SH101 and other monosynths

shopunit · Post by **shopunit** » Wed Jun 11, 2008 9:27 am

I have a somewhat problematic SH-101 and an even more problematic technician. A problem the synth has-- which reeeally bothers me-- is that when playing notes from low to high, the higher note will not "steal" the first lower note if I still have it held down. Going high to low, however, it works fine. I can hold down a high A and, with it still held down, I can press any key lower than it and it will successfully take over. It will NOT do the same if I press a key higher than it. It's as if there is a "priority" switch somewhere on the synth that I don't know about. My tech has no clue what the h**l is going on so I'm coming to you guys.

At first I thought this was just a problem with my particular synth, but when I was playing a Moog LP at Sam's a*s the other week, it had this same exact problem! Going high to low, no problem. Going low to high, problem. And this is coming from a brand new- not even sold yet- Moog.

I mean... is this normal? When I put my 106 into mono mode it works exactly how I want it to, higher notes stealing from held down lower notes, visa versa. Anybody have anything to say please let me know!
Thanks!

SickMonkey · Post by **SickMonkey** » Wed Jun 11, 2008 10:12 am

I'm pretty sure that's how the old monosynths work. They either scan the keyboard from the bottom up, or the other way. Can't have both.

Synthaholic · Post by **Synthaholic** » Wed Jun 11, 2008 1:27 pm

Most vintage monosynths don't "scan" the keyboard at all, as they don't have CPUs in them. Instead, the keyboard is just a voltage divider that generates a control voltage corresponding to the key pressed. Depending on how the keyboard is wired, either the lowest note will take priority or the highest.

Polysynths such as your 106 use a CPU to scan the keyboard, which allows a last-note (or first-note) priority scheme to be used.

The Moog LP does have a CPU, and I think its note priority can be changed. The one you played with was set to low-note priority, but I believe it can be set to high-note or last-note priority.

shopunit · Post by **shopunit** » Wed Jun 11, 2008 2:30 pm

Daaah. So I'll never get my way with this little thing I guess. Thanks for the advice.

Can it be rewired?

Post by **Solderman** » Wed Jun 11, 2008 4:04 pm

The 101 uses its CPU to scan the keyboard, so there is probably a way to reverse it, although I'd assume it's going to be hard wired one direction or the other.
What you can do is get a Kenton Pro-Solo or Pro 2000. Either unit will convert Midi to CV In, and allow the choice of key note priority. As a bonus, a Midi CC can change the direction on the fly.

I've also modded my 101 to send a CV to filter cutoff. Then I use an Aux channel on my Kenton converter to put out a CV for Midi Velocity, and presto, Velocity controlled cutoff for more expression.

MarkM · Post by **MarkM** » Wed Jun 11, 2008 4:17 pm

Synthaholic is correct regarding the Little Phatty. You can change the note priority just as he said. The Voyager can do it as well.

Mooger5 · Post by **Mooger5** » Wed Jun 11, 2008 5:41 pm

Shopunit, your SH-101 has low note priority typical of earlier monos like the Rogue. That´s indeed surprising as my 101, as well as another one I owned, both have last note priority. Recently I replaced a faulty cpu chip and the new one also features last note priority.

The keyboard in my MC-202 is scanned by a microprocessor just like the 101, but it has low note priority (which is adequate for entering notes but not so much for live use). So it can be a cpu program thing.

If every other function controlled by the cpu (like the seq, arp, and S&H) in your 101 is working normally, the chip seems OK but you might check the version. The 80C49 processor has built-in mask ROM which means it came pre-programmed from the factory. Current version should be TMP80C49P-6 7301. If the last four digits are different, chances are you have an early one. If not, well...

Synthaholic · Post by **Synthaholic** » Wed Jun 11, 2008 6:08 pm

I never knew the SH-101 had a CPU scanned keyboard, or a CPU for that matter. But I guess if it has a sequencer or arpeggiator, that would make sense.

Mooger5 · Post by **Mooger5** » Wed Jun 11, 2008 8:42 pm

Yes, instead of series resistors there´s a 4x8 matrix. So there are 12 wires going from the keyboard pcb to the cpu. The cpu constantly reads whatever matrix combination is on, attributes the note internally and sends the information to a dac that will translate to cv and gate signals. Looks complicated, but it takes way less time to calibrate.
So, under the keyboard there´s a 4 pin connector and an 8 pin connector for the 12 wires. The kb pcb is not of very good quality, the copper traces are really thin and it´s easy to brake them by pulling out a connector if you´re not careful. Bizarre malfunctions can happen. A loose matrix wire will mean a group of 8 keys will not play while the rest of the keyboard still works. Someone might want to solder the wires directly to the pcb, but if the wires are inadvertently swapped some groups of notes will sound in the wrong keyboard region. Still, I don´t see the matrix responsible for note priority. It´s all done inside the cpu.
The LFO Sample and Hold function is also software generated.

Mooger5 · Post by **Mooger5** » Wed Jun 11, 2008 9:32 pm

Keith Phillips wrote:On my SH101 it has switchable low-key priority and last-key priority by using the Gate/Gate+Trig toggle switch. Hitting extra keys above or below never changed the sound at all (except where it was supposed to, for doing the nice staccato bass stuff.

This was just posted at another thread. Funny how in all these years I´ve never used the Gate function for keyboard playing, just for sequenced effects.

Well, shopunit now you know where the "problem" is. But if it persists, it´s obvious where your tech shall look at.

So my guessings about an older chip version were wrong.
Now I´m going to find if the Gate+Trig/Gate is still managed by the cpu or not. Just to "grok" this synth, once and for all.

shopunit · Post by **shopunit** » Wed Jun 11, 2008 9:36 pm

this is crazy. i've had some issues with this particular 101. the pitch bender on the synth will bend notes up one full octave but not down one full octave. the mgs-1 grip will bend notes up about +10 semitones but not a full octave. I had my tech look at this for about a month and he couldn't figure out how to fix it so he gave it back to me (after charging me for labor, bless his heart). earlier I had the contacts under the keys replaced, which has made a noticeable difference. So yes- the synth has been worked on/tampered with recently. but this low note priority really sucks for live playing which I will be using the synth mostly for.
I'm considering selling the thing and starting over with a different one off eBay or something.

shopunit · Post by **shopunit** » Wed Jun 11, 2008 9:54 pm

WOW! I can't believe it, that completely fixes the problem. You guys are great- thanks so much for the discussion, advice, and help.

I switched over from guitarist to synthest (if that's a word) last year and I had gotten so used to people in the guitar world being such A-holes all the time- It's a fresh breath of air to be met with more courteous people in the keyboard world (both in actual music stores and online forums). Thanks again.

hfinn · Post by **hfinn** » Wed Jun 11, 2008 11:26 pm

shopunit wrote:this is crazy. i've had some issues with this particular 101. the pitch bender on the synth will bend notes up one full octave but not down one full octave. the mgs-1 grip will bend notes up about +10 semitones but not a full octave. I had my tech look at this for about a month and he couldn't figure out how to fix it

He couldn't even figure out the note priority (non) issue? For real? Time to get a new tech.

Post by **Solderman** » Thu Jun 12, 2008 5:21 am

shopunit wrote:i've had some issues with this particular 101. the pitch bender on the synth will bend notes up one full octave but not down one full octave. the mgs-1 grip will bend notes up about +10 semitones but not a full octave. I had my tech look at this for about a month and he couldn't figure out how to fix it so he gave it back to me

Sounds like either R6 was a short or R26 was an open. I agree with hfinn. Find a different tech.