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 Forum index » Clavia Nord Modular » Nord Modular G2 Discussion
G2X and moogerfooger Low Pass Filter
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varice



Joined: Dec 29, 2004
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PostPosted: Thu Jan 08, 2009 12:13 am    Post subject: Reply with quote  Mark this post and the followings unread

Jee-Bee wrote:
When i read this topic and i hear the samples i think i wait with the expansion board and buy a moogerfrooger first.
the only thing i don't understand the electotechnical stuff. and i can build in the expansion board as well


Hmmm... if you have a chance to get a G2 expansion, I would recommend to do that first, but I guess that it depends on how you want to use your G2....

But, in any case, post here if you have any questions about modifying your G2 for DC CV output.

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varice



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PostPosted: Thu Jan 08, 2009 1:08 am    Post subject: Reply with quote  Mark this post and the followings unread

varice wrote:
xav wrote:
I tried the mooger fooger yesterday and noticed a different sound than the g2, even when the mooger fooger is bypassed, unfortunately (less high frequencies).
But I was impressed by the G2 classic filter that's not ridiculous at all. Self modulation sounds really better on the mooger fooger (imho), especially in high frequencies.


Yes, the moogerfooger does not have a true bypass, the audio still goes through the drive circuit. Something to be aware of if you want use it in the conventional way. But, by the way that I use it in an external loop, the filter is only in the loop when I want to use it.

I had not noticed any loss of high frequencies when bypassed (normally I have the filter on all the time), something I will check.

There are interesting differences between the Moog and G2 Classic filters, especially at or near self oscillation resonance settings. But at lower settings, since I have had the moogerfooger for a while as a reference, I have learned how to patch the classic to sound closer to the Moog. Similar to the Moog, the classic will get a little more distorted as you drive it harder. And it seems to help to add a little saturation distortion before the classic input if you trying to get that nice and creamy Moog filter overdrive sound. Though, with a higher overdrive, the moogerfooger sound wins hands down!


xav,

Yes, you are very correct, there is a slight but very noticeable roll off of high frequency response with the MF-101 - even with the bypass on or with the filter opened up all the way. I had not noticed this before. I contacted Moog Music, and they suggested a modification. I have not tried their mod yet, but my own trials resulted in that I could add some "pre-emphasis" in the G2 output before the MF-101 to compensate... using an EQPeak module set to a freq of 16K, BW of 1 octave, gain of about +3dB... but my tests were using a primitive spectrum analyzer in a consumer GEQ and my bad ears... (I really do need a good spectrum analyzer...)

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Oli



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PostPosted: Mon Jan 19, 2009 7:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hey, what a great thread. Very glad I stumbled across this one.

I have been thinking about using an external filter with the G2 since I first tried it. I'm really not too impressed with the onboard filters so far, though I still have a lot to learn about controlling the G2's sound. I had hoped for something more inline with the Nord Lead 1, which was the only Nord synth I had really tried before buying my G2 untested in ebay.

I had been thinking of using either an SSM2044 or descrete Moog style filter, or even a 303 filter clone. I hadn't resolved the control scheme though. This audio output mod is an interesting idea though.

varice wrote:
...I have not tried their mod yet, but my own trials resulted in that I could add some "pre-emphasis" in the G2 output before the MF-101 to compensate...


Varice, are you (or have you been) a VHF/UHF engineer? I used to work in an HF radio company, and did some interfacing to VHF/UHF radios. The term "pre-emphasis" brings back memories.

Thanks so much for writing this all up, and for the interesting samples, too.

Cheers

Oli

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Oli



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PostPosted: Mon Jan 19, 2009 7:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

drapdap wrote:
One thing i wanted to tell you (and others who been messing with this) is that how great fun a passive Ge-diode ringmod is with a G2!


Hi róbert,

Sounds like you have really explored external modular patching with the G2; cool!

Not sure if your interested, but I was just looking at this paper on ring modulator modelling. Looks like the author has done a pretty decent job of modelling this.

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varice



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PostPosted: Tue Jan 20, 2009 12:43 am    Post subject: Reply with quote  Mark this post and the followings unread

Oli wrote:
Hey, what a great thread. Very glad I stumbled across this one... Thanks so much for writing this all up, and for the interesting samples, too.


