Single chip S&H

[EraSer]

I'm interested to know simply how SL' single chip sample&hold works befere adding it to my "under-construction SL" .Do I need a keyboard controller to use it

[fonik]

no, you don't need a keyboard controller.
the s&h adds unpredictability to your SL. it takes an incoming control voltage (from noise, LFO...) and takes a sample by a time selected by it's integrated clock. it holds the sampled voltage until the next sample is taken. it outputs the sampled and held voltage and the clock trigger.
you can select the source (LFO, AR, Noise...) and the clock time.
so depending on clock setting and soure it will provide random CV or stepped CV...
hope that helps (may be a little confusing)

cheers,
matthias

[EraSer]

Just a question:Could I substitute SP4T rotary switch with 3 SPST?

[fonik]

you could but you probably won't because in case you select more than one input the control voltages will be added and not mixed which will result in too high voltages.
one solution would be to never select more than one source (not desirable, cos you may will select two sources by accident and the TL084 can't handle input voltages higher than 15V)
the better solution would be to add a simple mixer circuit based on a TL072... (you can add as much inputs as you want to)

cheers,
matthias

[EraSer]

So is the TL072 mixer circuit used to prevent from high voltages?
Can you tell me if this schem is right?

Could I use 47kohm resistences?
thanks Matthias.


bye Matteo.

[fonik]

you got it right and the 49k is a typo! you can use almost any value. 47k and 100k are the most common values for SDIY.

the ratio between the resistors at the input stages and the resistor in the feedback path of the OPA define the amplification. replacing the resistor in the feedback path of one of the OPAs by an 50k pot will give you an additional depth control/attenuation wich could be useful...

cheers,
matthias