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Better circuit choices for Silent Way AC Encoder
MUFF WIGGLER Forum Index -> Expert Sleepers  
Author Better circuit choices for Silent Way AC Encoder
os
Since I published the details of the circuit I'd been using with Silent Way AC Encoder (http://www.expert-sleepers.co.uk/siwaacencoder.html) various people have written in with suggestions for improvements, so I thought I'd sit down and properly try them out. (A big thanks to everyone who wrote in, by the way.)

All tests were done with my Metric Halo Mobile I/O 2882 interface and an Analogue Systems RS-95 VCO.

The original circuit
This one:
I measure 8V at the output when not plugged in to anything, and get about 7 octaves of calibration.

(You'll see therefore that I have a bit of a problem with the remaining tests - 7 octaves is about as much as I can hear, and 8V is not far off the supply rails of the modular, so I can't really expect much improvement in my own setup. However, the results should be useful for those with interfaces with less output.)

An even simpler version
It was pointed out to me that one of the diodes (pick one, doesn't matter) is redundant in the circuit above. To test that theory I removed the diode from the TRS ring and left it floating. Exactly the same results as above - so yes, you can do the same thing with just one diode.

Just as simple, double the voltage
It was also mentioned that connecting the TRS shield to the TS shield is a possible source of ground loops. Moreover, the above circuit isn't taking advantage of the balanced output's full voltage swing.
So, I tried a basic half-wave rectifier (see http://www.play-hookey.com/ac_theory/ps_rectifiers.html) using the TRS's T & R as inputs, leaving the shield unconnected. So like this image, but with the capacitor as above across the TS plug:


(Side note: from here on I did all my soldering at the TS plug end, leaving the TRS shield in place to actually be a shield down the length of the cable.)

Using this circuit I measured 16V on a disconnected lead, as expected. This is clearly a no-brainer improvement over the first circuit above.

Bridge rectifier
For completeness I also tried a bridge rectifier (same link, http://www.play-hookey.com/ac_theory/ps_rectifiers.html).

The results were the same as for the half-way rectifier - 16V.

Voltage doubler
Now this is a very interesting circuit: http://www.play-hookey.com/ac_theory/ps_v_multipliers.html

I made that, and true enough, I measure 32V on a floating cable! Now that's a potentially dangerous amount of voltage to be putting into a modular, so I adjusted the 'Max Out' setting on Silent Way AC before proceeding with calibration tests.

As noted above, 32 octaves or even 12 octaves just isn't a feasible thing to hear or measure. I will say though that with this setup I measured the actual voltage on the cable when under load i.e. plugged into the VCO, and I was able to get that comfortably up to +12V.

So, for those who've been reporting only one or two octaves of calibration, do try this circuit - it's only one more capacitor than the first one, and really does double the voltage.

Let us know how it goes!
os
In case anyone wanted to try the new options, but wasn't sure how to translate the circuits above into cable wiring, here are some diagrams:

Half-wave rectifier:



Voltage doubler:

jenamu6
This is great..........I still have to try mine out.
Arnoid
I checked the voltage doubler circuit now i'm getting 4,60 V at max smile
Almost 5 octaves smile

First I had 2,84 V at max...
Arnoid
I just made a voltage tripler circuit hihi


Now i'm getting 7V !!! at maximum...
Solid tuning over 7 octaves It's peanut butter jelly time!
os
applause
rv0
Arnoid wrote:
I just made a voltage tripler circuit hihi


Now i'm getting 7V !!! at maximum...
Solid tuning over 7 octaves It's peanut butter jelly time!

applause thumbs up

incredible
Klipspringer
I made both the voltage doubler circuit and re-did the original circuit with the new suggestions.

Maximum output with the new half-wave 5.6 Volts.

Voltage doubler is, well double, 11.2 volts or so.

The original design gave me a max output of about 1.5 Volts. Seems to tracks OK now using the buffer of my MX61 into both the AsOL VCO-6 and ASol VCO-RM.

I've tried .22 uF and .1 uF caps. Seems to be good with both values.

This is with my FA-66. So it's tested and it works OK. Now I gotta buy Silent Way like I promised!

I think this needs a little box with maybe a variable cap or dip switches to select different capacitance (as that seems to be the variable for audio interface).

Sell it for maybe $39.95 applause
Johnisfaster
Klipspringer wrote:


Sell it for maybe $39.95 applause


I'd so buy that!
lombrose
How did you guys make the tests?


hmmm.....
oootini
hi guys. this all sounds totally amazing...
lombrose
Tested with m-audio lightbridge and presonus digimax fs, the original circuit, same as OS - 8v!!!


we're not worthy
SlayerBadger!
PolishMilk
I decided to have a go at this using a Focusrite Saffire audio interface. Put the voltage doubler circuit together on a breadboard using 0.1uf capacitors and 1N4148 diodes.

I'm pretty sure I put it all together right, but when it came to testing it on my modules it didn't work quite correctly. The voltage increases fine but when it comes to decreasing it gets stuck. So for example with an lfo on pitch cv it would reach the peak of the signal but never go down again.

However when I put my multimeter across the tip & sleeve of the output to measure voltage it does go down and the circuit behaves as normal, but only while the multimeter is touching. I decided to try putting a resistor [a large range of values work] between tip and sleeve of the output and hey presto it works fine. I get about 2.7v max output (even with the doubler circuit, so the interface presumably has a fairly rubbish output level) and good tracking for just over an octave.

So basically does anyone know what weirdness is going on here? Why do I need a resistor across the TS output to get the circuit to work properly? Anyone had any similar problems?

*Edit* It also does exactly the same thing using the original circuit and the half-wave rectifier
sgnelson
PolishMilk wrote:
I decided to have a go at this using a Focusrite Saffire audio interface. Put the voltage doubler circuit together on a breadboard using 0.1uf capacitors and 1N4148 diodes.

I'm pretty sure I put it all together right, but when it came to testing it on my modules it didn't work quite correctly. The voltage increases fine but when it comes to decreasing it gets stuck. So for example with an lfo on pitch cv it would reach the peak of the signal but never go down again.

