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Synth-Werk 901A/BBB: tuning thoughts
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Author Synth-Werk 901A/BBB: tuning thoughts
Sir Ruff
I finally received these beasts and while they sound great, they have not been without their share of troubles as far as figuring out how best to tune/control them.

I was initially using an Arturia Microfreak but after an hour+ warmup I was finding that I couldn't get a decent octave's worth of in-tune performance (bottom/top notes were sharp/flat respectively). Heat from my (relatively cool) QPS-1 supply was suspected as the culprit so I moved the 901s from the middle to the top of my case and the back case panel has been left off.

I also found that using my Kenton Pro solo yielded better performance, so I switched to that for pitch CV.

Jump to this morning where, after lengthy warmup, I was still getting off octaves. Was it heat? Was the 901A calibration somehow out of whack after shipping?

Almost ready to give up on these things, I remembered that the Kenton has a Scale function, which ultimately saved the day. I am now getting about 3 in-tune octaves and I now can play both the highest and lowest footages with almost no problem (after oscillator tuning is adjusted).

Throughout this process, I was wondering: how the hell did old 901s EVER stay in the right scale if they were sitting above the PSU in a Model 15/IIIP case? I.e., my PSU/case situation is not unique, and certainly my QPS-1 MUST be cooler than those older supply. The answer it seems lies in the "Scale" knob that old Moog keyboards had. That would be performing the same function as the Kenton now. I'm still using the MF for pitch (midi to Kenton) and pressure and gate.

Aside from (hopefully) being able to put the back back on the case, this also has me thinking about moving the 901s back to their traditional spot in the middle of the case. However, I actually quite like this new layout, and because of certain case-module placement limitations due to DIY construction, I actually can't have it exactly how I want with the 901s directly above the CP3 anyway, so I may just leave.

Curious to hear how other people have dealt with 901 (new or old) scaling issues!

Current case layout:
EPTC
How abrupt is the scale shift? I dunno, I love the idea of a waveform shifting around in color and sound. I thought that was the appeal of 901 v 921.

Does it sound like the notes are literally transposing uncontrollably, or just ebbing/flowing?
Sir Ruff
EPTC wrote:
How abrupt is the scale shift? I dunno, I love the idea of a waveform shifting around in color and sound. I thought that was the appeal of 901 v 921.

Does it sound like the notes are literally transposing uncontrollably, or just ebbing/flowing?


In the upper end of the scale you get some whacky transposition. What I am talking about is basic single octave tuning--just getting 12 chromatically in tune notes in the middle of the scale. Nothing to do with the character of the thing and more just to do with the primitive pitch CV circuit as far as I can tell. Scaled properly now with the Kenton, it sounds as "in tune" as should be expected for a vintage oscillator (or even better). I.e., not rigidly perfect but also not annoyingly off!

Regarding changes in the waveshapes at different octaves, these are new oscillators so I assume Gerhard did his best to match the resistors throughout for consistency--I certainly don't hear or see any major variation when looking at shapes with a scope.

But the oscillators themselves are certainly moving/"alive"--they jump up and down by 0.1 Hz pretty consistently.
josaka
had some issues with mine at the start.. but found over time I got more settled with them.. not sure what settings you are after in that photo.. (fine tune turned left and playing the 4ft.. ? )
I tend to tune mine to C when the knobs are at 12 and keep the ft switch at 1 or 2 get and 4 octaves or so..
the tuning on the osc themselves is very fine ..slightly out on 2 osc it can be great or horrible..
the sweetest tone(and biggest difference from other osc is the pulse with the pulse turned counterclockwuse (narrow) )
at first I was a little meh..used them on a few tracks...now they are on everything.. with the 921s..
Dave Peck
Oscs that are more prone to scaling drift when subjected to changes in the temp of their immediate surroundings (i.e. internal cabinet temp) need to be calibrated while they are in those immediate surroundings and operating at stable operating temp (this assumes the cabinet's internal temp is actually fairly stable after warm up). So when you buy an osc like this and put it into a new cabinet, as opposed to buying a completed synth that should have already been calibrated by the manufacturer, you will likely need to calibrate the osc's 1V/OCT response for accuracy in that specific operating environment.

