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 Forum index » DIY Hardware and Software
Bass-Fishing for CV controller
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Chrometuna



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PostPosted: Sun Oct 01, 2006 3:34 pm    Post subject:  Bass-Fishing for CV controller
Subject description: I got this idea, its probably been done so someone knows....
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I read up a little bit on finger-strip ribbon controllers.

Im not much of a keyboard player, but I AM a passable guitar/bass player.

So it occures to me that a bass has metal frets, the strongs are metal. So I could wire each fret with a corresponding resister so that when the string shorts accross that fret, it sends that value to the soundlab minisynth. I would have wires running down the bass' neck, but thats ok.

The things wouldnt even need to be in tune. But each string would have to have its own voltage/resistance in order to 'jump' up the scale.....I'll burn that bridge when I get to it.

fine tuners could help on each string, but I really think that through sheer coincidence and synchronicity, that the fret placement is just right for notes.

NOW, my real question...one I could answer myself if I wasnt so lazy to go searching posts....is: What do I need in order to interface between the instrument and the soundlab?

Seems to me this is just a VCO, so do I plug it straight in to the soundlab? Or do I need some kind of circuitry?

Cheers
bob c
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zipzap



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PostPosted: Mon Oct 02, 2006 4:34 am    Post subject: Reply with quote  Mark this post and the followings unread

Sounds interesting. I wonder what comes out! For interfacing all you need is an opamp to buffer the signal from the voltage dividers (frets).
If you use an independant psu or battery than the signal needs to be sent to the soundlab over a shielded cable, shield connecting the grounds of the two power circles. Should be all you need.

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Uncle Krunkus
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PostPosted: Mon Oct 02, 2006 5:47 am    Post subject: Reply with quote  Mark this post and the followings unread

You could wire this idea straight into Ray's "Single bus to CV&Gate" circuit, which I did a stripboard layout of.
If you want to use all four strings, it would require mulitple offset input buffers and an insulated bridge. But that's not beyond possibility.
You'd have to wire up the resistors to the frets either way, so I'd start it and sort out the other three strings later.
BTW, I've been wanting to do this for a while, but haven't gotten around to it, so I'd be interested to know how it goes. (I'm a bass player originally too)

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Chrometuna



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PostPosted: Mon Oct 02, 2006 9:58 am    Post subject: Reply with quote  Mark this post and the followings unread

zipzap wrote:
Sounds interesting. I wonder what comes out! For interfacing all you need is an opamp to buffer the signal from the voltage dividers (frets).
If you use an independant psu or battery than the signal needs to be sent to the soundlab over a shielded cable, shield connecting the grounds of the two power circles. Should be all you need.


I hadnt thought about there being an independent power supply for the bass, thanks for pointing that out. (Whats a psu?) Do you think Id need a seperate opamp for each fret? Or just coming off of the outputs of the whole fret system, OR the string itself? (If that makes any sense?)

Or should I have some sort of mixer in there for every string to create a singular output of the whole thing?

One of these days I will actually learn something about electronics!
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Chrometuna



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PostPosted: Mon Oct 02, 2006 10:13 am    Post subject: Reply with quote  Mark this post and the followings unread

Uncle Krunkus wrote:
You could wire this idea straight into Ray's "Single bus to CV&Gate" circuit, which I did a stripboard layout of.
If you want to use all four strings, it would require mulitple offset input buffers and an insulated bridge. But that's not beyond possibility.
You'd have to wire up the resistors to the frets either way, so I'd start it and sort out the other three strings later.
BTW, I've been wanting to do this for a while, but haven't gotten around to it, so I'd be interested to know how it goes. (I'm a bass player originally too)


By "insulated bridge" are you talking about the bridge on the bass itself? (The one that holds the strings up?) If so, that would be no problem to do: either some shrink-wrap, or something over the bridge, or maybe create a new bridge out of wood or plastic or something? (Or is "insulated bridge" a reference to some kind of circuit?)

'multiple offset input buffers' meaning one for each string going into the fret/deviders? Or coming OUT of them and into a combiner/mixer sort of thing that then goes into the synth?

I am thinking that I will leave the pickups on the thing and send the signal from those, as is normal for a guitar, to an amp or a different effects processor that is more conventional. (Like an octave/pitch shifter or chorus type of effect)

Is there any kind of arpegiator circuit that can be added to the soundlab, or maybe somewhere in the signal path from the bass to the soundlab?

What I am getting at is that I am a "one man band" (Ive been in bands all my life....and at this point, I wouldnt want to bother with a band if I cant just put the players on salary and give them a solid reason for putting up with my BS) Anyway....my 'act' consists of drum machines (Midi controlled off of my computer....but I hate midi, its just not reliable) and me playing over that. So in most ways what I am after is sounds that emulate a guitar and a keyboard playing arppegiated and pitch shifted parts all 'fired' from the bass.

