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 Forum index » DIY Hardware and Software
Electronotes 129 Thru Zero VCO MOD
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Sebo



Joined: Apr 27, 2007
Posts: 534
Location: Argentina

PostPosted: Sat Sep 08, 2012 4:05 pm    Post subject: Electronotes 129 Thru Zero VCO MOD
Subject description: Pitch independent Thru Zero control
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Hi:
I recently finished building the Electronotes 129 TZ VCO based on the PCB posted at this thread:
http://electro-music.com/forum/viewtopic.php?highlight=electronotes+129+tzvco&t=40616
Thank you Forbin for the PCB layout!!!
Reading the original article by Bernie Hutchins (thanks to him for the design):
http://electronotes.netfirms.com/EN129.pdf
I realized that if I want to modify the Thru Zero depth (using the initial linear knob) It also modifies the frequency of the VCO, as Mr. Hutchins explains at the end of the article. He also proposes a complicated way to avoid that (using a second exponential converter).
After thinking about it I came with a simple solution: to substract the voltage at the Initial Linear pot to the voltage that sets the VCO's reference current).
The MOD worked perfectly at first time.
The only trimming needed is to adjust the 20K trimm to null any pitch variation when moving the Initial Linear pot.
Also I'm posting a picture of the module (there are some errors in the labeling, as I did the panel before building the circuit).
I will try to post a video demostrating the MOD soon.


Electronotes TZ VCO - Back.jpg
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Electronotes TZ VCO - Front.jpg
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Sebo
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Luka



Joined: Jun 29, 2007
Posts: 1002
Location: Melb.

PostPosted: Sun Sep 09, 2012 2:13 am    Post subject: Reply with quote  Mark this post and the followings unread

Nice work sebo
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forbin



Joined: Jan 29, 2009
Posts: 115
Location: Fremantle, Australia

PostPosted: Sun Sep 09, 2012 9:26 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hey that's very cool! It also really nice to see the board made up. I have had a few PM's from people that have made the board successfully. I must drag mine out again as I had some tweaks that did a sort of sync thing as per what Ian Fritz was talking about... have been so busy over the last year or so Synth stuff has taken a bit of a back seat to life etc. Sad Hopefully when we move into our new house in a month or so I will be able to get it all setup again...
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Sebo



Joined: Apr 27, 2007
Posts: 534
Location: Argentina

PostPosted: Mon Sep 10, 2012 6:58 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Forbin, thanks again for the layout Smile
The VCO works great, I'm just starting to explore it, but is great!!!

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Sebo



Joined: Apr 27, 2007
Posts: 534
Location: Argentina

PostPosted: Wed Sep 12, 2012 8:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

Here is a video exploring a bit the sound palette:

http://youtu.be/XHX8rdDEKOE


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ryktnk



Joined: Apr 24, 2008
Posts: 196
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PostPosted: Sun Sep 16, 2012 2:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hello

I hope somebody can help.

I get some weiredness wiht this VCO when I
use a Linear FM freq obout 1khz and above.
When the VCO freq is lower.

Seems to get really unstable and produces some
unpleasant and unpredictable sound.

With FM freq below 1khz it is great.

Anybody else had this experience ?

Cheers
-ryk
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Sebo



Joined: Apr 27, 2007
Posts: 534
Location: Argentina

PostPosted: Sun Sep 16, 2012 3:36 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi, in the video the frequency of the VCO is always 2, 3 or 4 octaves above the modulator frequency. I use it that way because when they are at the same frequency the timbres I get are less interesting, and when the frecuency of the VCO is lower than the frequency of the modulator I get the modulator wave at the output.
But I didn't experiment any unstability at any frequency combination.

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CJ Miller



Joined: Jan 07, 2007
Posts: 371
Location: 127.0.0.1

PostPosted: Mon Sep 17, 2012 10:05 am    Post subject: Reply with quote  Mark this post and the followings unread

Nice work! I was just thinking about this VCO today, might need to try etching a few.
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ryktnk



Joined: Apr 24, 2008
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PostPosted: Tue Sep 18, 2012 3:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

Sebo wrote:
Hi, in the video the frequency of the VCO is always 2, 3 or 4 octaves above the modulator frequency. I use it that way because when they are at the same frequency the timbres I get are less interesting, and when the frecuency of the VCO is lower than the frequency of the modulator I get the modulator wave at the output.
But I didn't experiment any unstability at any frequency combination.


Hello

Thanks for the reply.

Not sure you should get the modulator wave at the output tho.

Cheers
-ryk
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