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 Feedback Wanted - New Module Proposal 
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Joined: Tue Feb 02, 2010 12:03 pm
Posts: 5
Post Feedback Wanted - New Module Proposal
I'm darms, the newbie PAiA elf (although a customer & user since the early 1970's). Our current CV spec is 0-10V and our older spec was 0-5V but I want to drive my Moog Voyager & Sequential Pro-One with our new modules. Problem is the Moog's CV spec is 0-5V for most & -2.5V-+2.5V for a few inputs & I'm certain the Pro-One is similar. I've designed an I/F translator circuit that can input any of these CV schemes and output in any other scheme. Since its functionality is not likely to be changed after it is built, I've proposed configuring it w/hard-wired jumpers making it a single purpose-built module w/4 I/F sections and it's up to the end-user how to configure & label the various I/Os. While the circuit itself is pretty simple, the problem with it is that it's pretty confusing as to how exactly to configure it, especially if we try to label the PWB. (Of course I can explain all of this in the manual)

My question to this community is - does anyone else see a justification for this module? Would it be worthwhile for PAiA to make a couple hundred of these? If the amount of discussion warrants it I'll post a copy of the schematic.


Fri Apr 16, 2010 3:57 pm
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Joined: Thu Sep 24, 2009 2:14 pm
Posts: 52
Post Re: Feedback Wanted - New Module Proposal
so.....
what does "I/F" refer to???

Remember the old 2720-12 Inverter/Buffer?
The little switch would change from Zero offset to +5.
This would make it an inverter or a non-inverting buffer.
Adding GAIN to the buffer would make it a preamp.

Your proposal would amount to a "times2" and a "divideby2" and "divideby4" module. Thereby, if U input zero-10volt, U could get 0-5V (divideby2), ...., or 0-2.5V (divideby4). Moreover, if U input zero-2-5volt, a "multiplyfunction" would be needed to make the output 0-10V (times2). Thus, U would need a 4-position switch that would change the gain of the opamp to output the range U need. This is all voltage not current.

Actually, this could have all been incorporated into the new 9754 preamp module!! To me, a preamp/inverter/buffer module with preset AND adjustable gains would be more useful to synthesists than "just" a preamp.

8-)

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Fri Apr 16, 2010 8:00 pm
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Joined: Tue Feb 02, 2010 12:03 pm
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Post Re: Feedback Wanted - New Module Proposal
toneman, I/F is 'darms speak' for InterFace. What I've proposed is a 4-channel I/F w/each channel's Av jumper-selectable as X2 or X0.5 w/the option of a 5V/2.5V/0V/-2.5V/-5V offset so we can go either way (which BTW is derived from a stable voltage reference, not a zener or voltage divider). I see no need to make this switch-selectable, once I built it as an I/F for my Moog there'd be no reason I'd want to change it later. Also I see no reason to add this to the 9754 as the preamp is:
1 - strictly for audio
2 - Cliff optimized its performance for audio
3 - all the balanced stuff (switch, XLR, circuitry) would have been wasted
4 - I want four of these in 1 RU not just 1

BTW, one of my philosophies is maximum function per RU. You'll be amazed at some of the new stuff in the pipeline & all the I/O & controls we're putting in a single Rack Unit (RU) while eliminating as many flying wires as possible. The pending 9747 was my design.


Fri Apr 16, 2010 10:57 pm
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Joined: Thu Sep 24, 2009 2:14 pm
Posts: 52
Post Re: Feedback Wanted - New Module Proposal
OK darms: I/F = "interface".

I was not aware that the minimoog used 0-5V :shock:
I always thought that 1V/oct synths were 0-10V CVs like my Prophet5 and MemoryMoog. Guess cause they used CurtisChips(?)

As for the 9754 preamp, yes, the panel is kinda full.
I do not have a schematic for the 9754, but I'm sure it's overkill for a synth module. Boosting vocal or guitar or ?? is a necessary stand-alone module, but specmanship is overkill for synth-processed audio. All the other audio processing modules, i.e. the mixers/attenuators, env/fol would have to have similar specs. The total audio signal is only as "good" as the sum of the series modules.

An inverter/buffer, probably a dual, is another necessary module, IMHO.

