SH-101 tuning.

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SH-101 tuning.

Postby Sammas » Wed Jul 07, 2010 12:50 pm

Hey guys, I have a few questions regarding tuning up an SH-101. It sounds swell, all functions work but the
tuning/scale are off. This is adjusted via two small trimmers, one for tuning the VCO and another to tune the
scale (spacing of octaves).

What a ball ache! I'm doing as the manual suggests by using a lissajous curve on a scope, externally synced to an
F note at 442Hz. When you adjust the VCO tune trim pot, it alters the scale trim pot so it is a case of bouncing between
the too constantly setting them so the lissajous curve is static. Easier said then done. The trimpots are so finicky that it
is next to impossible to get them to both stop perfectly. When I had them really close (ie, barely moving) the scale was still
off according to my tuner (notice by ear also).

Is this natural/unavoidable? Would it be worthwhile replacing those 25year old trimpots for newer ones? Or should I just scrap the scope
and use the tuner directly to tuner those pots (still a ball ache).

Also, why the 442Hz reference? I would have thought soft synths and the rest of modern electronic music world was referenced
to 440Hz by default?
Nath Turn bull.
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Re: SH-101 tuning.

Postby Futureman » Wed Jul 07, 2010 1:46 pm

I've had to tune plenty of synths.. you think the SH-101 is hard.. thats an easy one. lol.

I do it by ear, with another synth (prefer a digital one thats set to just a saw)

Play a low note on the digi synth, play the same low note on the 101. Adjust the offset trimmer till they sound the same.
(It helps is the 101 is just a saw, and no resonance)

Then play a high note on the digi synth, and the same note on the 101.. adjust scale until they match.

Repeat both steps for a while.. (Maybe 5-10 times) untill the changes you are making are miniscule.

You need to make sure the DAC is calibrated right (From memory.. I think you need a DMM to get that right)
And, I can't remember if there is a trimmer for the octave switch also.

It could be that your trimmers are shot.. But I've never had them die on a 101. (Also, if you can, use a plastic screwdriver.. but I'm not sure the 101 is sensitive to a metal one or not.. )

I hope that helps?

Regards
Mike
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Re: SH-101 tuning.

Postby Chinagraf » Wed Jul 07, 2010 2:15 pm

A 442 is what most classical orchestras tune to, although some tune even higher. 442 is common in Japan. There is also the story that Japanese musical instrument manufacturers wanted to corner the school band/orchestra market so they pushed the standard of 442 for all their stuff, including electronic ones.
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Re: SH-101 tuning.

Postby Sammas » Thu Jul 08, 2010 1:01 pm

Futureman wrote: you think the SH-101 is hard.. thats an easy one. lol.



Heh. So I've heard... I imagine tuning something like a polymoog always results in the tech sobbing into a stiff drink.

I left it on over night and it seems to have settled down quite a bit in terms of tuning. The problem with the small plastic
trimmers is they "click" as certain random spots, presumably due to mechanic resistance which causes the measured value to
jump substantially even though I only adjusted the trimmer by the smallest amount. Heck, even a gentle tap on top of the trimmer
alters the resistance!

Cheers, Andy. Back to 440Hz it goes. Apparently German orchestras are pushing a 445Hz tuning reference!
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Re: SH-101 tuning.

Postby Futureman » Thu Jul 08, 2010 1:08 pm

Hey one other thing..

I've found on quiet a few 101's that the power switch is a bit average after 30 or so years.

tap around the power switch while listening to the 101.. does the pitch wobble?

If so, you could replace it. (Chips for brains) or you just work the power switch 30 times every time you use your 101.
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Re: SH-101 tuning.

Postby Hybrid88 » Thu Jul 08, 2010 6:15 pm

Futureman wrote:Hey one other thing..

I've found on quiet a few 101's that the power switch is a bit average after 30 or so years.

tap around the power switch while listening to the 101.. does the pitch wobble?

If so, you could replace it. (Chips for brains) or you just work the power switch 30 times every time you use your 101.

Yes!, I have owned two 101's, first one had it bad, second one is better but not perfect. I reckon most 101 owners just don't notice it as a problem. Do you know what the cause of the pitch wobble is? I was wondering if some DeoxIt would help but I have got a spare switch that I got from chips for brains if it gets worse. By the way why does hitting the switch 30 times make a difference?
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Re: SH-101 tuning.

Postby Futureman » Thu Jul 08, 2010 8:28 pm

The 101's internal power supply is crazy. DC-> DC conversion.

I think a slightly poor contact makes it go a little crazy. Why 10 presses helps.. I guess it just works the contacts..

I've never tried de-oxit on them, I just ordered a replacement for mine.
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Re: SH-101 tuning.

Postby Thirteen » Sun Jul 11, 2010 8:30 pm

Forget the oscilloscope. Warm up the synth, plug in a guitar tuner and adjust the 2 trimmers with your fingers as you play the top and bottom keys. It should take less than 30 seconds, it is the about the simplest synth to scale in the world.
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Re: SH-101 tuning.

Postby Futureman » Fri Jul 16, 2010 7:20 pm

Futureman wrote:Hey one other thing..

I've found on quiet a few 101's that the power switch is a bit average after 30 or so years.

tap around the power switch while listening to the 101.. does the pitch wobble?


I just replaced the power switch in my SH-101.. heaps better. no more wobbly pitch if I tap around the power switch.
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