If you ever have a problem getting a matched quad of EL84 output tubes,
you can easily modify the SCA-35 to use two matched pairs instead. Just install
2 separate bypass capacitors and 2 separate bias resistors (each twice the value),
one set for each pair of output tubes, instead of only one of each for all 4 tubes.
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I'm sure the rather complex circuits detailed in this thread work fine but my aim was to provide a very simple high pass filter to be used only on the few records that I have that produce excessive 'cone flap'.
After a bit of research and calculation I have used 0.1uF capacitors in series followed by 270k resisters across the output of each channel. This provides a 6db per octave slope below 20hz when fed into my amp which has 100k input impedance.
I can switch this on or bypass with a switch. Works just fine and I can't hear any degrading of the sound when in use.
For my application I don't feel the need for anything more complex than this simple filter.
After a bit of research and calculation I have used 0.1uF capacitors in series followed by 270k resisters across the output of each channel. This provides a 6db per octave slope below 20hz when fed into my amp which has 100k input impedance.
I can switch this on or bypass with a switch. Works just fine and I can't hear any degrading of the sound when in use.
For my application I don't feel the need for anything more complex than this simple filter.
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