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The Synthasystem Discussion and Appreciation Thread
MUFF WIGGLER Forum Index -> Music Tech DIY Goto page Previous  1, 2, 3, 4, 5, 6  Next [all]
Author The Synthasystem Discussion and Appreciation Thread
bleeps
Isaiah
I saw your panels in the proofing thread (I didn't spot anything off btw), and I was wondering how important is the 1v/oct trimmer panel access? Does that need to be tweaked often?
Isaiah
bleeps
Thanks for looking at the panels!
Does the spacing look 'even' or 'balanced' to you?

I don't suppose the 1V/Oct trimmer is something that would need to be adjusted often. Apparently the tracking is stable.
I imagine it was kept on the front panel as much for aethetics as it was for practical reasons. The original Synthasystem VCOs and VCF had panel-mounted trimmers.
No harm in keeping them on the panel if you have the space.


By the way, I was trying out different panel layouts for a Dual VCO A (placing the knobs on a 28HP-sized piece of card).
You can actually fit all 8 output attenuators in a horizontal line (using Davies 1900 knobs, or some other ~12mm/0.5" diameter knobs), but I thought it looked kind of ugly/crowded/unbalanced.

I did think about a mono-synth (Minimoog or Synthacon) approach:
*Single individual outputs per waveform
*Two assignable outputs each with their own attenuators
*Each assignable output/attenuator fed by its own switch, one which selects Sine or Triangle, the other selecting Saw or Pulse.
It's not without its problems though, and I'm not completely sold on the idea.
Two attenuators seems a little clumsy.
One attenuator and a rotary switch to select waveform seems more elegant, certainly more mono-synth like, but uses up just as much panel space and it's more limited.
Of course, if we didn't need the output attenuators, it'd be much easier!
Rod Serling Fan Club
On the panel group buy I was going to propose dropping the trimmer, as it does seem a bit redundant to me. Then I would move the VC3 scale left, centered below the triangle attenuator so the knobs placement was completely balanced.

I am thinking about adding a linear FM input but seeing how I am the only one that has played with the mod so far I want to hear from others after they implement it. Anyone with a working VCO can test the LIN FM with an alligator clip connected to the end of R14 resistor going into the emitter of Q6. The other end of the clip connected to your FM source.

Personally I kind of like the big look of the larger panels and it makes wiring/diy a bit easier when you have more space to work with IMHO. If you are really looking for small panel/functional density, you could drop all the output attenuators, v/oct trim, the secondary outputs and even 1 or 2 of the inputs. Consider though, that the PCB is not small and you have 2 PCBs stacked per VCO (though you could probably get away with running 2 VCOs off of 1 power PCB).
synthcube
I posted a new topic called "Synthasystem Power Requirements Summary" with an attached PDF for a table I built, summarizing power needs for each module. Hope it is helpful.
Isaiah
RSFC

Yes, I like the look of the larger panels too.
Plenty of room to wiggle! Rockin' Banana!

The Dual VCO A isn't something I'm interested in build myself.
It'd be simple enough to design a layout for a general Euro system without the attenuators and some other things, like you say.
But to make it integrate best with a Synthasystem is bit of a challenge, and I'm not sure I can think of a satisfactory solution.

Ultimately, I'd I think I'd advise against a Dual VCO A for a Synthasystem, too.
I think I just have Dual VCOs on my mind at the moment (Dual 258J soon)!



I'll test the Lin FM mod, but I probably won't have my VCO running before the end of April.
Maybe Negativspace could be persuaded to test the mod hihi
What did you mean about the Lin FM signal having the opposite effect on pitch? Did you see my suggestion about using a CGS DC Mixer as an inverting amp to invert and attenuate the input?
Rod Serling Fan Club
I think it is inverted. Your idea sounds good to me, maybe there is a very simple inverting op-amp idea for perf board. I would like multiple opinions on the linear FM before implementing it on a panel for group-buy.
negativspace
An inverting opamp would help in 2 ways - first it'd fix the inversion, and second one could give it 2x gain (or more) for better depth of modulation. Such an addition is blindingly simple, just an IC and a couple of resistors.
bleeps
Isaiah wrote:
bleeps
Thanks for looking at the panels!
Does the spacing look 'even' or 'balanced' to you?

The spacing looks ok to me. I do agree with emdot about jacks above knobs though. I try to avoid that.

Quote:
I don't suppose the 1V/Oct trimmer is something that would need to be adjusted often. Apparently the tracking is stable.
I imagine it was kept on the front panel as much for aethetics as it was for practical reasons. The original Synthasystem VCOs and VCF had panel-mounted trimmers.
No harm in keeping them on the panel if you have the space.


By the way, I was trying out different panel layouts for a Dual VCO A (placing the knobs on a 28HP-sized piece of card).
You can actually fit all 8 output attenuators in a horizontal line (using Davies 1900 knobs, or some other ~12mm/0.5" diameter knobs), but I thought it looked kind of ugly/crowded/unbalanced.

