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Roland System 100
MUFF WIGGLER Forum Index -> Modular Synth General Discussion Goto page 1, 2  Next [all]
Author Roland System 100
Vincent
Hello people,

I have a Roland system 100, model 101 and I'm having trouble sending it keyboard CV from either my Moog Mother 32 or Doepfer M.A.U.S.I.

For sending most CV from my Moog to the roland I use booser (Erogenous Tones Levit8) BUT I thought the Keyboard CV should work just fine. It's all 1v/octave right? Specs didn't seem to clear to me.

I've managed to get it to work using the booster but it's fiddly as heck. Without it I lose about 30 cents an octave. What's up with that, this is a nightmare!

Love y'all. x
Paul Perry
Applying logic:
Do the Moog & the Doepfer produce exactly the same results on the Roland?
If so, then the Roland is out of adjustment (unsurprising for a synth that is 40 years old this year). It's to be expected.
Vincent
Hey Paul

I think they do produce the exact same results but your logic is incomplete.

It may mean that it needs adjusting (I did it myself very recently and don't find it unbelievable that I haven't done a pro job) but the Roland stays in tune when using its own keyboard so I suspect it just wants a hotter external CV signal than what I'm currently offering it.
Stevie Ray
Vincent wrote:
Hey Paul

I think they do produce the exact same results but your logic is incomplete.

It may mean that it needs adjusting (I did it myself very recently and don't find it unbelievable that I haven't done a pro job) but the Roland stays in tune when using its own keyboard so I suspect it just wants a hotter external CV signal than what I'm currently offering it.


"your logic is incomplete" FFS.

Paul Perry asked you a very pertinent question regarding the problem you were having and you waffle on and insult Paul with "your logic is incomplete".

Wow!
cycad73
you are using the input on the back, right?
CV should be 1V/oct and track identically to the keyboard.
Vincent
Stevie Ray wrote:
Vincent wrote:
Hey Paul

I think they do produce the exact same results but your logic is incomplete.

It may mean that it needs adjusting (I did it myself very recently and don't find it unbelievable that I haven't done a pro job) but the Roland stays in tune when using its own keyboard so I suspect it just wants a hotter external CV signal than what I'm currently offering it.


"your logic is incomplete" FFS.

Paul Perry asked you a very pertinent question regarding the problem you were having and you waffle on and insult Paul with "your logic is incomplete".

Wow!


?? Nice of you to look out for your wigglin' bros Stevie but no offence was intended.
Vincent
cycad73 wrote:
you are using the input on the back, right?
CV should be 1V/oct and track identically to the keyboard.


Thanks Cycad. I've tried back and front. Same goddam story.
depth20
Check the jacks so the aren't broken. Almost all of my jacks have gone faulty, you don't always feel that they're broken. The 101 is a joy to work on, easy to open up and easy to service. You just unscrew four screws on the top and fold up the panel, it's hinged.
Vincent
I've tried several jacks… doesn't appear to be that.

Yeah, I've been getting inside the beast. Agreed, It is a joy to service - I've actually just gone through the power, key cv and vco adjustments now to make sure I wasn't simply being an idiot.

Again, tracks near-perfectly across its own keyboard but again, loses about 30 cents an octave win external key CV. This is nuts right?

If anyone has an answer to this I will send them a lock of my hair.
Paul Perry
Nobody needs a lock of someone's hair than I do. meh

A possibility: the keyboard section is generating voltages that are a bit off, (compared to standard) and the oscillator section has been tuned to compensate for this.
Synthbuilder
Paul's quite possibly right. The System 100 is in tune with itself and to do that it doesn't need to be exactly 1V/octave. So long as the 101's VCO is trimmed to work with the 101's keyboard all will appear to be well with the 101.

The KCV ADJ trimmer in the 101 adjusts keyboard output voltage. This needs to be set so that you are producing exactly 1.000V/octave +/-2mV. However, this isn't so easy to set that accurately as the resistors in the keyboard circuitry aren't that precise. You'll find that you'll get a different voltage jump going between F1 & F2 and C1 & C2. It also depends on how good your voltmeter is.

Now once KCV ADJ has been trimmed to as close as you can get it, then you can re-trim the 101's VCO via VR201 and VR203 on the inside.

