API 550b interfacing for vintage console

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TubeMonkey

Well-known member
Joined
Jan 24, 2014
Messages
161
Location
Nashville, TN
Hey All,

I've found that sticking a 550b in my 74' API causes noticeable distortion related to the fader. If fader is jumper'd the signal is clean, however, if I insert the fader (600ohm) there is noticeable low end distortion and frappy garbage.....  putting a 550, 554, or multiple other 500 series in the same slot cleans it up.  Is there a strange output property or pinout for the 550b that could cause this? (fyi this is one of the first 550b's... serial #090)

API gurus appreciated!

Ethan B
 
Bryan McCurry is a gentleman and informed me it might be a weak opamp in the output stage. He was right....  I popped out the springfield 2520 and put  in a gar 2520 and all is good.

Thanks Bryan!

EB
 
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