This is a story of how Discos developed, and in particular,
mine. I will be adding pictures as I find them.
Mobile Discos began in the late 1960s, something of a spin-off from what were called Sound Systems. Sound Sytems were generally one very large box housing one very large loudspeaker (for lots of bass), a powerful amplifier and one record deck. These 'systems' pounded out Bluebeat, Ska, Reggae (just beginning to evolve) and of course good old Soul, though rarely Motown. They were the province of mainly, West Indians and Jamacians - but that said I went to many parties and first tasted Goat Curry to a pounding bass line. In 1970,when I started, there were very few 'Disco Shops'. I am going to ramble on about Discos in the South. Karillion and FunkyParrot will give you a great insight as to how things developed 'Up North'.
Garrard SP25 Mk III
Garrard SP25 Mk IV
Decks sorted, next on the list was a mixer. Not far from Laskys is The Edgware Road,and it is there that you
could find Henrys Radio and a whole row of shops selling surplus electronics. The mixer I bought then still
survives, looking a bit different but essentially the same, in Maplins. It was a four channel mic mixer,powered
by a PP3 9V battery. Inside there was a one transistor amplifier - and that was it, four pots (faders), four
jacks in,one out. In the pictures of my Disco that show how it grew,despite all the electronics you can see,the
mixer was a copy of that circuit - I just added treble/bass/monitor/Vu etc (and a mains supply). I paid £9.00
for the mixer, in Henrys Radio. You're going to get bored with lots of words, so a few more pics should keep
you here a bit longer.Here are a few consoles. Be honest, a little tear welling up there? I now (yes now)
use two SP25 MkIV - they still fetch good money bids on Ebay.
The mixer I bought then still
survives, looking a bit different but essentially the same, in Maplins and other such places. Its on the right.The mixer in the picture is typical but much more up-market than the one I
bought since it has a master level too, and notice, vrey few slide faders so far. This was 1970 to 1972 and such
wonderous things were only just entering the domestic market. The now famous op-amp (if you're not that way inclined,
then sorry), the 741 had just been invented. I bought two, got them very hot and very dead, and went back to transistors.
|But before we move on, here is the Sonotone in a Garrard headshell....These days I use Shure M75EJs. And this brings us to Amps, and do I have an issue with specs !|
So we get to the Amplifier, and the thing that annoys me the most about Maplins and many other shops; 'Music
Power'. Let's sort this out first. There is no such thing as 'Music Power'. There are no instruments designed
to measure it and there are no units (such as Watts) that relate to 'Music Power' in a scientific way. 'Music
Power' is a term coined in the 70s to make cheap Music Centres,Record Players etc, look better than they really
were. Put simply,this is how it goes: Flodelity HiFi Ltd design a stereo record player. It will have a BSR deck
(complete with plastic turntable that had a tendency to warp), and a crystal (not ceramic) pick-up. The amplifier
will be two cheap ICs, each producing about 5W RMS. Now, RMS is the true measure of power and an amplifier that can
deliver some RMS measured output might easily hit twice that on a peak,that is a very short duration sound that shoots
up for a very short time (if it keeps doing it the amp and/or the speakers are going to go bang). Aha, say the
marketing department, we can have 10W peaks,so we could call it say, 'Music Power'. But wait,there are two speakers
so really we have a 20W system, hmm, yes,but in theory if it was 'bridged' we could get something approaching 40W,
and with peaks even higher, why we have a 50W music power amp! (Bridging invloves driving a speaker stack from BOTH
audio channels at the same time which, in effect, quadruples the power (its all boring maths).....
....which is why you can today go into a certain well
known 'Disco Shop' and buy yourself a 500W (Max - always the 'max' word is there).amplifier, except it isn't.
What you really have are two channels that produce around 80W rms (if you are lucky) and when bridged,
may hit 500W peaks, mono. You take your shiny new amp to your next gig,wind it up,and wonder why the speakers sound
awful long before your 'massive' amp has 'blown away' your audience.
