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 Forum index » DIY Hardware and Software
Jim Patchell's Control Voltage Splitter
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funkyfarm



Joined: Jan 21, 2007
Posts: 583
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PostPosted: Mon Apr 30, 2007 1:35 am    Post subject: Jim Patchell's Control Voltage Splitter
Subject description: 2001 ideal diode circuit
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Does anyone ever give a try to the Jim Patchell's Control Voltage Splitter ?


http://www.oldcrows.net/~patchell/misc/splitter.html


Quote:
"It is just an ideal diode circuit."


I've always wanted to be able to "extract" the posivite or negative part of a CV signal...

Posted Image, might have been reduced in size. Click Image to view fullscreen.

seems to work quite well at first sight (the test was LED based - no audio)
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Dan Lavin



Joined: Nov 09, 2006
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PostPosted: Mon Apr 30, 2007 5:21 am    Post subject: Reply with quote  Mark this post and the followings unread

Interesting. I drew up a similar circuit for a new keyboard I'm working on. I am using a joystick controller with pitch on the X-axis and two separate modulation types for the Y-axis. The plan is to have the Y-axis hooked to -V and +V and have the circuit split 0 to +V voltages for positive Y-axis and split 0 to -V for negative axis. The 0 to -V voltage would then be inverted for positive voltage control. Each CV would drive 2 separate VCA's. One siginal would be a sine or triangle wave and the other a low frequency noise wave like the minimoog.

This circuit would work for that if -V break is set to ground (0V).
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Fernando



Joined: Dec 30, 2006
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PostPosted: Mon May 14, 2007 2:42 am    Post subject: Reply with quote  Mark this post and the followings unread

It is very interesting. I stored the circuit time ago but never build it.

I was thinking in a CV processing tool but a couple of months ago I was thinking in it as a noise comparator to produce noise grains.

???
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funkyfarm



Joined: Jan 21, 2007
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PostPosted: Mon May 14, 2007 1:06 pm    Post subject: Reply with quote  Mark this post and the followings unread

On my side, it's long time I've been thinking of adding somewhere on a blank panel four sockets : one INPUT socket linked to 1n4148 anode to another OUTPUT socket.
With two of these, I could extract the positive and negative part of any incoming signal... I left this idea because of 0.3Ge and 0.7Si negative clipping...

Anyway, this design is cool !

And I still have to further explore the VC-BREAK part of it !

I've use it as "double gate"

Put +/-5V SQUARE LFO
REVERSE NEGATIVE OUTPUT
When positive gate or incoming signal shuts down, the reversed negative one becomes active...

Nice for adding accent (CV of 292 LPG) and shifted CUT OFF controlling of a couple of filters (stereo fx)

Samples are not best for illustrative purposes, but I can say that I have real fun with this little thing. Wink

Last SWING series sample
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Fernando



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PostPosted: Mon May 14, 2007 3:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

maybe useful too for processing a random source and get two "related" random signals...

and the -Vbreak controlled by another random signal...

that may be taken from Vo1 or Vo2, scaled with an attenunverter, providing some feedback (correlation) to the thing

'drunken

and up to audio freqs now


(hey, great sgniw!)
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funkyfarm



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PostPosted: Wed May 16, 2007 10:16 am    Post subject: Reply with quote  Mark this post and the followings unread

Fernando wrote:
maybe useful too for processing a random source and get two "related" random signals...

and the -Vbreak controlled by another random signal...

that may be taken from Vo1 or Vo2, scaled with an attenunverter, providing some feedback (correlation) to the thing

'drunken

and up to audio freqs now


(hey, great sgniw!)


?!

For sure you need one Cool
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asterisk



Joined: Sep 17, 2011
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PostPosted: Sun Jan 08, 2012 12:03 am    Post subject: Reply with quote  Mark this post and the followings unread

so is this kind of a max/min circuit with an adjustable center?

