la3a gain and peak reduction doubts

[fffaustino]

hi guys,

I have recently acquired my second Urei La3a and i have some doubts about its performance.

The new compressor is having too much compression w/50dB selected, much more than my other la3a, and unity gain is reached with the gain knob at around 2 or 3 max. With my other comp you get same results with gain at 4-5 and peak reduction at 5-6, but with the new one you can´t go further than 2 without really smashing the signal.

I have recapped it, swapped the optos, and installed nos transistors at Q9, Q10 and Q11, but nothing has changed. Both are terminated, both have the same R14 mod, and correct bias...

Since i have no reference unit, i have compared the results of the two with the waves plugin, and my old la3a performance is more similar to the plugin than the new one.

Any clue? it´s normal to find those differences between vintage units?

Thanks in advance, any help really appreciated .

Alfredo

 

[Bo Deadly]

Try adjusting STEREO ADJ. Put them both in the middle, compare and then adjust one up / other down slightly until they're the same.

Note that the gain control knob just controls the level of signal getting in so you will need to carefully consider the level going in before you make any comparison. Meaning set your level going in and then don't change it. Swap the cable to the other unit and then compare. Otherwise, saying gain is 3 or 4 or whatever is quite meaningless.

If that doesn't sort it out, it could be that someone changed a part. These things are old and get fiddled on all the time. It's really unusual to find a vintage unit that doesn't have a hack on it.

 

[fazer]

What Bo said. Also check for a linear input pot. It should be log. Compare to your other unit.

 

[fffaustino]

Bo, Fazer, thanks so much for your fast help.

I have checked Stereo Adj and nothing has changed but i think both of you are right, i have realized that the only non original parts are the pots..so maybe those non original pots are linear instead of 100k log pots...i will check it and let you know

Thanks and nice day!

 

[fffaustino]

Solved! Installing new pots was the solution…thanks so much and best regards from Spain!