Cause we all know that I cant be onstage without holding some big phalic bass or guitar shaped object!
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Uncle Krunkus
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PostPosted: Mon Oct 02, 2006 5:25 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yeah the actual bridge on the bass. Shrinkwrap wouldn't do, as the weight of the strings would cut through it very quickly. Very hard plastic insulators might do it (under the string) but you also need to think about where the knob on the end of the string grabs 'cos that would also be a point of conductivity. Also, putting things under the strings might throw out your intonation. The whole bridge re-made from high impact ceramic would be great! $$$$ Laughing
Don't worry to much about the circuit behind the strings just yet. I know it's possible, but the other stuff is probably harder to implement.
Make sure you read up on Ray's Single bus to CV&Gate converter. You need to understand that circuit to some extent to get it right.
And don't go spending big $$$$s until you're sure you can see it through. I've done that in the past with big projects, and it just leaves you disappointed. Wink

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Chrometuna



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PostPosted: Tue Oct 03, 2006 12:16 am    Post subject: Reply with quote  Mark this post and the followings unread

Uncle Krunkus wrote:
Yeah the actual bridge on the bass. Shrinkwrap wouldn't do, as the weight of the strings would cut through it very quickly. Very hard plastic insulators might do it (under the string) but you also need to think about where the knob on the end of the string grabs 'cos that would also be a point of conductivity. Also, putting things under the strings might throw out your intonation. The whole bridge re-made from high impact ceramic would be great! $$$$ Laughing
Don't worry to much about the circuit behind the strings just yet. I know it's possible, but the other stuff is probably harder to implement.
Make sure you read up on Ray's Single bus to CV&Gate converter. You need to understand that circuit to some extent to get it right.
And don't go spending big $$$$s until you're sure you can see it through. I've done that in the past with big projects, and it just leaves you disappointed. Wink


I guess it all depends on what bass I use. I'm certainly not going to tear up one of the stingrays.

I'd love to find a cheap stienberg copy (The skinny 2X4 thingy like Sting played) to use.
But Ive got access to an old crappy no-brand bass that wont matter if it ends up being "yard art".

I can probably figure out something non-conductive to use on the bridge and anchor. Fish aquarium pump tubing? Maybe some kind of 'lost-wax' casting of the bridge made out of an epoxy resin type material?

Another 'attachment' I want to make and use is very similar to the ribbon controller: except mount it inside of a bicycle pump, so pumping it produces a wide range of notes/sounds. I was thinking of mounting THAT hanging below the bass body.

But what exactly is a CV&Gate converter?

Thanks
cheers
bob c
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Uncle Krunkus
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PostPosted: Tue Oct 03, 2006 2:20 am    Post subject: Reply with quote  Mark this post and the followings unread

The SoundLab (like most analogue synths) likes input in the form of a Control Voltage, and a Gate signal. The CV is a steady voltage which tells the VCOs what frequency to oscillate at. The standard is 1 Volt per Octave which is a logarithmic scale. The gate is a signal which goes from 0 Volts to, say, 9 Volts whenever any key is pressed. It generally triggers Envelope generators which are the dynamic volume and timbre processors of the synth.
So the gate will trigger the SoundLabs envelope whenever a string touches a fret, and the CV will tell the SoundLab what fret is being held (tuning wise).

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Chrometuna



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PostPosted: Tue Oct 03, 2006 12:08 pm    Post subject: Reply with quote  Mark this post and the followings unread

Uncle Krunkus wrote:
The SoundLab (like most analogue synths) likes input in the form of a Control Voltage, and a Gate signal. The CV is a steady voltage which tells the VCOs what frequency to oscillate at. The standard is 1 Volt per Octave which is a logarithmic scale. The gate is a signal which goes from 0 Volts to, say, 9 Volts whenever any key is pressed. It generally triggers Envelope generators which are the dynamic volume and timbre processors of the synth.
So the gate will trigger the SoundLabs envelope whenever a string touches a fret, and the CV will tell the SoundLab what fret is being held (tuning wise).


OK, thanks. This almost makes sense to my ADD little brain.

I wish someone could draw me a nice picture in crayon explaining the whole "1 volt per octave" thing? Does that mean that the octave of c below middle c would be 1 volt, and the octave of middle c would be 2 volts and so on?

The terms of "gates" in these contexts always confuses me, but maybe the idea is the same: I have been a live sound engineer for years. So in my world a "gate" is a device that you use to squelch out any sound below X level, and when that sound level is exceeded, the gate opens and lets that sound through.

On drums, these gates are used to shut out all of the other stage noise, and then when that drum/mic is hit, it opens the gate and only THAT drum/mic comes through.

Those kinds of gates can also be used to trigger some OTHER device: Like sometimes you can get a cool snare sound by micing up an old AM radio tuned to pure static, and triggering THAT mic from a mic or trigger on the snare drum. (Or triggering a gate on a very sloppy bass guitar to the kick drum, which suddenly makes them sound tight.....still a crappy sound, but at least its not highlighting a really crappy bass player)

So I tend to think of "gates" in that context. Which I suppose is the same thing that the gate that you describe is doing?

So the gate "opens" when the current/fret/circuit contact is made?
THEN the CV tells the synth what note/frequency to play?

