MOTM-300 Ultra VCOs

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JohnLRice

MOTM-300 Ultra VCOs

Post by JohnLRice » Tue Jul 06, 2010 1:18 am

I'll let you folks stew on this for a while . . . :twisted:

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syzygywell
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Post by syzygywell » Tue Jul 06, 2010 1:29 am

:woah:

what is with that knob? I wanna touch it.
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Post by dude » Tue Jul 06, 2010 1:35 am

john, are those 10 turn? every time is see those knobs it gives me this strange feeling of being in gym class trying to open my locker.

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Post by BlueOctopus » Tue Jul 06, 2010 1:37 am

Mighty Purty

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Post by slovo » Tue Jul 06, 2010 1:57 am

:jawdrop:
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John Nonjohn
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Post by John Nonjohn » Tue Jul 06, 2010 1:59 am

So, how about this: replace the fine pot with a FM #3 pot, and stick an FM #3 jack on the front panel!?
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Post by SepticUnderground » Tue Jul 06, 2010 2:29 am

dude wrote:john, are those 10 turn? every time is see those knobs it gives me this strange feeling of being in gym class trying to open my locker.

nice modules yeah, crack the safe 300â„¢ hehe

isnt 4 a bit too much JLR :D
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Post by bwhittington » Tue Jul 06, 2010 6:19 am

Wow, it looks like you jacked those from the (so far) mythical Macbeth oscillator.

Cheers,
Brian

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Post by bwhittington » Tue Jul 06, 2010 6:21 am

dude wrote:john, are those 10 turn? every time is see those knobs it gives me this strange feeling of being in gym class trying to open my locker.
. . . but not being able to because you were in awe of the guy next to you with the giant knob? :mrgreen:

Cheers,
Brian

Babaluma

Post by Babaluma » Tue Jul 06, 2010 6:27 am

looking nice, a bit of the old vcs3 style vernier geared dials?

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Post by essex sound lab » Tue Jul 06, 2010 6:33 am

bwhittington wrote:Wow, it looks like you jacked those from the (so far) mythical Macbeth oscillator.
I too thought: hmmm, John couldn't wait for Ken anymore!
:drinking:

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Post by BTByrd » Tue Jul 06, 2010 7:44 am

:love:

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Post by sduck » Tue Jul 06, 2010 9:38 am

So what are those? What's the point of having 10-turns on the coarse knob anyway? C'mon, fess up!

And you know that there are 10-turns that'd fit a LOT better and not look so out of place, right?

edit, a few minutes later - I was pondering why John L. Riceâ„¢, an otherwise sane and reasonably able technically modular type guy would put those outlandish knobs on his 300's. Didn't make sense, even though he is the kind of guy who actually likes those chrome hex bolts. What sprang to mind is that perhaps he's gotten those knobs for some other project - say a JH living VC0 or something, and just replaced those knobs temporarily, just for a picture (perhaps to flummox us?). That kind of makes sense, and I noticed that it looks like the knobs aren't sitting tight on the faceplate, like they'd need to to work. Or perhaps aliens have replaced them?
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essex sound lab
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Post by essex sound lab » Tue Jul 06, 2010 10:02 am

I'm still trying to figure out why he mounts his VCOs below his VCFs, but that's just me.

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Post by scarymcclary » Tue Jul 06, 2010 10:16 am

what happens when you forget the combination?

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Post by Noiseconformist » Tue Jul 06, 2010 10:34 am

scarymcclary wrote:what happens when you forget the combination?
it's gonna be out of tune then ... :deadbanana:

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Post by BTByrd » Tue Jul 06, 2010 10:40 am

essex sound lab wrote:I'm still trying to figure out why he mounts his VCOs below his VCFs, but that's just me.
Hehe... I was thinking that as well.

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Post by cornutt » Tue Jul 06, 2010 2:00 pm

scarymcclary wrote:what happens when you forget the combination?
A synthetic voice comes on and says, "YOU ARE TOO CLOSE TO THE SYNTHESIZER! PLEASE STEP BACK!"
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Post by babysealclub » Tue Jul 06, 2010 2:17 pm

Hey who doesn't like a locker room?

Really though you should go all the way and put multiturns on all the pots.

Do you have any plans for a "Monotron"?

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Post by emdot_ambient » Tue Jul 06, 2010 5:13 pm

Beavis: "He he, they said 'knobs'!"