However when I put my multimeter across the tip & sleeve of the output to measure voltage it does go down and the circuit behaves as normal, but only while the multimeter is touching. I decided to try putting a resistor [a large range of values work] between tip and sleeve of the output and hey presto it works fine. I get about 2.7v max output (even with the doubler circuit, so the interface presumably has a fairly rubbish output level) and good tracking for just over an octave.

So basically does anyone know what weirdness is going on here? Why do I need a resistor across the TS output to get the circuit to work properly? Anyone had any similar problems?

*Edit* It also does exactly the same thing using the original circuit and the half-wave rectifier


I have a Focusrite Saffire LE and I've had problems with mine as well. Mine would decrease, but it wouldn't track for damn, and it was always incredibly unstable (like someone using a modwheel as fast as they could), and horribly out of tune.

That was using the original designed cable with both a 1uf and .22 capacitor. I haven't messed with it much in a few weeks, but I may try your resistor trick and see how that works, along with using the doubling voltage trick as well.

What value resistor did you use?
os
PolishMilk wrote:
Why do I need a resistor across the TS output to get the circuit to work properly?

The capacitor does need a discharge path. Normally this is provided by whatever it's plugged into, but in your case you seem to be dealing with a module with a very high input impedance. What modules are you testing with?

2.7V is an astonishingly low output from the doubler circuit. Have you tried measuring the AC voltage output from the Saffire in normal use (e.g. when outputting audio)?
PolishMilk
sgnelson wrote:

That was using the original designed cable with both a 1uf and .22 capacitor. I haven't messed with it much in a few weeks, but I may try your resistor trick and see how that works, along with using the doubling voltage trick as well.
What value resistor did you use?


I tried all the resistors I had (from a lucky dip multipack) and every one of them worked in terms of fixing the voltage decrease problem, but each one gave different tracking behaviour. Some would give me no tracking at all and some would give me an octave of tracking that started half way through the octave. I eventually settled on quite a small value (though I forget what that value was - I'll have to look when I get home) but this gave me totally different tracking behaviour when I changed the tune pot on my module. Was very confusing so I just settled on the small range I could get it to work in!



The module I was using to test on was an Analogue Solutions VCO-Sub. Makes sense about the high impedance, I can also try it on my Arp Axxe tonight to see if that helps - I didn't use it earlier because I didnt want to zap my baby if things went wrong!

Actually I've just thought - I had a bit of an odd setup with my TS wire because I didn't have a spare 1/4" to 3.5mm cable/adaptor. I had a TS 1/4" to RCA adaptor followed by an rca cable followed by an rca to 3.5mm jack! Could this be causing the high impedance?



I was surprised about the low maximum voltage of 2.7 too. I haven't tried measuring the normal output yet but I will when I get home tonight. According to the specs of the interface from the internet -
Nominal output level 0dBFS = 16dBu, electronically balanced
Which is fairly reasonable?
bsmith
Does capacitor choice not matter as much if using the half-wave rectifier or voltage doubler or will there still be an optimal choice depending on the interface?
os
Capacitor choice still matters.
PolishMilk
Finally got my problems solved. The low output was a stupid one - there was a toggle on the software mixer for the audio interface that was dipping the volume of the output for some reason (I bought the interface new for use with Silent Way so didnt know how to use it!) With that sorted I'm getting 6v with the half-wave rectifier, 12v on the doubler and 6 octaves of perfect tracking, so SW does work with the Focusrite Saffire.

The problem with the impedance does seem to be linked to the module I was using. The cables work fine on my Arp Axxe but when plugged into the Analogue Solutions VCO-Sub the pitch rises but never falls again.

Is there a better solution to this than just strapping a resistor across the tip & sleeve? Using the Axxe as a CV master for the VCO-sub has always worked fine so there must be a workaround?
os
PolishMilk wrote:
Is there a better solution to this than just strapping a resistor across the tip & sleeve? Using the Axxe as a CV master for the VCO-sub has always worked fine so there must be a workaround?

I think the resistor is the workaround. The Axxe might have a non-capacitative output (e.g. direct out from an op-amp) or might have a resistor across the output internally.

The better solution for all of this is to build an active AC Encoder interface circuit - that's still on my plan, but it will be a while before I have time to try it properly.
bsmith
I got one of the rean send/return boxes detailed in this thread:
https://www.muffwiggler.com/forum/viewtopic.php?t=11494
It works great for my lexicon mpx500's two outs, but I'd love to use it as well with with the ac encoder - it'd be nice having all the silent way stuff come out of it. Trying one of my soldered cables which works on its own I'm getting nothing when trying to run it through the box - have tried variations on different adapters, etc.. but am not getting signal through it using ac encoder/special cable. Any suggestion on how I could get this to work?
os
How exactly is your AC Encoder cable wired?
bsmith
Half wave rectifier
os
Is the box simply a passive set of sockets all wired up, or is there more to it?

Is it somehow shorting the cable ends together (because it's expecting a TRS input)?
bsmith
It's passive, I peeked inside it hoping I could just use it as a shell to ac encoderify it, but it has a little pcb for each channel with the send/return stuff on them. Yeah, I believe that it is expecting TRS. So to clarify, I'm wanting to find out what the cable would look like between the interface and this box - how would this be wired?
os
At a guess you want to use a TRS plug at the box end, not using the ring.

As a quick test though just plug a TRS-TRS jack lead into it and use a continuity tester/multimeter/whatever to see what gets connected to what, with and without anything plugged into the sockets that are going to the synth.
bsmith
Thanks Os.
Interesting. It was actually the opposite of that - I hadn't tried using a TS plug into the box, just the trs. Using my cable (which is 1/8 TS on the synth end) with a 18>1/4 TS adapter into the box works fine.
Thanks again- just hadn't poked around far enough.
PolishMilk
os wrote:
PolishMilk wrote:
Is there a better solution to this than just strapping a resistor across the tip & sleeve? Using the Axxe as a CV master for the VCO-sub has always worked fine so there must be a workaround?

I think the resistor is the workaround. The Axxe might have a non-capacitative output (e.g. direct out from an op-amp) or might have a resistor across the output internally.

The better solution for all of this is to build an active AC Encoder interface circuit - that's still on my plan, but it will be a while before I have time to try it properly.


OK, so I looked into this active circuit stuff and built the following circuit (ripped off from the dc mixer circuit on the doepfer DIY page and also from the MFOS dc mixer)



The input is from my modified ac-encoder cables with the voltage doubler circuit built in. The circuit uses a tl072 chip which has 2 op-amps built in, both of which are used in an inverting configuration.

