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 Forum index » DIY Hardware and Software » YuSynth
Wavefolder mods
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numbertalk



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PostPosted: Mon May 21, 2018 6:54 pm    Post subject: Wavefolder mods Reply with quote  Mark this post and the followings unread

I’m planning to build the wavefolder module but would like to make 2 mods:

1) I would like to add a DC offset control and input to shift the VCO input signal. Which point in the circuit would this need to be connected to? For this input would I need anything else in series (resistor, opamp, etc) with the jack? Then if I also wanted to have a pot to provide DC would I simply wire one side of the pot to 15v and the other to -15v? Actually assuming I really only need +/-5v shift I’ll likely wire up a voltage divider off each rail. Then if that pot connects at the same point on the circuit with the input jack does there need to be an opamp or something to help sum the voltages from the 2 sources?

2) How could I add voltage control to the Shape control?

Any help or tips greatly appreciated, thanks!
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Grumble



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PostPosted: Mon May 21, 2018 10:01 pm    Post subject: Reply with quote  Mark this post and the followings unread

Which wave folder?

(plz. add link or schematics)

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numbertalk



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PostPosted: Tue May 22, 2018 7:12 am    Post subject: Reply with quote  Mark this post and the followings unread

Ah sorry http://www.yusynth.net/Modular/EN/WAVEFOLDER/index.html
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wackelpeter



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PostPosted: Tue May 22, 2018 9:32 am    Post subject: Reply with quote  Mark this post and the followings unread

for voltage Control of the shape i would opt for an easy mod with a vactrol in parallel to the shape pot...

adding a attentuator to the vactrol CV Input would also make sense...

a simple Driver for the LED (if you use low current ones and might roll your own vactrol) is here

http://www.birthofasynth.com/Scott_Stites/PDF/Mutant/mutant_filter.pdf

i usually get away with 1,5-3mA max. with this Driver and you can omit the trimmer if you have found the best value for good Response...

cheers Bastian

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numbertalk



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PostPosted: Tue May 22, 2018 10:10 am    Post subject: Reply with quote  Mark this post and the followings unread

Forgive me but I'm a little rusty (used to be on here and building all the time for years, but haven't built much in a long time). I'm not exactly sure what part of the schematic for Scott's filter I would need here to be honest. I see > 1 vactrols there, but I'm really not sure what and how much of his circuit around the vactrol to extract and how to apply it to the wavefolder circuit. If I'm understanding your suggestion correctly (and it does ring a bell, replacing or supplementing a pot with a vactrol to add VC to a parameter), I would just add a vactrol in series with an input jack that connects in parallel to the same spot with the Shape pot, likely with an attenuator pot on the new input jack. What I'm not sure about is what else I'd need to add (a resistor, transistor, etc) and how exactly to wire the vactrol. If it makes it easier I have vactrols, so don't need to roll my own, if you don't mind walking me through a little more how to wire it up. I need to see what kinds of vactrols I have lying around too in terms of speed of response.

Thanks!


wackelpeter wrote:
for voltage Control of the shape i would opt for an easy mod with a vactrol in parallel to the shape pot...

adding a attentuator to the vactrol CV Input would also make sense...

a simple Driver for the LED (if you use low current ones and might roll your own vactrol) is here

http://www.birthofasynth.com/Scott_Stites/PDF/Mutant/mutant_filter.pdf

i usually get away with 1,5-3mA max. with this Driver and you can omit the trimmer if you have found the best value for good Response...

cheers Bastian
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wackelpeter



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PostPosted: Tue May 22, 2018 11:43 am    Post subject: Reply with quote  Mark this post and the followings unread

if you look at the schematic for the LPF section for example you would Need the bit's what is left to the Name/description

you can reduce that to the CV1 Input (the attentuated Input) and omit CV2 Input, V/oct and initial frequency... at the base of Q1 2n3906 you would only have now your CVinput and the R32 with the trimmer... you can omit the trimmer with a fixed one if you have set the best Response for the LED, as this trimmer you adjust the brightness of the LED when on... i had to Play a bit with this reistor combi-values as my LED'S always glowed a Little bit, perhaps because i roll my own vactrols out of low current LED's and the tiny bits of uA light them slightly when a normal LED as in Vactrol is still dark...

