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 Forum index » DIY Hardware and Software » Ken Stone designs - CGS
Super Psycho LFO Modifications
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Tasmanian Alkaloid



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PostPosted: Tue Sep 09, 2008 4:43 am    Post subject: Super Psycho LFO Modifications Reply with quote  Mark this post and the followings unread

Hi,
i am about to embark on building a few CGS modules, and i was wondering if there are any documented modifications for the Super Psycho LFO? For example, cv inputs per oscillator. Is such a modification desirable or even worth it?
Cheers!
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fluxmonkey



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PostPosted: Tue Sep 09, 2008 7:21 am    Post subject: Reply with quote  Mark this post and the followings unread

you could add CV via vactrols (commercial or homebrew), either in series or parallel w/ the speed pots...

b

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neandrewthal



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PostPosted: Tue Sep 09, 2008 9:17 am    Post subject: Reply with quote  Mark this post and the followings unread

I would add a mixer pot for each oscillator, instead of just an on off switch.
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Tasmanian Alkaloid



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PostPosted: Tue Sep 16, 2008 12:36 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for both those recommendations. I'm waiting on a couple of CGS kits, so when it's actually in front of me, i'll be able to see what's doing what, in terms of controls.
I've been meaning to make a few hairballs, & this may just be the place to do so.
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macumbista



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PostPosted: Thu Sep 24, 2009 7:55 am    Post subject: Reply with quote  Mark this post and the followings unread

I was thinking about modding mine as well... The Cyndustries version of this has a single CV input, which I guess modulates all the oscillators. Now this could be done (tediously) with a vactrol on each oscillator, but what about using a single vactrol to modulate the reference voltage the schmidt triggers use? Wouldn't that modulate the speed of the whole circuit? Just thinking out loud here...
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synthmonger



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PostPosted: Thu Sep 24, 2009 10:08 am    Post subject: Reply with quote  Mark this post and the followings unread

check out my super simple 40106 VCO in the Lunetta forum for a way of adding cv to the super pyscho lfo.

Also, by adding a diode in either direction across the input and output pins will give you a sawtooth wave. I'd recommend using a on/off/on switch for switching between wave forms. The square wave output will turn into 1% or 99% wave with the diode active.

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macumbista



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PostPosted: Thu Sep 24, 2009 2:55 pm    Post subject: Reply with quote  Mark this post and the followings unread

Did you mean this?

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

According to your notes, it's good for a narrow pulse. Is that because of the transistor action after the gate? Is the stuff in the left-most boxes (linear/expo CV) enough for just voltage control?

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synthmonger



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PostPosted: Thu Sep 24, 2009 3:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

macumbista wrote:
Did you mean this?

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

According to your notes, it's good for a narrow pulse. Is that because of the transistor action after the gate? Is the stuff in the left-most boxes (linear/expo CV) enough for just voltage control?



Yes if it leave it as is. The Super pyscho LFO has a buffer and offset processor on the 'triangle' output of the hex gate. If you use this same exact setup on the output of the 'falling ramp' you will get a nice clean +/- 5V sawtooth. The diode must be left in the direction it is in or else it will not oscillate, unless you reverse the current source.

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macumbista



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PostPosted: Sun Sep 27, 2009 7:18 am    Post subject: Reply with quote  Mark this post and the followings unread

One other thing I'd like to "mod" about this module... the LEDs draw current off the power rails like mad, it's very audible and actually modulates the frequencies of other modules in the same rack.

Ken Stone knows this, and actually recommends a second "dirty" power supply to keep this module off the "clean" one. But short of sticking a whole other power supply in the rack, I've thought that one could either remove the LEDs (permanently or via a switch that cuts off their supply) or run a separate regulated line from the same PSU just to power the LEDs.

Anybody have any thoughts about this? Would the second solution work, or would the noise leak through a regulator anyways? Would throwing some big caps onto the power rails help as well?

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Adam-V



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PostPosted: Sun Sep 27, 2009 4:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

You could try increasing the current limiting resistors to reduce the amount of current they draw. They will obviously not be as bright but it might reduce the supply noise a bit.