Thanks Oli for your kind comments. It really is my pleasure to share this. I'm really glad that my little experiment is of some interest...

Oli wrote:
I have been thinking about using an external filter with the G2 since I first tried it. I'm really not too impressed with the onboard filters so far, though I still have a lot to learn about controlling the G2's sound.


Yes, I agree with your first impressions about the sound of the G2. But, the G2 can easily be patched to sound less cold (digital) - don't hesitate to use some EQ - roll off the ultra high freqs a bit, boost the low freqs... add just a little touch of saturation distortion... throw in Rob's tilt filter if necessary...

Oli wrote:
I had been thinking of using either an SSM2044 or descrete Moog style filter, or even a 303 filter clone. I hadn't resolved the control scheme though. This audio output mod is an interesting idea though.


I would highly recommend modifying your G2 to get a DC CV output to modulate the cutoff freq of the filter of your desire... this mod is just great for monophonic G2 synth patches to be used with an external filter...

Oli wrote:
Varice, are you (or have you been) a VHF/UHF engineer? I used to work in an HF radio company, and did some interfacing to VHF/UHF radios. The term "pre-emphasis" brings back memories.


Hell no! VHF/UHF stuff is too freaky and complicated for me - (dating myself as an old man) I conjured the "pre-emphasis" term from long ago... used for analog tape recording EQ/noise reduction... (and maybe for phonograph mastering EQs?)

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Oli



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PostPosted: Tue Jan 20, 2009 3:27 am    Post subject: Reply with quote  Mark this post and the followings unread

varice wrote:
Thanks Oli for your kind comments. It really is my pleasure to share this. I'm really glad that my little experiment is of some interest...


Yes, most definitely of interest!

varice wrote:
Yes, I agree with your first impressions about the sound of the G2. But, the G2 can easily be patched to sound less cold (digital) - don't hesitate to use some EQ - roll off the ultra high freqs a bit, boost the low freqs... add just a little touch of saturation distortion... throw in Rob's tilt filter if necessary...


It is a bit dissapointing that Nord can produce filters for the Lead 1 that sound to me as really fantiastic virtual analogue filters, and yet the G2 several years later comes up with such weak, mild, forgettable filter sounds, that I don't even want to show my friends. Lead 1 filters didn't really sound truly analogue, but I think they sound great all the same. Analogue-esq, but really clean and cutting. A great sound.

I do enjoy some dirtier patches from the archive. I love one ARP2600 clone, and a detuned Oberheim 4 voice clone. I haven't analysed the patches yet, though. I have pretty much got out of the habit of thinking about filters with the G2. It has lots of strong points, but the native filters are not amongst them. I am still really just a n00b with the G2 though.

varice wrote:
I would highly recommend modifying your G2 to get a DC CV output to modulate the cutoff freq of the filter of your desire... this mod is just great for monophonic G2 synth patches to be used with an external filter...


This one is going on my build list. I'm trying to complete a few DIY projects already (been going on for a while), plus repairs to some other synths. This job will be tagged on to the end of the list, along with a filter board, and possibly a couple of other things.

varice wrote:
Hell no! VHF/UHF stuff is too freaky and complicated for me - (dating myself as an old man) I conjured the "pre-emphasis" term from long ago... used for analog tape recording EQ/noise reduction... (and maybe for phonograph mastering EQs?)


Ahh, I see. Well, the same principle applies to FM transmission. The higher frequency signal components incur more noise, so pre and post emphasis is used. Actually, various forms of this gets use in a lot of applications.

Cheers,

Oli

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PostPosted: Thu Feb 19, 2009 2:40 am    Post subject: Filter Comparison Patch Reply with quote  Mark this post and the followings unread

Here is a little noise-making patch that I used to help compare the sound of the Moog MF-101 with the G2 Classic filter. It has two parts - the first part located at the top of the Editor VA window plays the bass line and has a switch that allows either the Moog or the Classic filter to be selected. The other part plays the lead line. This version of the patch has the Classic filter selected for all variations. The modules for the Moog CV signal and audio I/O are in place (but muted) to show how the signals are patched to interface the Moog filter with the G2X. Variation 7 was tweaked to the point that it is not easy to hear the difference between the Moog and the Classic filters. Note the LevAmp1 and Saturate1 modules that are used to set the drive level and add some distortion to the Classic to match the sound of the MF-101 set to a moderate drive level.

