distortion free".
A real ring modulator is not. The diode voltage drops introduce distortion, as do any impedence/drive issues with the transformers. A real ring modulator has a more classic "dirtier" sound to it. Note that by real ring modulator, I am not referring specifically to the CGS one either.

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Adam-V



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PostPosted: Sun Aug 17, 2008 7:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

Good point. I was thinking more in terms of signal loss, but this is probably best compensated for with buffers as mentioned in the initial post.

Cheers,
Adam-V

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certain2



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PostPosted: Fri Nov 21, 2008 4:56 am    Post subject: Reply with quote  Mark this post and the followings unread

I'm not sure I understand this. The standard advice is to use germanium
diodes rather than silicon since they have a turn on voltage of 0.35V rather
than 0.7V, consequently silicon cause some clipping and distortion.
RF enthusiasts building balanced modulators use schottky diodes
which have an even lower turn on ~0.25V to minimise distortion. Avago
(ex agilent ex HP) make matched schottky quads specifically for this
application. Has anyone tried these in a real ringmodulator in an
electronic music context?
Or is it that germanium diodes give "just the right amount" of distortion?
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Blue Hell
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PostPosted: Fri Nov 21, 2008 1:12 pm    Post subject: Reply with quote  Mark this post and the followings unread

Welcome certain2,

germanium diodes also have a softer knee I think, which could play a role too. But it would be pretty cheap to experiment a bit that Wink

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LektroiD



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PostPosted: Tue Jan 06, 2009 7:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

How can you spot a germanium diode?

I have some ancient looking diodes here that I've picked up over the years, such as these metal cased diodes, that are about twice the thickness of an average resistor, and simply have the number 4 stamped on them. Maybe someone could shed some light?


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Blue Hell
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PostPosted: Tue Jan 06, 2009 7:54 pm    Post subject: Reply with quote  Mark this post and the followings unread

OMG ... that might even be selenium Laughing

When you put 'm in series with a 1k resistor and connect that to a 9V battery you can measure the voltage over the diodes, GE should give 0.3 .. 0.4V, SI 0.6 .. 0.7V and for SE I really wouldn't know. When you measure about 9 V please reverse the battery.

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Sebo



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PostPosted: Wed Jan 07, 2009 3:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi:
I have some questions about the diodes.
I read they have to be old germanium diodes, but not any specific. Any
rules about that?
Could 1N60 work?
Some people say that used old computer diodes, from what computers?
(early PC, Commodores, older?).
Thank you.

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andrewF



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PostPosted: Wed Jan 07, 2009 7:50 pm    Post subject: Reply with quote  Mark this post and the followings unread

I have used 1n60 in a RRM - no problems
Probably any old ge diode will be fine.

I think the old computers Ken refers to are REALLY old, from the 60s.
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Uncle Krunkus
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PostPosted: Wed Jan 07, 2009 11:33 pm    Post subject: Reply with quote  Mark this post and the followings unread

I've got some old black glass ones (an OA74, an OA79 and an OA85) I've also got some "new" Ge diodes of various types. Do they have to be the same type? If so, I think I'd start by experimenting with the new ones, but I'd like to see if the old ones will work.
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Blue Hell
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PostPosted: Thu Jan 08, 2009 3:53 am    Post subject: Reply with quote  Mark this post and the followings unread

Uncle Krunkus wrote:
Do they have to be the same type?


At least pair wise I'd think (but which pairs thinking Laughing), but best all the same.

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Sebo



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PostPosted: Thu Jan 08, 2009 6:14 am    Post subject: Reply with quote  Mark this post and the followings unread

I will try 1N60 first.
Thank you.

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Adam-V



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PostPosted: Thu Jan 08, 2009 5:37 pm    Post subject: Reply with quote  Mark this post and the followings unread

Uncle Krunkus wrote:
I've got some old black glass ones (an OA74, an OA79 and an OA85) I've also got some "new" Ge diodes of various types. Do they have to be the same type? If so, I think I'd start by experimenting with the new ones, but I'd like to see if the old ones will work.


You could probably get away with mixing the types but ideally you should match them for the same forward voltage drop. I reckon you could also use Schottky signal diodes in this circuit if you select them for the lowest possible forward voltage drop.

Cheers,
Adam-V

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Uncle Krunkus
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PostPosted: Thu Jan 08, 2009 6:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

Is it just about overcoming the small forward voltage drop in order to send top and bottom parts of the wave in different directions, or does the linearity/non-linearity of the diodes have some impact on the operation?
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LektroiD



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PostPosted: Thu Jan 08, 2009 7:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

Which transformers should I use for this?

Are any of these any good:
http://www.maplin.co.uk/Module.aspx?ModuleNo=3709
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Adam-V



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PostPosted: Sun Jan 11, 2009 2:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

Uncle Krunkus wrote:
Is it just about overcoming the small forward voltage drop in order to send top and bottom parts of the wave in different directions, or does the linearity/non-linearity of the diodes have some impact on the operation?


That's a very good question, I think it's a little from column A and a little from column B.

Cheers,
Adam-V

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scriptstyle



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PostPosted: Sun Jan 11, 2009 5:55 pm    Post subject: Reply with quote  Mark this post and the followings unread

Uncle Krunkus wrote:
Is it just about overcoming the small forward voltage drop in order to send top and bottom parts of the wave in different directions, or does the linearity/non-linearity of the diodes have some impact on the operation?


im not really sure(probally), but i do know that forward threshold for silicon is about .7volt and germanium is about .3 volt
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frijitz



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PostPosted: Tue Jan 13, 2009 8:47 pm    Post subject: Reply with quote  Mark this post and the followings unread

otherunicorn wrote:
Adam-V wrote:
I wonder if you could replace the diodes with op-amps set up as ideal diodes?
I also wonder if it would be worth while?

Cheers,
Adam-V


You would be defeating the purpose. Most "ring modulators" in synths are actually 4 quadrant multipliers, which on the whole are "distortion free".
A real ring modulator is not.


Hmmm .... Trying to get my head around this. Wouldn't an ideal diode just act as a switch? So any finite modulation would just switch the polarity of the signal, as if it were large amplitude square wave modulation.

Very Happy

Ian
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Lofi Ninja



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PostPosted: Sat Feb 28, 2009 7:45 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi guys..

Found this thread last night, and I imediatly threw togheter a passive ring mod..

Diodes are un-numbered silicon ones, the ones that are glass like with the orange stuff inside..

Transformers are nr. 273-1380 from the shack..
Impedance: 1KHz, 1V, 0mADC
Input:1Kohm 10%
Output: 8 ohm (loaded)
DC resistance (input): 70ohms 20%
DC resistance (output): 0.62 20%
Frequency response: 300-10,000 Hz 3dB

I've never had my hands on a ringmod before, so I'm not sure if it's working very well, but I like the result very much..

BTW. Matching diode pairs, in this schema, top pic,
http://www.cgs.synth.net/modules/pic/schem_cgsrr.gif would the pairs be the ones that are parallel, and the ones crossing ? Or is it one of each per pair ? Thank you very much!

I will make a video for you now so you can hear it in action Very Happy

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