JohnLRice

Post by JohnLRice » Wed Jul 07, 2010 1:55 am

LOL, I've enjoyed reading everyones comments! :lol: 8_)

Basically, the stock Spectrol pots are way too touchy for me, meaning the torque required to turn the knob is extremely light! Many times I've accidentally bumped a knob and thrown a patch I'd been working on for a long time out of wack or just trying to get the course knob set reasonably close and letting go of the knob without changing it is difficult for me sometimes (I've had somewhat shaky hands since . . . 1st grade . . .and I had ulcers a couple years before that . . and people wonder why I'm "so stressed" nowadays . . seems natural to me! :lol: )

Anyways, I had 4 of those big Spectrol counting dials I had got last year on Ebay for a deal and I started thinking about using 10 turn pots for my VCOs (or just using some Alps/Alpha pots, the kind with a nice blob 'o grease, and a regular knob) but I decided not to because of the stated stability of the original Spectrol pots used and the potential temperature instability of using carbon or wirewound etc. (maybe it wouldn't be a big deal but i love overkill)

These dials just barely fit . . but I like the way they look anyways! :razz: If someone makes a nice looking counting dial that is about 1.25 to 1.5 inches in diameter I'd love to hear about them!!! I bought some cool looking expensive as hell Kilo brand single turn locking dials that I thought would look shaweet (although on the small side)
Image
but . . they offer zero turning torque so the only advantage was that they are lockable.

I also tried a Kilo "push to turn" knob
Image that I thought would be cool but . . . they had TOO MUCH torque when they weren't pushed in so they
would still turn the Spectrol pots! :bang: :deadbanana: Dees knobs is $20 a pop so this experimentation didn't come cheaply! :cry:

With the big Spectrol dials, they have the most beautiful smooth turning torque and for the most part I can just fine tune using the course pot now! :nana:

With these big dials you are supposed to drill a small hole in the front panel for a pin/nub to go into to keep the dial body from spinning but I didn't want to modify the panels. Since the dial was half covering one of the panel's mounting screw holes, I decided to just cut a gap in the dial edge and then cut off the nub. It worked great (except for two of the notches are a hair big so I have to fill it with something . . maybe heat shrink . . . .
Image

Image

Another thing I had to do was to remove the backside nut from the pot so the shaft would stick out far enough so the allen nut would grab it!

I then wanted to make sure the Fine pots were reacting the same in all VCO's. (I'd get confused sometimes) I planned to do this mod by Larry Hendry to make the fine tune range narrower/finer: http://www.wiseguysynth.com/larry/mods/300mod.htm

I had purchased all 4 VCO's used from third parties (two from the very nice David Highlander and the other two from different Ebay dealers I think). David had already done Larry's mod on the two he build

Image
but the other two had yet to be done. David had used 270k resistors but I decided to use 200k for all 4 (mainly becuase I didn't have any 270k resistors here but I had 4 200k!) This value worked out well and gives me a range of about 4 or 5 half steps if I remember correctly.

I'm going to do this similar mod for my two MOTM-310's but I'm gonna wait for the 10 meg resistors to arrive: http://www.wiseguysynth.com/larry/mods/310mod.htm



Then I decided to do Paul Haneberg's tracking modification to all 4 VCO's too: http://www.wiseguysynth.com/larry/mods/VCO_track.pdf

I checked and three of the VCO's still had the original spec'd 2.2 meg resistor installed and 1 had a 1.8 instead! I'd often wonder why I had some tracking issues in the high end. Since it was 4th of July holiday weekend and I wanted to GET IT DONE I spent what seemed like a couple hours looking through my bin of mixed 1% metal film resistors. If you EVER think you are going to be smart by buying a big discount pack of mixed resistors . . .DO NOT DO IT!!!!

Anyways, I ended up using two resistors in series for a total of 1.62
megs.

Image
Seems to have worked well and I now have very solid tracking across a 7 octave range (C1 to C8). I could have made it even more solid if I didn't care about the top octave but I compromised the lower octaves a little so it would sound decent up there.

