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 Forum index » DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
How to use that extra OTA...
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Pehr



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PostPosted: Tue Dec 19, 2006 11:27 pm    Post subject: How to use that extra OTA...
Subject description: IC3 spare OTA applications.
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If anyone hasn't noticed yet the Sound Lab VCA only uses ½ LM13700 (IC3).
The other half of it is unused! Shocked

So I had an Idea that I'm going to modify my two SL's using this extra OTA. Twisted Evil

A first glance through the LM13700 datasheet gave me the Ideas of a voltage controlled high pass filter
for one of the labs and a four quadrant multiplier or a amplitude modulator (ring modulator) for the other.

Other Ideas are: Extra VCA, VCO, VCLPF etc...

Any other ideas for cool single OTA applications?

I'll be testing different circuits and post the Schematics in this thread.
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Pehr



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PostPosted: Wed Dec 20, 2006 5:57 am    Post subject: Reply with quote  Mark this post and the followings unread

The plans are to test these circuits:

The multiplier should perhaps have a bypass switch or something...

I have no idea wether these circuits work like this. Especially the "mixing part" of the hpf...
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Wild Zebra



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PostPosted: Wed Dec 20, 2006 7:46 am    Post subject: Reply with quote  Mark this post and the followings unread

Good idea Pehr. I still have a "dummy" ring mod in my SL. I was eventually going to buy one of Ken Stones's passive ring mods. What about that those circuits run off +-15 volts?
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richardc64



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PostPosted: Wed Dec 20, 2006 8:31 am    Post subject: Reply with quote  Mark this post and the followings unread

Datasheet examples should be viewed with skepticism. See this:
http://www.ori.org/~aaronc/synth/RingMod_V1.pdf
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Pehr



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PostPosted: Wed Dec 20, 2006 12:53 pm    Post subject: Reply with quote  Mark this post and the followings unread

Wild Zebra wrote:
Good idea Pehr. I still have a "dummy" ring mod in my SL. I was eventually going to buy one of Ken Stones's passive ring mods. What about that those circuits run off +-15 volts?


Yes, I know. I'll modify the for +-9 V. Smile
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Pehr



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PostPosted: Wed Dec 20, 2006 12:55 pm    Post subject: Reply with quote  Mark this post and the followings unread

richardc64 wrote:
Datasheet examples should be viewed with skepticism. See this:
http://www.ori.org/~aaronc/synth/RingMod_V1.pdf


of course. The datasheet is just for ideas. I've seen Aarons ring mod and I think I'll try it somehow. But without the buffer amps...
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synthmonger



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PostPosted: Wed Feb 14, 2007 2:10 am    Post subject: Reply with quote  Mark this post and the followings unread

Pehr did you get yours to work w/o op-amp buffers? I tried it and it was a really low and dirty sounding ring modulator ;X Didn't work too well.
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Pehr



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PostPosted: Wed Feb 14, 2007 10:45 pm    Post subject: Reply with quote  Mark this post and the followings unread

I haven't had time to try that one yet Embarassed
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Pehr



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PostPosted: Tue Mar 20, 2007 2:23 am    Post subject: Reply with quote  Mark this post and the followings unread

0k, so I have tested to build a ring modulator or a four quadrant multiplier outof that extra ota, but I dont hear that much difference... I use osc 1 as the modulator and the osc 2 as the signal in...

I'm going to test it a little bit more and see if I get get som cool sounds from it... Cool

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