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Forums :: Ask Amp Tech Expert Skip Simmons

1948 Knight Phono Amp

2 replies [Last post]
Sun, 11/28/2021 - 09:55
JoelPM
JoelPM's picture
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Joined: 07/10/2020

Hello Skip

I recently acquired a 1948 Knight 93-103 model amplifier. It is a dedicated phono amp with an expansion control and has no mic input. If I restored it to the original specs would it have any practical use or would I be better off copying the circuit from a PA model?  Schematic for my amp in the link below.

Thank you

Joel

Schematic: https://share.icloud.com/photos/08FdSA6a6IuvK1rm7r2pUXzSQ

 

Photo of amp:https://share.icloud.com/photos/0vwfk6VgDth5kRtdANnI4cpvg

 

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Sun, 11/28/2021 - 22:40
#1
Expert Skip Simmons
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Joined: 01/18/2010
Hello Joel- Thanks for

Hello Joel- Thanks for writing. That is sure one cool-looking amp, but the circuit is really not what you would be looking for in a harp amp. The "expansion" circuit is designed to raise the volume of quieter passages on a recording- the opposite of "compression. An experienced builder would be better off copying a simpler PA-type circuit like a Masco uses.
530-771-7345
www.skipsimmonsamps.com

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Tue, 11/30/2021 - 09:54
#2
JoelPM
JoelPM's picture
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Level 7
Joined: 07/10/2020
Thanks very much for your

Thanks very much for your advice Skip. I think I will adapt the amp to look more like the 93-024 model which has a mic input (schematic via link below). I'll keep the original tone circuit though to begin with.

https://share.icloud.com/photos/0qQvIS26aV3LJqNnniLbHH25w

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