VCA Decay and VCA ADSR questions

Discuss mods, hacks, tweaks, etc.

Moderators: altitude, adafruit_support_bill, adafruit, phono, hamburgers

Please be positive and constructive with your questions and comments.
Locked
User avatar
isak
 
Posts: 835
Joined: Wed May 27, 2009 3:54 pm

VCA Decay and VCA ADSR questions

Post by isak »

Hi guys

i tryed to put this mod but i didnt succeed.
i replaced r123 with two jumper wires that connects to 1m pot and 500k resistor.
and the mod didnt work, it dont do nothing, when i turn the pot all the way down or up the sound stays the same.
i took the mod from here :
http://www.subatomicglue.com/x0xl0g/mod ... _VCA_Decay
and this is how i did that:
Image

maybe i connect something wrong?

UPDATE :
i made a search on the forum on VCA decay i found Guests ADSR mod
http://www.ladyada.net/wiki/_detail/x0x ... %3Avcamods
i dont know how to even start doing it.. :(
can someone please explane
1: where i start to connect the VCA ADSR mod?
2: do i need to built it on a PCB first and then connect it?

any help will be much appreciated
thanks

Isak :)

guest
 
Posts: 3155
Joined: Fri Feb 17, 2006 5:35 am

Re: VCA Decay and VCA ADSR questions

Post by guest »

with the vca mod youre building
set your tempo to really slow when testing it
most notes are too short to notice the decay time at all

with the one i designed
all the parts labeled with designators
for example q31
are parts on the board
the rest needs to be added on an external board

User avatar
isak
 
Posts: 835
Joined: Wed May 27, 2009 3:54 pm

Re: VCA Decay and VCA ADSR questions

Post by isak »

Hi Guest and thanks for u'r replay

further quetions
1 : if i do the VCA ADSR mod..is the original envelope is still relevant?
2 : do i need to take out the parts from the x0x and put them on the PCB ?
3 : can i do in the x0x VCF ADSR mod ?
thanks guest

Isak :)

guest
 
Posts: 3155
Joined: Fri Feb 17, 2006 5:35 am

Re: VCA Decay and VCA ADSR questions

Post by guest »

it will be difficult to get the original envelope after doing the mod

you dont need to put any x0x parts on the pcb
but you do need to remove some x0x parts
as they are not used

i havent given much thought to a vcf adsr
there is already decay control
and if you replace r152 with a pot
you can get attack control
but the rest wouldnt be that easy

User avatar
isak
 
Posts: 835
Joined: Wed May 27, 2009 3:54 pm

Re: VCA Decay and VCA ADSR questions

Post by isak »

Ok Guest thanks again.
:)

User avatar
isak
 
Posts: 835
Joined: Wed May 27, 2009 3:54 pm

Re: VCA Decay and VCA ADSR questions

Post by isak »

Hi guest

a question..
can i do only the release from the VCA ADSR ?

guest
 
Posts: 3155
Joined: Fri Feb 17, 2006 5:35 am

Re: VCA Decay and VCA ADSR questions

Post by guest »

that is the same as the mod you have above

try replacing the 500k resistor on your schematic
with a 10k resistor
and see if you get a more dramatic effect

User avatar
isak
 
Posts: 835
Joined: Wed May 27, 2009 3:54 pm

Re: VCA Decay and VCA ADSR questions

Post by isak »

ok guest
i will and i'll let u know

thanks :)

User avatar
isak
 
Posts: 835
Joined: Wed May 27, 2009 3:54 pm

Re: VCA Decay and VCA ADSR questions

Post by isak »

Hi guest

i connected the 1M pot without the 10k resistor (i figure that 10k will not make much difference), it didnt effect, the only effect that i had is when the pot is all the down i had no sound.

do i need to put the 10k resistor anyway?

thanks guest and have a great week

Isak :)

guest
 
Posts: 3155
Joined: Fri Feb 17, 2006 5:35 am

Re: VCA Decay and VCA ADSR questions

Post by guest »

you need the 10k
because at the very low end of travel of the pot
its hard to set a small amount of change
it goes from 100k to 0ohm really quickly

are you using an audio taper pot as well
they have two ways you can use them
one gives it better sensitivity than the other

User avatar
isak
 
Posts: 835
Joined: Wed May 27, 2009 3:54 pm

Re: VCA Decay and VCA ADSR questions

Post by isak »

Hi guest
are you using an audio taper pot as well
they have two ways you can use them
one gives it better sensitivity than the other
what is an audio taper pot? :oops:
and what is the two ways i can u it ?

thanks

isak

guest
 
Posts: 3155
Joined: Fri Feb 17, 2006 5:35 am

Re: VCA Decay and VCA ADSR questions

Post by guest »

there are two main types of pots
audio taper and linear taper
the x0x uses both of them
generally and audio taper is labeled as 10ka or 10kd
whereas a linear taper is labeled 10kb
where the 10k part is the resistance
and the last letter is the taper type

audio taper is also called log taper
as it has a logrithmic response
just like the human ear to sound

when you turn a pot
the resistance changes
if its a linear taper pot
the resistance changes linearly with rotation
so it doesnt matter which way you connect it up
the middle pin will always just be a ratio of the two outside pins

on an audio taper pot
the resistance decreases really quickly for a small bit of turn
right at the beginning of travel
and then it changes really slowly
for the remainder of the travel
so the center pin always goes to your control point
but if you take the two outer pins and reverse them
you can either get a really sensitive change
or a basically on/off effect

User avatar
isak
 
Posts: 835
Joined: Wed May 27, 2009 3:54 pm

Re: VCA Decay and VCA ADSR questions

Post by isak »

i understand, thanks a lot for the explanation.
i dont know if the 1M pot is linear or logrithmic
it says B1M on the pot.

i guess u recommend on the lin pot..right?

thanks
Isak :)

guest
 
Posts: 3155
Joined: Fri Feb 17, 2006 5:35 am

Re: VCA Decay and VCA ADSR questions

Post by guest »

i would guess thats a linear pot
you can measure it by taking measurements
of its resistance
at various percentages of its rotation

the log pot would be the thing to use for this application

User avatar
isak
 
Posts: 835
Joined: Wed May 27, 2009 3:54 pm

Re: VCA Decay and VCA ADSR questions

Post by isak »

ok guest
so we have 1M log pot and 10k resistor.
i'll update ASAP.

thanks
Isak :)

Locked
Please be positive and constructive with your questions and comments.

Return to “x0xm0dz”