Other related pages:
- Wonderland Audio Stuff
- The Tale of… Space Probe 7
- Space Probe Audio
- Those Ride P.A. Systems
- The Tale… of The Sound Room.
- Wild Life Park Audio
- The Woolshed
A long one for the technical minded folks out there.
By Kent Learned
I like to think of that I’m a problem solver and a solution creator. I’m naturally a modest person at heart, but this is the only way I can describe what I’ve done most of my life. I just quietly go about solving problems and creating solutions. The numbers of solutions speak for themselves.
All the audio in the park was originally powered by Australian made 250 watt amplifiers, and the signal was distributed around the park by a 100 volt constant voltage system. At each green mushroom, there was a step-down transformer that reduced the 100 volts(v) down to 8v, which equalled 10 watts(w) of power to each mushroom speaker. The biggest problem with the system is these step-down transformers. You could buy an “ok” one for $10, a cheap one for $4, and $90 for something really good. We ended up using the $10 version. The biggest problem is all audio transformers have trouble with the low bass sounds. To reproduce deep bass with a transformer, means making them really big, heavy, and expensive. So I used to compromise with the $10 transformers and I then filtered out the deeper bass from the audio systems to minimise distortion. It worked fairly well for the background sound system.
In the 1980’s, car radios started coming out with new amplifiers that put out 15watts, instead of the usual 6 or 7 watts. A background sound company in Florida took these new amplifier integrated circuits and turned them into a 15w module that mounted on the back of the speaker and powered it with a distributed 24 volt power system. Because of all my work in step-down transformers while working in the R & D section of Disney, I felt it would be quite effective to get rid of transformers and improve the sound quality with small distributed amp modules. We bought in a few sample modules from the local importer and started experimenting. I was able to read a part number off one of the integrated circuits, and found it in a data book. I then used this knowledge to create our own early prototype version but on steroids so it had a 30w output. The early versions had 3 wires
There were many other PCB’s made for other things as well, more on them in a later instalment.connecting them onto the system. Common, +24vdc, and signal. They worked as well as the commercial ones, and had twice the power. We made about 10 of these early ones and put them into use in some different situations in the park to see how they survived. (Yes they had lightening protection.) Everything I made had lightening protection.
We then built an upgraded version with an loudspeaker crossover on it. These were installed in the original 20 Dino’s after the Attack Of The Dinosaurs in H.B. Theatre had finished.
Connecting pro audio gear to them was usually ok, but sometimes there were buzz or level matching problems, so we made a new version, that was designed to connect happily to “Balanced” pro audio gear, with the level matching problems taken care of. We made many of these 4 wire system modules, +24vdc, common, + audio & – audio. There were about 16 of them in the space probe alone. Four in the outdoor cue line, two in each tunnel, three in pre-launch, Three or four on the launch pad, and at the top of tower, 3 for evacuation announcements.
The next prototype was the balanced 4 wire version with two amp channels and an electronics crossover creating a “Bi-Amp” system, eliminating the traditional/more expensive passive speaker crossover. It worked well, but I ran out of time to work out a few bugs. We needed about 60 of them pretty quickly for the park wide speaker replacement project(Dino MkIII’s). Instead I just designed a new printed circuit board(pcb), combining the balanced input amp with the existing passive speaker crossover pcb, and had a finished product quickly.
PCB’s are a thin sheet of fibreglass, which has many thin copper tracks connecting the many holes on the board, where the electronic components are soldered. I learned how to design and layout pcb’s when I worked at one of the console manufacturers. It was a very good skill to have. It has saved untold amounts of work assembling electronic equipment. Every one of the 24vdc amps ever made was made with a pcb except the very first prototype. I have one example of most of the amps in the shed.
We made at least:
3 wire version, 20
3 wire w/ crossover 20
4 wire version 30
Plaza Shop system 60
4 wire Park speaker
project 60
190 total amp modules