The patch uses looping Random Pattern generator modules to produce note values, stepped filter cutoff frequency modulation signals, and some note gates. The patch will play a loop for four bars and then a couple of clocked random step modules get triggered to generate new values to modulate all the pattern generators.


Rapid Fire 8mf b.pch2
 Description:
Filter Comparison Patch

Download
 Filename:  Rapid Fire 8mf b.pch2
 Filesize:  6.74 KB
 Downloaded:  662 Time(s)


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PostPosted: Fri Jan 22, 2010 6:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

varice wrote:
davep wrote:
Hey, do you think this mod would work for the original NM1 as well? Since the NM1 has no midi out modules, a mod like this could be very VERY cool for folks who have an NM1 but no G2. It would allow you to control your analog modular synths from control signals generated in the NM1.


I think that the NM1 could be used this way.

Up to 4 CV or gate signals - generated at high resolution - by whatever modules you can patch in the NM1! Sounds pretty interesting...


Hmmm - unfortunately there seems to be some problem with the G1 output levels. Sven (3phase) mentions in this thread:

http://electro-music.com/forum/post-280954.html&highlight=#280954

that he bypassed the output caps but had trouble getting the output levels to track properly. I haven't tried this mod on my G1 yet. It would be a shame that it does not work well. I have been kicking around the idea of modifying my Realistic Concertmate MG-1 (a non-MIDI analog monophonic synth built by Moog) to accept CV outputs from my G1 for filter cutoff and VCA (the MG-1 already has a jack input for pitch CV). This G1/MG-1 hybrid would greatly expand the capabilities of the MG-1:

* MIDI note and external CC interface
* G1 pitch CV from internal sequencers and other pitch generators
* the ability to mix in G1 oscillators and other sound generators
* better envelope generators for filter and VCA modulation
* vasty expanded modulation abilities with multiple LFOs, etc.

All while keeping an analog signal path with the goodness of a real Moog ladder filter and no digital aliasing!

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PostPosted: Fri Jan 22, 2010 6:20 pm    Post subject: Update Reply with quote  Mark this post and the followings unread

A note I should mention:

I had suggested using a Saturate module before the G2 Classic filter to better emulate the sound of an overdriven Moog filter, but I have noticed that the Saturate module generates a lot of aliasing noise (very noticeable with high pitch notes), even with mild saturation settings (sigh). The Overdrive module suffers this affliction also. Rolling Eyes

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PostPosted: Tue Mar 23, 2010 1:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

varice wrote:
mosc wrote:
Another way to get a CV out of the G2 if you don't want to go the MIDI route some constant audio through a VCA one of the outputs, and use an outboard envelope follower circuit.


At first I had thought about using the MF-101 envelope follower to get a filter cutoff signal from a G2X output into the fooger - but this would have required a modification of the fooger to separate the envelope follower input from the fooger audio input. And I assumed that the follower would probably have been too slow to follow fast envelope changes anyway.


But, if you would rather modify the moogerfooger filter to separate the envelope follower from the filter audio input, Bob Moog himself gave instructions on how to make the modification. The instructions are posted recently on the Moog Music forum:

http://www.moogmusic.com/forum/topic-9020.html

Here is a copy of the OP instructions:

JimF wrote:
Hi everyone,

Sorry about the delay in getting this info up - I promised it several weeks ago.

The question was how to modify an MF101 to accept a second audio signal in to the envelope follower, so that the filtering of the main signal can be enveloped by a second audio signal.

I did this to my MF101 about 10 years ago, after sending a couple of e-mails to Big Briar, and receiving answers from Bob Moog himself with explicit directions. I no longer have the computer on which the e-mails were received, and I have no backups from that time. So the following is retyped from printouts of the e-mails. Points to note:
- these instructions apply to a Big Briar MF101, vintage 1999. I have no idea whether the board and circuit of the current version of the MF101 are the same.
- I haven't got around to taking photos of the guts of mine - sorry...
- these directions are provided under the motto "no responsibility taken" - if you wreck your MF101, that's your problem Smile
- BUT I know that the instructions work - my MF101 has been doing this happily since 2000, when I made the modification.

