ZEN include active crossover without additional OP AMP for ultimate sounding PHL1230 - diyAudio
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Old 9th November 2009, 08:36 PM   #1
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Default ZEN include active crossover without additional OP AMP for ultimate sounding PHL1230

Here a new approach for an active crossover network (high pass): To get enhancement by the dynamic range in a very high quality audio system of one of my customers I have decided to introduce an active crossover network.
But the disadvantage is, that there are additional active components such operational amplifiers in the path of the signal.
But what about, if I use the ZEN topology itself as operational amplifier?
Because the ZEN isn't power source follower (it is a grounded source) I cannot use the "Sallen Key" topology. Instead of this I must use the so called "multiple feedback" topology.
But one disadvantage there is without additional operational amplifiers: a too low open loop gain. Therefore I have make a combination of both, i. e. active and passive network for the high pass.
The result is to see in the attachement. That work I have performed already 6 years ago. Now the PHL bass-midrange (Typ 1230) will be replaced by a pure midrange, again from PHL. For this reason, the crossover frequency must be increased to approximately 500 Hz and therefore I get back this single ended ZEN special amp to do this re-match. From this ZEN device I have make three photos (see below)

I would be interested to know whether there are experience with an active crossover by ZEN projects without additional operational amplifiers.

Thank you very much
Attached Images
File Type: jpg Decker ZEN front low res.jpg (118.8 KB, 1031 views)
Attached Files
File Type: pdf ZEN+active MFB+passive HP f-3db=270Hz.pdf (4.9 KB, 384 views)
File Type: pdf ZEN+active MFB+passive HP f-3db=270Hz.pdf.pdf (11.2 KB, 282 views)
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Old 9th November 2009, 08:39 PM   #2
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additional photos (please note: the power supply isn't include, it is a separate dual mono unit, installed on the wall behind a table
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File Type: jpg Decker ZEN left low res.jpg (125.0 KB, 984 views)
File Type: jpg Decker ZEN top low res.jpg (146.7 KB, 965 views)
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Old 10th November 2009, 07:35 AM   #3
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Wonderful piece of work, tiefbassuebertr!
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Old 10th November 2009, 09:04 PM   #4
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Interestingly enough, I noted the similarity between the topology of discrete opamps and j-aleph, or my own variant, LTP Zen.

I was interested in the idea of using a zen amp with Linkwitz transform feedback to extend the lf response of a subwoofer.
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Old 12th November 2009, 09:02 AM   #5
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Quote:
Originally Posted by Allen Newby View Post
Interestingly enough, I noted the similarity between the topology of discrete opamps and j-aleph, or my own variant, LTP Zen.

I was interested in the idea of using a zen amp with Linkwitz transform feedback to extend the lf response of a subwoofer.
Because you use an additional differential input stage, there are more open loop gain than the orig. ZEN with only one stage, (voltage and current at the same time). Thus you can calculate as by normal op amp active crossover. Additional you can use two modes: the non inverted mode for "Sallen-Key" topology and the inverted mode for the MFB topology (multiple negative feed back). I would prefer the last for your fourth order acoustical 24db Linkwitz Riley high pass transfer function (12-18db BU characteristic actice crossover in combination with some passive components for mesured 24db Linkwitz Riley high pass transfer function).

Please note by creating of actice crossover - the Sallen-Key topology (multiple positive feed back) is only recommend for low pass function at low frequencies below approximately 300Hz (e. g. sub woofer), because the higher distortions there not critical.
Because a continuous control of the crossover frequency is easily to realize, this topology is used here in most cases.

Last edited by tiefbassuebertr; 12th November 2009 at 09:12 AM.
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Old 2nd February 2010, 08:13 PM   #6
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Are there no others uses single ended power amps for tweeters and integrated crossover networks?
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Old 19th October 2011, 09:30 AM   #7
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Quote:
Originally Posted by tiefbassuebertr View Post
Are there no others uses single ended power amps for tweeters and integrated crossover networks?
in this case this thread is of interest:
First Watt for 112 and 109 db speakers
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Old 10th December 2012, 12:31 PM   #8
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Interesting
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