audio visualizer

[crane]

Hi guys and happy holidays!
I was thinking about ways to make my bands performance a little bit interesting and came up with this - and audio visualizer from an old TV.
May be someone finds it interesting
Sorry about crappy guitar sounds - impossible to play and film at the same time.
http://youtu.be/pEG89ANuPXE

[mattoverse]

How did you make it?

[jimbeaux]

Personally I would NOT experiment with old CRT type Televisions / Monitors.

Usually they were manufactured with a Hot Chassis (not ground) - probably a minimum of about 250 volts - Flyback Transformers can be anywhere from 10,000 volts up to around 30,000 volts.

So we're talking LETHAL voltages (the tv you're using appears to be a small ac/dc powered unit - not sure what voltages they use -

Just sayin'

[crane]

Chassis is grounded.
Color  CRT TV will have voltages around 30kV while black and white will have voltages around 11kV. If you know what you are doing it is not that bad.
About the construction - audio signal goes into TVs audio amp. The output of the audio amp drives vertical coil of the CRT.
It is really much safer to do this if you have the schematics of the TV (forunately I did have it).

[amptramp]

There was an article many years ago in one magazine about a circuit that would turn your TV into an oscilloscope but the sweep was fixed at the vertical frequency (60 Hz) and the trace moved to the left or right of the vertical line depending on voltage.  The design used the input voltage to control a delay which would gate the CRT spot a certain amount of time after the retrace (horizontal) and put the spot to the left or right of the vertical line in the centre.  Just turn the set on its side and it would look like a normal scope.

[PRR]

> signal goes into TVs audio amp. The output of the audio amp drives vertical coil of the CRT.

The Vertical amplifier is often a bigger "audio amp" than the speaker amp, and is already wired to the yoke. Impedence etc already engineered.

Figure out how to lame the Vertical Oscillator, bleed some signal into it, signal will drive the yoke.

If you just lame the V-Osc, so it dribbles pulses without an input, there will be sweep even when you rest. This may prolong the time before phosphor burn (from stationary trace) makes the CRT too dim to enjoy. Probably not a problem for a seasoned CRT in a home. Phorphor burn may be an issue if you turn the Brightness way up for shows.

Obviously this means some understanding of the V-Osc stage. They are not complicated, but can be tricky, and sometimes they eat a high voltage for better linearity.

[petey twofinger]

ot - i was gifted a projector , so we run a line out of the board to an older dual core machine with winamp and a few other standalone apps for visualiztions , and project that as we make music in our living room

i know its really cheesy , thats the point .

the software is older so it runs very smoothly , some of it is a bit fast .

i enjoy it quite a bit , but it also can feel dissociative at times . the projector was from a sanctuary , we run it a lot closer . i believe it is a high output unit as i saw it in the church , in full daylight it worked well . it puts out quite a bit of heat , and its actually a bit "too bright" i think and a few of us use sunglasses . we have been relishing it , only using it when we have company as i believe the bulb is out of my price range by a few hundred dollars but . maybe i should get the old fog machine out of storage ... they do set the smoke alarm off though .

thanks Bjorn !!