However, if it were me, I'd trim my 101 VCO (via VR201 and VR203) to track the external CV first as we can probably assume that the Moog is putting out an accurate 1.000V/octave. Then adjust KCV ADJ to make the 101's keyboard fit the newly trimmed VCO.

Tony
flo
It could have to do with the fact that with only the 101, you only have one PSU. While you have several when using external sequencers. The 0V references could be off between the PSUs.

Also, there's a rather long thread about impedance problems with the M32 keyboard CV output... I would not trust it to put out 1.000V/oct. https://www.muffwiggler.com/forum/viewtopic.php?t=153912&start=0
Synthbuilder
flo wrote:
It could have to do with the fact that with only the 101, you only have one PSU. While you have several when using external sequencers. The 0V references could be off between the PSUs.


Could be but I would expect there to be a problem with all notes if this were the case. That said a good strong connection between 0V is always to be recommended.

Quote:
Also, there's a rather long thread about impedance problems with the M32 keyboard CV output... I would not trust it to put out 1.000V/oct. https://www.muffwiggler.com/forum/viewtopic.php?t=153912&start=0


Oh dear. So it could be that Moog have got a 1K resistor in their CV output? That's pretty poor if that is the case. But the OP's Doepfer does the same too which would suggest that MAUSI has the same problem. Time for a buffered multiple perhaps.

It's certainly worth checking the output of the Moog when it's plugged into the 101. If it can't manage 1.000V/octave then a buffered mult may be the best option.

Tony
cycad73
Synthbuilder wrote:

Oh dear. So it could be that Moog have got a 1K resistor in their CV output? That's pretty poor if that is the case. But the OP's Doepfer does the same too which would suggest that MAUSI has the same problem. Time for a buffered multiple perhaps.


Paul's explanation, that the keyboard output voltage was badly scaled (say, 1.1 V/Oct) and the oscillators were tuned to compensate, is simpler and more plausible.

I had exactly this problem with an Odyssey once, it was easily fixed.

Seems worth it to have a tech look this over.
Vincent
Wow thank you all so much! we're not worthy
What a bunch of cool guys.

This all makes perfect sense. I'll look into it when I can and let you all know how it went.

Thanks again!
Paul Perry
I haven't seen the Moog or Doepfer 1K "output" resistors, but maybe they are inside the feedback loop as in this Ken Stone CGS circuit http://www.cgs.synth.net/modules/cgs04_mix.html I believe that this does not suffer from loading, since the feedback is taken from the circuit output (not the chip pin). It is there to protect the chip against a direct short on the output pin.
Vincent
Hi all,

Despite saying "this all makes perfect sense" (I saw your posts after a few drinks) I'm pretty lost while reading some of this.

But now I see that the Mom32 is not quite outputting 1v/octave. It's more like 0.98v/octave. And, yeah, the manual is super vague on calibration.

Does anybody know what I can do to fix this? I've read of an internal trim pot, anybody got any info on this?

What's a buffered multi?

Cheers everyone x
Paul Perry
Vincent wrote:

What's a buffered multi?


An unbuffered multi is just a bunch of jacks connected together, so a voltage sent to one can be sent unchanged from all the others.

Now imagine that instead of electric currents, you were doing this with a junction of water pipes. Connect one end to a tap, and you get water at the same pressure at all the other outlets........ BUT!!!... when you draw off any water, the pressure drops.

And with a modular it's the same, connect stuff up to the mult and as you add more gear the voltage falls a bit & everything detunes. Unless you have an active mult, which is a module (or part module) that looks like a normal mult, but has electronics inside that maintain the original input voltage at the outputs.
Vincent
Ah Thank you Paul!!

This makes sense but now I'm struggling to imagine how it'd help regulate the voltage coming from the Moog.
Nils
Synthbuilder wrote:
Paul's quite possibly right. The System 100 is in tune with itself and to do that it doesn't need to be exactly 1V/octave. So long as the 101's VCO is trimmed to work with the 101's keyboard all will appear to be well with the 101.


I've had this with several Roland SH synths.
rsaintjohn
I'm going to piggyback on this same topic as I'm running into a curiosity with my Model 101. I'm running into a problem where the pitch slowly increases out of tune over time.