I did check out the new 9753 envelope follower. It's too bad that an inverter was not added to this module to do "reverse following". Like for creating a wah/antiwah effect. :(

I look forward to seeing more new modules from PAiA.

afn
T

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Mon Apr 19, 2010 11:08 am
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Joined: Wed Jun 17, 2009 5:17 pm
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Post Re: Feedback Wanted - New Module Proposal
I like this new module idea! Mine and Brad's research showed that every Frac sized module used 0-10V as a CV standard, at least the two big ones (Doepfer and Blacet). Instead of "fighting" them by sticking to a 0-5V CV setup, we were trying to encourage interoperability between our stuff and theirs. Too bad there is that whole power connector issue, but I think there are commercial solutions available to fix this (as well as simple DIY ones). The whole 5V vs. 10V CV ranges is pretty annoying IMO and something like David has proposed is a bitchin idea and something that would be doing the whole synth world a big favor.

I tried to make the inverter/gain section on the linear-to-exponential converter as flexible as possible but sticking with the 1U rackspace really can limit functionality sometimes, especially on the dual function modules. An inverter on the envelope follower is definitely not out of the question though, I will keep this though on the back burner for when we go to do the new board revs. David, I look forward to seeing your idea in full detail for this new module :).


Tue Apr 20, 2010 1:46 am
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Joined: Tue Feb 02, 2010 12:03 pm
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Post Re: Feedback Wanted - New Module Proposal
The 9747 form factor puts 16 3.5mm jacks in a single RU space so that's the limit of what we can cram in there. As SM jacks & switches are a bit problematic we could probably get 4 inverter buffers w/offset switches in a single RU. Moog Voyager specs are here on page 98 of the pdf.

Here is my preliminary work on what I'm calling the 9748 Level Shifter. I'm using two inverting amps for the 0.5 Av instead of a front-end attenuator & a single non-inverting gain stage of 2x. Gains & offsets are selected via a two-row header & a single jumper. I will definitely use through-hole resistors such that there will be positions the user can customize although most of the r's will be SMDs.

Scott, if you're out there, can you point me to some PAiA hosted drive space? Also sorry, but the BBS software didn't tell me there were replies.


Sun Apr 25, 2010 12:33 am
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Joined: Sun Nov 09, 2008 2:49 pm
Posts: 585
Post CV ranging
That looks like a handy device, especially in a situation where you've got to change a big group of CVs, like with a MIDI2CV8 converting Control Change messages to 0-10v CVs and the receiving device, ie a lighting controller, etc. is expecting bi-polar -5 to +5 control.

It would be great having an invert function too. There's never enough of these and it is a particularly useful thing, having a complement of some other function.

When considering interoperability, triggering is a concern and if this module also had the ability to convert a gate-trigger or pulse-trigger to an s-trigger (switch-trigger) it would be even more useful. The MIDI2CV8 has open-collector transistor outputs for this, but it once in the analog module realm it can be a stumbling block.

I don't recall the specific unit right now, but some trigger inputs are even bi-polar with the transition ranging something like +3 to -8??? It might be good to have footprints for trims as well as fixed, through-hole parts. An experimenter's corner that could have a relay, opto-triac, etc. easily wired in would be a plus.

As Cliff mentioned, the 9753 can be used to invert, boost/attenuate, and offset a CV and this is likely to be sufficient in translating control from one system to another.

Also, it isn't always such an obstacle when the operating ranges of different devices don't match if you understand what's going on with each. For example, if the summing inputs at the front-end of a VCO have a potentiometer connected as a voltage divider for Coarse control of Initial Frequency and an external input ranged for a bi-polar control, simply adjusting the panel control for a lower voltage will have the same effect as would offsetting a uni-polar control, negatively (nearly anyway, and maybe enough...). It's important to remember that Pitch CVs representing notes can't be run through other than x1 gain stages without the notes being affected--a sequencer outputting pitch cvs ranging from 0-10v can't be passed through a x0.5 gain stage without it's v/octave scaling changing to 0.5v/octave.

Related, there's a schematic for a CV ranging circuit over in the technical-bulletins / assembly-notes section of this site:

viewtopic.php?f=7&t=56

David. I have copied the schematic you included and it is linked below:

9748 Level Shifter schematic

Attachment:
9748 Level Shifter sch.pdf [22.09 KiB]
Downloaded 1040 times


If there are others you would like me to add, add them to our common drive or send them in an email.