(a fixed max/min is always centered around 0v right?)
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diablojoy



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PostPosted: Sun Jan 08, 2012 1:13 am    Post subject: Reply with quote  Mark this post and the followings unread

had not seen this one before
nice samples funkyfarm
i think i may try playing around with this one a bit
might even put a couple behind a panel

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fonik



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PostPosted: Sun Jan 08, 2012 8:12 am    Post subject: Reply with quote  Mark this post and the followings unread

funkyfarm wrote:
And I still have to further explore the VC-BREAK part of it !

take a look at im's vocal filter, especially the voltage controlled CV breakpoints. i once wanted to build htem as stand alone modules but never got it done...

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diablojoy



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PostPosted: Sun Jan 08, 2012 4:20 pm    Post subject: Reply with quote  Mark this post and the followings unread

will try it first with a tl074
i can use the extra opamp for an extra inverted input
then i can use a positive cv output from a seq to move the breakpoint around
simple enough
maybe an attenuverting offset control could be added also

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PHOBoS



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PostPosted: Wed Jan 11, 2012 4:34 pm    Post subject: Wave Wiper
Subject description: based on Jim Patchell's Control Voltage Splitter
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I just gave it a try to see what it really does and then used it to design a
circuit that merges the top and bottom halves of 2 waveforms together.
With the CV/pot you can 'wipe' between the 2 input signals. Because the
ouputs behave inverted (top1+bottom2 VS top2+bottom1) it makes a
very nice (auto)cross-panner.

I'm not sure if this is one of the things hinted in the posts above, but I
think it's a very useful circuit. Smile

Exclamation edit: flipped the diodes around compared to the previous schematic, more info later.


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Last edited by PHOBoS on Thu Jan 12, 2012 7:16 am; edited 2 times in total
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diablojoy



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PostPosted: Wed Jan 11, 2012 4:43 pm    Post subject: Reply with quote  Mark this post and the followings unread

nice work Cool
I think it is a very usefull cct too well done

so can you try inputting 2 differant wave forms
say a tri and a square at the same and differing frequencies
and check the outputs to see what you get please
scope shots would be nice if you can.
not originally what i was looking for but i know rikhaard
was looking in that direction trying to rediscover something
he did long ago.

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asterisk



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PostPosted: Thu Jan 12, 2012 12:07 am    Post subject: Reply with quote  Mark this post and the followings unread

phobos,
your circuit looks interesting.
it has 2 outputs, are you saying output 1 is regular and output 2 is inverted version of output 1?
ill have to try to breadboard this one and test it out. seems fun.
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PHOBoS



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PostPosted: Thu Jan 12, 2012 10:21 am    Post subject: Wave Wiper example graph Reply with quote  Mark this post and the followings unread

asterisk wrote:

it has 2 outputs, are you saying output 1 is regular and output 2 is inverted version of output 1?

not exactly.
Inverted in the way that one output wipes from IN 1 to IN 2,
while the other output wipes from IN 2 to IN 1.

I made an example with 2 waveforms (triangle/square, 10Vpp) with the same
frequency at 5 different CV settings. This should make it a bit more clear
what it does. The also shows the reason for flipping the diodes around in
the updated schematic, because to me it makes more sense to have IN 1
on OUT 1, and IN 2 on OUT 2 with a positive CV, and the other way around
with a negative CV.

once I've put it on perf I'll do some more tests with different kinds of input
signals and maybe I will be able to provide some scope shots. Cool


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asterisk



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PostPosted: Thu Jan 12, 2012 10:27 am    Post subject: Reply with quote  Mark this post and the followings unread

that makes sense to me now, thanks for the explanation.

im going to try to breadboard this soon.
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diablojoy



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PostPosted: Thu Jan 12, 2012 4:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
I made an example with 2 waveforms (triangle/square, 10Vpp) with the same
frequency at 5 different CV settings. This should make it a bit more clear
what it does. The also shows the reason for flipping the diodes around in
the updated schematic, because to me it makes more sense to have IN 1
on OUT 1, and IN 2 on OUT 2 with a positive CV, and the other way around
with a negative CV.

