Tuner output circuit from Etherwave hotrodding manual

Posted: 6/4/2018 3:21:08 AM
Jason

From: Sammamish, Washington

Joined: 2/13/2005

I'm thinking of adding the tuner output circuit to my Etherwave and was wondering if others here have built it and how well it worked for you.

http://www.suonoelettronico.com/downloads/HotRodEtherwav.pdf

Posted: 6/4/2018 5:48:35 AM
Thierry

From: Colmar, France

Joined: 12/31/2007

I’ve built and installed that circuit several times as a kind of custom mod. Works without problems. Although the CA3080 has become obsolete, it’s still easy to find on eBay and similar platforms.

Posted: 6/4/2018 4:35:15 PM
Jason

From: Sammamish, Washington

Joined: 2/13/2005

Thanks Thierry! Is there a replacement chip you'd recommend and any changes to the circuit?

Posted: 6/4/2018 11:10:14 PM
Thierry

From: Colmar, France

Joined: 12/31/2007

No, unfortunately this kind of current controlled transconduction op-amp is definitively obsolete. The CA3080 had already a successor, the LM13700 which is used as VCA processor and for wave shaping in all Etherwaves (up to the Pro), the series 91, the Ethervox theremins, and most analog Moog synthesizers and analog pedals, is obsolete and out of production, too. But there is enough NOS (new old stock) of both for the years to come, so that the spare part and hobby builder market will not dry out, soon. Thus, you might buy this IC on ebay, ali express, or wherever and just be happy without worrying.

Posted: 6/4/2018 11:28:52 PM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

Why are they specifying a CA3080 in the first place?  The circuit doesn't appear to use / need electrically variable gain.

Or is it distortion harmonics they're looking for in pitch preview?  I'm confused.

Posted: 6/5/2018 7:11:31 AM
Thierry

From: Colmar, France

Joined: 12/31/2007

With the actual fixed gain setting and dc offset, it does some nice soft clipping, transforming the raw U-formed wave into a nice rounded almost 50:50 square which can easily processed by an external instrument tuner.

Posted: 6/5/2018 11:11:19 AM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

Ah, I see, thanks!

Posted: 6/5/2018 3:38:11 PM
Thierry

From: Colmar, France

Joined: 12/31/2007

Second, I think that we have to understand that in the 80ies and 90ies, these OTAs were Bob Moog's "daily bread" which he used in almost all his designs. So, he was for sure very familiar with these and preferred their use, even if other variants or choices would have been possible.

Posted: 6/5/2018 3:41:33 PM
Jason

From: Sammamish, Washington

Joined: 2/13/2005

Great point. It would be nice to have a more up-to-date circuit design for adding a tuner output with modern parts. I'll go ahead and build this one though. Thanks for all the information!

Posted: 6/5/2018 8:06:52 PM
Jason

From: Sammamish, Washington

Joined: 2/13/2005

Woah, that's awesome! Definitely worth the price for an experiment. Thanks!

Edit: they don't specify that it includes a pinout, but I could probably trace and figure that out.

I'm working on a little hack project using a Teensy+AudioSheild and the tuner routines from its audio library. I don't expect it to be super fast, but for my experiment, it might not need to be. I'll reveal more once I have a fully working prototype.

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