Best way to pad a Altec 436c

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API

Well-known member
Joined
Nov 25, 2005
Messages
869
Location
Sweden
Hi.

Recently fired up my old Altec 436c compressor.
It had an extremely hot signal and after doing some research i understood that this is a common problem.
And the most common way to solve it is to pad the input.
But which is the best way to do it???
Is a shure mic pad adapter enough or should i modify the circuit??
And if so , how???

Regards,
Dennis
 
Nice pictures you got there!!
My Altec looks a bit different, has the meter in the middle.
So a variable switch with resistors is good???
I could only see a output switch though.
Mine has a nice McIntosh input pot though!!

Would be so much easier though with just a simple pad on the input.

Dennis
 
I have a 436B and do not have the Attack, Release and Threshold Controls.

If I want to modify it, What type of pots shouldthose be? Linear, Audio Taper? I'm not sure what to use and why.

Also what about adding the Balance and meter control pots? What should those be?
 
All of the pots are linear taper.

The compressor in my photos began life as a 436A. I only used a two-position input attenuator because the customer didn't want more than four holes added to the front panel. But I was able to find a space inside the chassis for a DPDT toggle. If space is not a problem, it would be better to use an attenuator with more than just two steps.

2-pole, 11-position, MBB rotary switches are available--or at least there's an Alpha 2-pole, 12-pos. MBB rotary (available from Mouser) which has no end stop, but can be kludged into an 11-pos. with an end stop. That's what I used for the output "T" attenuator. The same switch could be used for a stepped dual pot for the input. 3dB steps should be fine; between that and the threshold pot, you'd have plenty of control over the theshold of gain reduction.

I didn't use a dual track (non-stepped) pot, as in the original 436C, because the two sides of the pot are never going to track well enough to avoid introducing imbalance into the push-pull action of the amplifier.
 

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