You can also compensate for poor 1V/OCT response by adjusting the output of the device that is providing the pitch CV, as you did with the Kenton, but that will only work if all of the oscs are out of calibration by the same amount. It's best to do the calibration at each osc. And it will have to be re-done on a regular basis, and also re-done any time the overall operating temp changes, like if your studio is a lot warmer in the summer than in the winter. This is normal.
josaka
having said this I did buy a 4th SW 901 and annoyingly it doesnt track well at all .. goes way out over 2 octaves.. gerhard was trying to sat it was a 'moog' thing.. so.. it could be an SW error.. but frustrating that you buy something and kind of feel like its your fault for them going out.. my 5 SW 921s all track perfectly.. just one erronious 901.

are all of your osc behaving the same..? or are they all different or is it just one..

if its all the same I would look at things you are doing..
Sir Ruff
DP
Sir Ruff
josaka wrote:
had some issues with mine at the start.. but found over time I got more settled with them.. not sure what settings you are after in that photo.. (fine tune turned left and playing the 4ft.. ? )


No specific tuning per se--Gerhard suggested started at Fixed Octave 4 Variable 0, and Oscillator 8' (i.e., 480 Hz) and then working down to check that internal scaling was accurate. So that's where they've been. But doesn't really make any difference since they sound fine at lower Fixed voltages now too (thanks to Kenton).

Dave Peck wrote:
You can also compensate for poor 1V/OCT response by adjusting the output of the device that is providing the pitch CV, as you did with the Kenton, but that will only work if all of the oscs are out of calibration by the same amount. It's best to do the calibration at each osc. And it will have to be re-done on a regular basis, and also re-done any time the overall operating temp changes, like if your studio is a lot warmer in the summer than in the winter. This is normal.


Good to know. I guess this will be the case if I throw the back on again. Right now it's been relatively cool here but once summer temps really kick in (in a no AC studio) then I'm guessing this will be more of an issue.
Sir Ruff
josaka wrote:
having said this I did buy a 4th SW 901 and annoyingly it doesnt track well at all .. goes way out over 2 octaves.. gerhard was trying to sat it was a 'moog' thing.. so.. it could be an SW error.. but frustrating that you buy something and kind of feel like its your fault for them going out.. my 5 SW 921s all track perfectly.. just one erronious 901.

are all of your osc behaving the same..? or are they all different or is it just one..

if its all the same I would look at things you are doing..


The oscillators themselves all behave largely the same--internal octave scaling is pretty much spot on for all of them and they all track from the 901A consistently, i.e., when one is out of tune, all are out of tune. Octave switching on the A OTOH has been much less accurate, so this has really pointed to the 901A and the CV input there as being the issue. I've ruled out all other variables so not sure there is anything else I can do other than rely on the Kenton scaling. Gerhard really couldn't suggest more than reduced temperature as much as possible, which i've now done.

I'm sorry to hear about your 901--that does sound like an oscillator specific problem. Can you try calibrating it? Gerhard seems reluctant to go that option but I personally wouldn't be able to deal with an oscillator that couldn't hold rough tune for two octaves (again, mine aren't perfect, but there is only a difference in a few beats between oscillators over that many octaves).

