Author Topic: Input impedance of older, non-switchable MP573?

August 03, 2024, 05:54:28 AM
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biasvoltage

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Hi JPK - I have an MP573 that I built in 2015, that does not have the input impedance switch. I'd like to build another to pair it with, and was wondering what the nominal impedance of the input is on the original one so I can set the switch on the new one to match.  

August 04, 2024, 06:32:00 PM
Reply #1

JPK

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The input impedance can be set with the jumper JMP1 (in front of the input transformer):
o   o - o   o     1200 ohms
o - o   o - o     300 ohms
JPK

August 04, 2024, 08:10:18 PM
Reply #2

biasvoltage

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Ah yes - it's been so long since I built it that I forgot about the jumper!  Thanks for the quick response.