The RMS power of an amplifier is the power it can deliver, continuosly,and we have already seen why the speakers should
be rated at least 50% higher than the amp. Emerging,newly trained to repair TVs et al, from Slough Training Centre, the
theory I had learned proved that 20Watts should blow the roof off. At that time there was a simple rule for Amps;
a pound a watt. Earning,then, £15.00 a week, Amps were expensive. A company called Linear ( I often wonder if that was
the birth of the now huge Linear Devices), produced the Linear70 and it was the benchmark for many Discos (down here),
and yes, that was RMS. A few Discos had moved up to 100W and a fellow DJ I knew ran 200W - back then that was a lot of
sound. With very few 'Disco Amps' about, Amps used by bands were common as were home-brews. Some of the ready built
amps had a strong home-brew look too. Names like FAL and RSC should jog a few memories. Also, back then, a young man named
Clive Sinclair was marketing a number of modules, in particular for a HiFi system called 'Project 60', yep,20W RMS/channel.
So it was that my first few gigs were run with a Z30 (20W)Sinclair module. Of course, the theory fell to bits because
speakers are so very inefficent that most of the 20W gets lost (in ways we needn't talk about). I had two coloumn speakers,
each containing four eight inch speakers. We need some more pictures.
And here it is, the Project 60 advert showing the Z30 module (yes just one), that I bought. It wasn't even 30W, even good old Clive had to sex-up the spec; the Z30 pumped out 20W. We really need some pics to send us back to those glory days, pics like these, and that onthe right is the Vox amp I bought.
Well here are a few more to bring tears to your eyes. I used a Marshall like the one shown for a while and I borrowed a Simms-Watt like this one for an outdoor gig at Slough Cricket ground. Way over the other side of the pitch there was a block of flats. I was so chuffed when the Police turned up and asked me to turn it down.
So back to the tale...I only did a few gigs to find out how bad it all was. My first upgrade was to a VOX 60W guitar amp with a pair of matching speakers (two cabinets, each had two ten inch units). This was okay, for a while. I should jump in here to say that back then I could easily copy stuff and join bits together, but I did not really have any design skills. The VOX soon became too quiet - well to be honest,it blew up. This time I took a trip to Wood Green, North London. There was a road there that was like a smaller version of the Edgeware Road, and it wasin one on those shops (the same one I bought coils and crystals from as a boy to make crystal sets), that I bought a 50W Amp (later tested and found to around 40W RMS), but it waspart of a plan. The first thing I did was take it to bits and trace the circuit. I then built four of them, and put the lot into a case, 4 mono channels, Volume/Treble/Bass on all, and around 150W RMS. I had arrived! But my speakers hadn't.
Speakers were, and still are, a pricey item - don't get me going on that Max/Music Power thing again, check out any Ebay
item and look for 'RMS'....Back on The Edgeware Road, RSC were selling a 25W 12" Fane, in a cabinet, for £25.00 - not bad
considering. My first step was to buy six (I had been doing quite well at gigs),which I simply bolted together so that I
had two coloumns of 3. Step 2 was another pilgramage to RSC to buy 6 speakers sans cabinet,which came in at £12.00 each
-bargain. I had picked them up whilst doing my TV repair calls. Arriving back at the workshop I stacked them on a couple
of TVs. Now,if you remember when TVs did all sort of weird things then you will remember when you could see a big red patch
in one corner and a TV engineer mumbling about purity and deguass.With the size of the magnets on those speakers, both the
tubes in the two TVs were done for (and no,I did not get the sack). Some carpentry later and I had four pretty impressive
coloumns of Fane 12" speakers, 12 of them. Later I would add not two, but four 18" Bass bins - you have to hear Free's
'Alright Now' through that lot (although what I have now blows it away). This is the actual RSC 1 X 12" cabinet I used, bolted together. I used the spare handles
for other bits of kit and for the 3 X12 cabinets I later had made. I recently found it on the Internet, for sale, 230 Euros.
