[retailer]

Not that long ago I built a copy of the LA2A Optical compressor for my son's home recording, his cousin asked it I would also build another unit for him he has a similar interest in recording the only difference being that I think he actually makes money out of it.

Here is the finished item, the chassis came from an old solid state PA amp salvaged from the rubble of a demolished factory, I was able to straighten out the chassis well enough to use it, as the rear panel was a heavy al extrusion cum heat sink I bent up a new rear panel, and cut a new front panel from some scrap 3mm al. The mains transformer was one I had on hand that only needed the secondaries rewound to suit, hum shields were added at the same time, the input transformer came from the salvaged PA amp.

The output transformer was wound using a old M core lamination set that had been salvaged from a junked bit of vintage Telefunken gear, 5:1 turns ratio - it turned out quite well with frequency response from 27Hz to well over 40Khz. The winding layout used was 1/2 secondary - full primary - 1/2 secondary, primary 1200 turns secondary 6000 turns .13mm wire. My homemade coil winder came in handy for this one, I did though experience some wire breakage at first - even with the static brake fully backed off. Not wanting to have any joins in the wire I just started over if the wire broke, I think my issues were caused by drag from the grease in the despooler spindle bearings, I also found that soft start for the bobbin spindle would a good idea, even with all of the slack taken up in the wire, the sudden start of the bobbin spindle would immediately break the wire, I had to resort to turning the speed control right down to zero, slowly bring it up and then start the bobbin spindle turning by hand at the right moment, once the bobbin spindle was turning I found I could increase the speed up to around 300 RPM, I may have been able to go faster but did not want to risk it.

Just about everything bar the optical module and the VU meter was salvaged from junked gear. The VU meter was sourced from the 'bay, advertised as a VU meter it turned out to be just a panel meter with a VU scale, I had to make up rectifier and shunts so it would read correctly as a VU meter.

A coat of paint, some expanded al mesh for cooling, a set of vintage instrument knobs and water slide transfers for panel graphics finished it off nicely.