First e-mail from Bob Moog, 2 March 2000:
"If you're adept at desoldering resistors on circuit board with plated-through holes, you can lift the end of R5 and connect your external signal to it. If you have access to shop equipment, you can drill an extra hole on the back panel of the MF-101, mount a bridging jack in that hole, and then wire the jack up to the R5 part of the circuit."

Several months later, when I finally got around to doing this, I asked for more explicit instructions:
Second e-mail from Bob Moog, 5th October 2000:
"1. DO NOT REMOVE THE CIRCUIT BOARD. Remove the bottom panel and face the jacks away from you. Identify U2 (LM324A).
2. Immediately to the left of U2, starting at the top, are a) two diodes, b) a 270K resistor, c) a 100K resistor, and d) four more resistors. That 100K, right below the 270K, is R5.
3. Carefully unsolder the left end of R5, that is, the end away from U2. Apply your signal to that end of the resistor."

So that's it, folks. It's actually quite easy, and it works like a charm. Like everyone else on this forum, I'm eternally indebted to Bob Moog (may he rest in peace) for his generosity and willingness to help - as well as for the great instruments!

So, have fun!

Cheers,

Jim F.

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PostPosted: Tue Mar 23, 2010 11:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

hello varice,

thanks for this very interesting information. it is quite touching to read the instructions how to modify the mf-101 written by robert moog himself: what a nice person he was.

i hope to experiment with my nm in combination with my moog equipment soon. i believe this way one can make use the of the best of both worlds (digital and analog).


best regards

eike
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PostPosted: Thu Mar 25, 2010 10:57 am    Post subject: Reply with quote  Mark this post and the followings unread

I wonder if one of these could be modded to receive cv input from a G2?

http://createdigitalmusic.com/2010/03/24/korg-monotron-pocketable-85-real-analog-synth-with-ms-filter-hackable/
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PostPosted: Thu Mar 25, 2010 1:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

klangumsetzer wrote:
hello varice,

thanks for this very interesting information. it is quite touching to read the instructions how to modify the mf-101 written by robert moog himself: what a nice person he was.


Hello eike,

You’re welcome. There is something that I regret very badly, that I did not take the opportunity to meet Bob before he died and thank him for how much he influenced my life with his synth inventions. By all accounts, he was a very friendly and accessible man.

klangumsetzer wrote:
i hope to experiment with my nm in combination with my moog equipment soon. i believe this way one can make use the of the best of both worlds (digital and analog).


I agree. Both digital and analog synthesizers have advantages and disadvantages. The best trick is to combine them when possible to maximize the advantages, and minimize the disadvantages!

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PostPosted: Thu Mar 25, 2010 1:15 pm    Post subject: The Korg monotron Reply with quote  Mark this post and the followings unread

grimley wrote:
I wonder if one of these could be modded to receive cv input from a G2?

http://createdigitalmusic.com/2010/03/24/korg-monotron-pocketable-85-real-analog-synth-with-ms-filter-hackable/


http://www.korg.com/Product.aspx?pd=571

Hmmm… maybe… possibly…?

Wow, that monotron is so small though. Probably no room to add CV input jacks! Laughing It is so small that I think that it does not use discrete components for the circuitry, maybe a custom IC. Still, the points to add CV input for VCO pitch and VCF cutoff frequency should be easy to find. Since it runs on two 1.5 volt batteries, the required CV input range is also probably small. The max +4/-4 volt CV output of the G2 would likely be just fine.

I wonder how close they got this thing to sound like the MS-20 filter.

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PostPosted: Sat Mar 27, 2010 10:59 am    Post subject: Reply with quote  Mark this post and the followings unread

interesting indeed ... im interested to see what happens ...
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PostPosted: Sun Mar 28, 2010 9:51 am    Post subject: Re: The Korg monotron Reply with quote  Mark this post and the followings unread

While i was happy to see a new Korg analogue mini, i had some afterthoughts...

