Lowpass xover with gain and Linkwitz Transform.Gain question - Electronic Circuits Projects Diagrams Free

mikee55 · 12th January 2006, 12:04 AM

Hi all,I'm a noobie here and don't seem to get much from other Forums so I thought I'd give this one a go.I'm trying to put together a circuit for a Subwoofer controller that consists of the following.

Ist an op-amp buffer stage,then a 24db Linkwitz Reily lowpass filter set at 40 hz,then a gain stage.The signal then goes thru a 12db Linkwitz Reily High pass filter at 7 hz to a Linkwitz Transform and bridge stage to drive a pair of mono amps.

The Linkwitz Reily website gives details of a similar controller for use with his Thor subwoofer ( http://www.linkwitzlab.com/thor-orion.htm) but he doesn't use a highpass filter to remove subsonics,where should this stage be best put?And also, two resistors normaly added to an op-amp makes a gain stage,I'd like to make this variable,so could the two resistors be replaced by a Pot?

I did build a basic circuit with just the buffer,24 db lowpass and Linkwitz Transform.It worked in my car and indoors and sounded amazing but I felt it needed more gain to drive the amplifier properly.I went back to Linkwitz's site and discovered I hadn't added the gain stage.Without knowing how much gain to add and not being good at Math,I found the basic building block of a gain stage and decided to use a pot instead of resistors, now I'm thinking that when I've found the correct level I can substitute the pot(after measuring with me meter) with the correct resistors.

What do you think of my description? Is the Highpass filter and Gain stage in the right order?

Many Thanks Y'all. Mikee55

**Nigel Goodwin** · 12th January 2006, 09:21 AM

Quote:

Originally Posted by mikee55

The Linkwitz Reily website gives details of a similar controller for use with his Thor subwoofer ( http://www.linkwitzlab.com/thor-orion.htm) but he doesn't use a highpass filter to remove subsonics,where should this stage be best put?And also, two resistors normaly added to an op-amp makes a gain stage,I'd like to make this variable,so could the two resistors be replaced by a Pot?

It's a common technique to add a variable resistor to adjust the feedback, it's often used in PA amplifiers and mixers to set the input gain.

I would suggest you have the two filters first, then the gain stage afterwards.

Quote:

I did build a basic circuit with just the buffer,24 db lowpass and Linkwitz Transform.It worked in my car and indoors and sounded amazing but I felt it needed more gain to drive the amplifier properly.I went back to Linkwitz's site and discovered I hadn't added the gain stage.Without knowing how much gain to add and not being good at Math,I found the basic building block of a gain stage and decided to use a pot instead of resistors, now I'm thinking that when I've found the correct level I can substitute the pot(after measuring with me meter) with the correct resistors.

You might have a look at http://sound.westhost.com/projects-3.htm which has a number of interesting projects.

mikee55 · 12th January 2006, 10:44 PM

....start with Buffer,then lowpass and highpass,followed by gain and lastly linkwitz transform?What would be a starting value for the pot of the gain stage?I wouldn't know where to begin,calculating the loss of gain in the entire circuit.Both amplifiers I used with the previous circuit I had made, had their input gain turned to max.Normal level is 1 volt,and high 2 volts,so I guess I'd need a volt or two of gain?

Thanks for your reply,I can't wait to plug me Iron in and burn the carpet,ha ha! :lol:

Cheers.Mikee55

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12th January 2006, 12:04 AM	(permalink)
mikee55	Lowpass xover with gain and Linkwitz Transform.Gain question Hi all,I'm a noobie here and don't seem to get much from other Forums so I thought I'd give this one a go.I'm trying to put together a circuit for a Subwoofer controller that consists of the following. Ist an op-amp buffer stage,then a 24db Linkwitz Reily lowpass filter set at 40 hz,then a gain stage.The signal then goes thru a 12db Linkwitz Reily High pass filter at 7 hz to a Linkwitz Transform and bridge stage to drive a pair of mono amps. The Linkwitz Reily website gives details of a similar controller for use with his Thor subwoofer ( http://www.linkwitzlab.com/thor-orion.htm) but he doesn't use a highpass filter to remove subsonics,where should this stage be best put?And also, two resistors normaly added to an op-amp makes a gain stage,I'd like to make this variable,so could the two resistors be replaced by a Pot? I did build a basic circuit with just the buffer,24 db lowpass and Linkwitz Transform.It worked in my car and indoors and sounded amazing but I felt it needed more gain to drive the amplifier properly.I went back to Linkwitz's site and discovered I hadn't added the gain stage.Without knowing how much gain to add and not being good at Math,I found the basic building block of a gain stage and decided to use a pot instead of resistors, now I'm thinking that when I've found the correct level I can substitute the pot(after measuring with me meter) with the correct resistors. What do you think of my description? Is the Highpass filter and Gain stage in the right order? Many Thanks Y'all. Mikee55 __________________ It worked before I took it apart,now what am I to do???

12th January 2006, 10:44 PM	(permalink)
mikee55	So can I .... ....start with Buffer,then lowpass and highpass,followed by gain and lastly linkwitz transform?What would be a starting value for the pot of the gain stage?I wouldn't know where to begin,calculating the loss of gain in the entire circuit.Both amplifiers I used with the previous circuit I had made, had their input gain turned to max.Normal level is 1 volt,and high 2 volts,so I guess I'd need a volt or two of gain? Thanks for your reply,I can't wait to plug me Iron in and burn the carpet,ha ha! :lol: Cheers.Mikee55 __________________ It worked before I took it apart,now what am I to do???