Aleph P.17 1st order high pass filter - diyAudio
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Old 29th October 2002, 04:35 PM   #1
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Default Aleph P.17 1st order high pass filter

I want to change the value of the out put caps on my Aleph P1.7 so that it will act as a first order high pass filter at 120 Hz to drive ESL63s electrostatics.

My current power amp (3BST) has an input impedance of 10K to ground balanced. If my math is correct the 10K of the amp and the 4.75K of R49 of the AlephP approximate to 3K220. (Pass X is my next project).

If this is true then I think I can replace the 30uF in the Aleph P1.7 with 0.4uF to get the 120 Hz high pass. Am I correct with my math?

The 0.4uF caps will feed the power amp which drives ESL63s. The 0.4uF will also feed through a 30K resistors each the +/- inputs of an OPA2134 which I think will give a high pass of 13Hz. The OPA2134 will convert balanced to single ended to feed a Gradient 2nd order low pass with fc at 120 Hz this in turn will feed a power amp driving Gradient sub woofers.

Is my theory correct or have I made some fatal mistake with the above. Any suggestions as to a better method of achieving the high low pass at 120Fc would be greatly appreciated. I am anxiously awaiting the Pass crossover design.

Thanks to a great forum
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Old 30th October 2002, 01:19 PM   #2
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That is an interesting question. I'm thinking about similar setup with my preamp. To confuse things more, what about the volume control at the preamp's output?
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Old 30th October 2002, 07:56 PM   #3
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Peter:

My volume control is now on the output. I think it is a shunt type (one resistor between + / - ). It works great in this configuration as it attenuates the same feed to both panels and subs.

I just replaced the 10uF with a 0.47uF and it seems to be working well although I am not quite sure the shoulder frequency is exactly 120Hz, but it must be close. All the low frequency load has dropped off the panels, but the bass feed to the sub woofers seems great.

I need to get some better quality 0.47uF caps., but I am really pleased with the sound and tonal mix. I have not yet checked the phase difference between the subs and the panels.
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