And I assume that this gate is adjustable for ADSR so I can either have a very short staccato, or a much longer drawn out note?

Id like a sound, or effect where there is a short initial staccato, but then ALSO some kind of arppegiated or different sound, maybe in a different (pitch shifted) octave. (Like perhaps an "orchestral hit" sound?)

I think I'll leave the pickups on this bass, and use THOSE to play a regular bass amp to give me the low-end thump that I want to.

Or maybe Ive had enough coffee for this morning?
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Uncle Krunkus
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PostPosted: Tue Oct 03, 2006 3:31 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yeah, I know about the other kind of gates too. The similarity is that when activated, something gets through, and when not the signal is shut off quickly. So the synth gate has voltage on it only when the key (or string) is down. As soon as it's released the gate shuts.
Whether the sound is that abrupt is the job of your envelope generator (Attack, Decay, Sustain, Release) I'll do a quick pic for ya.


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Uncle Krunkus
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PostPosted: Tue Oct 03, 2006 3:34 pm    Post subject: Reply with quote  Mark this post and the followings unread

Note that I didn't include Decay in the pics to keep them simple.
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goodrevdoc



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PostPosted: Tue Oct 03, 2006 4:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

Here' s another pic that may help explain things. I know it shed some light for myself...
-justin
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Uncle Krunkus
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PostPosted: Tue Oct 03, 2006 7:29 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yes, of course, trust Ray to have it already done and set to go.
The only thing not obvious on that pic is the relationship between the gate timing and the ENV. As usual, I should have just said, "do some searches on this forum, and you'll soon find all the info you need." Instead of trying to re-invent the wheel. Very Happy

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goodrevdoc



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PostPosted: Tue Oct 03, 2006 11:31 pm    Post subject: Reply with quote  Mark this post and the followings unread

Uncle K., as usual, is wise beyond his robot years. Hope you got all the info you needed. Also keep us posted, this is a cool project.
-justin
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Chrometuna



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PostPosted: Tue Oct 10, 2006 3:34 pm    Post subject: Reply with quote  Mark this post and the followings unread

goodrevdoc wrote:
Uncle K., as usual, is wise beyond his robot years. Hope you got all the info you needed. Also keep us posted, this is a cool project.
-justin


Thanks both of you!
My little brain is beginning to understand.

BTW: My soundlab came in the mail today!
I am doing a happy little jig of joy.

Question...and I might cross-post this in another thread:
I have one of those "Instant hot/instant cold" soldering irons. It uses a shorting accross conductive material to creat the heat....but it makes little sparks as it connects and disconnects.

This will harm my IC's wont it? Are there other components that it would destroy?

I am going to use IC sockets, so the IC's wont actually be on the board as I solder....but are there other components that can be friend using this soldering iron?

Or should I just use a conventional iron?

Cheers
bob c
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Uncle Krunkus
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PostPosted: Tue Oct 10, 2006 4:30 pm    Post subject: Reply with quote  Mark this post and the followings unread

I wouldn't recommend using one of those "gun" type instant heat soldering irons. Go and get yourself a new (25Wmax) soldering iron. They only cost AU$20 for a reasonably decent one, and building your SoundLab will be so much more enjoyable because of it.

BTW, (to anyone reading this) don't underestimate the power of good tools. The point where I got my temperature controlled Goot soldering station was literally the point where all my electronics projects began to work, first time, (almost) every time. Struggling with inappropriate or poor quality tools will do your head in.

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goodrevdoc



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PostPosted: Tue Oct 10, 2006 7:51 pm    Post subject: Reply with quote  Mark this post and the followings unread

In my experience, those "quick-heat" guns are not very suited for any electronics work in general, much less soldering at all! Wink The tips don't last too long and they are expensive to replace, also large and cumbersome with PCB work. Go to rat shack if you must, but especailly going into a solder heavy project like the SL, a sturdy rig is a must. 10-20$ should get you something to start with. I believe they have a 15/30W selectable model. 15 for boards, 30 for pots,jacks, switches, etc. Mine still works today, although not well, and was purchased in the late 80's. There are several soldering stations for slightly more, and from there the sky's the limit. You've got to start someplace though, and IMHO, those "quick-heat" type guns should probably not be the place.
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Chrometuna



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PostPosted: Sun Oct 15, 2006 10:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

goodrevdoc wrote:
Go to rat shack if you must,

There are several soldering stations for slightly more, and from there the sky's the limit. You've got to start someplace though, and IMHO, those "quick-heat" type guns should probably not be the place.


This kind of electronics is something I am getting back into after a long leave of absense persuing other things. Its frustrating to find out how much I forgot, and how much I never knew in the first place.

Another peice of gear I need to go buy (again) is a multimeter. I was in our State Surplus depot the other week, and I spotted this really cool ANCIENT volt meter. It had a wooden case, and a meter that was nearly a FOOT wide! I forget how much they wanted for it, but the last thing I need is to drag home yet ANOTHER "cool" old thing.

Rat Shack disapoints me more and more these days.
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