VCF CV in

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guest
 
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Re: VCF CV in

Post by guest »

the base of q10 goes to r71 and r63 and r72
so you can connect to any of those points

the sleeve should go to ground

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isak
 
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Re: VCF CV in

Post by isak »

thank guest :)

everything is set up like u said, now i need to find out how to do automation for the VCF in BANNED :shock:

guest
 
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Re: VCF CV in

Post by guest »

if you want to test it out
you could connect the cv out of the x0x
to the new mod
it will probably sound best on higher notes

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isak
 
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Re: VCF CV in

Post by isak »

thanks guest
can i use another x0x CV out and control from there on the new mod?

guest
 
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Re: VCF CV in

Post by guest »

that should work

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isak
 
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Re: VCF CV in

Post by isak »

if i use the keyboard and if i understand this right that means that the higher the note i play the cutoff needs to open the lower the note the cutoff should be closed..right?

guest
 
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Re: VCF CV in

Post by guest »

that is correct
although it may work a bit odd
as there is a 3v offset the vcf is expecting
so the highest notes will probably work best

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isak
 
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Re: VCF CV in

Post by isak »

Hi guest.

its not working, i connect the cv out from another x0x to the VCF cv in x0x, i played with the x0x the highest octave from C4 to C5 and didnt worked.
i tryed with all the pots all the way down, i tryed with only the reso pot all the way up and cutoff pot all the way down..still nothing.
i used 100K resistor with mono jack, pics..

Image
Image

guest
 
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Re: VCF CV in

Post by guest »

you have the brown wire
soldered to the wrong point
it should go to the trace above that one
the one that goes up and splits into a Y at top

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isak
 
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Re: VCF CV in

Post by isak »

didnt u said to the base (middle) of Q10? :oops:

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isak
 
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Re: VCF CV in

Post by isak »

IT WORKSSSSSSSSSSSSSSSSSSSSSS :D
million thanks guest, now connect to BANNED and try to do automation :mrgreen:

guest
 
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Re: VCF CV in

Post by guest »

awesome
youll have to figure out what voltages
make for what cutoff frequencies now

on the transistors in the x0x
they go b-c-e

bcbox
 
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Re: VCF CV in

Post by bcbox »

I haven't checked in in a few days, sorry I could have saved some headaches. Filter CV In is fairly straightforward but there is a quirk.

- As mentioned, the filter cv input is at the base of Q10.
- The resting voltage of the filter cv input is ~3.26V. This is basically because the 303/x0x is run off a single supply. In order to have both positive and negative swings in cutoff frequency versus the current position of the Cutoff control you need to reference it somewhere in the middle.
- This is what Q9 is for. If you're into electronics you can see that the voltage at the emitter of Q9 is...(5.33V + 0V)/2 + 0.6 = ~3.26V, basically the average of 5.33V and 0V (because of R64 & R65 are same value), plus Vbe of Q9 which is 0.6V. You don't need to know this so ignore if not interested!

Image

- On my schematic you have the Filter CV In coming in on the tip of the jack, through the 100k resistors and to the designation V, which is the base of Q10, the filter cv input.
- I would use 100k to get good range with typical 0-5V control.
- The second connection V on my schematic is so that when a cable is not plugged into the normally-closed jack the external filter cv input is connected to the reference voltage (3.26V), so that there is no possibility of stray voltage coming into the filter cv input, so you won't get any minor modulation or noise coming in to the CV input. Same idea as you would do with any other external CV input, such as the keyboard CV input, except usually you're referencing to ground. In this case you're reference to a particular voltage, as U is connected to the 3.26V bias voltage at the emitter of Q9/Q11.

Image

- as Guest mentioned, if you're doing normal voltage control from BANNED or whatever no AC-coupling cap is required. If you want to modulate filter cutoff with an audio rate signal put a 1uF cap in series with the resistor.

guest
 
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Re: VCF CV in

Post by guest »

that makes a lot more sense
i was wondering about that connection at V
i didnt see a juncture dot

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isak
 
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Re: VCF CV in

Post by isak »

Q:

if i want to do it like Brian says and where U should be (r47) i have a jumper wire (filter all the way down mod) should i still connect the wire to r47 left leg (x0x board)?

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