Using this circuit I could control the Analogue Solutions VCO-sub module perfectly.

However I ran into problems when I tried to add a DC offset to the circuit. At the moment I'm getting 0-12 volts output so I wanted to offset by -6v to get -6 to +6v. The part of the circuit in red is my attempt to do this. I was measuring -6v on the 1M resistor before I soldered it in but then once I did I only got -1v offset on the output. I tried loads of different resistor values but all of them just give -1v offset!

Does anybody have any ideas about whats going wrong?
os
This is the (similar) circuit I was going to base my prototype on:

http://www.musicfromouterspace.com/analogsynth/oddsandends.html#LEVELS HIFTER

PolishMilk
Amazing. Thanks a lot os. I stuck the offset voltage into the + input of the second op-amp and it works great. Now getting -6v to +6v which gives me the total audible range of the synth. The circuit I used is...



Next step is build 7 more and stick it in a module!
os
I started a new thread for my active prototype:

https://www.muffwiggler.com/forum/viewtopic.php?t=15928
thenapking
Bit of a noob question here. To check: i'm going to build an unbalanced version of either the half-wave or voltage doubler cable. Since the ground is unconnected on the TRS version it's irrelevant, right?
os
It depends to some extent on the exact output circuitry of the balanced output that's driving the TRS.

But if you're building an unbalanced version, you only have T & S to play with, so it's a moot point.
thenapking
thanks. that's what i'd thought. I've got an old m-audio usb interface which doesn't get much use these days which i thought i'd press into service for this. I'll let you know if it works!
Navs
I just tried the half-wave rectification circuit with an unbalanced audio interface - an Emagic emi26, which uses RCA/ cinch jacks.

It's output is pretty weak, but the signal also seemed to droop over time. Switching channels got me the maximum output again, but this too would fade gradually.

Is this maybe down to the unbalanced outputs i.e. is the interface not suitable or would the ES-1 solve this? A square-wave LFO sounded slewed, which shouldn't be the case, should it?

I tried both a 1uF and 0.1uF cap and various AC Encoder settings.
os
RCA outputs will probably be quite weak, so that's expected, but I can't think why the output would droop. Does it fade away completely, or just drop a bit? Is this with the output unconnected, or driving a module?

An ES-1 ought to help, by presenting the audio interface with a proper high-impedance input, and by applying some gain to the CV. I believe others have used the ES-1 with RCA outputs successfully.
Navs
Thanks, Os.

I hope to get an ES-1, but want to make sure the emi26 is capable first and will troubleshoot this tomorrow using my RME interface as a control.

The signal doesn't fade away completely. The droop is noticeable whether the output is connected to another module or just the multi-meter.

One thought I did have was whether it might have something to do with using the emi26 as an aggregate device. AudioMIDISetup displayed something about 'up-sampling' to match the FF400 which was providing the master clock.
os
Do you have a simple buffer module you could pass the emi26 through before applying the rectifier? That would simulate the es-1's input buffer stage.
Navs
I've just had another idea: if all the circuit does is rectify the signal, I could send it to an A-119 or VCS/ Maths, boost it and take the envelope follower (rectified) signal out, right?

Guess there's only one way to find out ...
os
You'll want to smooth it too.
Sablerock
Hi guys,

I'm really excited to get things going with Silent Way! OS confirmed for me yesterday that my M-Audio Delta 1010LT card will work (the version with the RCA harness, not the breakout box).

Because it uses the RCA (unbalanced non-TRS) connections, how would that change the circuit design? Also, should I be building the amplification circuit and how would the wiring differ there as well? I plan on using Silent way to control the Korg Monotron as well as other analog synths. Any help would be greatly appreciated....

UPDATE: I have come across a device called 'The Matchbox' by Henry Engineering. http://www.henryeng.com/matchbox.html the version I have isn't the HD but has near identical specs. Would this overcome the need for any custom circuit building to work with my AC Coupled device? Can I directly connect my RCA's to the device and expect a sufficient output voltage? On the front of the device it is labeled as "Direct Coupled" also "IHF to PRO". It is powered by 120vac. I'm hoping that this might be an easy, off-the shelf solution to those of us with AC Coupled Devices that also use unbalanced RCA jacks... OS, any input on this one?

Update #2: With the Matchbox, I'd have 2 unbalanced input (-10db) from RCA (Delta1010lt) impedance adjusted to 2 Balanced outputs (+4db) with adjustable output gain. I'm hoping that 2 channels is all I'd need to accomplish Pitch and Gate functionality from Silent Way. Could this device possibly eliminate the ned for the AC Encoder as well?

Erik Hines
os
The Matchbox would certainly boost your levels. However it's not going to remove the need for the AC Encoder - your 1010 is still AC-coupled (presumably - do we know this for sure?) and it only takes one AC-coupled link in the chain to break the DC-coupling.

The simplest thing to try is this:

but where you see 'ring' on the TRS jack use the sleeve on the RCA jack.

If you then need more voltage, take it from there.
Sablerock
Great! Thanks Os.

I'm going to give it a shot once I head over to Electronics City and get the needed diodes and caps. I'll be testing both with\without the 'Matchbox' to see what kinds of voltages I get. Stated earlier I'll only be focusing on Pitch CV and Gate (2 channels) initially, but if it works, than I'll dedicate a few more channels for modulation sources...EXCITED!!!

Erik
Sablerock
Os and gang,

So I put together my cables last night for use with the Delta 1010 (actually, ended up using spare outs on the Delta 410 PCI instead) for use with the AC Encoder Plugin.

The first test I did was without the 'Matchbox' from Henry Engineering, I was able to squeeze about 3.8 volts max when feeding a saw wave sweep to 44khz. Because I expect to use more than 3.5 Octaves, I added the matchbox between the Delta outputs and the circuit and got EXCELLENT voltages!! Because the 'Matchbox" has an adjustable output, I calibrated to 12V when feeding the Saw wave at 44khz. I didn't max the output gain but am expecting that I can obtain up to 24V with the Matchbox.

2 questions arise from this test:

#1: What should be my maximum value for CV output? Should I use the full 24V output if I have it?

