api 325 LINE AMP

[audioez]

Hello GeekSlutz!!!

For over a year I've been tinkering around with a bunch of api325 LINE AMP cards. I took apart a 1U rack that was made to work with (2)550A. After rewiring the edge connectors, I was able to make it all work. Each 325 card has a total of 3 balanced O/P, in theory you can have a 1:3 DA.

What I'd like to do is to have one of the O/P windings work for me as a speaker O/P to feed some powered monitors, any one have a good starting place for a rotary pot??? or any tips??? thanks ezra

[dasbin]

Are you talking about a seperate output attenuator / volume control just for the monitor-output winding?

In that case take a look at these circuits:

http://www.uneeda-audio.com/pads/

You should just be able to make a variable balanced pad and stick it between the output trafo and your monitor.


BTW, not sure if you're interested in this and/or if you already know, but these line-amp API cards can very easily be made into 312-ish mic preamps with just the addition of an input transformer and features.

[audioez]

Originally Posted by dasbin

Are you talking about a seperate output attenuator / volume control just for the monitor-output winding?

Yes, that's what I'm talking about. Thanks for the help, ezra.

[audioez]

any one else?

[audioez]

ok well I bought a 100k stereo pot from radio shack, wired one of the secondary windings to the pot...works well, tracks like it's from radio shack.

Thing is the O/P from the 325 card is balanced, and I had to tie the (-) and shield(common) together to make it work, which it did. Is there such thing as a balanced stereo pot??? any one??? ez

[phalaris]

This is, I think, where it gets a bit confusing and expensive. Check out www.dact.com I think these are really expensive. Stepped switches aren't cheap.

[audioez]

Originally Posted by kc8mob

yes there is such a thing your looking for, its just 4 pots in one. So think about your stereo pot you got from rat shack
and double it, its the same thing that would be used on a 4 channel amplifier (volume pot)

If you cant find one new look for a piece of shit device you can use for parts.

Thanks so much!!! After wiring up the rat shack stereo, now I understand what you are talking about, thanks KC!!!! read your PM as well!!! thumbsup

[phalaris]

In a Balanced attenuator, the matching of the resistors, I think, is very critical. a balanced pot may not track very well at all, where as a stepped attenuator will.

[audioez]

so I re wired the whole rack....I'll be using this as my broadcast DA/control room monitor from here on out...This tuesday it will see it's first use. thanks for all your replys.


So the whole chain is Midas Venice-->33609-->api325(LINE AMP/CONTROL ROOM MONITOR)--> to 88 million cable subscribers in the USA.