I did think about a mono-synth (Minimoog or Synthacon) approach:
*Single individual outputs per waveform
*Two assignable outputs each with their own attenuators
*Each assignable output/attenuator fed by its own switch, one which selects Sine or Triangle, the other selecting Saw or Pulse.
It's not without its problems though, and I'm not completely sold on the idea.
Two attenuators seems a little clumsy.
One attenuator and a rotary switch to select waveform seems more elegant, certainly more mono-synth like, but uses up just as much panel space and it's more limited.
Of course, if we didn't need the output attenuators, it'd be much easier!

The reason I was asking about the trimmer is that I have been working on a triple VCO 28hp panel (see below). There's plenty of space in the front but that's going to be one hell of a PCB sandwich and if I needed to dig through all that to adjust the trimmer all the time, I'd just as well put it on the front. How are those trimmers mounted to the panel? Is it possible to power three VCOs from two power PCBs? Am I crazy?


This isn't final, just a sketch to see if I could fit everything I wanted to fit into 28hp.
diophantine
Isaiah wrote:
Diophantine seems to be the Synthasystem Master around here, I'm sure he'll chime in if you're looking for opinions on certain modules.

oops I wish I could lay claim to this title! 8_)

But yeah, I'm more than happy to help out with any module thoughts or whatnot! Should have the Sequencer done this weekend, leaving me only waiting for my next paycheck to pick up panels for my voltage processor, input amp, and tuner/monitor modules. Otherwise I have at least one of every module done. (Not sure if i will build any VCO-Bs.)

Just to lay it out there, probably the Triple EG and Frequency Divider would be the most unique and/or interesting in a non-Synthasystem modular. Of course, the VCF is great too and if you don't have a phaser, that is nice too. While i love having the VCA/Mixer combo, with a mixed system you may not find it optimal without an attenuator on the VC input. The +12/-10V offset range on the Selective Inverter, etc. is a bit extreme and again, in a non-Synthasystem setting, you may want to mod with a couple of voltage dividers.

Apologies for the slowness in updating the blog lately... jury duty + work + nearly dead laptop = ugh!
diophantine
Oh, and yeah, the V/Oct trimmer on the VCO is probably a tad overkill, if you are doing your own panels and are using the THAT ic with tempco, etc. Should be fine to just have it on the board. I got mine tracking nicely over 5 octaves - only reason I may have to readjust is if I get a frequency counter or a proper tuner.... my oscillscope has better resolution than my ears. hihi

Bleeps: best to ask David, but you might be able to get away with using a single power PCB for three VCOs. Or, at least, you could try it with just one! smile

If this triple VCO is going to be used in a non-Synthasystem mosular you might consider cutting down the size of the coarse knob and adding an attenuator for the PWM input. Perhaps even add the VC2 input with a regular attenuator.
bleeps
diophantine wrote:
you might consider cutting down the size of the coarse knob

sad banana

Quote:
and adding an attenuator for the PWM input. Perhaps even add the VC2 input with a regular attenuator.
Good call on the attenuator for the PWM. I can add that easily. Thanks for the input on the trimmer too!
diophantine
Of course, you can keep the big knobs! smile Just meant that you might have to if adding other attenuators or inputs.
bleeps
Here's what David said about a triple VCO/multiple VCOs from one PSU PCB in case anyone else is thinking about this:
Quote:
A triple VCO module would be excellent, and I can understand why you would like to have only one Power PCB for the trio.

It would probably be fine, but I would caution you VCOs can start to lock to each other depending on how the power supply cables are connected. Take Jurgen Haible’s Livign VCO trio. He put a separate power supply path and connector for each VCO on the PCB so each VCO was isolated from the other. One question people were asking about Jurgen Haible’s Living VCO was could you daisy chain these power supply connectors or do you have to run three separate cables to the main power supply? Turns out, this isn’t a problem on this trio, but I can’t guarantee you won’t see it on these VCOs if you tie all three to one PowerPCB, especially if the power cables are relatively short.

On another note, the Power PCB has three general functions. First, it lets the user build it to run off of basically any power supply that is commonly in use and thereby end up with +12 and -10 volts. While I think (and have heard) these modules should run form +/- 12 volts, for the VCO at least, in the pulse wave shaping circuit, and in the sine shaping circuit, there are some transistors which are connected to the -10 or “-V” signals and so have biasing set for -10 volts, not -12 . The bottom line is those circuits may have problems on -12, so I always recommend converting any minus supply to -10 volts.

Second, the Power PCB adds some general decoupling and filtering. Not a huge deal I think with how clean modern supplies are.