#2: When I put the output on the O-Scope and fed a pure sine wave, it comes back with what looks like the effects of capacitor discharge. My sine ended up looking more like a saw, with a slight sine ramp up and logarithmic tail after the peak. The capacitor I used is 1uF Tantalum Cap. Should I try for a lower value? Should I go Electrolytic instead? I'm concerned that any LFO's fed from Silent Way will be affected...

Before I go ripping my cables apart, I wanted to get your input on this one....

Erik
os
Don't feed your synths with CVs more than the synth's supply voltages (e.g. 12V for Eurorack).

Not quite clear where this 44kHz sweep is coming into things. Is that your input to the AC Encoder? Or are you testing your cables with an external oscillator?

If you're viewing the output of the rectifier cable on your scope, you should be looking at a flattish DC value if you feed it a constant amplitude signal.
Sablerock
10-4 Os on the voltage limits,
The 44khz signal is being fed from a waveform generated by Soundforge (audio editing program) to the outputs I've allocated for CV use. I do obtain a flat(ish) DC level at constant amp signal, solid as a rock and tunable to 10mv.

I just picked up some .47uf and .22 uf caps and will bread-board them tonight to see if the time constant decreases on discharge. I've been reading posts re: Tantalum vs. common Electrolytic and seems that the Tantalum type are NOT recommended for this type of application.

I'll post results once complete. Perfect sine wave or not, it was fun being able to modulate my Electrix Filter Factory with my 1-44khz sweep thru CV last night. Can't wait to test it on the Korg Maxi and MonoPoly!!!

Erik
Sablerock
Os and Gang,

So I have AC Encoder running into my M-AudioDelta 410, Half Rectifier Cables with the voltage doubler circuit, and all this connected to the Korg Monotron CV Mod (www.dinsync.info/2010/06/how-to-modify-korg-monotron.html).

I am able to run the calibration process and trigger notes via Midi, and get about 5 Octaves. Unfortunately, it seems that the capacitors in the Half_Rec cables I made have a high time constant for capacitor discharge, and so the dischgarge causes notes pitch-fade down after each keypress releases. How do I need to modify the circuit to allow for a much shorter time constant at key release?

BTW, the caps are .47uf 50v

Thanks,

Erik
os
Shorter time constant just means a smaller capacitor value.

However I'm slightly confused by what you describe, since the pitch shouldn't change at all if you just release a key. Too large a capacitor will give you a 'glide' effect between notes, but not just at the end of one note played and released.
Sablerock
Thanks for the response OZ. I'll do a capacitor swap once I get my gruuby finger on some lower value caps. As to the question of this affecting pitch: Apparently with the Monotron (per other users), the Gate voltage is tied to the pitch, so as long as the gate value stays constant there isn't any issue. I don't know why Korg did this, maybe as some sort of 'tuning' abitlity. As a workaround I did the following:

1) calibrated the Korg with the gate voltage in ACEncoder at max (1.000), ditto for VoiceController Gate output voltage.
2) after calibrating (I get about 5 octaves), I adjust the Gate output voltage down to the lowest thereshold the Monotron recognizes (approx 1.5 V). Since the voltage drop in the Gate on key-release causes the signal to ramp down from cap discharge, it falls below the threshold, in effect eliminating the symptoms.
4) Because I had to adjust the Gate (affecting pitch on the monotron), I either transpose the midi notes to tune, or use the VoiceControllers Detune to get it perfectly in tune.

I know this is only a temporary workaround, but until I get the Cap Discharge to a much smaller time constant, it is what I'm doing...

I'm probably looking at going down to a .1uf cap. I hear people talk about the smaller values having side effects when it comes to range. Will I lose Octaves going too low in Cap value?

Erik
os
Interesting info, thanks.

If you use too small a capacitor the whole thing just becomes unstable. You'll know it if you hear it!

The right capacitor value varies so much from synth to synth, it's impossible to predict what the ideal choice will be. You just have to experiment.
Mans
Are these circuits useful when using a DC capable soundcard like the motu's? I have an ultralite coming my way and think I can expect about 4V from its outputs? Will the voltage doubler circuit boost this to 8V?
os
Yes, you can use the voltage doubler with DC-coupled interfaces too.
Automageddon
Big question, how do I check the voltage output?
(Noob question I know).
I have a digital multimeter available.
os
Plug a cable into the output.

Hold the multimeter probes in contact with the tip and sleeve of the plug at the other end of the cable.

Read voltage off multimeter.
Automageddon
I get a miserable 1.2 with a 1uF capacitor, using the half-way rectifier cables on a m-audio fast track ultra.
I'll now try to find an electronic shop in the area and hopefully get hold of smaller values.
Then I'll try the voltage doubler circuit.

I know I'll give up in the end and get the ES-1 module, but I'm loving the learning process.
PrimateSynthesis
This might be a bit off-thread, but I just read the Expert Sleepers page, and I'm curious what VCA's have to do with the CV input, how could a CV input work with an input that is AC coupled? hmmm.....
os
PrimateSynthesis wrote:
This might be a bit off-thread, but I just read the Expert Sleepers page, and I'm curious what VCA's have to do with the CV input, how could a CV input work with an input that is AC coupled? hmmm.....


PrimateSynthesis
Thanks, now I see what you mean. Although I think it would be easier to have it written somewhere...
billmeirelles
Sablerock wrote:
Thanks for the response OZ. I'll do a capacitor swap once I get my gruuby finger on some lower value caps. As to the question of this affecting pitch: Apparently with the Monotron (per other users), the Gate voltage is tied to the pitch, so as long as the gate value stays constant there isn't any issue. I don't know why Korg did this, maybe as some sort of 'tuning' abitlity. As a workaround I did the following:

1) calibrated the Korg with the gate voltage in ACEncoder at max (1.000), ditto for VoiceController Gate output voltage.
2) after calibrating (I get about 5 octaves), I adjust the Gate output voltage down to the lowest thereshold the Monotron recognizes (approx 1.5 V). Since the voltage drop in the Gate on key-release causes the signal to ramp down from cap discharge, it falls below the threshold, in effect eliminating the symptoms.
4) Because I had to adjust the Gate (affecting pitch on the monotron), I either transpose the midi notes to tune, or use the VoiceControllers Detune to get it perfectly in tune.