Biggest screw up on this project? One of the VCO's had its MTA power header polarizing clip (the white part that sticks up) broken off. It wasn't a big deal but, since I had the module part way apart already I thought, hey, peice of cake! NOT! I totally destroyed the underside solder pads and the through hole plating trying to get that damn thing out! (It was late and I was tired but still . . . ) I managed to rescue it with a little point to point wiring.
syzygywell wrote:what is with that knob? I wanna touch it.
:hmm: . . . I'll let you touch mine if you'll let me touch yo. . . oh . . never mind! :oops:
SepticUnderground wrote:nice modules yeah, crack the safe 300â„¢ hehe
We need a safe cracker emoticon!
bwhittington wrote:
dude wrote:john, are those 10 turn? every time is see those knobs it gives me this strange feeling of being in gym class trying to open my locker.
. . . but not being able to because you were in awe of the guy next to you with the giant knob? :mrgreen:
Little Johhny raises his hand in junior high gym class "Mister coach sir, could I be excussed? I just got a brand new great big knob today and I really want to go home and play with it."
bwhittington wrote:Wow, it looks like you jacked those from the (so far) mythical Macbeth oscillator.
Yes, I was inspired by both Ken's and JH's VCOs!
sduck wrote:And you know that there are 10-turns that'd fit a LOT better and not look so out of place, right?
Shows me the fitting ones you speak of, precious!
sduck wrote:edit, a few minutes later - I was pondering why John L. Riceâ„¢, an otherwise sane and reasonably able technically modular type guy would put those outlandish knobs on his 300's. Didn't make sense, even though he is the kind of guy who actually likes those chrome hex bolts. What sprang to mind is that perhaps he's gotten those knobs for
some other project - say a JH living VC0 or something, and just replaced those knobs temporarily, just for a picture (perhaps to flummox us?). That kind of makes sense, and I noticed that it looks like the knobs aren't sitting tight on the faceplate, like they'd need to to work. Or perhaps aliens have replaced them?
Wrong on all counts, my friend! I'm totally mentally frilled (been watching Farscape DVD box lately ;-). Not for any project in particular, but they are here to stay on the 300's! The knobs are sitting flat. Maybe what you are seeing is the gap the brake level travels in? I'M A GOIN' OFF-GRID BABY, YEEEEHAAAAAAAWWW
BTByrd wrote:
essex sound lab wrote:I'm still trying to figure out why he mounts his VCOs below his VCFs, but that's just me.
Hehe... I was thinking that as well.
If you force your VCOs to pump uphill, it will create more tension on the wave forms and you'll get a tighter more rubbery sproingier sound! 8_) Actually, when I first set things up, I had VCO's on top but, I tend to fiddle with the VCF's a lot more than the VCO's and having the VCF's on top means less cable clutter.

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Post by dude » Wed Jul 07, 2010 2:47 am

john thanks so much for the fun and informative explanation. your pictures make everything look so damn amazing! much respect. i hear you on the over-sensitivity on some pots. my filter cutoff and resonance knobs on my oakley super diode ladder filter are waaaayyy too touchy. i actually use other fixed voltage modules to 'turn those knobs' only because i can actually get it to stay where i damn want. you are an inspiration!

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Post by sduck » Wed Jul 07, 2010 9:39 am

JohnLRice wrote:
sduck wrote:And you know that there are 10-turns that'd fit a LOT better and not look so out of place, right?
Shows me the fitting ones you speak of, precious!
Now that I know what you're doing, I don't know of any! I have some smaller ones that look great, but they're designed for 10 turn pots, instead of being geared like yours. I would also be reluctant to switch this particular pot out for even a nice 10 turn spectrol pot, although they exist.
JohnLRice wrote:
sduck wrote:edit, a few minutes later - I was pondering why John L. Riceâ„¢, an otherwise sane and reasonably able technically modular type guy would put those outlandish knobs on his 300's. Didn't make sense, even though he is the kind of guy who actually likes those chrome hex bolts. What sprang to mind is that perhaps he's gotten those knobs for
some other project - say a JH living VC0 or something, and just replaced those knobs temporarily, just for a picture (perhaps to flummox us?). That kind of makes sense, and I noticed that it looks like the knobs aren't sitting tight on the faceplate, like they'd need to to work. Or perhaps aliens have replaced them?
Wrong on all counts, my friend! I'm totally mentally frilled (been watching Farscape DVD box lately ;-). Not for any project in particular, but they are here to stay on the 300's! The knobs are sitting flat. Maybe what you are seeing is the gap the brake level travels in?
I stand corrected! (I'm actually sitting, but often I'm standing while being corrected, hence the original turn of phrase) Although I'm glad to see that aliens were actually involved.
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