Moritz Klein Simple sample and hold

I built this module and it seemed to work fine on breadboard. When I put it on strip board I could only seem to get it to take the gate signal from my LFO if I wired it straight into the non-inverting input on the op amp. Even then it was acting strangely but not terribly. LOL. For some reason running it through the wave shaper will not work at all. I tried it again on the breadboard and I got the same result. I’ve had similar issues with other circuits working on breadboard then not working at all. The gate I’m using is around 7 volts + and -. Would it help if I put resistance between the non-inverting and the output on the op amp? I’m wondering if my gate just doesn’t have enough power…

1 Like

I’ve decided to do some experiments and just managed to “fix” the problem. Lol. I switched out the 1nf cap at the gate input for a 10nf and placed it where the diode was, and placed the diode where the cap was. Traded places. Now it works just fine. Great super simple module all together!

I don’t really understand the point of that diode anyway. The comparator threshold is positive (12*33/133 = 3 V) so anything negative isn’t going to affect it. All I can see it doing is it reduces the input voltage. Unless the op amp is single supply, then maybe the diode makes sense as protection. I haven’t watched the video but I’m guessing that isn’t the case.

In the original the RC time is 1 nF*(100k+100k) = 200 µs. In your modification the RC time is 10 nF*100k = 1 ms. I have no idea why it would work on breadboard and not on stripboard, but presumably the 5x longer trigger pulse overcame whatever it was.

I’ve had other similar experiences with breadboard testing. I have success with the test then I solder a strip board that doesn’t work as intended or even at all. I then move back to the breadboard to troubleshoot and then THAT circuit may or may not work…in this case the breadboard no longer worked right either. You’ve helped me with this type of problem before. I just got lucky and managed to guess in the right direction this time. I don’t like to give up either. I am persistent. Thanks for having a look at it. It’s a super neat module. I never even used a SH before. Im gonna build that YASH too.

Update: I’m about to add some modifications to this module…an internal gate source with a switch and a switchable stand alone slew circuit. I found the mods at Erica synths website. You gotta download the user manual for the es edu mk sample and hold. I don’t wanna just post it. It’s free to download. I just feel like they might want you to at least check out the site… :wink:

I was about to breadboard this and noticed that Jan Knipper (@jkb) has an almost identical design in his github. Apart from the addition of a noise source (amplified by the spare op amp one has in a quad package), there is a different arrangement of the components at the trigger input. Perhaps there’s something better to try?

1 Like

The configuration at the trigger input detects a rising edge and only passes the positive component of that. This gives us a short impulse to sample at a specific point in time and not over a longer range.

1 Like

I had to do some rearranging of the trigger input components with this schematic as well. I just had to switch the places of the diode and the capacitor. I couldn’t get it to work at all the other way around.

I’ve got white noise on mine, but I’m gonna build the MK noise generator with white blue and pink noise. That with the internal clock and slew added on will give some spice to this little s and h.

1 Like

I was thinking that with a quad opamp, the spare opamp could be used as an internal clock generator for the S&H circuit.

1 Like

Definitely. The modified circuit does just that, and the slew circuit is a super simple add-on as well. I just glued an lm358 straight to an empty spot on the back of the panel and did a point to point soldering job without any strip board. I may as well post it. I mean it is free to download on Erica synths website…

So far I have done the clock and the slew. I just need to wait for some supplies then I can do the noise generator. On a fun side note, I actually have a tattoo of that clock generator on my arm.


I tried the noise module only to find my s and h won’t take the signal…I tried the white noise circuit that I already had on the strip board with the s and h and it doesn’t take that one either. It still works with my lfo but I’ve tried 4 different white noise circuits and it just does nothing :roll_eyes::thinking:

Do the noise circuits work fine by themselves?

I built the noise circuit a couple of times and it works just fine. Levels are good. :+1: The main only error possible is the transitor installed the wrong way…

Are you trying to trigger the S&H with noise instead of an LFO connected to external trigger? I wouldn’t expect that to work. I would expect it to be able to sample noise if connected to the signal input though.

Yeah, they all worked as noise. I could get something if I unground the output jack of the wht noise from the breadboard of either of them. Grounded I got nothing. I wonder if I didn’t have enough decoupling on the power rails. I usually just keep them plugged into the power rails on my breadboard. I don’t remember adding any though. Breadboard has a delay circuit on it as well but it’s got plenty of decoupling. I put the module back in and hooked up to the regular rack and power source. I did another test before I went to bed last night because I was restless and the white noise coming from my module seems to be working fine as a source at the moment…:grimacing: I will try again this evening…

Yeah I played with different transistors and all of them got tried in every orientation just to be sure. :joy:

No, I’m trying to use it as a random source signal. The trigger is coming from my clock divider. Trigger works with nearly every pulse I’ve tried. I have the trigger components arranged a lil different from the schematics, tho. I couldn’t get any trigger to work as the schematics have the input.

Can you show how you have arranged the trigger circuit, ideally a small schematic of that section. If youve already solved the problem forget about the schematic, but please share how you got it working as Id like to build this once Ive finished the ADSR project Im working on currently.

There are some more simple S&H circuits here:

I built the YASH. Works pretty well, but with the specified values the droop rate is high. I’m planning on changing out the 1nF and 470pF caps for 10 nF and 4.7 nF which should be an improvement.