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S&H sequence generator
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andrewF



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PostPosted: Tue Sep 23, 2008 6:16 am    Post subject: S&H sequence generator Reply with quote  Mark this post and the followings unread

Have been intrigued by this design for a while in Hal Chamberlin's book, Musical Applications of Microprocessors.
It would be easy enough to patch up....but funnily enough I only have one very basic S&H (from kuni921), never really got into using it much.

Anyone with 4 or 5 S&H modules and a mixer care to patch this up and report back?

I imagine 4 or 5 or more LF398 chips, a LM324, selectable feedback paths via an attenuator and individual stage outputs would add up to an awesome pattern generator.


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Etaoin



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PostPosted: Tue Sep 23, 2008 6:29 am    Post subject: Reply with quote  Mark this post and the followings unread

It might be patchable with a S&H and Ken Stone's ASR. I'll give it a try...
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Scott Stites
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PostPosted: Tue Sep 23, 2008 7:42 am    Post subject: Reply with quote  Mark this post and the followings unread

I was thinking about something along these lines a couple of weeks ago. I thought about calling it "Sample and Klee". Laughing

Double the number of LF398s and you would be in some very new territory.

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loss1234



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PostPosted: Tue Sep 23, 2008 8:13 am    Post subject: Reply with quote  Mark this post and the followings unread

you need to make yourself some more sample and holds!
when you run em through a quantizer or a slew...wow. they are so useful.

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andrewF



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PostPosted: Tue Sep 23, 2008 8:25 am    Post subject: Reply with quote  Mark this post and the followings unread

Scott Stites wrote:
I was thinking about something along these lines a couple of weeks ago. I thought about calling it "Sample and Klee". Laughing

Double the number of LF398s and you would be in some very new territory.


Let's make it 16 stages, shall we Smile
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bubblechamber



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PostPosted: Tue Sep 23, 2008 10:58 am    Post subject: Reply with quote  Mark this post and the followings unread

16 sounds good. always up for moving into new territory.
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loss1234



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PostPosted: Tue Sep 23, 2008 11:15 am    Post subject: Reply with quote  Mark this post and the followings unread

can someone recommend/post a SIMPLE schematic for a sample and hold, either using an lf398 or an opamp, so that i could try and make 4, 6 or 8...or more as a big module to try out this idea?

thanks

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Scott Stites
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PostPosted: Tue Sep 23, 2008 12:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

The simplest schematic using an LF398 is Rene Schmitz's YASH, IMO. It's got quite a bit of droop, but you can increase the size of the sample cap and sample width cap to decrease that.

It's really a nice little circuit - complete with clock, S&H, and external clock input using very few parts.

http://www.uni-bonn.de/~uzs159/

Click on "S&H" to the left, then click on "YASH" (Yet Another Sample and Hold).

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Scott Stites
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PostPosted: Tue Sep 23, 2008 12:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

You can also put a SPST switch across the pulse cap (470 pF), and it becomes a Track and Hold when you close the switch.
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bubblechamber



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PostPosted: Tue Sep 23, 2008 3:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

Scott Stites wrote:
You can also put a SPST switch across the pulse cap (470 pF), and it becomes a Track and Hold when you close the switch.


i'm a little shaky on the basics... are you talking about using a switch to bypass the 470 pF cap?
thanks
d

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Sine



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PostPosted: Tue Sep 23, 2008 4:07 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ooh, tricky ... even more if you want to daisy-chain them
precision becomes a huge factor because you will be adding an amount of error with each step.
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andrewF



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PostPosted: Tue Sep 23, 2008 4:50 pm    Post subject: Reply with quote  Mark this post and the followings unread

loss1234 wrote:
can someone recommend/post a SIMPLE schematic for a sample and hold, either using an lf398 or an opamp, so that i could try and make 4, 6 or 8...or more as a big module to try out this idea?

thanks

this is Kunii921's, about as minimal as it gets
Posted Image, might have been reduced in size. Click Image to view fullscreen.

http://masa921.hp.infoseek.co.jp/image/kairo/sh.gif
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bubblechamber



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PostPosted: Tue Sep 23, 2008 6:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

is this from the future?


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fluxmonkey



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PostPosted: Tue Sep 23, 2008 6:07 pm    Post subject: Reply with quote  Mark this post and the followings unread

bubblechamber wrote:
is this from the future?


no, from japan (which is similar)...

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andrewF



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PostPosted: Tue Sep 23, 2008 6:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

Sadly no, it is Japanese style YYMMDD
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Blue Hell
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PostPosted: Tue Sep 23, 2008 6:17 pm    Post subject: Reply with quote  Mark this post and the followings unread

andrewF wrote:
Sadly no, it is Japanese style YYMMDD


Almost ISO notation, good!

