PSN-L Email List Message
Subject: preamp design
From: Geoff gmvoeth@.........
Date: Tue, 11 Dec 2012 23:04:39 +0000
Hey Guys,
Just got to try an old Idea i learned a long
time ago but never tried.
If you dont have a big 3Meg resistor to go
with that 1u condensor for your op amp filter
just string together three attenuators in series
that are like this
AmpOut--R6800--R--6800--R--6800--R--AmpMinusInput
3 3 3
3 3 3
0 0 0
G G G
Then put the 1U cap across all three 6800 ohm resistors
it works like this
((1/(330/(6800 + 330)) ^ 3) * 330) for the equivelent resistance in ohms
like ==> 3,328,440 ohms with your 1u poly condensor
im using this now in my circuit. just never tried it before.
thats about a 1/20.9 hertz.
lpf equalization.
regards
geoff
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