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Combining two Q125 modules into one. ;-)
MUFF WIGGLER Forum Index -> 5U Format Modules  
Author Combining two Q125 modules into one. ;-)
JohnLRice
I finally finished this project where I combined two #Synthesizers.com Q125 Signal Processor modules into one single MU panel by using dual concentric pots with center detents and knobs. The labeling doesn’t reflect what it does for the most part since I used a stock attenuator panel that Ben at RE:Synthesis sells but I wanted to get it done without taking the time and expense to design and order a 'perfect' panel. I just had to drill 4 holes for the PCB supports and I could have made it shallower of course if I had drilled 4 more holes and not stacked the PCBs.

Still need to make some power cables and test it so, I hope it works OK! oops





Synth Con Meo
That's a pretty cool idea. I like the idea of the dual concentric Pots. About the only thing so far that I've done as far as combining modules is I ordered a couple of Q106ACK conversion kits for a couple of my Q106's. They seem to retain all the functions of the Q106 + adding the functions of the Q141 VCO aid.

I have been a little reluctant with some of the other conversion kits like for Dotcom modules. Some of them that convert from 2 MU to 1 MU it looks like you loose a couple functions/inputs/outputs. And I am still such a Noob and don't have enough experience to know if whether or not it will really make a difference of what I end up missing with the conversion.

So yeah right now I am probably still burning up some MU space that I can gain back with some of those conversions. I am sure as time goes on I will get a better feel of what I can do without and do the conversions.

Sorry for the long rant, Great work!
josaka
planning to do this with two slew limiters.. ..looks great John. thumbs up
Flareless
Nice! applause
JohnLRice
Thanks folks! Unfortunately one section isn't working d'oh! so I'll need to trouble shoot it . . . later when I'm not so tired.
Rex Coil 7
JohnLRice wrote:
I finally finished this project where I combined two #Synthesizers.com Q125 Signal Processor modules into one ....
Inspired work, John. Keep on truckin' man. thumbs up
Rex Coil 7
JohnLRice wrote:
I finally finished this project where I combined two #Synthesizers.com Q125 Signal Processor modules into one single MU panel ...



Hold up ... those are two totally different boards. Their mounting holes don't even line up. And the top board has ten connection headers, while the bottom board has twelve. What's going on there?

hmmm.....
JohnLRice
Rex Coil 7 wrote:
JohnLRice wrote:
I finally finished this project where I combined two #Synthesizers.com Q125 Signal Processor modules into one single MU panel ...



Hold up ... those are two totally different boards. Their mounting holes don't even line up. And the top board has ten connection headers, while the bottom board has twelve. What's going on there?

hmmm.....
I think the alignment looks weird just because of lock washers I used and the way I tightened them down.

But yes, the boards are a bit different but are both Q125 boards. One is a very early version from 2001 and the other is a more recent one from 2015. The earlier one doesn't have jumpers for AC/DC coupling and some components are in slightly different places like the 100%/200% jumpers and some of the caps etc. Also the headers for the offset pots are rotated 180 degrees.
diophantine
Nice!! Where did you pick up the dual concentric pots & knobs? Or are the larger knobs drilled-out Cosmo-clones? lol

Will be curious to hear how the center detents line up. I can't remember if those PCBs have trimpots or not, but doesn't look like it. Most (if not all) of the Blacet modules center-detent pots have trimpots to calibrate the detent point.
JohnLRice
diophantine wrote:
Nice!! Where did you pick up the dual concentric pots & knobs? Or are the larger knobs drilled-out Cosmo-clones? lol
I paid a fairly ridiculous amount for the knobs and pots for this project, like $120 total! MY ASS IS BLEEDING But I really liked the look of the knobs and I went ahead and got the pots from the same place http://www.guitarpartsfactory.com/ because I didn't want to take the time to research the pots and figured that Fender branded pots would at least be better then bad? hmmm.....
Fender DLX JAZZ BASS STACKED KNOB 004-9411-000
Fender 100K CONCENTRIC STACKED POT 005-3736-000

diophantine wrote:
Will be curious to hear how the center detents line up. I can't remember if those PCBs have trimpots or not, but doesn't look like it. Most (if not all) of the Blacet modules center-detent pots have trimpots to calibrate the detent point.
The detents line up close but not perfect and I knew I'd probably need some trimmers but I was hoping to get lucky so tried it first without. Mr. Green I originally thought I was smart to get detents because the panel I used wasn't labeled correctly for the functions and I could just tell by feel where zero is but . . . without trimmers setting the pots perfectly at zero is near impossible because of the detents. d'oh! In hind sight getting pots without detents AND getting a panel that was labeled properly would have been smarter! oops

