Announced via publication in Popular Electronics Magazine October 1970 issue, the Universal Tiger amplifier was nominally rated at 80W RMS into an 8 ohm load. My college buddies and I built probably 10 channels worth of these amplifiers. The picture shows one of my stereo chassis.

One interesting feature of our amplifiers was that I modified the board artwork published in the magazine to have a card edge connector for all but the audio input, and left space for an RCA male plug to be used as the audio input on the board. The chassis had a matching RCA female on it, so that when the board was plugged into the edge connector, the RCA jack supported the other end of the board.

I've still got two channels of Universal Tiger in service in my "main" stereo, powering the mid-range horns in my tri-amped Klipsch horns.

The unit in the photo is a little "different" in that I didn't use a normal power transformer with center tapped secondary, because I was an impoverished student and couldn't afford one. But I did have a transformer that was was powerful enough, but it has a single 36 volt secondary (instead of the normal 62 volt center tapped one).

As a result, the power supply is "funny". It uses a half wave "doubler" circuit to get the plus and minus 45v rails, but since this transformer had a bit too much output, I used a 6 volt filament transformer to "buck" the primary, as well as some simple transistor regulators (those two heatsinks at the bottom of the photo) to drop the DC output voltage to plus and minus 44 volts. There are 1 ohm 10 watt resistors between the rectifier diodes and the 20,000uF caps (to reduce the inrush current), and a relay that shorts out those resistors once the voltage is up to +/- 35 volts or so.

There are LEDs mounted in the front panel that flash when the amplifier clips, driven by a circuit on that perf board in the lower right of the photo.

FAQ

Q. Will you make one for me?

A. No, I'm retired and so not interested in a job.

Disclaimer/Warning

This is just my documentation for an old build. I don't claim that building this is safe or recommended.

Soldering irons are dangerous, be careful. Oh, and don't eat the solder.

William Dudley
February 21, 2021