single-ended power supply (12V) based active crossover - diyAudio
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Old 16th July 2003, 07:53 PM   #1
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Default single-ended power supply (12V) based active crossover

Could anybody suggest me a crossover schematic for my car with the opamps being run on single-ended power supply of 12 Volts?. 18-24 dB/octave is fine.

Thanks.
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Old 23rd July 2003, 12:17 AM   #2
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Some questions for you...


Do you have any particular op-amps in mind or are you starting completely from scratch?

Any particular configuration (i.e. 2-way, 3-way, HP, LP, BP) or do you really just need the information on power supply?

The very simplest way is to make a voltage divider from 2 equal resistors that will draw significantly more current than the rest of the circuit. Capacitively couple the signal leads on both ends.
This method certainly has its drawbacks including excessive current draw and supply rails that may not be symmetrical.
You can use another op-amp to derive symmetrical supply rails, but current availability is limited.
There are a ton of op-amps out there designed with single-supply operation in mind.

If you're looking for a complete schematic, would a single HP or LP section be sufficient to work from?


Tim
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Old 25th July 2003, 05:32 AM   #3
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Smith, thanks for your reply.

NE5532 is what we use in this part of the world. I am looking for a decent schematic -- 2way 18 dB is fine, but I am not particular. I have no problems with power supply. My car is an old tin box than runs more out of habit than on the principles of internal combustion. I dont think I should spend time on delicate/elegant configurations for this tin-box-on-wheels.

Any schematic?
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Old 25th July 2003, 08:04 AM   #4
moamps is offline moamps  Croatia
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Hi,

look at www.ti.com app.note SLOA058
"A Single-Supply Op-Amp Circuit Collection"

Regards
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Old 26th July 2003, 07:19 PM   #5
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moamps, thanks.

I have just visited the site you suggested and downloaded the pdf file. Basic topology sheets, but with text-book authority. Thanks again.
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Old 27th July 2003, 03:53 AM   #6
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"My car is an old tin box than runs more out of habit than on the principles of internal combustion"

Thanks for the laugh.

I'll have to make this two posts, one for a voltage divider and one for a filter schematic.

First, the voltage divider is a quick and easy way to run most any op amp from +12V. A transistor turn-on section is included which may be replaced with a relay if more convenient. Or, you can delete the section and power it from an ignition source if you really want to cut corners...

MPS2222 is a fine transistor to replace ktc-1815, or any small NPN for switching should work.
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Old 27th July 2003, 04:07 AM   #7
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Part 2...

This is a 4th order Linkwitz-Riley filter taken directly from Siegfried Linkwitz' site. It is simply two equal 2nd order Butterworth sections cascaded for a L-R response. The -3dB frequency of the two sections combined is the same as that individual sections, only the Q changes along with the slope. I like it because of the many equal component values.

If you are using the filter between a subwoofer and full range speakers, you may want to leave the last high pass section off for an asymmetrical 2nd order high pass and 4th order low pass.

To change filter frequency, just scale component values linearly or recalculate from the formula given.
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Old 15th April 2011, 11:13 AM   #8
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Bit of thread necromancy going on here,

But could anyone recommend an op-amp for the above 4th order LW crossover that would work off a single 12V supply without having to use the voltage divider? I am trying to build a circuit with as little current draw as possible the the divider doesn't seem to fit that.
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Old 15th April 2011, 08:44 PM   #9
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You'll have to have something (divider, IC...) to bias the op-amp to 1/2 of B+. You could use very high values of resistors and drive the non-inverting input of an op-amp to get the necessary bias current. THIS is another option. The TLC2272 may be an option for the op-amps.
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