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<blockquote data-quote="thch" data-source="post: 1535091" data-attributes="member: 562032">its very easy to build.&nbsp; as i said, look up &quot;Twin T&quot; on google.<a href="http://www.radio-electronics.com/info/circuits/rc_notch_filter/twin_t_notch_filter.php" target="_blank">http://www.radio-electronics.com/info/circuits/rc_notch_filter/twin_t_notch_filter.php</a>use 4 resistrors and 4 caps.&nbsp; to get R/2, place two resistors in parallel.&nbsp; to get 2C, place two caps in parallel.&nbsp; try something like 100Kohm resistors and 26nF caps.&nbsp; note that you&#039;ll have to change the test tones accordingly.&nbsp; note that you need some high voltage rated film or metalized film capacitor.&nbsp; it should be rated for line use!on the downside, note that i&#039;ve only tested this in my lab, and not one real amps.&nbsp; this circuit doens&#039;t seem to present a signifigant HF capacitance to the amp, but you may concider placing a 100ohm resistor in series with the input just in case.&nbsp; if the amp makes odd noises when you attach the circuit, you should remove the circuit.you will still need linearly increaseing (amplitude) sine waves at various frequencies.</blockquote>

[QUOTE="thch, post: 1535091, member: 562032"] its very easy to build. as i said, look up "Twin T" on google. [URL="http://www.radio-electronics.com/info/circuits/rc_notch_filter/twin_t_notch_filter.php"]http://www.radio-electronics.com/info/circuits/rc_notch_filter/twin_t_notch_filter.php[/URL] use 4 resistrors and 4 caps. to get R/2, place two resistors in parallel. to get 2C, place two caps in parallel. try something like 100Kohm resistors and 26nF caps. note that you'll have to change the test tones accordingly. note that you need some high voltage rated film or metalized film capacitor. it should be rated for line use! on the downside, note that i've only tested this in my lab, and not one real amps. this circuit doens't seem to present a signifigant HF capacitance to the amp, but you may concider placing a 100ohm resistor in series with the input just in case. if the amp makes odd noises when you attach the circuit, you should remove the circuit. you will still need linearly increaseing (amplitude) sine waves at various frequencies. [/QUOTE]

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