Details: I've been running MIDI sequences to the Roland SBX-1 Sync Box and out CV/Gate to the 101. It's only in the past week that I've been playing along with other gear, and noticed that the 101 was slowly going out of tune. I spent last night and today doing a bunch of troubleshooting to see if I could ID the culprit.

Initially, I was running CV/Gate to the 101 to its front panel; specifically, the "Ext CV Input" jack in the VCO section, and "Ext Gate Input" in the Envelope section. I made sure the 101 was tuned to "A", and ran a continuous note to it. Using a tuner app, I saw that the pitch was slowly rising about 5 cents per minute. After an hour or so, the pitch is way up. But, really, it's only a matter of minutes before the 101 sounds out of whack with everything else that's running.

I tried some different sources, made sure the temperature in the room was stable, but I could always repeat this result. I did notice that once it went out of tune, the osc would re-tune itself to the proper pitch if I tapped the A4 key on the keyboard (even though you can't hear it when these jacks are plugged in).

Out of curiosity, I unplugged the jacks, put a weight down on A4, and walked away for a few minutes. Came back, and tuning had not drifted at all. Went shopping, came back, all good.

Then I tried plugging the CV and Gate cables to the back of the 101, to CV In and Trig In. Ran the test again, and again, rock solid. No drift at all, and tracking was perfect.

So this last one (use the back jacks) is a good workaround to the pitch drift I get when I plug into the front surface, but I don't understand why I'm seeing a difference. If it was just the keyboard alone that managed to stay in tune, I'd guess that the answer was as above, "oscillator tuned to irregular keyboard voltage". But I'd expect the Ext CV input on the back and on the top/front to produce the same results.

I looked over the service manual, but it's mostly beyond me. I could try to do some further testing with a multimeter, but I'm not sure what to look for as I don't have any reason to think that the SBX is putting out slowly increasing voltage. I have a decent workaround, so it's not a showstopper, but I'm curious as to the cause, and if there is something I could or should do to get that input stable.

Any advice appreciated!
cycad73
Sure, with the slider all the way up, the Ext CV in the VCO section doesn't track over more than 2-3 octaves.

Fortunately it over-tracks, so one can usually back off on the slider and get something in tune when adding modulations to the main sequence. I've always thought it's meant more for FM or interfacing with the 104, where one can adjust the knobs to keep things in tune (but seems you have temperature drift, which is not typical)

As you discovered, the back CV control is the main control and should track 100% (especially because there's no slider).

With the 102, main CV/gate inputs move to the front panel (Kybd CV/gate), so it's less confusing. 102 also has the slider-controlled Ext CV, which behaves in exactly the same way.
rsaintjohn
Thanks for the reply. I'll have my 102 shortly, so I'll have something similar to which to compare; and I'll be interested to see how they interact with each other.

I did check the 101 and the front panel jacks in pair with the 104 feeding it notes, but get the same results over time. Pitch slowly drifts up.

cycad73 wrote:
(but seems you have temperature drift, which is not typical)


So is that the most likely explanation? Internal temperature is causing the osc to drift?

Thanks again!
ranix
No, if one CV input is rock solid and the other input is drifting you do not have temperature drift.

I think it's more likely the input on the front is an exponential input intended for frequency modulation and the input on the rear is a 1v/oct input intended for pitch tracking. But I know nothing about the System 100 and have never seen or used one in person, so don't take my word for it. If the front input is obviously for the keyboard, maybe there is something wrong with that part of the circuit.
rsaintjohn
ranix wrote:
No, if one CV input is rock solid and the other input is drifting you do not have temperature drift.

I think it's more likely the input on the front is an exponential input intended for frequency modulation and the input on the rear is a 1v/oct input intended for pitch tracking. But I know nothing about the System 100 and have never seen or used one in person, so don't take my word for it. If the front input is obviously for the keyboard, maybe there is something wrong with that part of the circuit.


That makes sense, thanks. That panel is not really used for the keyboard as the keyboard is already directly attached. The documentation is great, but aimed at the "this is your first synth" crowd of the day, and not very deep. I'll know more in a few weeks.
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