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Old 14th August 2015, 02:32 AM   #1
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Default MX50 - Input gain

Hi all just Registered with diyAudio [raymond1311] trying to find my way around.

Just a quick one on the MX50 assembled boath board they worked first time no
problems. The input according to speck is 1.2v my preamp does not have enough drive. Is there a simple mod i can do to the mx50 to lower the input to
say 600mv to 800mv ??? or any ideas?. I hope i am in the right place for this post many thanks.
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Old 14th August 2015, 03:41 AM   #2
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Voltage gain is 34 times [(33K +1K)/1k]
1.2 x 34 = 40.8V (100W/8 is 200W peak, is 40V)

40V divided by 0.8 is 50
50 = [(49K +1K)/1K]
You'd have to exchange the 33k (R7) resistor by e.g. a 48.7K (E96 series)
Other option is to lower the 1K (R9) resistor to 680 ohm [(33k + 680)/ 680 = 49.5]

Similar story if you wish to change the input sensitivity to 0.6V for 100W continuous power.
Hasi bo best

Last edited by jacco vermeulen; 14th August 2015 at 03:58 AM.
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