I know this is only a temporary workaround, but until I get the Cap Discharge to a much smaller time constant, it is what I'm doing...

I'm probably looking at going down to a .1uf cap. I hear people talk about the smaller values having side effects when it comes to range. Will I lose Octaves going too low in Cap value?

Erik


This is exactly what I have done on my monotron mod, with a 0.1uf cap the problems with the gate are gone, I still get 5 octaves with a voltage doubler for pitch, using a 1uf cap for pitch is a bad choice too, it will give the signal a sort of gliding effect, I'm using 0.1uf caps for everything, works fine with the monotron.
frijitz
os wrote:
In case anyone wanted to try the new options, but wasn't sure how to translate the circuits above into cable wiring, here are some diagrams:

Half-wave rectifier:



Voltage doubler:


For clarification, if you wanted the half-wave rectification to use the full swing of the balanced output you would leave the TRS shield disconnected and connect the TRS ring to the output shield, as in the lower diagram?

grin

Ian
os
The ring-to-shield connection in the lower diagram is probably not a good idea (I realise now). In fact the half-wave rectifer used to show the ring-to-shield connection, and I changed it.
frijitz
os wrote:
The ring-to-shield connection in the lower diagram is probably not a good idea (I realise now). In fact the half-wave rectifer used to show the ring-to-shield connection, and I changed it.

seriously, i just don't get it
So then the output voltages are?
Sorry, I'm totally confused with all the variations.

grin

Ian
os
What are you trying to connect to what? If you let us know that, maybe we can advise the best solution.
frijitz
os wrote:
What are you trying to connect to what? If you let us know that, maybe we can advise the best solution.

Right now I'm trying to figure out how your schematics work, in preparation for updating my interface. I'll just have to figure it out myself. After all, it's not exactly rocket science!

grin

Ian
Tronketz
Is it possible to make a voltage increasing circuit with just TS to TS or do I need TRS to TS?
os
You can use an unbalanced (TS) connection.
Tronketz
Which circuit do you suggest for TS to TS?
os
The original voltage doubler above will work:

just connect the sleeve on the left where the ring is shown connected (which arguably is the correct circuit for a TRS plug, too).
knob_alchemist
Very Interesting...I want to try this solution...When I well understand with this circuit is not possibile to have a negative voltage or? But what range can I achieve? 0-5 V?
os
No, you won't get negative voltages from this. The range you can achieve is entirely dependent on what you're feeding into it.
mirarimusic
so how does this go for banana??
sad banana
mirarimusic
Man Im lost .. ive attempted .. but im honestly so lost .. there are so many capacitor types, variations, values, etc...

is there a parts list...?

i went to radia shack and attempted to make this on a breadboard...but im lost.

Dead Banana
os
mirarimusic wrote:
so how does this go for banana??
sad banana

You'd need to run a ground connection from the synth to the connections that would otherwise go to the cable shield.

Quote:
is there a parts list...?

A 1uF electrolytic capacitor and a 1N4148 diode is a good starting point.
mirarimusic
os wrote:
The original voltage doubler above will work:

just connect the sleeve on the left where the ring is shown connected (which arguably is the correct circuit for a TRS plug, too).


ok so ive done this cable.. but i have no voltage change and my output.

I do get a peak voltage and then it slowly drops out to almost nothing...

here is my cable below .. is it correct? .. it seems simple..

red wire here is tip... and the black cable on the right goes to the buchla ground.

but what am i doing wrong?


mirarimusic
by the way.. i wanted to be clear in what im using...

i am using Ableton>Silent way or Volta> MOTU Ultralite > Buchla 281e.

.. and ive just tried the half wave rectifier and i get less output than originaly
(3.6v as opposed to 4.06v)

here is a pic of that one.


i know i MUST be doing something wrong i just dont know what.
seriously, i just don't get it very frustrating
os
Are you simply forgetting to use Silent Way AC Encoder?
mirarimusic
ARE you shittin me???

I was under the impression that it would just double the voltage coming off my MOTU ultralite..

i feel like a schmuck....

so what exactly do i need to make this work.. im not attached to teh ultra lite at all..

i need to get ideally up to 10v(positive voltage only)..
bsmith
insert that ac encoder plug as the final silent way plugin of whatever chain on the outputs you're wanting to send voltage through, and click the 'enable' button for the side(s) you are wanting to use it on.
Filch
os wrote:
What are you trying to connect to what? If you let us know that, maybe we can advise the best solution.


I'd be wanting to connect my RME Multiface II outputs to my euro. What would be the best solution for me? These would be going through a 1/4" - 1/4" patchbay , but I don't think that will affect this.
mirarimusic
https://www.muffwiggler.com/forum/images/smiles/icon_hail.gif

THANK YOU B SMITH!!

but its still not enough to trigger the281 e i guess..

gonna add more.. but thank you
bsmith
np! wasn't there like a superduper voltage dodecadupler circuit (or at least tripler) earlier in this thread? maybe try that out - or if you have an offset handy you can mix gate with somehow to nudge it up there.
here's a lame vid i did last summer showing buchla 261e calibration with silent way(albeit without needing to use the ac encoder):
mirarimusic
yea i think a volt tripler .. im gonna try now..
mirarimusic
ALRIGHT!!!!! The Voltage trippler worked . now i need to get some more diodes...
os
Filch wrote:
I'd be wanting to connect my RME Multiface II outputs to my euro. What would be the best solution for me?

Go buy an ES-3. Or an ES-1.

Otherwise, build the rectifier cables as above.
LonDonsen
Hey guys, I will build a small box, with the voltage doubler circuit below, very soon (for use with AC Encoder). Will 1N4001 diodes work too or are they too sluggish? Should I prefer the 1N4148? What if I want to add a signal LED per cable or stereo jack, where exactly would I have to place it in the schematic? Would this require an additional resistor? Sorry, double post. I'm not able to delete the other one.

os
1N4001 should be fine.

An LED would connect to the tip on the TS jack. Yes, you'd need a series resistor.
paris
hi!
i'm new to silent way and just trying to get the demo calibrated with my set up. i've been reading all the threads and have a question...

my audio interface is an m-audio fast track ultra.
right now gate is working but can't calibrate CV and realize i need to build a cable.
in the case of this audio device, it appears from what i've read here that i should build the voltage doubler, correct?
and any advice on best capacitor values for this interface?

thank you and sorry if this is a repeat.
os
Voltage doubler or the basic half-wave rectifier, yes.