Did you check the box, "Notify me when a reply is posted"? Below the Message Body box, this one one of the Options. It could just be a something that needs to be tweaked and I'm not up on this yet. Right now I'm working on figuring out why the Search feature isn't so effective. However, the second one down on the PAiA homepage will point to things here on PAiA Talk, ie enter 9505 and you'll get links to the Assembly Manual, Tips & Suggestions, etc. etc. etc.




Thanks.

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Tue Apr 27, 2010 1:36 pm
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Joined: Tue Feb 02, 2010 12:03 pm
Posts: 5
Post Re: Feedback Wanted - New Module Proposal
[url=http.www.io.com/~darms/9748LevelShiftersch.pdf]Here[/url] is a level shifter closer to what Scott has in mind. As drawn the invert will not work but can be fixed at a later time. Is this too complex for most normal music technicians to figure out?

Damn, this forum software is retarded. What worked last week is broken this week.


Sat May 01, 2010 12:21 am
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Joined: Thu Sep 24, 2009 2:14 pm
Posts: 52
Post Re: Feedback Wanted - New Module Proposal
You forgot the colon and the 2 backslashes after the "http".

Link works fine when these are added ;)

More comments in a bit.................

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Sat May 01, 2010 8:44 am
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Joined: Thu Sep 24, 2009 2:14 pm
Posts: 52
Post Re: Feedback Wanted - New Module Proposal
Hi David,
Looks like this is shaping up to be a good PAIA module. “9748”?? I think U will have to find a different number, since the 9748 is already assigned to the new Balanced Modulator, and 9747 is assigned to the new passive Mixer/Splitter. How about the 9749 LevelShifter?? J

CLIFF wrote:
Quote:
The whole 5V vs. 10V CV ranges is pretty annoying IMO and something like David has proposed is a bitchin idea and something that would be doing the whole synth world a big favor.

Well, don’t know about any “controversy”, but having a module that can change/shift voltage ranges is just a good idea. MusicFromOuterSpace(MFOS) proposed a similar “shifter” idea quite some time ago: http://www.musicfromouterspace.com/anal ... VELSHIFTER

I like your proposal of a “quad module” in a single width FracPanel.
I like your implementation of the J1 and J2 jumpers to set the gains and offsets.
But, having 1 or 2 “live” offsets with the inverter/buffer would be good for things such as “unbalancing” a Balanced Modulator. Check out the Design Analysis section of the ol’ 4710 Balanced Modulator manual for more info on this. A small trim pot with a tiny shaft such as the 323-409H from Mouser could be soldered on a daughter board and mounted between the jacks, sticking thru the panel for a “real-time” offset. I was going to use these for a “nano-Gnome” concept that I was working on several years ago but never finished.

CLIFF also wrote:
Quote:
I tried to make the inverter/gain section on the linear-to-exponential converter as flexible as possible but sticking with the 1U rackspace really can limit functionality sometimes, especially on the dual function modules. An inverter on the envelope follower is definitely not out of the question though;

A definite Yes!! to all of the above: inv/buf flexibility, limited panel space, and possible addition to EnvFol !

SCOTT wrote:
Quote:
That looks like a handy device, especially in a situation where you've got to change a big group of CVs, like with a MIDI2CV8 converting Control Change messages to 0-10v CVs and the receiving device, i.e. a lighting controller, etc. is expecting (a) bi-polar -5 to +5 control.

I’m thinking that this application would be the main selling point of your proposed module; Don't know if the MoogTriggers are as necessary as a real-time Inv/Buf Offset(?) But, what about other applications? What are some other applications and uses for this module? And, BTW, (for Cliff), What are some applications for the 9756 Lin-2-Expo converter?? The only one that I can think of is adding an expo out to the Gnome’s linear ribbon. Since the ribbon is inherently Linear, an Expo converter could drive the internal linear VCO making it “easier” to play tunes on the Gnome. Can I put my synthesizer.com linear keyboard output thru the 9756 and drive a 4720A. If anyone can think of other applications for the proposed LevelShifter or the new 9756, please, speak up!!.

SCOTT also wrote:
Quote:
It would be great having an invert function too. There are never enough of these and it is a particularly useful thing, having a complement of some other function.

Totally agreed here!! That’s why I’ve been urging for an update to the ol’ 2720-12 for the 9700 series. And, it wouldn't hurt to ADD Inverter/Buffers to other modules to increase their versatility and their PAiA bang-4-the-buck!

Enough 4 now.
tone
sacramento, california, usa, earth, milkyway

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Sat May 01, 2010 9:47 am
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