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Old 28th March 2004, 12:00 AM   #1
Aunkst is offline Aunkst  United States
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Default Linkwitz Transform Circuit Design?

Has anyone had any success with a Linkwitz Transform? What set up are you running with? Any schematics?

I spent this afternoon playing with a rudimentary LT, and I found that it sends my amp into protection mode pretty quick also I got some ocillation. except for that I think the concept is good. I just need to tweak it .
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Old 28th March 2004, 12:54 AM   #2
johnnyx is offline johnnyx  United Kingdom
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Default re Linkwitz Transform

Jeff Macaulay publshed a design for a sub using a LT, and he said that it is very sensitive to component variations., especially with Q.
In the same way that state variable filters are less sensitive to component variations than Sallen - Key filters, I have a circuit that does the same thing as the LT, but is configured like a state variable filter. It uses a couple of integrators with feedback around them to perform the same function.
This was another project I never got round to; using a LT type boost and comparing it to MFB.
The circuit is from a paper published by the Audio Engineering Society, so it should be good. I'll see if I can dig it out.
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Old 28th March 2004, 05:12 AM   #3
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ESP project 71 - Circuit and PC board at http://sound.westhost.com/project71.htm

A useful spreadsheet at:
http://www.pvconsultants.com/audio/eq/linktran.htm
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Old 28th March 2004, 11:32 AM   #4
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I'd be interested in seeing that paper, johnnyx. Are you aware of Jeff Macaulay's second sub project in Electronics World where he used some kind of state-variable filter to perform the same function as a Linkwitz Transform? I wonder if this circuit is the same as what you have.
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Old 28th March 2004, 12:21 PM   #5
Aunkst is offline Aunkst  United States
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I have been following the project 71.

I will give it another go this week.
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Old 28th March 2004, 06:29 PM   #6
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Might be worth buying the circuit board, as the circuit will be more fully developed and debugged. The results will be more deterministic. I have not seen anyone mention oscillation concerns with the PC board.

If you buy via credit card and let the card do the conversion the price will likely be better than the PayPal price.
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Old 28th March 2004, 07:37 PM   #7
Aunkst is offline Aunkst  United States
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I built the circuit on a bread board from school, using "close values" that I had on hand. It was actually my first venture with active equilization and crossovers. I really don't know if it was osscilating, just that some unpleasent noises came out, and it drove the amp to cut after about 30 seconds. hum started low then got louder untill the amp went into shut down.

I appreciate the advice , but I will try again this week with more accurate parts, and a more carefull aproach to assyembly. I'm sure that I made a mistake somewhere.

I appoligize for posting this query twice, I really didn't know how many people view both forums.
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Old 28th March 2004, 08:38 PM   #8
johnnyx is offline johnnyx  United Kingdom
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Quote:
Originally posted by richie00boy
Are you aware of Jeff Macaulay's second sub project in Electronics World where he used some kind of state-variable filter to perform the same function as a Linkwitz Transform? I wonder if this circuit is the same as what you have.

I've seen his circuit, it made me want to try it out. His method is different to the one I have, but I cann't remember the details. the one I have was published by the JAES, and it's ..somewhere..
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Old 29th March 2004, 01:07 AM   #9
angel is offline angel  Norway
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Has anyone tried cheating a driver into working in a horn or TL by changing the Q with a LT circuit?
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Old 31st March 2004, 12:21 PM   #10
mikemcd is offline mikemcd  United States
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Default Linkwitz Transform

I used the ESP linkwitz transform and power supply boards. Both work great. There are 2 different spreadsheets for this circuit. They appear to be the same, but some components are labeled differently, and can cause you problems if you're not careful.

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