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MOX - active crossover
MOX - active crossover
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Old 29th February 2004, 06:24 PM   #81
promitheus is offline promitheus  Europe
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MOX - active crossover
I also have found that good discrete opamps sound a lot better than opamps like opa627 or opa637. I have tested that in a simple preamp.

Has anybody built any of the above circuits or are there any pcbs made for them?
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Old 29th February 2004, 11:11 PM   #82
JensRasmussen is offline JensRasmussen  Denmark
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Default Just a note about the filter and changing Q

Hi,

You problably all know this, but be sure to have a gain adjustment on the output of the filter section.

When you change the Q of a sallen and key filter by means of the qain, you also change the pass band gain.

So of gain is = 2 you must have a gain of 0.5 on the output to ensure that the following stages are not clipping.

\Jens
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Old 1st March 2004, 12:36 AM   #83
grataku is offline grataku  United States
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Great work moamps, thanks for posting it here.
The last time I tried an active X-over I wasn't too impressed but being a discrete design with everything variable it maybe time to give it another try

I am definitely interested in getting a couple of boards (whatever many boards one needs to get a stereo two way balanced filter).
I would do the board but I don't have any time to spare right now.
Maybe we should all wait for the chinese to get it done.
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Old 1st March 2004, 06:31 AM   #84
JensRasmussen is offline JensRasmussen  Denmark
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Default I'm not chinese but....

Hi,

I'll do it. I'm starting on the schmatics for one block today. when done ill post the result.

Please comment if the schematics posted already are like you want them, or if they schould be changed in any way.

Also, ill do the layout using dual opamps, so if you want a descrete opamp make a dual one that can fit in a 8 pin DIL socket.

\Jens
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Old 1st March 2004, 06:46 AM   #85
Blitz is offline Blitz  Germany
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Great, Jens. Many thanks upfront.
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Old 1st March 2004, 07:02 AM   #86
Blitz is offline Blitz  Germany
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Why don't you want to go for the discrete opapms ? Can't you have a more robust connection option on the board for the discrete ones ? DIP8 only is a bit fragile when looking at the Boards of Moamps.
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Old 1st March 2004, 07:22 AM   #87
JensRasmussen is offline JensRasmussen  Denmark
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Default Opamps

Hi,

I feel that a Q of 1 is a bit too littel, so how about making the option og Q go from 0.5 to 2.0 in steps of 0.1?

The reason is that this gives the option of using the HP section as a low frew EQ for a sub or small speaker system.

I do not think that descrete opamps bettet are than some of the IC's you can get, if they were, opamp designers would have made them into a commeciel product many years ago.

\Jens
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Old 1st March 2004, 07:53 AM   #88
Blitz is offline Blitz  Germany
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Having variable Q is a good idea. I would be especially interestd to have an eq for the super-trebles above 15khz.

Understand your theory about discrete opamps, but have you actual listening experiences you can share ? Anyhow, it would be great to have the option to use discrete opamps with a stabile connection.
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Old 1st March 2004, 09:16 AM   #89
promitheus is offline promitheus  Europe
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MOX - active crossover
Hi,

I am very interested in making an active crossover but only if it is with dicrete opamps. One thing that is always missing is equalisation at different frequencies. Specially woofers have dips and peaks that have to be corrected. How do you do that? For instance my Peerless woofers have a peak +3 dB at 1,8 KHz from 800 Hz to 3KHz. I correct that passive with an LRC series network. It would be helpfull to also do this active.
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Old 1st March 2004, 09:22 AM   #90
JensRasmussen is offline JensRasmussen  Denmark
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Default Eq

Hi,

Check this dok for info on EQ and active cross overs

http://www.delta-audio.com/Active%20filter%20one.htm

\Jens
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