Author Topic: Stereo mixer amplifier  (Read 972 times)

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Offline DonKuTopic starter

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Stereo mixer amplifier
« on: October 06, 2019, 03:04:18 pm »
Greetings,

An article about my stereo mixer-amplifier project is now available.

http://crcomp.net/electronic/mixeramp/index.php

Thank you, 73,

--
Don Kuenz KB7RPU
There was a young lady named Bright Whose speed was far faster than light;
She set out one day In a relative way And returned on the previous night.
 

Offline moffy

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Re: Stereo mixer amplifier
« Reply #1 on: October 07, 2019, 08:44:57 am »
The specs for the isolation transformers says: 10. Total Harmonic Distortion < 0.5% between 275Hz and3.5KHz. It looks like they were primarily meant for telephone systems, rather than audio/hifi. Pretty high distortion levels in the band, will be higher outside.
 

Online Zero999

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Re: Stereo mixer amplifier
« Reply #2 on: October 07, 2019, 09:23:00 am »
The load on the secondary of the transformers is fairly low anyway, so you could do away with the op-amp mixer and connect the secondary windings of all of the transformer in series, to mix the signals passively. The only downside is some power from each signal will leak over into the others, but if the load on the transformer secondary windings is high impedance, it will be negligible.
 

Offline DonKuTopic starter

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Re: Stereo mixer amplifier
« Reply #3 on: October 07, 2019, 03:19:53 pm »
The specs for the isolation transformers says: 10. Total Harmonic Distortion < 0.5% between 275Hz and3.5KHz. It looks like they were primarily meant for telephone systems, rather than audio/hifi. Pretty high distortion levels in the band, will be higher outside.

Good information. If you don't mind me asking, do you know of a better, readily available transformer?
« Last Edit: October 07, 2019, 03:32:12 pm by DonKu »
 

Offline DonKuTopic starter

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Re: Stereo mixer amplifier
« Reply #4 on: October 07, 2019, 03:22:56 pm »
The load on the secondary of the transformers is fairly low anyway, so you could do away with the op-amp mixer and connect the secondary windings of all of the transformer in series, to mix the signals passively. The only downside is some power from each signal will leak over into the others, but if the load on the transformer secondary windings is high impedance, it will be negligible.

Interesting idea.
 

Offline moffy

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Re: Stereo mixer amplifier
« Reply #5 on: October 07, 2019, 03:31:11 pm »
https://jensen-transformers.com/wp-content/uploads/2014/09/Audio-Transformers-Chapter.pdf. High nickel mu metal core material gives between 0.001% to 0.01% distortion. They are a lot more expensive though.
 

Offline DonKuTopic starter

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Re: Stereo mixer amplifier
« Reply #6 on: October 07, 2019, 03:36:21 pm »
https://jensen-transformers.com/wp-content/uploads/2014/09/Audio-Transformers-Chapter.pdf. High nickel mu metal core material gives between 0.001% to 0.01% distortion. They are a lot more expensive though.

Bill Whitlock's literature is well known to me. As you say, his excellent solutions are much more expensive (deservedly so) than my own humble telephone quality solution.
« Last Edit: October 07, 2019, 03:41:08 pm by DonKu »
 


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