yes that does make more sense to me as well
also what you have drawn is what i imagined the outputs would look like,
if it bears out in real life the same this will be a very usefull circuit indeed Cool it could make a very good VC waveshaper

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vladosh



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PostPosted: Thu Jan 12, 2012 5:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

I already cut a piece of stripboard Smile
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asterisk



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PostPosted: Thu Jan 12, 2012 6:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

would a TL074/084 quad op-amp work fine in this circuit instead of the LM324?
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PHOBoS



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PostPosted: Thu Jan 12, 2012 7:45 pm    Post subject: Reply with quote  Mark this post and the followings unread

asterisk wrote:
would a TL074/084 quad op-amp work fine in this circuit instead of the LM324?


yes, that should work fine.
(I'm running a bit low on TL074's at the moment and still got a bunch of LM324's Wink)

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PHOBoS



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PostPosted: Fri Jan 13, 2012 1:50 pm    Post subject: tuning the Wiper Reply with quote  Mark this post and the followings unread

For those brave enough to try it, here's how to test and set the 47K trimpot:

Don't connect any signals to the inputs (incl. CV), better yet connect them to GND.
Turn the trimpot to it's minimum resistance, and the 100K "WIPE" pot to -12V.
You should measure a voltage of roughly +2V on OUT 1 and OUT 2. Now turn
the "WIPE" pot to +12V and measure the outputs, they should now be roughly -2V.
(if you measured a voltage way above and below 2V you could have the
trimpot turned the wrong way. else you need to check the circuit.)

Next, with the "WIPE" pot still at +12V turn the trimpot so that both outputs
are 0V. Now turn the "WIPE" pot back to -12V, the outputs should stay at 0V.
adjust the 47K trimpot if necessary. that's it Smile (at least for now)

note: the circuit should work fine on +/-15V but you might want to
increase the 220K resistor attached to the "WIPE" pot.

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emdot_ambient



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PostPosted: Fri Jan 13, 2012 1:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

vladosh wrote:
I already cut a piece of stripboard Smile

[greedy design thief] Don't forget to share the stripboard design! [/greedy design thief]
Wink

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PHOBoS



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PostPosted: Fri Jan 13, 2012 2:32 pm    Post subject: Reply with quote  Mark this post and the followings unread

some more tests in case you don't have a scope and can't see if it's
working correct:

CV source connected to IN1 (pot between +/- 5V is useful for testing)
"WIPE" pot at +12V
OUT1 should follow IN1, OUT2 should be 0V

"WIPE" pot at -12V:
OUT1 should be 0V, OUT2 should follow IN1

CV source connected to IN2
"WIPE" pot at +12V:
OUT1 should be 0V, OUT2 should follow IN2

"WIPE" pot at -12V:
OUT1 should follow IN2, OUT2 should be 0V

for a final test you can connect a DC voltage to IN1 and a different voltage
to IN2. With the "WIPE" pot you should be able to control the outputs
between these voltages (where OUT2 does the opposite of OUT1).

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vladosh



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PostPosted: Fri Jan 13, 2012 4:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

Here's my layout Smile , the power conection on LM324 is missing as i'm gonna make that with wire ,simply no space that's how these stripboards are ..
greetings

(fixed layout with pin 5 and 10 to ground)


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PHOBoS



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PostPosted: Sat Jan 14, 2012 6:29 am    Post subject: Reply with quote  Mark this post and the followings unread

vladosh wrote:
Here's my layout Smile

I think you forgot to ground pin 5 and 10 of the LM324,
or are you gonna use wires for those ? Wink

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vladosh



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PostPosted: Sat Jan 14, 2012 6:32 am    Post subject: Reply with quote  Mark this post and the followings unread

heh :/
thanks for checking the layout Phobos , i always do that kind of stuff and then wonder ..
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