1970s disco light displays

[Malcolm T]

Such a lot has changed in the lighting world now, however can anyone advise me on the lights and the driver circuits used in the early mid 1970s to fabricate audio responsive displays.
From my distant memory the lights were 240V ES colored spots maybe 80Watts or higher.
I think i remember seeing some designs in the electronics mags of that era but cannot remember the articles or the magazines , can anyone point me in some directions here please.

Thank You

[mickm3for]

Hi i recall them well they used a thyristor or 3 to switch in time with the music
pw had some circuits late 70s called "sound to light" almost the same circuit used in the Maplin one they sold until they closed, so search pw mag around the 70s see https://www.vintage-radio.net/forum/...ad.php?t=99483
Mick

[julie_m]

The one I built used SCRs to switch half-wave mains to the lamps (suppose I could have added a bridge rectifier, but for some reason I didn't) and drove the gates via pulse transformers (for electrical isolation) from a simple filter network taking its input from the speaker output.

[Refugee]

The posh ones has an active cross over to split the frequencies and triacs to drive the bulbs.

[Malcolm T]

Thanks for the link Mick, i found it in December 1976 , quite a few ICs there , probably un obtainable now however worth considering.

[bobhowe]

Google Pulsar zero 3000 this was a popular lighting controller & the popular lamps used then were RO 80 if my memory is right you could get them in 60w & 100w & PAR 38 & the old wattage was 100w & 150w and this lamp had toughened Glass very heavy lamp & could be used outdoors kid regards Bob

[Aub]

I built one in1986, from a circuit in one of the magazine's ( can't remember which ). It was quite a simple circuit, each of the three channels using a transistor to drive a pulse transformer to trigger a triac. Each channel had simple audio filtering to be either bass, middle or treble. I still have it up in the loft with the three coloured spotlights it used to feed. Great for house parties .

I can get it down if anyone's really interested.

Cheers to all

Aub

[Ed_Dinning]

Hi Folks, I think Texas Instruments did a quite good design that the published in the excellent theory books that were presented with their yearly seminars in the 70's

Ed

[AndiiT]

Hi, the simplest "sound to light" unit I ever encountered consisted of a "back to front" audio output transformer driving the gate of a thyristor which was wired in series with a set of incandescent coloured bulbs. The bulbs were, of course, mounted in a tall case with some fancy plastic frontage to make them look the part.

When I say "back to front' transformer, quite simply the low impedance winding was connected across the speaker output of a high wattage amplifier and the high impedance winding was in series with the mains driven thyristor and bulbs.

Regards

Andrew

[Malcolm T]

Interesting . So each bulb was assigned a frequency / channel or could the bulbs be re assigned at random by the logic circuits ?.

[broadgage]

IME, the lamps were indeed screw base, usually R63 or R80 sizes. They came in wide selection of colours sometimes marketed as "disco bulbs"
Often 3 channels of lighting controlled by different audio frequencies.

Par 38 lamps were sometimes used but less often as they were expensive, heavy, and in a limited range of colours.

I built such a unit, from a published circuit but duplicated the blue channel, thereby allowing twice the wattage of blue lamps. Blue filtered incandescent lamps tend to look very dim if compared to other colours and being able to use twice the wattage of blue helped.

Slightly more professional units used clear GLS lamps for cheapness, behind stage lighting colour filter medium to give coloured light.

I once made a unit that used coloured fluorescent lamps, but this was not common.

If considering present day use of a vintage sound to light unit, be very careful. Many used rather dangerous multi pole connections to the lamps often with line voltage exposed. Bulgin made a multi pole connector of doubtful safety by todays standards.
Even worse were 12N or 12S multi pole connectors intended for lights on vehicle trailers. Lethal on mains.

[Cobaltblue]

I built several sound to light converters in the mid 70's but the later ones were Chroma chasers.

The problem with sound to light converters is getting the right balance and enough light.

The Chasers the amount of light was more or less constant the music effected the speed at which changes occurred.

They became so cheap it wasn't worth building them, I still have a TUAC one kicking around somewhere.

Cheers

Mike T

[bobhowe]

Hi broadgage you are right about safety standards without going OT trailer cable on 240v DJ spilling his pint of beer ( 10.30 pm ) or 1.30 AM in night clubs on the light controller or the mixer

[Radio Wrangler]

And no personal protective equipment in sight, just dozens and dozens of pairs of purple flares.

Whenever you consider current safety standards and look back at things we once did, you wonder how we survived. Maybe modern standards are OTT. Maybe we should educate the stupid, not just try to engineer the world around them?

Whatever you legislate, whatever standards you create and enforce, there is always someone smart enough to find a way around them while simultaneously being stupid enough to do so.

David

[jamesperrett]

Originally Posted by bobhowe

Google Pulsar zero 3000 this was a popular lighting controller & the popular lamps used then were RO 80 if my memory is right

I've still got a Zero 3000 here which had 3 channels which could handle up to 1000W of lighting each (hence the 3000). The sound to light function was certainly better than many of the alternatives and it had a couple of chase modes too as well as manual push button control. I used mine with RO80 bulbs although I remember the coloured film on the front of the bulbs used to crack if they were switched on for too long.

I also built a Powertran Chromatheque 5000 from a kit which had 5 channels but I found it a bit disappointing compared to the Zero 3000.

[arjoll]

There was one published in ETI at some point in the 70s, I remember seeing it in one of dad's ETI project books. I'll see if he's still got it, and if so throw a scan on here.

[broadgage]

Originally Posted by Malcolm T

Interesting . So each bulb was assigned a frequency / channel or could the bulbs be re assigned at random by the logic circuits ?.

All the ones that I saw had one circuit wired to respond to one frequency range.
Eg blue=bass
Green=mid range
Red=treble.

The user could of course swap the lamps around if desired inserting for example red lamps into the circuit previously used for green.

[Malcolm T]

Thanks for the input on this, i think most of today's lighting is mostly LED based.
I found some of the ICs used in the Practical wireless design are still available, amazing.

[deswradio]

This brought back memories, probably for others too. I recall in my early teens building a version of the "Spectreuphon" - a simple 3-channel (bass, mid-range, treble) filter-based lamp driver. I built it using a set of 6 MES torch bulbs in a row for each channel, mounted behind some matt perspex. Each set of bulbs was driven by an OC28 transistor. It worked surprisingly well. This memory caused me to find the original Practical Wireless article in October 1964, rather grandly sub-titled "Some ideas for experiments with chromasonic displays".
Des

[Panrock]

My very first project in 1969 was to build a box I called the 'Phonochromatascope'. This was a home designed sound-to-light unit that used three valve audio amplifiers ending in EL34s, energising colour filtered 12v 21w car brake bulbs, through output transformers of course.

The display was viewed on a mixing screen made more 'sparkly' by the use of some bathroom window glass.

Steve