Passive Crossover Upstream of Amp?

NV&H · 20th June 2009, 03:44 AM

Any reason a cross-over circuit has to be active (with op-amps and such) just because it's upstream of the amp? I have a wideband driver that doesn't need all that much protection from low frequencies. 1st order is fine. The amp I want to use is short on power and I would like NOT to throw any of it away on a passive downstream crossover. If I'm interested in a 1st order high-pass crossover, why not put a capacitor UPSTREAM of the amp? Am I missing something?

planet10 · 20th June 2009, 03:48 AM

Passive line Level Crossover

dave

NV&H · 20th June 2009, 03:55 AM

SWEET. My amp has a high input impedance, so this should work fine.

EUVL · 20th June 2009, 04:14 AM

Your source has to be very low impedance to drive the passive filter before the power amp.

I am doing exactly that, but my preamp (which drives the filter) is capable of driving 200R load.

Also you need a buffer after the passive filter, unless you install the filter right next to the input stage of the power amp.

I use a John Curl JFET follower as buffer after the filter, as my power amp has 10k input impedance.

Patrick

20th June 2009, 03:44 AM	#1
NV&H diyAudio Member Join Date: Feb 2005 Location: Charlotte, North Carolina	Passive Crossover Upstream of Amp? Any reason a cross-over circuit has to be active (with op-amps and such) just because it's upstream of the amp? I have a wideband driver that doesn't need all that much protection from low frequencies. 1st order is fine. The amp I want to use is short on power and I would like NOT to throw any of it away on a passive downstream crossover. If I'm interested in a 1st order high-pass crossover, why not put a capacitor UPSTREAM of the amp? Am I missing something? __________________ NV&H

20th June 2009, 03:48 AM	#2
planet10 frugal-phile(tm) diyAudio Moderator Join Date: Oct 2001 Location: Victoria, BC, NA, Sol III Blog Entries: 4	Passive line Level Crossover dave __________________ community sites t-linespeakers.org, frugal-horn.com ........ commercial site planet10-HiFi p10-hifi forum here at diyA

20th June 2009, 03:55 AM	#3
NV&H diyAudio Member Join Date: Feb 2005 Location: Charlotte, North Carolina	SWEET. My amp has a high input impedance, so this should work fine. __________________ NV&H

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20th June 2009, 04:14 AM	#4
EUVL diyAudio Member Join Date: Oct 2003	Your source has to be very low impedance to drive the passive filter before the power amp. I am doing exactly that, but my preamp (which drives the filter) is capable of driving 200R load. Also you need a buffer after the passive filter, unless you install the filter right next to the input stage of the power amp. I use a John Curl JFET follower as buffer after the filter, as my power amp has 10k input impedance. Patrick

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