CV keyboard for Sound Lab

Penetrovisk · Joined: Sep 22, 2005 Posts: 15 Location: Brazil

hy ! Someone here built the Ray´s Matrix Scanning 1V/Octave Keyboard Circuit for control notes on Sound Lab????

lanxe · Posted: Fri May 19, 2006 7:44 am Post subject:

yeah, i built that keyboard.......it works pretty good, but i have a couple of bad switches in the keys that makes some of the notes erratic.

whats the problem?

Ryan

Penetrovisk · Joined: Sep 22, 2005 Posts: 15 Location: Brazil

i intend use an old 49 note CASIO keyboard.. the keyboard keys are good, but I need remake the wiring scheme for work in Ray´s project.. I did not find reed switchs here.. tries to make the same ok? In your project you have sucess to reach many octaves in correct tuning?? Sorry, my english is poor..

lanxe · Posted: Fri May 19, 2006 10:11 am Post subject:

yeah, i just used an old hammond organ keyboard. it used a ground bus which makes it a little harder to do the matrix scanning because i had to paint the ground bus with non conductive paint and make little contacts for the switches to hit.

The keyboard is only 3.5 octaves, but it tracks fairly well over the full range of the keys........then the oscillators are used to select which range i am playing in.

Ryan

toppobrillo · Posted: Fri May 19, 2006 5:16 pm Post subject:

hey penetrovisk,

i have converted a couple of casio/yamaha 'toy' keyboards for use with a matrix scanning circuit. both of these were originally 6x6 [6 notes per 6 buses] matrices, so i wired them for 8x4 [8 notes per 4 buses], which is compatible with the existing circuit you see on Ray's site, as it is controlled by a binary counter. you may have to cut the circuit board, drill new holes, etc... just make sure whatever you do, it will fit back together and function mechanically.

josh

Penetrovisk · Joined: Sep 22, 2005 Posts: 15 Location: Brazil

Josh..
yeah, the way is this!!
I am working in the project. I remove the old tracks of the keyboard plate, kept de carbon contacts, but I drill new roles in contacts for a new wiring diagram to improve 8 bus.. Originally the plate have 6 buses.. I believe to finish the work on next week. I will place pics.. Thanks..

neo644 · Joined: Aug 18, 2005 Posts: 43 Location: Argentina

what about the single bus keyboard?
http://www.musicfromouterspace.com/analogsynth/keybrdcontroller.html

i'm getting my hands on 2 toy keyboards which have only 2 octaves, so maybe making a matrix is just too much of a hassle for something so small.

anybody knows something about this type of keyboard? does it work okey just like a matrix one?

Uncle Krunkus · Posted: Mon May 22, 2006 2:17 pm Post subject:

Yeah I built the single bus circuit from Ray's site. (and did a stripboard layout if you want a copy) It works fine, and tracks perfectly across at least 3 octaves.

toppobrillo · Posted: Mon May 22, 2006 5:13 pm Post subject:

yeah actually, those membrane type switches have their own resistance across them, that varies from switch to switch and with the pressure you put on the pad....

but... if you buffer the voltage with a non-inverting follower, this small resistance, as illustrated here in a simulation i ran about this [see attachment], is insignifigant, as the input impedence of the op-amp in this configuaration is so high. so, it should work just fine if you use the tl08_ op-amps.

hmm, mayyyyybeeee, perhaps, you could also stick an inverting amp on the bus with a not-so high input impedence that this resistance would become a factor in gain, and, could be used as pressure voltage or 'velocity' type thing.

there was just a thing about this in the DIY section. sounds like something to try at least... if you set the gain at unity for the average resistance of the switch, then your increased/decreased resistance input would change the gain of the amp and raise or lower the output... subtracted or added to the base voltage from the non-inverter then.... hm. all the switches would have to have nearly identical resistances for it to work properly, but i'm not that into proper really.

josh

edit***** woops!! i didnt look at that schematic close enough... well ray has a diode and a resistor in parallel on the bus to hold it slightly negative...

this does present a problem with the membrane pads resistance...

new simulation shows that it won't work properly if you build it this way.

kb test.jpg

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voltage on the output remains constant while the potentiometer goes from min to max resistance.

also, i used 10k which is more than your switches will have i believe.