Third, on some modules, Nyle had additional filter/decoupling on the power supply lines. I’ve never really gone into the reasons why, I just made sure I included the option to have the extra filtering on the Power PCB. The VCO uses both the straight +12 and -10 from the main supply (regulated and conditioned on the Power PCB) as well as separate signal paths for the additional filtered +12 and -10 which are labeled V+ and V- on the schematics.

Bottom line is I think using one Power PCB for the trio would probably be fine electrically so long as you are sure to connect the straight +12 and -10 and the extra filtered V+ and V-. Beware you might end up with parasitic locking.

One other “form factor” hiccup for a shallow euro system is the HF Compensation mini PCB. Although when Nyle tuned my VCOs he disconnected the HF Compensation PCB, I think these days, most people don’t want all the “character” of the old VCO designs. You will need to figure out how to best mount these little guys if you want to use them.


I did forget about the HF comp boards. That will definitely add to the complexity of the build. Not sure what can be done to avoid the locking short of using all three PSU boards. I did a quick search here and at e-m and I couldn't find anything relevant.
diophantine
bleeps wrote:
I did forget about the HF comp boards.

Me too! I don't know how you intend to use these VCOs, but if you aren't too concerned with tracking (i.e. you aren't playing from a keyboard, or sending offset voltages to change notes & octaves, etc.) you may be able to live without them. With the HF boards I got mine tracking over 5 octaves, from 100 Hz to 3.2 kHz - but even without the HF board it was pretty close. (I didn't try anything beyond those tests, at least not yet.)
diophantine
Sneak peek for the wigglers:



w00t

Only "problem" was that I put a switch in upside-down. Fixed that in 30 seconds and otherwise it seems to work great!
Rod Serling Fan Club
dio - That sequencer looks great! With banana jacks and LEDs its like a rainbow in the dark.



I finally trimmed up my oscillator (sounds great!) and messed around with the linear FM mod some more. I no longer think that it is inverted but, I think it could use an amp at the input. It's a bit quirky but a fun timberal option as is. The exponential FM is great. Loving this oscillator, I need to build a second.
Isaiah
Diophantine
Your Sequencer looks great!
The combination of S-Trig outputs and banana jacks should prove very flexible!
I ordered a Sequencer PCB set from David last week.



Finally finished my first Synthasystem module (Noise Generator) today.
Getting some nice timbres by using the output to modulate the VCF Frequency on my SEM,
while varying the Level and sweeping between White and Pink noise.
The noise, at either extreme or any mix of White and Pink, sound quite pleasant and 'musical'.



Hope to have my Phaser, VCF, VCA and Triple EG completed in time for the Coventry Modular Meet this Saturday.
Everything is finished except the wiring and calibration (not looking forward to wiring the Triple EG! eek! ).
Rod Serling Fan Club
I think I've settled on the synthasystem I am going to build. I've already got 1VCO, both VCFs, VCA and EG built. I picked up a 6ux84 case and I think thats enough for a nice, compact system. I just ordered the rest of the PCBs. Here is what I'm looking at:
VCO A x2
VCA/Mix
VCF
Noise
Balanced Modulator
phase shifter
3xEG
Trigger generator
Sample & Hold
Voltage Follower
& CGS synthacon VCF
diophantine
Thanks RSFC & Isaiah!

(Sorry, didn't see your comments 'til now.)

The full pics are up in my blog. I need to get busy with the Synthasystem again... have been beyond distracted with jury duty (lasting from Jan 27 to May 16th!), plus waiting on stupid things like rack screws.

Rod Serling Fan Club wrote:
With banana jacks and LEDs its like a rainbow in the dark.

SlayerBadger!
diophantine
Isaiah wrote:
Hope to have my Phaser, VCF, VCA and Triple EG completed in time for the Coventry Modular Meet this Saturday.
Everything is finished except the wiring and calibration (not looking forward to wiring the Triple EG! eek! ).

Hope that all got done fine! The wiring on the Triple EG is definitely a bit of a pain; I'm planning to make 2 more, and will probably do them at the same time so that I only have to go through all the pain once more, haha.
Rod Serling Fan Club
I got my panels today! PCBs have been populated for some time. Now for some wiring & any troubleshooting then SlayerBadger!

diophantine
screaming goo yo SlayerBadger! !!!
MechaSeb
Hello guys !

Been a while since my first posts on this topic.

Actually i finished 4 of the planned modules : Phase Shifter, 2x Volt Proc/Mixer & Dual Volt Follower.

All of the others PCB are almost finished to be populated and i'm waiting for some components regarding the build of 2xVCO, 2xVCF, 2xVCA & EG. Can't wait to starting up building the earth of the system.

A picture of my first attempt in building a cabinet:



And another one of the built modules :
Picture file
MechaSeb
And an another one : Input Amplifier. Had a bit of trouble with one of the SPDT switches but now, it works !! applause
Rod Serling Fan Club
looks nice mech
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