Help with RC values

davidlzimmer · 6th November 2006, 03:32 PM

What I want to do, if possible, is change the values of this circuit to use this circuit for a crude subwoofer amp for my 14 year old. Is it possible also, to use a 20k pot, instead of the two 10k resistors, to make the crossover frequincy adjustable? I'd like to get it down to 100 Hz or lower. The Fo of this circuit is 1kHz.

Any suggestions appreciated. Not expecting miracles!

Thanks!

BobEllis · 6th November 2006, 06:03 PM

See Rod Elliot's site sound.westhost.com for a Linkwitz Reilly crossover calculator. (which is what you have shown.) It's really easy to use - pick a capacitor value and crossover frequency, and it spits out the resistor value.

You'd need a dual pot to adjust the frequency of the filter.

Although that's fairly easy to make on a piece of breadboard, I bought a few extra active filter boards. Two boards ($11) would allow you to make the low pass for the sub and a pair of high pass filters for the mains, as well as giving you the opportunity to make the filter not so crude. See the thread in the group buys section for discussion. Ordering and some more filter guidance on my www button below.

davidlzimmer · 6th November 2006, 07:36 PM

Thanks Dude!!!!!

Too easy now!!!!

Now to find a simple circuit, using same chip, to mix the two chanels to mono.

BobEllis · 6th November 2006, 08:01 PM

How about a buffer for each channel and then tie them together wiht a 10K resistor? In theory you could just mix the inputs with 10K or so, but I have found that induces crosstalk, at least with my sound card and 10K input filters.

Buffers are included on the AF4 boards, too.

6th November 2006, 07:36 PM	#3
davidlzimmer diyAudio Member Join Date: Jan 2006 Location: Fairmount, GA	Thanks Dude!!!!! Too easy now!!!! Now to find a simple circuit, using same chip, to mix the two chanels to mono. __________________ Poor stereo mix? Switch to mono! Perfect.

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6th November 2006, 06:03 PM	#2
BobEllis diyAudio Member Join Date: Sep 2003 Location: Upstate NY	See Rod Elliot's site sound.westhost.com for a Linkwitz Reilly crossover calculator. (which is what you have shown.) It's really easy to use - pick a capacitor value and crossover frequency, and it spits out the resistor value. You'd need a dual pot to adjust the frequency of the filter. Although that's fairly easy to make on a piece of breadboard, I bought a few extra active filter boards. Two boards ($11) would allow you to make the low pass for the sub and a pair of high pass filters for the mains, as well as giving you the opportunity to make the filter not so crude. See the thread in the group buys section for discussion. Ordering and some more filter guidance on my www button below.

6th November 2006, 08:01 PM	#4
BobEllis diyAudio Member Join Date: Sep 2003 Location: Upstate NY	How about a buffer for each channel and then tie them together wiht a 10K resistor? In theory you could just mix the inputs with 10K or so, but I have found that induces crosstalk, at least with my sound card and 10K input filters. Buffers are included on the AF4 boards, too.

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