Hi all,
I'm not too familiar with these two units but I see them in racks all the time. What are the differences in the LA-3 and LA-4? Also, what are the differences in the blackface and silverface models? And finally, what are they ideally used for? Any favorite applications? Thanks for your time.

Brandon

Both are electro optical compressors and the classic applications for them are vocals and bass but can of course be used with success on other sources aswell. That's the similarity of them, the difference is in controls, design and sound. The LA-3 has two modes, compress or limit (the switch is on the backside... why did UA not put it on the frontpanel on the re-issue...???? ) and on the front you have two knobs, input and peakreduction. The LA-4 on the other hand has, if I remember this correctly without one in front of me, threshold and ratio controls. more "modern" controls if you like. I'm not that much of a tech but I know the LA-4 uses op-amps and the LA-3 does not. Unfortunately these op-amps (and there are 4 of them I think) are not that brilliant and you can clearly notice a loss of high frequencies when it compresses a lot. I've heard it's a common LA-4 mod to replace the op-amps. Most people choose LA-3 over LA-4.

The LA-3 is a discrete, transformer coupled design with a real T4 electroluminscent panel as the gain reduction element, like the LA-2a

The LA-4 is entirely based on op-amp (integrated circuits) and uses a simple LED / photoresistor as a gain reduction element (like a guitar stomp box).

The LED / photoresistor has a very different characteristic than a real EL panel, especially the time constants. The LA4 is a feedback compressor, also. This gives a much gentler sound to the compression.

Just bought a UREI LA-4 myself. Did a track with a bluesy lead. KM84i > API 512 > 550A > LA4. Sounded smooth, deep and sweet. Bit of a newbie, so I don't have a lot of different points of reference. I have a Distressor as well, which I love. Cleaner. But for this application, the LA4 worked nicely.

P

I have a silver faced LA-4 and a Distressor. Many, many times I've decided on the LA-4 instead. I love it to death and wish I had a couple more. I've never even touched an LA-2A or an LA-3 or even an 1176 for that matter. (dreaming now)
Big bang for the buck. I got my LA-4 for $400 with rack ears.
jason