Does the A SOL MC-202 modular kit work on the SH-101?

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Synthbuilder
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Post by Synthbuilder » Wed Nov 03, 2010 8:11 am

meatcliff wrote:You can get the VCO outputs directly from the CEM ic
Not quite. Firstly all outputs should be put through a 1K resistor to prevent the VCO chip being put under too much stress should you short the outputs.

Secondly, the triangle wave from the 3340 is not buffered and should never be used to drive an output directly. Use a follower - I normally use a J201 FET follower - to buffer the signal.

Tony

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Post by boothnavy » Wed Nov 03, 2010 12:45 pm

Synthbuilder wrote:
Secondly, the triangle wave from the 3340 is not buffered and should never be used to drive an output directly. Use a follower - I normally use a J201 FET follower - to buffer the signal.

Tony
Any chance you have a little schemo for this arrangement?

something like this?

http://www.muzique.com/schem/eagle.htm

the in being from the Tri out of the chip and the out being the buffered output to a panel jack?
Last edited by boothnavy on Wed Nov 03, 2010 12:52 pm, edited 1 time in total.
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Post by meatcliff » Wed Nov 03, 2010 12:48 pm

Thank you for that, Tony. It's been years since I modded my sh101 and forgot about the sinking problems the triangle output has... Can't remember if I actually did buffer it when I did the mods, though - I yanked all the inividual in/out shortly after since I didn't use them frequently.

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Post by giorgio » Wed Nov 03, 2010 12:55 pm

i don't think i'll need the tri out, I might just toss a filter CV input and something else into the holes normally used for the mod grip and call it a day. trying to think what the 2nd best mod besides the filter input would be.... I have some 1/8" jacks... sitting at the post office
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Post by slow_riot » Wed Nov 03, 2010 1:05 pm

beware of individual audio outs from oscillator.

This caused a lot of bleedthru type noise into the main output after filter.

I had the mod done by ASol, and had to remove the audio outs.

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Post by boothnavy » Wed Nov 03, 2010 2:09 pm

slow_riot wrote:beware of individual audio outs from oscillator.

This caused a lot of bleedthru type noise into the main output after filter.

I had the mod done by ASol, and had to remove the audio outs.

DAMN.

anyone else have this problem?

that's kind of a deal breaker...
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Post by giorgio » Wed Nov 03, 2010 2:36 pm

what kinda of bleedthrough, like the VCOs bleed into the main output? trying to think why that would happen.

tony - what are you after? I think the filter CV input is mostly what I'm missing while using the SH-101, as I could use my clockwork's midi synced LFO to control it for some great basslines
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Post by slow_riot » Wed Nov 03, 2010 6:58 pm

yep bleedthru from oscs to main out. Not terrible, but for me it made the 202 pretty unuseable.

I did a little detective work before simply desoldering the cables. There is a big piece of cardboard covered in foil in the rear of the 202 case. I think this is possibly a shield against interferences? It was connected to ground. ANyways if I moved this sheild away from the new audio out cables from osc, this made the bleedthru better.

You could possibly use better shielded cables to carry osc signals. This is what Tom Carpenter at Asol recommended. He referred to the problem as crosstalk, and said it was unavoidable. The cables that he used for audio outs were not shielded.

I think that's everything I know. I'm not an expert in this subject by any stretch of the imagination.

I stuck with just using the CV mods and audio into filter. I sold the device in the end.

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Post by boothnavy » Wed Nov 03, 2010 7:10 pm

giorgio wrote: tony - what are you after? I think the filter CV input is mostly what I'm missing while using the SH-101, as I could use my clockwork's midi synced LFO to control it for some great basslines
yeah thats a big one. also the audio in to the filter would be nice. if i didnt end up doing the individual outs for the VCO, i may still do the LFO outs?

maybe i'll do nothing? I've had this thing 20 years now and never touched it...
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Post by Synthbuilder » Thu Nov 04, 2010 2:52 am

boothnavy wrote:Any chance you have a little schemo for this arrangement?

something like this?

http://www.muzique.com/schem/eagle.htm
That's a bit more than you need since you don't need to bias the input. All you need is the transistor, the output cap C2, the resistors R4 and R5. And I would add a 1K resistor in series to the output socket.

But watch out for the power supplies in the SH-101. There's some unusual grounding and floating rails due to the need to run it from batteries. If in doubt get someone to do it for you.

Tony

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Post by Synthbuilder » Thu Nov 04, 2010 3:00 am

slow_riot wrote:yep bleedthru from oscs to main out. Not terrible, but for me it made the 202 pretty unuseable.
Screened cables would have certainly helped although careful placement of any wiring should work too. Sometimes simply routing the audio wires away from the sensitive areas can drop crosstalk to almost nothing.

One of the problems with these sorts of mods is the sheer number of additional wires. And in the MC202 there is barely enough room for the Roland electronics let alone any extra stuff. The SH101 will be better in this regard because of the larger internal spaces within the instrument. Even so extra wiring to sockets mounted on the case does make future servicing a lot harder.

Tony

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Post by boothnavy » Thu Nov 04, 2010 4:36 am

Synthbuilder wrote: The SH101 will be better in this regard because of the larger internal spaces within the instrument. Even so extra wiring to sockets mounted on the case does make future servicing a lot harder.

Tony
the voice of experience... tis something i hadn't thought of..

WHAT? MY SH WILL NEVER NEED SERVICE...

:lol:
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