Cheers,
Adam-V

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synthmonger



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PostPosted: Mon Sep 28, 2009 6:10 am    Post subject: Reply with quote  Mark this post and the followings unread

Adam-V wrote:
You could try increasing the current limiting resistors to reduce the amount of current they draw. They will obviously not be as bright but it might reduce the supply noise a bit.

Cheers,
Adam-V


What he said Razz

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macumbista



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PostPosted: Sun Oct 04, 2009 3:07 am    Post subject: Reply with quote  Mark this post and the followings unread

Weeeellllllll... I realized I had UltraBright LEDs in there! I'll rip those out and put in some low current ones. Tom Bugs recommends using a 4k7 limiting resistor with the ones he has for 2.5 mA draw. I'm scared to think what each UltraBright is pulling!!!! My guess is almost 10 times that...

Any rule of thumb or estimates of how much current draw it takes to audibly change a VCO frequency in a system? I guess it depends on the PSU and what else is in the rack I suppose, but I'd like to know how many LEDs you can get away with. Most EuroRack systems seem to have dozens running off the same PSU, while other systems (like Buchla) have dedicated power lines for digital stuff and LEDs.

EDIT: I made a new thread in the general DIY forum for this topic, since I think it's not specific to CGS or the SuperPsycho alone:

http://electro-music.com/forum/post-266538.html

D.

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kruse



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PostPosted: Sat Nov 28, 2009 1:12 pm    Post subject: Reply with quote  Mark this post and the followings unread

so from what i gather on this thread is you have 4 mods.

1/ volume knobs for each LFO

what value pots would be best?

2/a saw wave mod (by adding diodes)

what kind of diodes?

3/CV for each lfo (vactrols added to speed pot)



4/CV that modulates all osc'



does anyone have pics or more detailed instructions as to how to do them.

If i wanted to just take the LEDS out would that solve all problems or would i have alter the circuits that are supporting the LED.

Last edited by kruse on Sat Nov 28, 2009 11:11 pm; edited 2 times in total
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kruse



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PostPosted: Sat Nov 28, 2009 2:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

another thread with other mods that have been discussed.
http://electro-music.com/forum/topic-26830.html
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Tasmanian Alkaloid



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PostPosted: Thu Dec 03, 2009 1:29 am    Post subject: Reply with quote  Mark this post and the followings unread

kruse wrote:
so from what i gather on this thread is you have 4 mods.

1/ volume knobs for each LFO

what value pots would be best?

2/a saw wave mod (by adding diodes)

what kind of diodes?

3/CV for each lfo (vactrols added to speed pot)



4/CV that modulates all osc'



does anyone have pics or more detailed instructions as to how to do them.

If i wanted to just take the LEDS out would that solve all problems or would i have alter the circuits that are supporting the LED.


Hi, i never got around to doing any modifications to mine- i built it as per the instructions & moved on.
I didn't really have a clue what to do anyway (i have only slightly more understanding of circuits now).
But i'm sure something's possible Smile
Let us know if you do have success!
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blue hell
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PostPosted: Thu Dec 03, 2009 9:54 am    Post subject: Reply with quote  Mark this post and the followings unread

macumbista wrote:
I'm scared to think what each UltraBright is pulling!!!! My guess is almost 10 times that...


erm no ... no need to be scared and it wont be 10 times as much, as it is you who decides how much current will flow through the LED, and you do this calculating the right series resistor. It does not matter here if hyte LED is ultrabright or not, only thing is an ultrabright has better effeciency and so will produce more light with the same amount of current running through it.

So .. how to determine the series resistor ... you'll need to know three things, that is the supply voltage, the voltage falling over the LED and Ohm's law. Put these toghether and you'll get :

Rs = (Vsupply - Vled) / Iled

Where Rs is the series resistor in kOhms, Vled = 2 Volt, Iled is the amount of current in mA you want to flow through the LED.

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also .. could someone please turn down the thermostat a bit.
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