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ian fritz threeler 4U/bridechamber
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airfrankenstein



Joined: Jan 10, 2010
Posts: 60
Location: france

PostPosted: Mon Mar 18, 2019 5:42 am    Post subject: ian fritz threeler 4U/bridechamber
Subject description: 2P4T rotary wiring conflicting information
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Hi and sorry for going back to this subject which seems to have been dealt with in depth. I reman a bit stumped by some conflicting info about how to wire a rotary for the threeler vcf :
I'm using a 2P6T sealed switch with two center lugs and 12 surrounding lugs.
I've set the number of throws to 4 and have wired the following :

GND = 1,3,5,6 and V+ = 2,4,7,8
with that setting filter modes LLL and HLH sound the same as do LHL and HHH
L is low
H is high

So I tried bridechamber's wiring
GND = 1,3,7,8 and V+ = 2,4,9,10
and now it sounds like there are no connections in mode HLH and HHH

when I check the connections on my rotary switch with a multimeter
it seems like I should wire as follows
GND = 1,2,3,4 V+=7,8,9,10
but then I get no sound at all !
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The Bad Producer



Joined: Mar 08, 2009
Posts: 282
Location: The Manhole

PostPosted: Thu Mar 21, 2019 4:06 am    Post subject: Reply with quote  Mark this post and the followings unread

I've just built one, using this:

GND = 1, 2, 7, 9
+V = 3, 4, 8, 10

Set to 4 stops, like yours - where 1-6 is 'A' and 7-12 is 'B'.

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airfrankenstein



Joined: Jan 10, 2010
Posts: 60
Location: france

PostPosted: Sun Mar 24, 2019 5:43 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks...just tried that configuration and I'm only getting an output on 2 of the 4 modes which leads me to believe the problem lies elsewhere.
When I use 1,3,5,6 to gnd and 2,4,7,8 to V+ I get sound on all outputs but it only seems like two modes are audible.
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The Bad Producer



Joined: Mar 08, 2009
Posts: 282
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PostPosted: Sun Mar 24, 2019 6:53 am    Post subject: Reply with quote  Mark this post and the followings unread

Yes, it does sound like the problem is elsewhere - the wiring I used is on the schematic and I've built many like this which all work. Are you sure you have good 3280's? I've had bad Ebay ones which caused strange problems with this VCF.

Also, output 3 (on all modes) needs a bump from resonance to work as far as I understand. This output comes after the res OTA (U2a) so I guess needs some cv from the res input circuitry (external or knob control) to work - point 'b' on the schematic.

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airfrankenstein



Joined: Jan 10, 2010
Posts: 60
Location: france

PostPosted: Mon Mar 25, 2019 7:10 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for your help.
I've tried a couple of 3280's.
I'v also tried switching the 3280's, the DG409's and the OPA2134's around to see if that makes any difference.
Nothing changes...I'll have to check voltages or maybe get some know good 3280's as the ones I have come from unverifiable sources.
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elmegil



Joined: Mar 20, 2012
Posts: 2111
Location: Chicago
Audio files: 16

PostPosted: Tue Mar 26, 2019 4:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

Probably not your problem, but I assume your switch is "non-shorting" as you turn it? I had a shorting switch in one at one time and it caused lots of supply problems.
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airfrankenstein



Joined: Jan 10, 2010
Posts: 60
Location: france

PostPosted: Wed Mar 27, 2019 12:14 am    Post subject: Reply with quote  Mark this post and the followings unread

I added a 10k resistor to ground to exclude that possibility when I first built the module --- don't think that's the cause but thanks
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airfrankenstein



Joined: Jan 10, 2010
Posts: 60
Location: france

PostPosted: Sat Apr 13, 2019 10:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

I guess I'll order some CA3280s from Synthcube unless anyone knows of a EU dealer with competitive pricing. Synthcube has them at 22 USD per pair.
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