Of Course you would then only need then one of the LED's (Vactrols)...
Then you have only to solder the lugs of the LDR in your Vactrol parellel to the shape pot...
Well 2 resistors in parellel will slightly alter the normal behaviour and your Vactrol doesn't go to Zero ohm like the pot does but it should give you reasonable Control over the shape function...

You could also totally replace that shape pot with the LDR and then you would use the initial frequency pot as your Manual shape pot... but then as said before you will not reach Zero ohm with the Vactrol and perhaps should place a fixed resistor of 47, 51 or 56k parellel to the LDR, thus keeping the resistance there in the nearby range as in the original build.

Perhaps a further short note, the thicker/bigger arrows pointing downwards are gnd and the smaller/thin arrows pointing downwards -15V... sometimes i'm prone to mess and mix those up when i don't see the most often used gnd sign... Wink

Edith says:
Well don't know why i didn't made it shorter and more explicit at the first time.... But you could drop of R27,R28, R29 and everything what is connected left to them...

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numbertalk



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PostPosted: Wed May 23, 2018 6:43 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for clarifying. So referring to the CV part of the LPF schematic, I would need R26, R32 & R10 (where R32 is the trimmer, so I should be able to replace R32 & R10 with a single resistor, yes?), Q1, R11, Q2 then the vactrol? Looks like there's a double vactrol in this LPF circuit - guess I don't need that here, that a single vactrol would do? Also then where do I take the output to connect to where the Shape control connects to the Wavefolder circuit? In this schematic I don't see where the CV output is ultimately connected to the rest of the circuit.

Also what is "best response" for the LED, in terms of trimming and determining a resistor value for that spot? I'm just checking for what gives me the best rage of control voltages over this control here?

Thanks again.

wackelpeter wrote:
if you look at the schematic for the LPF section for example you would Need the bit's what is left to the Name/description

you can reduce that to the CV1 Input (the attentuated Input) and omit CV2 Input, V/oct and initial frequency... at the base of Q1 2n3906 you would only have now your CVinput and the R32 with the trimmer... you can omit the trimmer with a fixed one if you have set the best Response for the LED, as this trimmer you adjust the brightness of the LED when on... i had to Play a bit with this reistor combi-values as my LED'S always glowed a Little bit, perhaps because i roll my own vactrols out of low current LED's and the tiny bits of uA light them slightly when a normal LED as in Vactrol is still dark...

Of Course you would then only need then one of the LED's (Vactrols)...
Then you have only to solder the lugs of the LDR in your Vactrol parellel to the shape pot...
Well 2 resistors in parellel will slightly alter the normal behaviour and your Vactrol doesn't go to Zero ohm like the pot does but it should give you reasonable Control over the shape function...

You could also totally replace that shape pot with the LDR and then you would use the initial frequency pot as your Manual shape pot... but then as said before you will not reach Zero ohm with the Vactrol and perhaps should place a fixed resistor of 47, 51 or 56k parellel to the LDR, thus keeping the resistance there in the nearby range as in the original build.

Perhaps a further short note, the thicker/bigger arrows pointing downwards are gnd and the smaller/thin arrows pointing downwards -15V... sometimes i'm prone to mess and mix those up when i don't see the most often used gnd sign... Wink

Edith says:
Well don't know why i didn't made it shorter and more explicit at the first time.... But you could drop of R27,R28, R29 and everything what is connected left to them...
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PostPosted: Wed May 23, 2018 8:50 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi,

excuse my wacky drawing skills, but this is how it would look like if you want to implement a Vactrol for the shape ctrl.

If you use the first Option, the vactrol has no effect when the resistance of the shape pot is zero...

In the second you would Control the Manual and the CV shape via Vactrol, you would then solder the LDR of the Vactrol where to shape pot was and also in parallel a 47-68K resistor to Keep the resistance when the LED is off in range as the LDR goes up in the Megaohm range...

That's it, guess this should work and it's easy to test with a breadbord and a completed waveshaper...

