Comments on: Hi-Gain PA Amplifier Circa 1950

By: Mark Weiss, P.E.

Mark Weiss, P.E. — Thu, 07 Nov 2013 03:50:15 +0000

That Neon, with the current limiting resistors, was most likely a peak power indicator. It flashes on program peaks, and is likely calibrated to illuminate whenever the amplifier power passes 50%. This is similar to a design with the Fisher AZ-80, the latter being improved with a potentiometer to enable calibration of the neon lamp’s turn on threshold.

By: Nick Arden

Nick Arden — Mon, 01 Apr 2013 02:15:26 +0000

One bad feature of this project as shown in the photos is the transformer with the hook up terminals on the top. Common in old British and Australian practice, it’s not a very safe or ergonomic practice.

By: rrusston

rrusston — Wed, 20 Mar 2013 03:56:12 +0000

What’s the neon bulb across the primary for? Can you even get those any more?

By: bafflegab

bafflegab — Tue, 19 Mar 2013 16:55:31 +0000

It would be nice to have a full set of those magazines either paper or on good .pdfs…But most of the audio projects were pro forma like this one. The columns and ads are the interesting part to me. Millett has a nice book chock full of these forties PA amp/mixer/mic pre type things on his site if that’s your thing, but there is a reason most people gut out these Websters and Newcombs and put Fender circuits in them.

The Baxandall tone control was the last word until you get into full parametric or graphic EQ. Ampeg used it in their guitar amps. Fender used simpler circuits that are good for making guitars sound like people want guitars to sound, unless they are going for the Les Paul or Hank Marvin thing.