Before I leave the speakers, a few words of caution. Watch a modern band or video - nearly always,if you look carefully, you will spot a Marshall stack. Checkout Marshall sales on Ebay - four figures is quite common. Why ? Well,again put in (I hope) not too boring tones), its all about distortion - the kind so loved by Rock guitarist; just listen to Gary Moore's 'Parisienne Walkways'. Its also about valves. When a valve amp is thrashed the kind of distortion (a sort of fuzz) is quite acceptable to human ears (and to electronic bits too). Feedback howl can be and is used as part of the track. but transistor amps work a bit differently. Whilst you can pretty much do what you like to Marshall, Simms-Watt, WEM and Carlsborough to name a few, try it with a transistor amp(or rather,don't). Here's what happens. Draw a circle. The top of your circle is the Max output of your amp (don't start with that Music Power rubbish). You decide to wind up the master fader - it all sounds a bit distorted, but so what, its a bit louder. Draw a line across the top of the circle, just below the top - that is what the Amp is doing and it is the distortion you can hear. It's called 'clipping' and most high power Amps have a clipping indicator, because its so dangerous. That straight line is current in the Amp output and worse, current in the speakers. It is not going up and down as the sound should - it is steady. In a fairly short time the Amp will get hot, so will the speakers. Then the Amp will die,and often the speakers too. That's why there is a clipping indicator. The reason this is not really a problem with valve amps doesn't matter here.The sound of an amp clipping is not very nice.
I am going to do a bit about Mics later, but first let's do lights. A Sound-to-light system
was mandatory in the 70s. There were a few around that could be bought, but a great many were
made from the pages of Electronic Magazines such as Practical Electronics (PE). The first one I built
was very simple, caused lots of interference, and was pretty bad. It drove a strip of 9 60W
coloured bulbs, 3 for each channel. The next one I built was a bit better but then PE published
a run of monthly articles to build a 'state of the art' system called 'Aurora'. I still have
the articles on all three units. I cut down the project (which was designed as eight channels
housed in two cabinets, into one box of three channels - and it knocked the pants of any other
sound-to-light I ever saw. Back then I could build the stuff okay, but I could not have designed
most of the stuff I built. For some reason I promised myself that one day I would have another
go at the 'Aurora'...As it was it ended up with the 9 60W bulbs built into the deck console,
and two banks of 5 coloured spots, again, quite a lot for the time.
I never got into lightscreens (then), but there were many about. What I did have though was a pair of tall boxes (lined with tin foil of course), that sequenced. Microprocessers were only just emerging and Logic chips too - few of us knew how to use them. This was easily solved thanks to John Bull Electrical (South London) from whom I purchased what was; a row of sixteem micro- switches mounted on a shaft. At one end there was a motor and a row of movable cams so that as the motor turned the shaft a cam would press a micro-switch. It worked great, and every click of a micro-switch came out as a loud click over the PA...Picture time.
Here is a collection of the time from FAL - I suppose that then, when you've seen one you've seen 'em all. Then. but back to the Aurora. Now, you can choose from many sound-to- light systems. Some look quite good, most don't, and at a few family Do's I have been to, they seem to consist of maybe four spots and some (quite clever) LED pods, or similar. I achieved another ambition when I re-started the Disco. I designed a new Aurora from the ground up and added a micro for sequence effects too. It has eight channels and drives 32, 70W spots (so far). I am currently building a 4X4 high power LED matrix to add to it. You can see it in its current form on the main page and others, but what about those lightscreens on my home page ?
|This time around I have no Transit so all the gear has to go in the car (and was designed that way). I set out a few design rules, the main being that everything had to do more than one job. The lightscreens are built into the lids of my four record boxes - in the 70s there were two, each holding 600 singles. I had to cut them in half this time 'cos they're ble***ng heavy! Each lid is 14" x 24". Inside there is a strip of 12v festoon bulbs up the middle, and a strip of high power leds running up each side. In the Mixer cover I have built a PIC micro (last count there are 21 PICs in the system...), which turns the sound into numbers that it sends to the screens. With very low sound the bulbs chase up and the leds down, but with loud sounds they act as Vu levels. The effect of the coloured bulb glow and the harsh LEDs looks great.|
In the 70s every Disco had a sound-to-light system of some sort, a Strobe and a projector.