Would also recommend to complete the waveshaper as per original and then add the other circuitry after it'S calibrated... perhaps you have to calibrate it again but you can see how it should work first and compare if this method would fit your demands.

cheers Bastian

Edit:

have drawn some parts of the original components, i just want to make clear that you only have to touch the shape pot by soldering the vactrol LDR parallel to it or replace it with the Vactrol... everything else would be left as per the original schematic...


IMG_0292.JPG
 Description:
second option
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IMG_0292.JPG



IMG_0291.JPG
 Description:
first option
 Filesize:  2.52 MB
 Viewed:  19 Time(s)
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IMG_0291.JPG



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numbertalk



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PostPosted: Wed May 23, 2018 9:20 am    Post subject: Reply with quote  Mark this post and the followings unread

This is great and super helpful, thank you. A couple things I'm still uncertain of from your drawings:

1) In option 1, now the shape pot is directly connected to ground, not to connection point 8 of U1C on the Wavefolder schematic?
2) In option 1 am I adding a resistor (something between 47K-68K?) in parallel to the resistor in the vactrol? In your first drawing I'm confused by the arrow you have pointing down from that "47-68K" annotation - not sure what the arrow is pointing down to (looks like the arrow going UP is to that resistor).
3) If I'm understanding the drawing for my first question, then not sure exactly how U1C connects back up. In the original schematic it connects up through the diode array/network, one end going to the right of R13, the 27K resistor, and then the other side connecting the negative input of U1A. In your drawing I just see a single connection coming out of U1C and it goes up to the new resistor parallel to the vactrol which then connects to the left of the 27K resistor, not the right. If you don't mind elaborating a bit more here.

Thanks again, this is great, I really appreciate it. Sorry it's taking me a bit to get my head around it.
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wackelpeter



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PostPosted: Wed May 23, 2018 9:43 am    Post subject: Reply with quote  Mark this post and the followings unread

sorry... the downwards arrow from the 47-68k can be ignored, i intended to add some further Information but forgot, i'm getting old... Smile
the upwards arrow from the labelling 47k-68k is for the one resistor that should be in parallel with the Vactrol LDR, indicating it's value range, to avoid that the range would go in the megaohm range when the LED is off...

Please take note that the first Picture is Option 2 and the second Option 1... was a bit too fast while adding the Attachements so i had to reload the first one which was replaced by the 2nd...


please look at my edit in the post above, everything else in the Wavefolder should remain as in the original, except that with the one Option you only solder both legs of the LDR from the Vactrol to the both legs on the shape pot so that These resistances are in parallel or in the other Option you replace the shape pot with an 47k to 68k resistor and solder both Vactrol LDR legs one to each side of that resistor and put the shape pot on the LED CV Control and use it's 3 legs the outer legsto +15V to gnd and the whiper goes via 110K (something between 100 or 120K should do it too) to the base of the 2n3906 where also the trimmer and the 110K from the CV Input connects.

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numbertalk



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PostPosted: Wed May 23, 2018 10:26 am    Post subject: Reply with quote  Mark this post and the followings unread

Great, I think I finally got it thanks again! Very Happy

In terms of the other mod, the DC offset, I'm good with wiring up a pot to provide the voltages (50K pot voltage divider between ground and +15V), but if I also wanted to include an input jack for this, would I simply run a connection from that to the same spot in the circuit I connect the pot to (pin 9 of U1)? Planning to connect the pot via a 100K resistor to that spot - would I also need another 100K resistor in series with the input jack? And the pot and the jack can simply both connect to pin 9, right?
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wackelpeter



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PostPosted: Wed May 23, 2018 11:02 am    Post subject: Reply with quote  Mark this post and the followings unread

DC shift of the signal can be done like here:

http://www.yusynth.net/Modular/Commun/VCA/VCA-sch.gif

http://www.schmitzbits.de/vca.html#

it's the Offset that might be interesting for you, but i can'T recommend to do this as i have no idea if and how the circuit then works or if it still works properly with a DC Offset Input signal...

the Manual Offset for the VCA is already included, that's the range pot...

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PostPosted: Wed May 23, 2018 12:07 pm    Post subject: Reply with quote  Mark this post and the followings unread

Got it, thanks again!
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