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acidblue
Joined: Jun 26, 2009 Posts: 226 Location: The Darkside
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gdavis
Joined: Feb 27, 2013 Posts: 359 Location: San Diego
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Posted: Fri Apr 11, 2014 9:50 pm Post subject:
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Google search turned up this blog which discusses the circuit and suggests values for the resistors:
http://blog.skincontact.com/2010/08/
"Suggested values are R1 & R3 1k-10k, R2 & R4 100k or more, and C3 maybe another 1uF. Trial and Error." _________________ My synth build blog: http://gndsynth.blogspot.com/ |
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acidblue
Joined: Jun 26, 2009 Posts: 226 Location: The Darkside
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Posted: Sat Apr 12, 2014 6:00 pm Post subject:
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That link is dead.
Getting "Server not found" error.
But I'll try different R values when I get a chance and see if that makes any difference. |
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gdavis
Joined: Feb 27, 2013 Posts: 359 Location: San Diego
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Posted: Sun Apr 13, 2014 10:07 pm Post subject:
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Wow, I quoted the relevant info in case someone came across this thread a year from now or something and the link was dead, but didn't expect it to die after one day
There wasn't much else that would be helpful as I recall. The impression I got is that it's just a simple but crude circuit for people to experiment with, not really something that's reliable and stable enough to just build and expect to work perfectly, even if built "correctly".
Anyway, good luck. _________________ My synth build blog: http://gndsynth.blogspot.com/ |
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acidblue
Joined: Jun 26, 2009 Posts: 226 Location: The Darkside
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Posted: Tue Apr 15, 2014 2:24 pm Post subject:
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I've tried everything, 1k , 10k , 100k, No k, just straight from pin 3 to the pot
and I just can't get this circuit to work.
It's a shame cause it's a simple shcem. |
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ElektroBoy
Joined: Apr 16, 2014 Posts: 1 Location: Sweden
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wackelpeter
Joined: May 05, 2013 Posts: 461 Location: germany
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acidblue
Joined: Jun 26, 2009 Posts: 226 Location: The Darkside
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Posted: Wed Apr 16, 2014 12:20 pm Post subject:
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Thanks for your replies.
But I've tried every thing and still cant get this to work.
When I disconnect the first pot I get an amplified signal from
my square waves osc's. but nothing when connected.
I've tried single supply and VR supply, I think the LM358 will work
with a straight single supply, but I tried it with a VR as well, still nothing.
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PHOBoS
Joined: Jan 14, 2010 Posts: 5591 Location: Moon Base
Audio files: 705
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Posted: Sat May 10, 2014 6:42 am Post subject:
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ok I decided to give this one a try. The first thing I noticed is that the LP filter section can't really work well because it's directly connected to the low
impedance output of the opamp. So instead of taking the output signal from pin 1 use the connection between R3/VR2 and use the other half of the
LM358 as another voltage follower connected to that. So you end up with: signal -> passive HP -> buffer -> passive LP -> buffer.
I did a test with my modular lunetta as a signal source but becauseI have diodes on every output I needed an extra pulldown resistor. Since the output
signal is also very high I used a voltage divider (2x 10K) and then used another opamp as a buffer before going to the filter input. Component values
I used are:
HP: C1 = 100nF, R1 = 10K, VR1 = 100K
LP: C2 = 100nF, R3 = 10K, VR2 = 10K
(voltage supply 12V)
and that seems to work, but I did not test the CV inputs,. (yet) _________________ "My perf, it's full of holes!"
http://phobos.000space.com/
SoundCloud BandCamp MixCloud Stickney Synthyards Captain Collider Twitch YouTube |
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acidblue
Joined: Jun 26, 2009 Posts: 226 Location: The Darkside
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PHOBoS
Joined: Jan 14, 2010 Posts: 5591 Location: Moon Base
Audio files: 705
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acidblue
Joined: Jun 26, 2009 Posts: 226 Location: The Darkside
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Posted: Sun May 11, 2014 11:40 am Post subject:
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Ok I got it to work, mostly
The Low Pass side works fine, however the High Pass is proving to be difficult.
I'll explain, if I wire it exactly like the schematic, with the resistor/pot combo after the cap, I get nothing.
If I put the resistor/pot combo before the cap, I get sound, but adjusting the pot does little if anything, this is on the HP side of the circuit.
I tried different values for the resistor, (1k, 100k), same result.
Any ideas?? |
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PHOBoS
Joined: Jan 14, 2010 Posts: 5591 Location: Moon Base
Audio files: 705
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acidblue
Joined: Jun 26, 2009 Posts: 226 Location: The Darkside
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