And you are right, the fine tuning on these is very finicky--it goes from nice phasig to straight beating quickly.
josaka
Sir Ruff wrote:
josaka wrote:
had some issues with mine at the start.. but found over time I got more settled with them.. not sure what settings you are after in that photo.. (fine tune turned left and playing the 4ft.. ? )


No specific tuning per se--Gerhard suggested started at Fixed Octave 4 Variable 0, and Oscillator 8' (i.e., 480 Hz) and then working down to check that internal scaling was accurate. So that's where they've been. But doesn't really make any difference since they sound fine at lower Fixed voltages now too (thanks to Kenton).



tbf.. should not need the kenton to sort this.. I would keep trying to sort them without the kenton.. smile

they dont track brilliantly set on different octaves .. but I think that is actu
ally seen as part of the 'charm' smile
Sir Ruff
josaka wrote:
Sir Ruff wrote:
josaka wrote:
had some issues with mine at the start.. but found over time I got more settled with them.. not sure what settings you are after in that photo.. (fine tune turned left and playing the 4ft.. ? )


No specific tuning per se--Gerhard suggested started at Fixed Octave 4 Variable 0, and Oscillator 8' (i.e., 480 Hz) and then working down to check that internal scaling was accurate. So that's where they've been. But doesn't really make any difference since they sound fine at lower Fixed voltages now too (thanks to Kenton).



tbf.. should not need the kenton to sort this.. I would keep trying to sort them without the kenton.. smile


I've honestly tried every variable--been back and forth with Gerhard multiple times now--and don't have the patience or temperament (get it?) to use them as they were. I also don't want to get my hands dirty (yet) with trying to calibrate, especially since it's impossible to scale them while they are sitting in the actual case (I got as far as fiddling with the P1 trimmer but found there wasn't much difference so left it as it came and closed it back up!)
Sir Ruff
josaka wrote:
they dont track brilliantly set on different octaves .. but I think that is actu
ally seen as part of the 'charm' smile


that's the thing--I couldn't get them to track well over ANY octave except when I had them out of the case and on my desk. Was not acceptable at that point!
josaka
maybe send them back.. I hate doing this but..
Sir Ruff
josaka wrote:
maybe send them back.. I hate doing this but..


If I hadn't found any solution I may have, but I'm happy with them now... As Dave Peck mentioned above it seems de rigueur that I would have to adjust scaling upon receipt, in a new case, etc.

p.s. just realized--we actually chatted about the 901s on FB ages ago. You were part of the reason I ended up buying them wink
trentpmcd
Possibly a different beast altogether, but using the Mos-Lab 901s, if I go through a mult, other than an active mult, I get about an octave or so before the signal starts to attenuate and they all go out of tune by the same amount. That's even if nothing else is plugged in to the multiple. Using an active multiples or going straight from my midi to cv I do pretty good for at least 4 or 5 octaves. At this time my pitch CV always goes through an stg active multiple, even if i don't touch the 901s, just to save the headache....
Sir Ruff
trentpmcd wrote:
Possibly a different beast altogether, but using the Mos-Lab 901s, if I go through a mult, other than an active mult, I get about an octave or so before the signal starts to attenuate and they all go out of tune by the same amount. That's even if nothing else is plugged in to the multiple. Using an active multiples or going straight from my midi to cv I do pretty good for at least 4 or 5 octaves. At this time my pitch CV always goes through an stg active multiple, even if i don't touch the 901s, just to save the headache....


that's really interesting to hear because I thought was experiencing something similar with the voltage summer on the Moon M544CP utility panel I use to direct pitch CV. It's not clear whether it's passive or active, but it's largely fine so the voltages sags I was receiving may not have been from that.

If anyone has any CP spaces in their case BTW, I highly recommend the 544--it's a really efficient one-stop shop for basic CV/Gate routing.
Dave Peck
trentpmcd wrote:
Possibly a different beast altogether, but using the Mos-Lab 901s, if I go through a mult, other than an active mult, I get about an octave or so before the signal starts to attenuate and they all go out of tune by the same amount. That's even if nothing else is plugged in to the multiple. Using an active multiples or going straight from my midi to cv I do pretty good for at least 4 or 5 octaves. At this time my pitch CV always goes through an stg active multiple, even if i don't touch the 901s, just to save the headache....


