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DIY 1125 sample and hold...

System 55 • System 35 • Model 15

DIY 1125 sample and hold...

Postby noddyspuncture » Sat Dec 16, 2017 8:42 pm

Hi folks,

So, here's the first video of my DIY Moog 1125 sample & hold module... I got it working today.

Only using one channel of CV here, just the pitch for now, and playing my Minimoog. It's all working apart from the noise generator - the noise chip was getting warm so I removed it while I was debugging a few faults I had.

One IC I used which I already had - the 3080 - was faulty and would you believe, a transistor array IC that I bought brand new had one transistor in it that was open circuit..! I'm going to build this into a module to install in my Moog Modular... :D

Next up I need to check out the noise generator - would anyone know if the MM5837N should run warm to the touch...?

Here the video link: https://www.youtube.com/watch?v=0sOh4b2 ... e=youtu.be

Cheers,
Tom
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Re: DIY 1125 sample and hold...

Postby synthguy » Sun Dec 17, 2017 1:01 pm

Hi Tom:
Looks and sounds pretty cool! I've always liked S/H, and the Moog is a really good one. The section where you can mix in the sawtooth oscillator as a sample source is a great idea and yields a lot of cool sequencer-like riffs much like its more advanced LFO cousin in the Sonic Six, another fave.

The 5837s as I remember should not be warm to the touch, but even when these were new, they had a larger than average failure rate, at least for me. They also had a noticeable "repeating pattern" in the sound that was caused by the limitations of the technology at that time (internal shift register too short I believe).
Trying to find a good one these days could be difficult/frustrating.

After a while I went back to creating my own homegrown noise sources by using the old "reverse-biased transistor junction being amplified by a high gain opamp section" configuration. These are fairly simple to concoct and it's easy to find a transistor that produces a nice noise spectrum that works well as an audio source or as a random cv for something like your Sample and Hold.
Check some of the early Oberheim schematics for examples of this technique.

Again, awesome build, Tom!
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Re: DIY 1125 sample and hold...

Postby noddyspuncture » Sun Dec 17, 2017 5:24 pm

synthguy wrote:Hi Tom:
Looks and sounds pretty cool! I've always liked S/H, and the Moog is a really good one. The section where you can mix in the sawtooth oscillator as a sample source is a great idea and yields a lot of cool sequencer-like riffs much like its more advanced LFO cousin in the Sonic Six, another fave.

The 5837s as I remember should not be warm to the touch, but even when these were new, they had a larger than average failure rate, at least for me. They also had a noticeable "repeating pattern" in the sound that was caused by the limitations of the technology at that time (internal shift register too short I believe).
Trying to find a good one these days could be difficult/frustrating.

After a while I went back to creating my own homegrown noise sources by using the old "reverse-biased transistor junction being amplified by a high gain opamp section" configuration. These are fairly simple to concoct and it's easy to find a transistor that produces a nice noise spectrum that works well as an audio source or as a random cv for something like your Sample and Hold.
Check some of the early Oberheim schematics for examples of this technique.

Again, awesome build, Tom!


Thanks for the reply... regarding the noise chip - I actually bought two of those... from China... :roll: ... and both have no output. Nothing, dead..! I think I might have bought 'fakes'...!?

As my original 1125 has the same chip - and it might one day fail... I think I need to look into your suggestion.

I've built the noise generator from the Minimoog before now for my 700 series drum modules... :D

Cheers,
Tom
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Re: DIY 1125 sample and hold...

Postby ummagumma » Sun Dec 24, 2017 6:07 pm

just watched the vid, that is pretty wild!!

I hope you get it working 100%
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Re: DIY 1125 sample and hold...

Postby noddyspuncture » Mon Dec 25, 2017 9:24 pm

ummagumma wrote:just watched the vid, that is pretty wild!!

I hope you get it working 100%


Thanks, it is now working 100% - I've just not made another video of it yet... but here are a couple of photos I took today.

I am now working on the case - I have an R.A.Moog blanking plate, got a 'C' frame for it and am building the case from scratch. It's a lot to cram onto it so I'm taking my time and also engraving labels etc... still a way to go before it's done. :D

C_15.JPG

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Re: DIY 1125 sample and hold...

Postby ummagumma » Tue Dec 26, 2017 1:35 pm

wow!! supercool!!

merry xmas
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Re: DIY 1125 sample and hold...

Postby noddyspuncture » Tue Dec 26, 2017 3:36 pm

ummagumma wrote:wow!! supercool!!

merry xmas


Cheers... and A HAPPY NEW YEAR...! :D

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Re: DIY 1125 sample and hold...

Postby noddyspuncture » Sun Jan 07, 2018 1:15 pm

And the S&H module is now finished...!
Here's a vid... :D

https://www.youtube.com/watch?v=Fp7qjrLvT2U
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Re: DIY 1125 sample and hold...

Postby ummagumma » Wed Jan 10, 2018 10:08 am

YEAH!!!

how hard would it be to make those parameters CV controllable?
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Re: DIY 1125 sample and hold...

Postby noddyspuncture » Wed Jan 10, 2018 9:10 pm

ummagumma wrote:YEAH!!!

how hard would it be to make those parameters CV controllable?


Actually working on that idea... not for this module though... but as a modification to my actual 1125 unit..!

Gonna make the "Pattern" knob function CV controllable - a nice slow LFO sweep would do wonders on that one... :D
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Re: DIY 1125 sample and hold...

Postby ummagumma » Sat Jan 13, 2018 8:14 pm

hell yeah!

great idea
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Re: DIY 1125 sample and hold...

Postby synthguy » Sun Jan 14, 2018 9:58 pm

Wow! Your finished unit looks and sounds great, and has a lot of control over the functions.

How did you cut the slots for your slider pots? That has been one of those things that just seemed too difficult to do DIY for me, although I like sliders for some functions.

Congrats on an excellent build!
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Re: DIY 1125 sample and hold...

Postby noddyspuncture » Tue Jan 16, 2018 5:07 pm

synthguy wrote:Wow! Your finished unit looks and sounds great, and has a lot of control over the functions.

How did you cut the slots for your slider pots? That has been one of those things that just seemed too difficult to do DIY for me, although I like sliders for some functions.

Congrats on an excellent build!


Thanks..!
I marked three parallel lines and drilled a line of holes on each. I then used a coping saw with a blade for steel and joined them all together. Next I used needle files to slowly open then up into slits... took me ages, as I worked slowly. You can always take more off - got you can't put it back on... :)

Cheerz,
Tom
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Re: DIY 1125 sample and hold...

Postby noddyspuncture » Thu Feb 22, 2018 11:00 am

S&H unit installed in the Modular...

https://www.youtube.com/watch?v=nWiPjOx6N4M
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