Usually, the projector was filched from Dad who didn't really mind because it gave him
an excuse to buy a new one. I took the motor from my rubbish sequencer and spent hours
(with a file) making an aluminium wheel, which had holes covered in coloured film - you
can see it on one of the pics on this site. Around this time Rank-Aldis produced a projector
which is now legendary - so good that it is still highly prized (check out Ebay). It was the
Tutor; 250W quartz-halogen and exceptional optics. It also has a handy 12v ouput on the back,
and its design makes the fitting of effects a doddle. Some of the better Discos (and many bands)
began to use them, and eventually I scraped up £80.00 and bought one too,with an oil wheel from
Optokinetics. The images here are by kind permission of The FunkyParrot.com.
I will not attempt to repeat the excellent history that you will find on that website -make sure you visit it.
One thing I can add concerns the final Gnome version. If you find one - RUN. I got hold of two.
The fan has been changed and is now totally inadequate (both had broken heat filters and MELTED main lens carriers.
I replaced all on one of them - it lasted an hour. They went to the tip (except the transformers).
I now use five Tutor IIs (plus a couple of Moonflowers and a twin head unit from Abstract).
And on my left...the Rank Aldis Tutor II, and on my right - a pile of cack.
But what about the wheels you may ask, or not. Take a good long wander through Karillion if you want to know all about the development of these, still popular, effects. Read on for my 'secrets' that I have developed to make easy, cheap and strong, Perspex wheels. Oh, yes, really.
|It has always been 'The Way' that oil wheels are made from thin sheets of glass. Over a few months of experiments I have developed a way to make them easily, and cheaply, from Perspex - in fact a £15.00 sheet from B&Q yields at least ten double wheels - three discs per wheel for multicolours. I will be doing a page on how to make them, eventually. One other thing; I went to an audition in London (which saw me sent off to Germany), and one of the Discos there was actually having the attentions of a soldering iron to get it going.Another was opened up to reveal a complete mess of wiring which the DeeJay was trying to fix.... So this time around I started with a rule : every part of the Disco must fit together with no tools at all, and it does.For my (many) oil wheels, I have designed a magnetic system which works like magic. I can swap a wheel in seconds, and set-up, take-down, is just as easy. It has proved totally reliable and I am able to use it with my one Optikinetics wheel too. When I do my 'How-To' on wheels I will include the details of this system.|
Then the was UV. Black light,UV,was relatively new and I first saw it used by a Disco that had two, 4' UV tubes.Of
course, that meant I had to get it too. I ended up with an HP UV lamp (the same as the ones used in UV Cannons now),
and a big ballast coil screwed under the deck stand. Now then, a word. DO NOT buy those lightbulbs that look like
UV lamps 'great for parties', or so they say,at around £5.99 from your local friendly Disco shop. DON'T. I bought six
of them, made boxes. Fitted them to the Disco.Total crap - you get more UV from the sun, when it's raining. I then
bought 6 8W UV tubes - amazing. In a carefully controlled scientific experiment, I turned out the light in the garage
and found that there was more UV from one 8W tube than all the rubbish 75W bulbs together. They went in the bin. Next I bought a
400W HP lamp. I made a case from an old CCTV case, used a stainless-steel salad bowl as a reflector,and housed the
ballast in a scrap Tutor II case (the result of the Gnome fiasco).
|The one on the left - DO NOT BUY, the one on the right DO BUY BUT read my 'how to' BEFORE YOU PLUG IT IN!!! HOW TO. On the right is a 400W HPS lamp - the very one used in the UV Cannons. To make it work you need a ballast - why doesn't matter, what does matter is that if you just plug it in it will go 'pop'. All you do with a simple ballast is wire it in series. Ballasts tend to be big and heavy (hence my use of the old Tutor), but by keeping it in another unit, the IV is very light and easy to hang from a rig. Pics of mine will be comming.|