Yes, this is also a factor - the ability of your CV source to accurately drive multiple oscs, so it is really sending exactly 1 volt when you play the associated keyboard key, and ALSO really sending exactly 5 volts when you play the key that is four octaves up.

And some midi to CV products are better than others. Some will drive several oscs accurately, but only up to a certain voltage, like 3.5V, so your oscs will play in tune for those first three and half octaves but will be flatter and flatter on notes higher than those. So the overall scaling isn't off, it's fine for lower octaves but off for higher octaves, and calibrating the 1V/OCT trim on the oscs can't fix this.

Other devices, like an Encore Expressionist, have a more robust output and can produce an accurate output voltage over a much wider range like eight octaves even when driving six or ten oscillators.
josaka
I did a stupid thing when I got my 901s.. unwittingly left a lead plugged into my Q174 'add in' jack ...not attached to anything.. added chaos.. took me a while to track it down !!



Sir Ruff wrote:


p.s. just realized--we actually chatted about the 901s on FB ages ago. You were part of the reason I ended up buying them wink


hope they are not dissapointing sonically.. I find mine great.. always get something good smile I would say maybe try a second filter too.. to 'focus' the goodness.. works well with the roland style filters and the korg 700 stlye brings a whole new tone to the table.. thumbs up
noddyspuncture
On my two R.A. (and one home-built) 901a's I have moved the three calibration controls to the rear panel so I can calibrate without pulling the modules. I've also have added a small modification to each which means I can compensate for any 'scale' drift, from the front panel - which I have to do a few times during a live set. I get 5 octaves in tune no problem if I keep on top of it.... cool
Sir Ruff
josaka wrote:
hope they are not dissapointing sonically.. I find mine great.. always get something good smile I would say maybe try a second filter too.. to 'focus' the goodness.. works well with the roland style filters and the korg 700 stlye brings a whole new tone to the table.. thumbs up


yeah, definitely living up to what I was expecting--maybe I'm not sounding like Plastic Cow Goes Moog or Claude Denjean right out of the box, but it feels really good knowing I have the key ingredients there.

I've actually got a FSFX Lopass gate module (with resonance) as well--interesting filter flavor. I had an Oakley Journeyman filter (700/MKorg clone) but bought a 5U version without realizing that 5U and MU are different! d'oh! I will probably grab another one of those... i've got the roland sound covered pretty well with some other vintage monos, but it would be interesting to add that flavor to Moog oscs--who is making Roland-style filters in MU format?
josaka
corsynth/frequency central do rolands as do oakley krisp1 with the cota.. the journeyman in hp mode into the moog is lethal.. the longer you have the 901s the more they seem to produce.. smile
josaka
Sir Ruff
josaka wrote:
corsynth/frequency central do rolands as do oakley krisp1 with the cota.. the journeyman in hp mode into the moog is lethal.. the longer you have the 901s the more they seem to produce.. smile


awesome. just went ahead and grabbed the journeyman they had in stock. Will probably swap out the lopass gate, which is cool--has a really nice plucky snap to it with short envelope decay times--but maybe not different enough from the 904A.
josaka
those low pass gates are really good at the buchla bongo type sounds.. but not a lot else.. smile the journeyman high pass can do a pretty good buchla bongo + a load of other hp and lp stuff its great for targeting low harmonics and creating huge subs (..I think korgs are my favourite filters!(I have 4.. 5 if you count the korgasmatron as 2!).. that 80s electro sound is pure korg..). good move.. thumbs up

korg poly 61 filter same filter as delta and a few others from then.

johny_gtr
It looks like a hardware limitation because I have the same.
Kenton Pro Solo helps a lot with scale parameter (i have mine with value of -14 or +14).
After this configuration, about 4 octaves are in tune.

I have many hopes for Expert Sleepers + Silent Way software that can configure each note manually but I didn't help => hw limitation.

Anyway, they are best sounding OSCs in analog domain that I've heard and owned.
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