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kb test.jpg

Description:

new simulation shows output voltage drops almost 200% when potentiometer varied from 0 to 10k.

woops duuuuuhhhh

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toppobrillo · Posted: Mon May 22, 2006 6:30 pm Post subject:

also, another simulation shows that if you just get rid of the 1M resistor to -V in the original circuit, the output voltage won't droop, but will rest at around only -155 mV [as oppsed to apprx. -480mV] with no 'keys down', which may or may not work with the rest of the circuit as shown, but would be easy to solve if not...

toppobrillo · Posted: Mon May 22, 2006 6:45 pm Post subject:

anyways, neo644, your keyboards are just 24 keys? or 32? 32 works out perfectly with the scanner circuit pretty much as shown [a coupla changes] because 32 values = 5 bits. 24 keys is 8 notes x 3 buses.. the circuit to scan that will be a bit different so, in my opinion, if you have 32 keys, i say go with the scanner, if you got 24, it's not too hard to come up with a circuit for that using 3 4051s [3 x 8]...i have a 24 key touch keyboard so i have thought of doing this.. but maybe you might try the resistor chain type.

neo644 · Joined: Aug 18, 2005 Posts: 43 Location: Argentina

i've read the info on the matrix type keyboard on ray's site, and i could just use his design with less rows to scan, which he already is doing, the last 3 rows are read but since nothing is connected it's just a wast of time, but in the end it's such a short time it doesnt affect playability. i could just use the first 3 rows and it will work perfectly.
but the thing is, since its only 24 keys, it might be much less of a hassle to build the resistor chain, less components and stuff. i think a matrix is intended if you have much more keys.
anyways i gotta get my hands on this nice little keyboards and check whats inside of them, maybe they already are arranged in a matrix sort of way which could let me use the mechanics of the original keyboard. but we'll have to wait and find out later on. Wink

toppobrillo · Posted: Tue May 23, 2006 1:39 am Post subject:

hmm. i actually kind of think the resistor chain circuit requires more in the way of components, especially when you consider that your diode per key is already to go in the toy keyboard. alot of the matrix stuff is digital, and is just very cheap ICs. haven't really looked at rays, though.

hey, you may have some luck with an integrated keyboard scanning chip, ken stone makes use of one on his site, i know they are available in different configurations, you might be able to get some as samples [for free] even. they are pretty much all-in-one, even a built in oscillator. all you gotta do is build a DAC, or easier yet, get an integrated one while you order your samples..

neo644 · Joined: Aug 18, 2005 Posts: 43 Location: Argentina

thanks for the info. i'll look into it when i get my keyboards.

i'll use this thread instead of making a new one since my question is related to the cv keyboards.
i was wondering, what would be the portamento? i see ray wilson's designs include pots to control this thing.

Pehr · Posted: Tue May 23, 2006 11:47 am Post subject:

neo644 · Joined: Aug 18, 2005 Posts: 43 Location: Argentina

heh, forgot about wikipedia, it really has everything!
thanks!

so if i have a very low portamento it may sound as if i were using some sort of ribbon controller?

Pehr · Posted: Tue May 23, 2006 8:54 pm Post subject:

neo644 · Joined: Aug 18, 2005 Posts: 43 Location: Argentina

well.. yea, i wasn't shure about that, but you get the idea.
cool, thanks!

lanxe · Posted: Thu May 25, 2006 3:12 pm Post subject:

Just FYI......
I just got the www.synthesizers.com MIDI to CV converter in the mail and have to say that it is pretty useful and tracks very very well.

its a pretty reasonable price too (i think it was around $180 USD).....the power supply can run off of +-15V +5V (synthesizers.com also sells a little pcb for $12 that converts your +-15V supply to run these modules)

Just another thought when considering controllers (its nice having both, opens up the possibilities)

rRyan