9v Sample and Hold

[Paul Perry (Frostwave)]

http://www.siliconchip.com.au/cms/A_101733/article.html
noise generator from Silicon Chip mag. At least it's designed for 9v!
Maybe try swapping transistors in the noise part, many noise circuits of the reverse junction breakdown type say to 'select transistor for max noise'.

[soggybag]

Here's an interesting S&H from the app notes of the LF412.
http://www.national.com/ds/LF/LF412.pdf
Look for typical application near the end of the document. It looks like Mouser lists TL072CN as a cross reference for this part. It seems to then that you could also use TL-082 for this design.

The white noise I had been getting souned pretty good and looked pretty good on the scope. But The transistor I'm using was the first one I pulled out of the bag, I used a 2n3904. I think you're right and the choice of transistor for the noise generator deserves more exploration.

[soggybag]

I found a very interesting article on Sample and holds here:
http://www.du.edu/~etuttle/electron/elect53.htm

It had a few things to say about capacitors. I think I'll have to read it through a few mores times to let all sink in.

[soggybag]

This is seeming to be the most succcessful attempt yet. Not perfect but it produced a very nice sample and hold especially when the duty cycle of the LFO was dialed to minimum. R2 sets the On duty cycle, it could be replaces with a very small resistor or even a wire. R1 sets the Off duty cycle. I used a 100K pot that worked well ffor testing but is too fast for real use, this will need a series resistance.

I auditioned every transistor in a bag of about 20 2n3904s and found there was one where the noise produced by it was far greater than the rest. Thanks for the suggestion Peter this may have helped a lot.

The Sample and Hold section here was taken from an App Hint on the LM13600 data sheet. The data sheet shoiws this running on a +-5V supply I just added a voltage divider.

The CV produced had a little more than 2V range and was very crisp and stair stepped.

[Jack]

This awsome I've always longed for someone with a better knowledge then me to put this circuit into 9v. Thankyou so much.
Just wondering, has anyone checked the ACTUAL CV range from the original schem?
Does anyone else think a two volt range, with perhaps a switchable voltage divider to select range would be a cool effect?

[soggybag]

I measured the original, that I made from the Tonepad PCB, and the CV range seems to be a little less than half the power supply about 8V.

The version that I made seems to have a range of a couple of Volts. This is not quite enough to make a CV for effects.

I think since the sample cap C4 is biased at Vr the CV range is going to always be a little less than Vr (a little less than 4.5V).

I have been thinking of ways to make the CV more useable. One method may be to use a LED/LDR, or maybe a photo FET.

I'm open to suggestions for improvements and ideas about how to get the best use of the CV. As is I think there is somemore work to be done.

I feel the diy effects community needs a good system of creating random voltages for controlling effects. Having it work from a single 9v supply makes it much easier to workw with.

[Paul Perry (Frostwave)]

I'm not saying this would be the most elegant way, but you could just add another amplification stage at the output of the 13600. If you use a rail-to-rail op amp, and get the biasing right, and the gain right, you should be able to get right from rail to rail.

[Eddie V]

fromhttp://www.analog-synth.de/synths/mod2/lfo_sh/lfo_sh.htm

how does that look?

im not sure what the deal is with power

[soggybag]

I wish there were smaller chip with with one or two switches on it. This looks worth a try. The 4066 is a 14 pin DIP and think this project would only end using one switch. I think it might take up too much space. There was a recent thread about using flip flops as oscillators. Which might be good, as the 4066 could be LFO and switch, this would eliminate one other chip from my plan.

[gez]

There was a recent thread about using flip flops as oscillators. Which might be good, as the 4066 could be LFO and switch, this would eliminate one other chip from my plan.

4066 isn't a Flip Flop.  However, as I pointed out in a previous post in this thread, you can wire up two switches of a 4016/4066 as a square wave oscillator and use one of the remaining devices as a switch.  Duty cycle can be altered using a diode(s).

There's a project that shows you how to do the oscillator over at Marcos/Munky's site.  Can't remember the name...CMOS Echo??

There's also info in Andy Flind's book Practical Oscillator Circuits on this type of oscillator (Babani Books).  The book is still in print and worth getting as it teaches the basics.

[zachary vex]

there's always an H11F1 or H11F3 optoisolator.

[soggybag]

Thanks for the suggestion. I have two of those left over from building a Neutron, I bought the optoisolators but ended up using LED/LDR.

I'm not quite sure how these work, since I have never used them for anything. Do these need to be biased in any way?

Looking at the App notes I find they suggest a very simple sample and hold circuit. Originally I had been thinking of using this as a system to convert my CV to a more useable range.

Thanks for bringing this up the H11F1 appears to ripe for exploitation!

[Jack]

Just curious to see if anyone's tried the h11F1 yet?

[Dave_B]

Just curious to see if anyone's tried the h11F1 yet?

I just ordered one yesterday for a triggered gate, similar in concept to R.G.'s stutter circuit if you're familiar with that.  The on-off times look pretty promising if it doesn't sound like a credit card in bicycle spokes.   

[soggybag]

I did try out the sample and hold app note for the H11F1/3. It worked pretty well. I had to put this idea aside for a little while and let it stew. But I think it may be time to get back to this and make some thing with it.

I got the best results from the H11F1 app note and the app note for the 13600. The problem seemed to be to scale the CV to a voltage range that was suitable to control something.

I had been thinking lately that the noise as a sample source may be limiting the range. It might be a good idea to try a pseudo random LFO made from a couple of inverters as the sample source.

[Jack]

It seems the problem comes from the circuit being lifted from a +_ 15v environment.
Why not lift the sample and hold section for a 9v environment, such as the SH-101:
Schematic halfway down

http://www.emusic-diy.org/RolandManuals

The noise generator is clearly marked on page 7, though I'm not sure about the sample and hold section.