wavemult troubleshoot

Luka · Joined: Jun 29, 2007 Posts: 1003 Location: Melb.

hey i have some strange behaviour on the pulse out of my wavemult
i was wondering if anyone can work out why it is happening

this is for the main folder btw

my fold out is working fine but when it hits the comperator the dc offset wont pan through negative to positive, it literally switches from -7v to +7v.

the inputs going into the comperator section look fine, the pwm looks nice, it rises and falls in voltage when i turn the knob and the signal input section also is fine, the dc offset rises and falls with the offset knob.

ive checked for shorts on the pins of the lm324 and swapped them around. i checked the resistance between the pins and doesnt seem to be anything to worry about.. so any help would be great

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andrewF · Posted: Wed Oct 28, 2009 8:18 pm Post subject:

have you installed the link from pin3 of the lm324 to ground - next to the 47k?
otherwise post up some photos of the offending area and give us a look Very Happy

Luka · Joined: Jun 29, 2007 Posts: 1003 Location: Melb.

here is a pic of the board
ive installed all links that i could see

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andrewF · Posted: Fri Oct 30, 2009 4:54 pm Post subject:

neat craftsmanship Smile

how have you wired the manual pwm pot, on the 6 pin plug it looks like there is no connection for 'R-' ?

Luka · Joined: Jun 29, 2007 Posts: 1003 Location: Melb.

my pwm control is set up as voltage divider with -15 and +15 on each wiper

i have some rail buses attached to all necessary pots originating from the +ve -ve near the power inlet connector. i used the +R to send voltage to my grinder vactrol circuit

how does the dc offset work with a comperator circuit?
im still wondering if this is functioning properly

if i have no signal going into a comperator circuit apart from dc offset, shouldnt the comperator just shunt it to the negative or postive pole limits? when i do this and i try balance offset pot at 12 oclock it sometimes turns into a square wave and i can modify the pulse width with the pwm control. But if the offset is biased just a fraction to either pole it will just lock to the pole limit.

edit.
i suppose the comperator output voltage range should minic the input

andrewF · Posted: Sun Nov 01, 2009 6:06 pm Post subject:

Luka · Joined: Jun 29, 2007 Posts: 1003 Location: Melb.

i meant from the manual offset knob which adds dc to the input signal feeding into the main signal

andrewF · Posted: Sun Nov 01, 2009 7:44 pm Post subject:

Glad to see you are having a busy Monday morning

sorry if this seems too obvious, I know you are an experienced builder.

With a VCO signal into the folder input.
can't remember if you hav a 'scope?
if so have a look at the 'folded' out signal in DC mode (on the 'scope setting). note the average voltage range of the signal, say between 0 and 4V.
Then put your probe on pin 1 of iC4 and adjust the PWM pot so the voltage on pin1 is approx halfway between the upper and lower voltages of the 'folded' output.
Now probe the pulse out, does it swing back n forth? If not = problem!

no scope? maybe you can do it with a multimeter, the precise valuse are not important, just the approx voltage range of the folded out signal is enough, and somewhere around the mid-point of that range on pin1.

The DCoffset on the input of the circuit affects folder behaviour (as Ken describes) rather than the offset of the signal when it reaches the folded output

Luka · Joined: Jun 29, 2007 Posts: 1003 Location: Melb.

hehe well before i was lurking on modular forums because i had some network problems that i couldnt fix, but i fixed that now, happy clients once again. Now i have to sift through complex abstracted census tables so here i am again Smile

I'll check this stuff out tonight once i get home (yeh i have a scope)

thanks again andrew,
it is so awesome to have someone to help debug

Luka · Joined: Jun 29, 2007 Posts: 1003 Location: Melb.

ok i fed a tri wave from my evolver (boosted up to 10p-p with my mixer) into the comparator (pin 5 of ic4). it turns into a square wave. the thing now is that the manual pwm control just inverts the square instead of changing the width, and the manual offset knob changes the pulse width. this gets stranger by the second

this is with folds at 0 btw

Luka · Joined: Jun 29, 2007 Posts: 1003 Location: Melb.

acually never mind hehe
now that i boosted my input upto 10p-p the module works perfectly
thanks andrew

andrewF · Posted: Mon Nov 02, 2009 3:56 am Post subject:

good to know it works

enjoy it, its a very beautiful module for ambient slowly evolving sounds.
i mean the folder, not the grinder Laughing

the grinder is a beast