1th: from the price of the monotron, i can diy myself 4
ms20 filter. no fiction, fact, as i did that, i have four of these inside my modular, (2 pair) with proper cv inputs.
this isn't an argument, i just decided it's not for me. it shure looks cute, but i'd rather buy another stack of OTA's and transistors. Smile

2nd: sometimes building is easier than modding.
So the other thing, while this topic is on top again, i did mod my G2 upon the influence of Varice (thanks again!)
but somehow i was feeling unsafe with the mod as i can't afford another (expanded) engine.
Those bastards doesn't even sell them anymore. (...)
So i took another route.
Amplification: One volt goes in, ten comes out, and i can control whatever. Tried it on my diy equipment, and tried it also on a friend's moogerfooger lowpass, - i was unshure if the fooger tolerates 10 volt or not, but it did. pheww... that thing sounds nice, the moog. really nice. so in the end i used Ken Stone's adapter's schematics, as a working solution. it really does work nice... this thing:
http://www.cgs.synth.net/modules/cgs60_sba.html
they are out of stock now, but to be honest, i didn't buy pcb's, just mocked one up for myself, it's so easy and built dual units.

so i send a g2 out thru these x10 amplifiers, and forgot modding, removed the jumpers, call me a sissi.
the other mod i did i left in, the microphone input for the engine. Smile

so now i can send a ten volts pp oscillator signal out of the nord to the ms20 filters if i really want to. or trigger an EG from G2 drummachines. Smile

róbert
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PostPosted: Sun Mar 28, 2010 10:16 am    Post subject: Re: The Korg monotron Reply with quote  Mark this post and the followings unread

varice wrote:


It is so small that I think that it does not use discrete components for the circuitry, maybe a custom IC. Still, the points to add CV input for VCO pitch and VCF cutoff frequency should be easy to find. Since it runs on two 1.5 volt batteries, the required CV input range is also probably small. The max +4/-4 volt CV output of the G2 would likely be just fine.

I wonder how close they got this thing to sound like the MS-20 filter.


it depends which Korg MS20, the one with the Korg 35ic, or the later Ota (lm13700) version. they are significantly different. (my bet is the latter, as that part is still in production, and it's a more stable design, you can tune the self oscillation, quite musical, imho.) btw. Varice, it never was discrete circuitry, it was never a transistor filter, maybe the traveller was (have to check) from which the korg 35 ic originates, but not in the MS10-20.

Ah, if Korg would only push back the MS20 into production...

r.
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PostPosted: Sun Mar 28, 2010 2:53 pm    Post subject: Reply with quote  Mark this post and the followings unread

drapdap wrote:
…and tried it also on a friend's moogerfooger lowpass …pheww... that thing sounds nice, the moog. really nice…

Hello róbert,

Exclamation Now you know why I am so jazzed about using the Moog filter with my G2X Exclamation Very Happy Cool

drapdap wrote:
… i did mod my G2 upon the influence of Varice (thanks again!) but somehow i was feeling unsafe with the mod as i can't afford another (expanded) engine… and forgot modding, removed the jumpers … So i took another route. Amplification: One volt goes in, ten comes out, and i can control whatever… …so in the end i used Ken Stone's adapter's schematics, as a working solution. it really does work nice... this thing:
http://www.cgs.synth.net/modules/cgs60_sba.html

Yes, just using a jumper to bypass the DC blocking caps could be a bit unsafe. But my mod adding a 1k resistor to the G2 output opamp is enough to protect the G2 circuits from a simple short to ground or to other line level signals. A proper DC buffer amp would make a bit safer CV output mod. Actually, although that Ken Stone circuit is designed for AC signals, it can easily be modified for use as a DC CV buffer/amplifier. It can be powered by the G2 PSU and the gain scaled for your particular analog gear CV range requirements.

varice wrote:
…It is so small that I think that it does not use discrete components for the circuitry, maybe a custom IC...

drapdap wrote:
…it never was discrete circuitry, it was never a transistor filter…

Oops! I didn’t mean to imply that all previous Korg synths used discrete parts. All I was trying to say is that I speculate that the monotron may use a single custom IC for the whole synth circuit (VCO, LFO, and VCF all in one). In that case, the monotron may be a bit less easy to mod and hack.

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PostPosted: Tue Mar 30, 2010 12:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hmmm. There are better ways to get a DC CV out of an AC coupled output. The best way is to build a simple pulse width decoder. I think I'll start a topic in the DIY section and see if we can't get something useful going there. If now, sigh, I'll design one myself. They are easy enough to do.