You'll just have to experiment for the best capacitor value. It depends on what you're controlling (i.e. the synth) as well as the interface.
paris
Thank you and btw the suite looks quite awesome!
beep
Hello

just built the cable with the voltage doubler.

I'm using a M-Audio Fast Track Pro.
Controlling DIY VCO, which gets nice response from 0 to 9V


If I use the default circuit, there is no response.
If I use voltage doubler, there is slightly a response, half an octave.
voltage is still too low. is it a known issue that the output voltage of the
FT Pro is lower than other audio interfaces?
os
I'd be surprised if it were that low.

Do you have a multimeter? Could you measure the voltage generated, when disconnected from the VCO and when plugged in?
obiex
Man, I wish somebody would make breakout boxes for us less technically proficient. I regrettably sold my ES-1 to make space in my 6U.
oculus
Arnoid wrote:
I just made a voltage trip.ler circuit hihi


Now i'm getting 7V !!! at maximum...
Solid tuning over 7 octaves It's peanut butter jelly time!



Do hou have a schematic of this ? Thought i saw it before but cant find now thanks kind regards f

Nevermind somehow the schematic picture wouldnt load up berore but now it does
snaper
Hi guys,

Built this AC stuff, but not into a cable, but before a simple amp to boost the signal.
My problem is that it doesnt work correctly...
With an LFO, its great, I can control filters, etc.
But.
If I set up a simple seq in Max, the pitch drops back on every step....ahm, like piu-piu-piu.

Is this OK?

Does the same with Silent Way...

Seems the voltage drops quickly, even if the signal there.
snaper
Weird,

Ive tried it directly from my macs soundcard, same problem.
os
Are you using the Silent Way AC Encoder plugin?
snaper
os wrote:
Are you using the Silent Way AC Encoder plugin?

Im confused.
I should the ac encoder plug and silent way together?
os
The AC Encoder is what makes the rectifier circuit work.
snaper
Ok, now it works!
Real magic man!
How does it work? If I may ask wink
Jsharpphoto
Sorry to resurrect a thread this old, and for my very first post...

I have a question about running this DC coupler cable. I do NOT have a modular synth, I have a moog sub 37. I'm not interested in trying to send CV to it from ableton, all I need to do is send clock signal to a Koma Electronk FT201. I saw a video where someone used the built in click in ableton, sent through a DC coupled sound card to a Make Noise Maths module for clock sync. Could I use this cable circuit to accomplish the same thing? I don't need to send specific tuning like for controlling an oscillator, just time.

If I just need clock, do I need expert sleepers at all?

Currently, the clock is syncing using a regular audio cable, but I'm getting a lot of retriggers, assuming it's because the output is AC coupled. It's a presonus firebox.
os
Are you using Live's click, or a proper clock pulse e.g. from Silent Way?
Jsharpphoto
The native click
os
That's an audio signal, so you're likely to get double triggers. Try an actual clock pulse.
Jsharpphoto
It seems to be working constantly, but I'm open to try other things. Where can I download a pulse file?
os
You could use the demo of Silent Way to generate a clock, and just record its output.
popmatik
Hello. I'm hoping someone can help.

I've made the cables to connect my Metric Halo 2882 using the Half-wave rectifier circuit but I'm not able to get anything to really work. Now i'm sure this is because of something I'm doing but I'm hoping someone might have a clue what I'm doing wrong.

I've followed the tutorial for setting up with Ableton and have everything routed correctly through the Metric Mio console.

When I plug a lead into the gate input I get a constant note. I can make this stop and only trigger the gate through MIDI if I adjust the AC encoder maximum to 0.072. Does that seem right?!

If I connect the other lead to Pitch/CV then I get a very high frequency from the synth. If I run calibrate it does a descending squeal but doesn't get to lower registers at all. I'm thinking there must be something up.

I'm using a TRS lead on both sides at the mini jack side I have soldered the ring to the shield as it says in the instructions. I'm using a 1uF 50v Capacitor and the diode it states in the instructions. Here are the images of the 1/4 inch side. I took a few different angles so hopefully you can make it out.





Any suggestions as to what I'm doing wrong I'd love to hear. I should point out the Synth is a Moog Prodigy with a kenton cv kit added. The cv works as expected when connected to my Microbrute.

Thanks anyone who can help! [/img]
popmatik
Hi again folks,

I made some progress with this this morning in terms of getting more info.

I disconnected the cables from my Moog Prodigy and plugged them into my microbrute. Thinking that maybe the Moog needs more voltage or something so wanted to test how the microbrute behaved.

With this setup I was able to get the synth calibrating but I could only get 10 notes... not even an octave :(

I'm wondering does this indicate not enough voltage? I cranked the output on the Metric 2882 to +28.5 db but that meant nothing happened. Reducing the gain to below 0db meant that the calibration was wonky and I got less notes.

Any ideas would be great! Thanks
popmatik
Hello again!

I've made a bit more progress smile

If I run the CV out of the metric 2882 into my Moog CP-251 attentunator and boost by 5V I'm able to calibrate the Prodigy and get 4 useable octaves. So I'm thinking this points to the cable I built not providing enough voltage to drive the Prodigy.

So what should my next steps be? Ideally I don't want to lose an attenuator on the CP-251 to do this so would trying another cable circuit be the thing to do?

OS in your tests with the Metric Halo what voltages were you getting out of it with your first cable circuit?

Thanks
popmatik
os

Just adding this in hope that it let's you know I'm here smile
os
The 2882 can output crazy voltage. You shouldn't have to boost it at all.

I would suggest that you don't worry about calibration to begin with. Just use Silent Way DC fed into the AC Encoder. Make sure you can get a decent voltage sweep just from moving the knobs in the DC plug-in.

Lots of things have to all work together to get the calibration to succeed so it's best to focus on one thing at a time.
popmatik
os
Thanks OS! I'll give it a go. I don't have a multimeter to read the voltages unfortunately (I can order one). Anything I can be doing in the meantime to help test?

