Ive just added a 5th x 911 EG to my cloned modular however, Ive noticed some unexpected results…i.e. trigger sometimes repeats during cycle and sustain sometimes wont turn off on 5th x 911
how many 911’s could the 3C or 55 take on the standard S trig line?
I’m using Midi to CV for keyboard control not a dedicated Moog Keyboard, maybe they output different Strig?
Ive made up and fitted the Strig booster which gives other bad results on the whole set of 911’s.
So in the expanded modulars just how are extra 911’s hooked up to the S trig circuit?
5 real 911s usually won’t load down an s-trigger.
At about 9 or 10, they might start some weirdness, but even then it’s often slow or incomplete attacks and/or lower sustain.
Does #5 work by itself? In pairs or triplets with your other 911 clones?
Have you tried measuring its gate in (s-trig) resistance or used a resistance box to weight it down?
I’m assuming you’re using s-trigs and not an inverter transistor for v-trigs.
Some mods to obtain v-trigs can weight down more easily than even regular s-trigs.
Both will get weighted down by higher and higher multed trigs eventually tho.
It would appear that the aggregate pull-up current on the destination inputs just becomes too great for the S-trig source to stay close to ground.
A Darlington configuration (or single Darlington transistor) would very likely help out, however it’s probably easier to just use a higher current transistor or different biasing on the S-trig source(s.)
That or an IC or opamp output.
There’s several opamps (even single voltage models or configurations) that can sink the load current.
Some diode-resistor clamping might also help, but I consider that more of a trick and it may mess with waveforms when used as an input due to half wave rectification.
thanx for your good information…at least I now know that 5 x 911’s should’nt be a problem so I will look more closely at the Midi to CV output…I have put a V to Strig transistor
in there which may be causing a problem, I’ll try further configurations with it and check voltages.
All the 5 x 911’s work perfectly well its just that adding the 5th causes a problem so I guess it has to be the v to Strig..I can try the set up with my Kenton which has a dedicated Strig output and pull up options.
if thats good then I will try and modify the v to strig transistor…(I have noticed that adding non Moog stuff into the system tends to cause problems)
so I assume that connecting extra Strig to 911’s on a modular was by a lead from one 911 to another into the front panel Jones connector?
If you’re talking about how I multed S-trigs, I’ve done it several ways.
I have several 1/4" to S-trig cables and can mult them using a standard 1/4" mult panel.
Also, using the normalling switches found on many moogs.
The 55 has some trig buffers (one for V-trig, one for S-trig), but they’re mostly for converting to external signals.
I don’t think they show up on the front panel or normals, but can be patched.
Did you you build a simple 1 transistor converter?
Bob Moog often published one when asked in regards to Minimoogs.
There’s two somewhat complex ones in figure 45 of the Moog modular service manual.
They’re not impossible to build, but one uses 6 resistors, 2 transistors and a cap.
The other, slightly less.
Adds up if making 5 or 6.
I’ve had good experiences using CMOS chips with Schmitt triggers.
Hex chips like 74C14 (and most variants like F or HC), CD4584, 4093 and 40106.
Using any of these, you’ll get a good 10-11vs out with less in (on 12 volt power, about 7-8 input volts will trigger.)
There’s almost immeasurable input current and on N-devices, they can sink around 15ma or more.
Kevin…thanx for this extra info, that solves one query regarding patching 911’s ..
as for the Strig problem I think Ive found it…on note on with 4 x 911’s the voltage drops to about .96 and all works fine, when connecting the 5th x 911 the voltage only drops down to 1.30 thereby giving odd results such as audio passing thru 902 with all 911 controls fully counter clockwise on the 5th 911–902
I’m using the one transistor, one resistor and one diode of the simple Moog V - trig to S-trig…so the problem is probably here. I’ll alter components and see if that will boost the signal. If that fails I’ll take a look at the one’s you suggested…
Fwiw, a 2N3904 is only good for about 200ma max collector current.
I doubt the aggregate current for five 911s would be anywhere near 40ma each, but you might check.
Also, a transistor may often decrease their input impedance as collector current demands are increased.
So while you may still trigger things well now with increased base current (and thus increased collector current), such a circuit may cease to work on low level audio signal inputs.
An opamp or comparator before the V to S trig converter may help by lowering the load on inputs and providing a more constant current for S-trigs.
This can be seen in the 952 S-trig converter circuits below.
(ignore that this pic is showing mods to obtain V-trigs instead of S-trigs.)
