driving counters in lunetta with GUITAR or audio?

loss1234

i'd love to be able to use external sounds (guitar, voice,etc) to clock or drive parts of the lunetta

is this possible?

i am NOT looking for accurate tracking...just noise

thanks

Adam-V · Posted: Thu Apr 17, 2008 10:06 pm Post subject:

You should be able to just run the guitar (or any other audio signal for that matter) through some sort of preamp circuit to bring the levels up to the appropriate size for your CMOS circuitry then pump the output through a schmitt trigger. Instant square(ish) wave-a-thon. You could then use said waves to clock your counter. I thik this is actually be the basis for most guitar synth pedals.

Cheers,
Adam-V

Inventor · Posted: Thu Apr 17, 2008 10:22 pm Post subject:

I'm just imagining this, so not sure if it would work, but here's an idea. Send the guitar into a band-pass filter tuned to pick up the fundamental frequency of a particular plucked string, then rectify it and low-pass filter the rectified signal to produce a signal that rises when you pluck that string. Clip the signal to make it digital and you have a clock pulse that fires every time you hit that note.

Or there are probably many other variations on that theme. Perhaps you could leave the band-pass filter off completely and just do the rectify/low-pass thing to the whole guitar signal, then clip it at a threshold voltage to separate new, loud notes from the lower amplitude sustained harmonics.

Just thinking out loud, don't cry foul if it doesn't work. Have fun!

scriptstyle · Joined: Jan 22, 2008 Posts: 250 Location: nj

what's funny is that I was wondering about something like this earlier today. I started thinking of rays audio signal to gate circuit. But I don't think it would work because its for a vca or vcf. I'm not really sure though?

loss1234 · Posted: Fri Apr 18, 2008 4:37 am Post subject:

well if its for a vca it would work

a gate or trigger can often be used to clock things so....

also take a look at rays SUB COMMANDER

i have been trying to understand that one but somewhere in there it converts the audio to a pulse wave...which might work for cmos?

thanks all

bugbrand · Posted: Fri Apr 18, 2008 5:36 am Post subject:

Umm, I think we've covered this sort of thing several times, no?!?!

You need a comparator!

loss1234 · Posted: Fri Apr 18, 2008 9:59 am Post subject:

wait wait-sorry if i missed this before...

a comparator is what will square the signal and turn it into a clock? if that is it, then i will build it right away. i thought it was much more complicated.

when you say build a comparator, it will just compare the input to +v or to gnd at a high enough rate to be audible as a square wave?

i am sorry if i sound like i am asking the same thing twice but in this thread i was specifically interested in turning audio into something that can feed counters or clock chips.

thanks

Inventor · Posted: Fri Apr 18, 2008 11:47 am Post subject:

A comparator is essentially an opamp that has been optimized for switching, aka decision making. It looks at its inputs and "compares" them, producing a logic 1 or logic 0 on its output node. You can set the inverting input to a voltage level with a potentiometer, then apply your guitar signal to the non-inverting input. Then, when the guitar is above the potentiometer-set threshold you get a logic 1 out else a zero.

You can also add hysteresis which is a small amount of positive feedback (usually with a huge MegOhm resistor) that prevents oscillation of the output for slow-chaning inputs. Also, open-collector outputs are common, which require a pull-up resistor on the output. You can tie two open-collector outputs to the same resistor to get a logic function.

Good luck and have fun.

jnuaury · Posted: Fri Apr 18, 2008 1:12 pm Post subject:

the simplest/cheapest solution is in nic collins hardware hacking book
and you dont even need to leave cmos 4000 chips to do it

he uses a 4069 to square up a guitar and then has different examples which involve running the squared guitar into a 4040 divider and another example that runs it into a 4093 nand gate

this lets you use your guitars frequency to drive the lunettas and the 4040 can go way down (divide by 4096!) so you can use the guitar to activate different rhythms depending on what notes you hit

the 4069 can be used to make some very interesting distortion circuits too

jnuaury · Posted: Fri Apr 18, 2008 1:26 pm Post subject:

oh and the ian fritz bar-graph circuit seems like an interesting bridge too

but youd have to do some changes to it as i believe his board takes a 0-5v signal and converts it to a 0-1v signal. i dont remember what voltage a guitar outputs but it is definitely not 5 volts

Inventor · Posted: Fri Apr 18, 2008 2:20 pm Post subject:

Guitars have very weak signals because they are generated in an electromotive way as the string moves within the magnetic field of the pickup. They require a preamp to boost the signal. (As far as I know...)

jnuaury · Posted: Fri Apr 18, 2008 2:41 pm Post subject:

yes yes i knew the guitar voltage is pretty low
the 4069 can be used as a preamp
the nic collins circuit uses multiple stages to square it up in addition to amping it and then follows it with schmidt trigger to completely square it

the 4069 is a wonderful preamp as you get 6 preamps per chip
sounds pretty good too though not audiophile quality

i dont think it capable of boosting it into standard synth levels but it works perfectly for lunetta purposes