The 1uf capacitor being 50v is ok? I have to admit I'm not an electronics person smile
popmatik
Just had a go with the DC plugin through the AC plugin into the Prodigy with me holding down a key. None of the knobs seemed to do anything until I moved the multiplier knob and that sent the pitch sky high but I was unable to get the pitch to come down from that point after that.

Any ideas?
os
The "Out -1->1" knob is the only one you need to use.
popmatik
Thanks os

If I plug the CV lead into my microbrute and turn that knob it works as expected. A sweeping pitch that starts below the middle of the range to supersonic.

If I do the same with the Prodigy though I get a screaming high pitch and no movement when I turn the knob.

So this leaves me with some conclusions:

1. The leads are working and soldered up correctly.
2. I'm getting something usable out of the Metric.
3. I've hopefully set things up in the Mio console right to route things (Direct outs on 3 and 4 receiving signal from DAW 3/4)
4. The Prodigy doesn't seem to like it.
5. The Kenton Kit I fitted to the Prodigy does work as I can get it to play using the Microbrute CV outs.

So I'm thinking a course of action would be to ask Kenton what Voltage the Prodigy needs to be driven? And get a multimeter to find out what I'm getting?

Anything else you'd suggest? Ever heard of a synth just doing a high pitched note and nothing else?

Thanks for all your help with this, I'm sure you are a busy chap so it's much appreciated!!
os
What that suggests to me is that the Prodigy has a very high impedance input, which is not providing the capacitor with a discharge path.

Try a moderate sized resistor (say, 10k to 100k) in parallel with the capacitor.
popmatik
os
Thanks very much for your expertise! I'll buy some resistors and give it a go. Unless I can find one to steal from a household item for now smile

When you say in parallel that means like this?



Would I need that on the gate lead too? I found that that wasn't triggering very reliably too.

Cheers again.[/img]
os
Yes, that's in parallel.

You'll just have to try it on the gate.
popmatik
os
Thanks will do! i'll let you know how I get on. Once I've got it working I'll do a video for you smile
popmatik
os
Hi Os,

I can't thank you enough for your help with this. I bobbed a 56k resistor in and boom working! grin

I had to put one in the gate lead too as that was holding notes too long if I didn't. So yeah I've got 5 octaves of working goodness (that's the limit of the synth I believe). Not to buy the plugin!

Cheers again.
os
w00t
Alex
Hey guys!

I have some questions since I can't seem to get this idea I had working.

I'm trying to control one (via the expression pedal input) one of those Line 6 M13 effects pedalboards by using the silent way AC encoder and the modified cables as seen in this thread.

I built the half-rectifier cable out of a typical 1/4" TRS cable. I'm using .22 uf caps and the diodes recommended in this thread (can't recall the part number that was given).

I have a tone generator in my DAW generating a 50 hz sine wave, then the silent way A/C encoder in the plugin chain after that (though I'm not sure it's necessary for this simple test?). If I measure the tip and sleeve of the cable it shows 3 volts or whatnot, and I can adjust that easily inside the DAW, or physically via potentiometers on my interface (Allen & Heath ZED R-16).

I've tried running the modified cable out of a channel's (you can digitally send a digital signal back into one of the mixer's channel strips with the R-16, which is what I'm doing since there's no actual "direct outs") Y insert jack, as well as bussing the channel's signal to an aux jack, and I get working DC voltage measurements from both, however when I plug the cable into the Line 6 M13 I can't seem to get it to control it at all!

Does anyone have any theories on what the problem might be? I've heard that the Line 6 M13 expression pedals are continuous voltage inputs, so I hoped it would work.

Here's a picture of my beaaaautiful cable!

os
It would be useful to know how the expression pedal is wired. Is it a TRS plug? Any more information about what it expects on the net somewhere?
Alex
From what I've read on the net it's a TS plug. I think there's a pretty standard design for CV expression pedals, but i'm not super great at electronics. smile

I think I might know the issue though - I think I need to short the ring to the shield on the TRS side entering the M13. I think that might be the issue, so i'll test that today.
Alex
Hmm, did that and still nothing. :\

Here's a post though where a lot people are talking about being able to control the unit with CV:

https://www.muffwiggler.com/forum/viewtopic.php?p=709295&sid=698c362cf 2ddf9d99e83f118ce7c3e9e
Alex
Hokay, so it turns out the Line 6 M13's CV input is weird in that it uses a mono cable instead of a TRS cable like most of the others.

So the M13's CV jack, the tip outputs about 3.2 volts and the sleeve is a just a sleeve! It connects to a variable resistor (which is what an expression pedal essentially is), tip to wiper, sleeve to "ground/reference" type thing, and that divides the voltage. You get the remainder of the voltage returning to the sleeve which the M16 then measures to figure out the pedal position.

So I think this diagram oughta do the trick. I won't know till I build and test it, though.

If anyone sees any reason this wouldn't work, let me know. Again, not my forte. smile

http://s4.postimg.org/3xfqu1w7x/diagram_wiring_m13.png

*Edit*

Doesn't work! I think it must be measuring the difference, not just taking the value that's returned to the sleeve. Unless anyone has any ideas I guess I'm going to have to try something a bit different like a JFET.
realitycontrol
I've spent some time crafting both the half wave rectifier and the voltage doubler using the diagrams on page 1.

Using an Echo Audio Layla interface and the AC encoder plugin I get a max of 0.13V with the half wave rectifier and 0.26V with the voltage doubler.

These values seem to be way off what other members have been able to get.
Does anyone suspect an issue on my interface or perhaps with my interpretation of the diagrams?

I have tried the following capacitors;
http://www.maplin.co.uk/p/01f-63v-85c-electrolytic-capacitor-au07h
http://www.maplin.co.uk/p/022f-63v-85c-electrolytic-capacitor-au08j
http://www.maplin.co.uk/p/1f-63v-85c-electrolytic-capacitor-au09k

And the following diode;
http://www.maplin.co.uk/p/1n4148-150ma-switching-diode-ql80b

Cheers.
os
Is the interface output actually turned all the way up?

Maybe post a photo of what you've built? Else it's hard to know if you've done it right.
realitycontrol
oops Computer audio was down.

Upon turning up the master volume I'm getting around 7V from the half wave rectifier, interestingly enough I am getting the same value when using just the DC plugin and a floating ring cable.

