Description
This Audimax is being refurbished in our workshops. The power supply has been rebuilt with a new 220 Volt transformer & upgraded reservoir caps. The audio side has modified release times and new front-panel input & output pots & knobs to replace the original preset pots and we’ve fitted XLR inputs and outputs
The Audimax is designed more as a leveller than a limiter or compressor, and most of the time it’s quite subtle in operation. It will tolerate a wide range of input levels and, when there is a fair amount of gain reduction going on, it imparts a wonderfully smooth finish to the sound. The effect works best on the mix bus, or on synth parts, where anything with a wide stereo image pushes & pulls the gain reduction in a really effective way, sounding smooth & exciting. Bass-heavy material tends to work the gain reduction too much and I am looking at the sidechain to see if it can be modified to reduce sensitivity to low frequencies
Release time is set by an internal preset three position switch – fast / medium / slow – and fast & medium are both very useable. I will look at bringing this control out to the front panel & experimenting with different release time settings. A faster release probably won’t sound as “good” but may be useful
The CBS 4450 is a classic broadcast AGC Leveller originally used in broadcasting to maximise loudness. Levellers like the 4450 helped define the sound of 1970s radio in the USA
The Audimax was often used to partner the CBS Volumax and the pair became known as “The Max Brothers”. The Audimax was the Automatic Gain Control (AGC) part of the duo and the Volumax controlled peak levels to avoid “overs” which would overmodulate the transmitter
These units were built to extremely high standards to conform to broadcast specifications. As a result they are reliable and well-documented. They’re suitable for modification – they are transistor-based and use through-hole components, the best available in the early 70s
The front panel of the 4450 has input & output level trims. In a broadcast chain these are designed to be set once & left. In a studio they can be tweaked to suit. In the centre is a gain reduction meter with green “Normal” and red “Heavy” sections but, in practice, your ears will tell you what is going on
“The “Max Brothers” of the 60’s and early 70’s gave Top-40 music a sound that, for me, increased the enjoyment of the music. Classic processors”
“I noticed that excessive input creates huge compression density and also makes these things pump like mad! I have heard them called Max Brothers, Audi Axes, Audi Smashers and Maxi Squashes”
“As long as the levels were within the floating window it wouldn’t keep chasing them. Not that it would stop the PD from cranking the input attenuator to make the box compress constantly. 😆 That’s where the gain pumping came in. Adjusted properly, they didn’t”
“A true Top 40 sound was A LA3A + Audiomax (set fast) + Graphic Equalizer + Volumax + Plate Reverb! Dub all the music to cart with a DBX118. Now that was Radio! LA3A”
“The Audimax was meant to gently ride gain and keep levels in the right ballpark to drive the Volumax at its “sweet spot” (much as one might use Ahpex’s Compellor ahead of their Dominator limiter). The idea was to second-guess sloppy board ops”
In good, vintage condition with some battle scars. Tested & working 100%. Refurbished & modified in our workshops. Photos show the unit for sale