One thing I would suggest to Q125 owners that are up for some mild DIY modifications (no drilling and just a little easy soldering): Replace the lower section pot on your Q125 with a dual concentric pot because you can then have the same capabilities as the top section! The switch in the lower section just servers as a "zero taper pot", meaning it works like a pot that is either 100% clockwise or 100% counter clockwise. I originally had ordered just single pots with push/pull switches for the bottom sections but literally right before I started to wire things up I realized that both sections of the circuit are identical. (I'm assuming Roger made the module this way to keep the panel from being too crowded and/or to keep costs lower?) And then, after the mod you'd still have a DPDT toggle switch in the panel that could be used to either enable/disable the 100%/200% gain structure OR enable/disable the AC/DC coupling (if you have the newer version) This is fun!
JohnLRice
JohnLRice wrote:
Thanks folks! Unfortunately one section isn't working d'oh! so I'll need to trouble shoot it . . . later when I'm not so tired.
I forgot to mention I resolved the issues. One was I had an output wire pinched between a stand-off and a pcb and it was shorting to ground and I also had the input and output jacks for that section in reversed positions. d'oh! meh lol
hsosdrum
Thanks for bringing this up, John. I never realized that the Q125 had a jumper that could convert the bottom section to +200% gain.

(As a guy who makes his living writing instruction manuals, I hang my head in shame at not having read my Q125 data sheet as thoroughly as I should have. d'oh! )

I have a third Q125 on order that will arrive with my 1U Q150A in a couple of weeks. When I get it I'll set its bottom section for 200% gain and convert both of my existing ones.

Thanks again! applause applause applause applause applause applause applause
diophantine
Glad you got it working alright!
JohnLRice wrote:
I paid a fairly ridiculous amount for the knobs and pots for this project, like $120 total! MY ASS IS BLEEDING

MY ASS IS BLEEDING indeed! hihi

JohnLRice wrote:
But I really liked the look of the knobs and I went ahead and got the pots from the same place http://www.guitarpartsfactory.com/ because I didn't want to take the time to research the pots and figured that Fender branded pots would at least be better then bad? hmmm.....

They do look nice, and dual concentric stuff is not easy to be found these days...

JohnLRice wrote:
The detents line up close but not perfect and I knew I'd probably need some trimmers but I was hoping to get lucky so tried it first without. Mr. Green I originally thought I was smart to get detents because the panel I used wasn't labeled correctly for the functions and I could just tell by feel where zero is but . . . without trimmers setting the pots perfectly at zero is near impossible because of the detents.

Before building the Blacet modules I'd always assumed that center-detent pots would be spot-on, without giving it any further thought.
JohnLRice
Just to follow up I've decided to not try to add trimmers in an attempt to make the center detents "perfect" zero nulls, at least for now. I fooled around with it for a while and even got some helpful info from diophantine Hug but in the end while the worst case output deviation when centered (with sending about +5v into an input) might be up to +-90 mA, often it was only +- 30 mA and sometimes even just in the 10ths of mA. Since I didn't intended to use these as on/off switches as well, it's not that critical to be able to completely and reliably remove all of the processing. I also noticed that when at center, the output deviation varied quite a bit depending on the speed, direction of travel and how I let go of the knob etc so . . .even if I added trimmers to set a perfect zero null, the center detents of these pots aren't constantly accurate so it just started to seem like a waste of time. Dead Banana

Still, I'm quite happy with the project as is! This is fun!
ualslosar
Those dual concentric posts are really cool, John

Curious if a dual pot could be wired into dotcom Q960 to give it frequency & pulse width control ?

- Would this work?

Thanks
Larry
JohnLRice
ualslosar wrote:
Curious if a dual pot could be wired into dotcom Q960 to give it frequency & pulse width control ?

- Would this work?
I would think it would work OK? As long as the pot you use will physically fit in the space between the panel and any PCBs?
diophantine
Glad you are happy with it, John! And yeah, while not perfect, that doesn't seem bad at all.

ualslosar wrote:
Curious if a dual pot could be wired into dotcom Q960 to give it frequency & pulse width control ?

At least some original 960s apparently had a pulse width trimpot. But it doesn't look like the Dotcom has one - perhaps it was replaced by precision resistors? So you'd either have to do some mods (assuming the Q960 works properly without a 90% duty cycle... and then probably make sure that it never gets to 0% or 100%.), or add another board with a comparator, etc. to just create a new signal at the main clock output.

I haven't look at the schematic in years & don't have it handy.
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