UREI LA-4 OPTO Experiments

ã 2000, 2001 & 2002 by Eddie Ciletti

NOTE:  The information on this page is not a current modification option for the LA-4.  It is simply to demonstrate the result of expermienting with Opto Device Speed.

Figures-1a and -1b (below) show an LA-4's reponse time when outfitted with the "stock" opto which is beautifully slow or with a high speed opto, which is actually too fast.  One of my Silver LA-4 experiments has been to add a mic input transformer, phantom power and a preamp.  It's very cool but a bit tedious.  There are two unused opamps in the LA-4, the mod turns them into an improved version of the Trident Series 80 preamp.

Related but completely different is a very extensive series of mods for the Alesis 3630 that should be available on Video in 2003.  Stay Tuned!

Meanwhile, here are the two Opto-Response pix...

Figure-1a: Top "0dB" trace is the Gain Reduction 
(GR) signal as sent to the LA-4's meter. 
GR pushes the trace down. 
Note the SLOW recovery time 
from two kick drum hits on a stock LA-4...
Figure-1b: The Vatrol VTL5C9 has incredibly fast 
recovery time compared to the Stock OPTO. 
Same kick drum hits.

Return to LA-4 Index
Go to the Dynamics Library
Go to Eddie's Home Page