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urbanscallywag



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PostPosted: Tue Sep 23, 2008 6:52 pm    Post subject: Reply with quote  Mark this post and the followings unread

I'm a big fan of ISO style dates. Every day just gives an "increment" of the date number. Smile
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frijitz



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PostPosted: Tue Sep 23, 2008 9:54 pm    Post subject: Re: S&H sequence generator Reply with quote  Mark this post and the followings unread

andrewF wrote:
Anyone with 4 or 5 S&H modules and a mixer care to patch this up and report back?

OK, I just tried it with seven stages. It gives interesting patterns, but it's hard to predict and control. Probably not my favorite method of pattern generation. I used my TGTSH generators and found that the patern could also be varied by clocking off a TRI wave and varying the different threshold levels.

But I agree with Dan, a bank of S/H modules is definitely worth having.

Very Happy

Ian
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Peake



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PostPosted: Tue Sep 23, 2008 10:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ah, Japanese design- that explains the initial WTF transistors are those! effect Laughing

Are there any ICs out there which house multiple S/H cells? Individual I/O or single I/multiple O? Isn't there an SSM or Curtis IC for that? It would be good for this application.

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bugbrand



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PostPosted: Wed Sep 24, 2008 2:07 am    Post subject: Reply with quote  Mark this post and the followings unread

Well -- you can often use Analog Switch ICs for creating S&Hs - these are easy enough to find in quad versions and not too $$$

Analog Devices do a few..
AD684 - but $$$ and only +/-5v supply...
There's also the SMP0x range but these look to have internal sample caps and some are multiplexed (not what you'd want for this?)

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Scott Stites
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PostPosted: Wed Sep 24, 2008 6:06 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
i'm a little shaky on the basics... are you talking about using a switch to bypass the 470 pF cap?


Yep. The LF398 will pass any signal as long as the clock input is high (if it's configured to do so, which it is on the YASH). The cap creates a very thin, 3 uS pulse, so the LF398 passes the signal for 3 uS, then shuts off the input and holds the sample on the cap. By bypassing that cap, instead of a fast pulse, you get a high for as long as the clock is high. So while the clock is high, the output of the LF398 tracks the input, and when the clock goes low, the LF398 freezes the sample at that point. Very cool effect, esp if you're using an LFO as the input.

Take care,
Scott

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andrewF



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PostPosted: Wed Sep 24, 2008 7:53 am    Post subject: Re: S&H sequence generator Reply with quote  Mark this post and the followings unread

frijitz wrote:

OK, I just tried it with seven stages. It gives interesting patterns, but it's hard to predict and control. Probably not my favorite method of pattern generation. I used my TGTSH generators and found that the patern could also be varied by clocking off a TRI wave and varying the different threshold levels.

But I agree with Dan, a bank of S/H modules is definitely worth having.

Very Happy

Ian

cheers
it sounds a good option would be a bank of S&H modules on one panel with all the in/outs and trigger inputs pre-patched and an inverting/non inverting scaling mixer for the feedback paths, like the one on the top of the CGS VCO . it may be easier to control with negative feedback
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andrewF



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PostPosted: Thu Nov 20, 2008 4:26 am    Post subject: Reply with quote  Mark this post and the followings unread

well I'm 16 hours away from some beer and 3 months summer holidays Very Happy Very Happy Very Happy Very Happy Very Happy drunken
and one of my plans is to develop a circuit based on a series of S&H sub-modules.

It seems to me a cmos 4066 or two would do the job of 4 or 8 FETs.

Is there any reason not to use 4066 for switching the S&H? FETs seem a lot more popular in these ccts...why?


cheers
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bugbrand



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PostPosted: Thu Nov 20, 2008 6:09 am    Post subject: Reply with quote  Mark this post and the followings unread

I'd say use something along the lines of the DG211 (there's many variants - and be aware that some are active high while others are active low - that's shot me before)

Pretty much the same as 4066, but good with bipolar signals. Probably makes your ideas a whole load easier!

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Tim Servo



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PostPosted: Sat Nov 22, 2008 9:02 pm    Post subject: S&H sequence generator Reply with quote  Mark this post and the followings unread

Hi All,

So I'm a tad confused on the concept. I haven't actually tried this, but if you had several S/Hs connected in series and triggered by the same pulse, wouldn't they all "capture" the same voltage level? I mean, while the sample pulse is high, the circuit simply passes the input to the output. If this happens on several circuits in series, aren't you essentially connecting all of them end to end?

I would think that you would actually need to pulse the last S/H first, and then pulse the upstream units in turn. Now, you could do this with a single pulse driving several integrators / comparators (each int/comp would have a slightly different time constant so that the S/H units were triggered sequentially). Another (MUCH simpler) way of implementing a cascaded S/H array is the method Ken Stone and others use, where you trigger each S/H in turn, and merely switch the outputs using an analog multiplexer:
http://www.cgs.synth.net/modules/cgs34_asr.html

Anyway, I've gotten a bit off track here, but my basic question is, does the S/H configuration shown in the first post actually work, or do all the outputs go to the same level?

I await wisdom from those who have actually hooked this up and looked at the various S/H outputs. Smile

Tim (watch, I'll be out when the UPS guy delivers the wisdom) Servo
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