However, both values slowly go down whilst taking a reading with a multimeter, after about 10 seconds it will be <5V. I believe I read a post earlier where someone else was experiencing the same issue, will see if I can find it.
realitycontrol
Turns out that the earlier post which I thought may hold the resolution to my problem was in regards to using the AC Encoder plugin.

I am using the AC encoder after the DC plugin along with the half wave rectifier cable and yet the voltage reading from the output just won't stay still. It generally starts around 7-9V then gradually drops.

This is the first time I've attempted to follow an electronics diagram so I presume my handywork is at fault.
I'd appreciate if someone could take a look.



For clarity;
TRS - Tip - A1
Diode - B1 to C6
Red Cable - A6 to A12
TS - Tip - B12

TRS - Shield - A3
Capacitor - B3 to B6
White Cable - F3 to F15
TS - Shield - E15
os
That looks OK. When you say it gradually drops, what does it drop to? Is that with something (e.g. a synth) connected at the TS end?
realitycontrol
Cheers for taking a look.

It takes a while, but eventually it drops to somewhere between 2 and 3 volts.
This is all whilst the TS end is not connected to anything other than a multimeter.
os
Try it actually plugged into something. A multimeter doesn't really present a realistic load on the circuit.
realitycontrol
I've basically been comparing the output from silent way againts a multimeter reading from the pitch out on the Microbrute which provides me with a stable voltage.

Plugged it into the X input on a Disting (Mode 4C) and experience something similar to the readings I was getting.

Video available here: https://youtu.be/qcfNNn_Xvvg
os
Which version of disting is that? If it's a really early one, you might want to try putting a largish resistor (say 100k) across the TS output.
realitycontrol
It's a mkII.
Cheers, I'll give that a go this evening, delivery of resistors from RS arrived today.
realitycontrol
I get the same result. Popped the resistors ends into C13 and D15 on the above breadboard.

Had a go with a Focusrite Scarlett 2i2 this morning. The output is voltage is much lower yet it still does not stay stable whether it is plugged into the disting or not.

You've mentioned elsewhere that one could expect this sort of a result if the interface is not DC coupled and one is not using the AC encoder plugin. Is there a chance that there is an issue with the way I am using the AC encoder? It's running on Ableton Live 9 64bit, Win 7 64 bit and it's if that makes any difference.

Cheers.
os
It's possible. Why not post a screenshot of your setup in Live?
realitycontrol
Sure;

os
That looks OK, assuming you're using output 7 on your audio interface.

Are you sure you have the right connections on the TRS jack? It's hard to see from the photo which part of the socket will make contact with which part of the plug.
realitycontrol
Thanks Os.
Assuming that I'm using output 7 would be correct.
Just used a multi-meter to confirm the connections, Tip is going into A1 and Shield is in A3 on the breadboard.
os
Grasping at straws now, but what sample rate are you running Live at?
realitycontrol
I was running live at 44.1 kHz, the sound card was running at 96kHz.
Have had a quick play around and get a similar result when both the DAW and Soundcard are set to the same sample rate.

Is there a particular sample rate which I should stick to for any future tests?
os
Quote:
I was running live at 44.1 kHz, the sound card was running at 96kHz.

Is that even possible?

Let's stick to 44.1 system-wide for now.
realitycontrol
It was outputting sound just fine! But yeah, bit of a mistake on my part.

Right so I finally think I'm making some head way.
I put together the bridge rectifier circuit and I am able to get a steady voltage of up to 19 volts out of it.
One little niggle though; the voltage takes a while to drop, going up in voltage is instantaneous and solid but I've got a constant slew when the notes are falling.

Any wise suggestions?

Edit: Resistor over the outputs, you've previously answered that question for me.
os
So you're good now?
realitycontrol
Yeah all good, thanks for sticking with me.
pwranml
What capacitors and diodes should I use? Going to try the original circuit to keep things as simple as I can. I have a Focusrite Saffire 6. Is it possible to take advantage of the rca outs as well? Also might be a dumb question but what about a laptop headphone jack?
os
Start with a 1uF capacitor and go up or down from there. Any diode will do but the 1N4148 is a popular choice.

The RCA outs will probably be very low level, but you could give them a go. Likewise the laptop headphone socket.
scott.lepore
Can anyone tell me if the input to SW, used to calibrate the pitch CV out, needs to be an AC cable, or is it a regular audio cable. (FWIW I'm using a Focusrite 18i20 and an 8i6.)

Thanks!
os
Regular audio.
scott.lepore
os wrote:
Regular audio.


Thanks os. I'm having a problem getting any real voltage out of the ADA8200 via my AC cables. The ADA is connected to a Focusrite 18i20 BTW.

I'm using Reaper and have followed pinksoir's basic setup instruction post https://www.muffwiggler.com/forum/viewtopic.php?t=81296&highlight= pretty much to the letter. I setup an AC encoder plug on each of the output tracks, though I didn't see any instructions on how to do this and may have gotten it wrong.

With the (software controlled) outputs on the ADA8200 cranked I get about .6 v on the gate out channel and nothing at all on the pitch cv. It looks like the no pitch cv is being received on the relevant track (no meter bounce at all within Reaper).

Do I need to build one of these voltage doublers, or triplers??

Thanks.
os
You won't have any pitch CV until you've done the calibration process.

0.6V sounds a bit low for the gate. What settings do you have on the AC Encoder?
ground_state
Based on
os wrote:
Likewise the laptop headphone socket.

I should be able to use the built-in hardware on my MBP + SW AC Encoder + frankencable (probably with voltage tripler) and get CV out?
cuz I'd drop $50 on SW in a heartbeat compared to SW + *any* of the audio interfaces I've seen discussed here. I'm a total amateur/dilettante, so explaining even a USD$200 audio interface to my spouse is a non-starter smile
(Aside for the curious; I'm starting my analog semi-modular foray by building an Anushri/Anookum - sink or swim, etc.)
ispot
sorry to bump this, i have somewhat succes with the voltage doubler circuit + a 10-100k resistor parallel with last capacitor, MH ULN2 with ADA8000 i get about 4,5 octaves. i just tried the voltage tripler with the resistor still in // with the last capacitor, but this results in fm noises. where do i place the resistor in the voltage tripler circuit? and does anybody have a diagram of the tripler? i'm doubting about my wiring atm. thanks! Mr. Green
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