In simple terms, you'd just use a square wave osc operating at about 10 KHz and modulate the pulse width. Outboard, you just integrate the signal and you'll get a voltage that is proportional to the pulse width. In the simplest case, you could do it with only one op amp and a capacitor. If you use two op amps you can at inversion, and scaling, as well as buffering.

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PostPosted: Tue Mar 30, 2010 1:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

OK, here is the thread I started in the other forum.

http://electro-music.com/forum/topic-41069.html

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PostPosted: Tue Mar 30, 2010 2:30 pm    Post subject: Reply with quote  Mark this post and the followings unread

Sorry, but you cannot derive a DC signal from an integrator that is getting an AC signal input! For that integrator idea to work, the input signal must already have an average DC offset!

If you are really scared of modifying the G2 for DC output, then amplitude modulate a square wave output and use a fast response envelope follower. That would work... kinda...

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PostPosted: Thu Apr 01, 2010 12:52 pm    Post subject: Reply with quote  Mark this post and the followings unread

varice wrote:
Sorry, but you cannot derive a DC signal from an integrator that is getting an AC signal input! For that integrator idea to work, the input signal must already have an average DC offset!


Good point. I've addressed this in the topic sited above. I suggest we keep the discussion of the PWM to CV conversion problem in that topic.

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varice



Joined: Dec 29, 2004
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Location: Northeastern shore of Toledo Bend
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PostPosted: Thu Apr 01, 2010 4:21 pm    Post subject: Reply with quote  Mark this post and the followings unread

mosc wrote:
Hmmm. There are better ways to get a DC CV out of an AC coupled output. The best way is to build a simple pulse width decoder. I think I'll start a topic in the DIY section and see if we can't get something useful going there. If now, sigh, I'll design one myself. They are easy enough to do.

In simple terms, you'd just use a square wave osc operating at about 10 KHz and modulate the pulse width. Outboard, you just integrate the signal and you'll get a voltage that is proportional to the pulse width. In the simplest case, you could do it with only one op amp and a capacitor. If you use two op amps you can at inversion, and scaling, as well as buffering.

mosc wrote:
varice wrote:
Sorry, but you cannot derive a DC signal from an integrator that is getting an AC signal input! For that integrator idea to work, the input signal must already have an average DC offset!


Good point. I've addressed this in the topic sited above. I suggest we keep the discussion of the PWM to CV conversion problem in that topic.

Well, you did complicate things a little bit by proposing the PWM integrator idea here in this topic, instead of just starting the new DIY topic. Now discussions of that proposal here in this topic, especially if they are directly related to the utility of the proposal as regards to this topic, would not be inappropriate, I would think. Smile

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funtykigs



Joined: Feb 09, 2010
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PostPosted: Sun Apr 25, 2010 2:54 pm    Post subject: Reply with quote  Mark this post and the followings unread

could the silent way AC encoder be used to get CV out of the G2 audio outputs without any internal modification?

http://www.expert-sleepers.co.uk/index_files/Silent-Way-AC-Encoder-video.php
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3phase



Joined: Jul 27, 2004
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PostPosted: Sun Apr 25, 2010 9:51 pm    Post subject: Reply with quote  Mark this post and the followings unread

funtykigs wrote:
could the silent way AC encoder be used to get CV out of the G2 audio outputs without any internal modification?

http://www.expert-sleepers.co.uk/index_files/Silent-Way-AC-Encoder-video.php


i could.. but the question is how much voltage it can create.. a one diode solution is not very efficiant..

i have a G2 with caps removed on 2 ports and a little protection resistor.. the voltage i get in the max is enough to get more than 3 octaves.. much less wouldnt be so nice..

Theese pulse w idea from mosc sounded interesting..what is the state there?
is that possible or not ?

actually i am thinking about external circuity aswell..but obviously not to avoid the removing of the caps.. i would like to find a way to send more than i cv over one port...

there are probably varios ways to achive that..

a plain ac to dc interface like the silent way could be maybe done with secific carrier frequencies and filters in the reciever..
or two gate signals can be generated on one port by utilizig the positive and negative half waves of the output.. BUT..

i am sure there are smarter ways when i see what was possible with an old fashioned modem...


good question..how does a modem work?
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