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Old 13th December 2003, 09:26 PM   #21
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Hi,

I know of at least 1 other forum member who posted some thing similar, but I guess various versions of your circuit have posted here. I'm sorry that it isn't that ground-breaking new but that doesn't mean it doesn't work.

I do see some practical issues.. like both sides of your circuits have to be capable of high current? So this is almost like building 2 amplifiers. But you could make it a bridge circuit (LM4780 anyone ;-)); (maybe even use cross-couple of distortion across both sides (X-topology anyone ;-)) . And the R13/R14 are gonna have to be adjustable for precision scaling of the signal, especially if the output stage has no feedback (=relative high output impedance) , it needs to be adjusted to speaker impednace?

I am afraid that practical thingies will prohibit this topology from really being usefull.


Best regards,
Thijs
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Old 13th December 2003, 09:29 PM   #22
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Quote:
Originally posted by johnferrier
But some of the distortion at/caused by the + inputs of X3 and X5 will look like signal.


JF

Could you explain what that means ?
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Old 13th December 2003, 09:36 PM   #23
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Quote:
Originally posted by tschrama
Hi,

I know of at least 1 other forum member who posted some thing similar, but I guess various versions of your circuit have posted here

I do see some practical issues.. like both sides of your circuits have to be capable of high current? So this is almost like building 2 amplifiers. maybe even use cross-couple of distortion across both sides (X-topology anyone ;-)) . And the R13/R14 are gonna have to be adjustable for precision scaling of the signal, especially if the output stage has no feedback (=relative high output impedance) , it needs to be adjusted to speaker impednace?
Do you have a link ? I am very interested.

Yes, its like two amps, but the right side can run from low voltage rails.

I got my problem with cross-coupling because I see no way to figure out how much coupling it has to be.

A pot between R13/R14 will do the job with scaling, but I leave it out for the sim. Theese are details...

Again: The output stage has to be inside the feedback loop for real world and normal condition sim.
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Old 13th December 2003, 09:38 PM   #24
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Quote:
Originally posted by Bernhard
Could you explain what that means ?
One of the distortion mechanisms in FET input opamps is that input capacitance varies with voltage. If the + and - inputs are the same impedance this tends to cancel. Okay, now with your circuit, if there is some type of distortion at +X3 there will also be similar distortion at -X5. This will appear to both opamps like the signal. So to the extent that the distortion at +X3 and -X5 are the same, the distortion will not cancel. (If it cancels, then signal cancels too.) Transistor input opamps will have their own distortion mechanism.


JF
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Old 13th December 2003, 09:52 PM   #25
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NE5532 is no fet op amp.

What can I do if I use one fet op amp ?
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Old 13th December 2003, 09:57 PM   #26
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Same curve like before, but with output stage inside feedback loop. Still while clipping to see the effect.

Black curve is output of right side output stage.

Black and blue add each other to green.

Click the image to open in full size.
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Old 13th December 2003, 09:59 PM   #27
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hehehe...

I've abandoned my cross-coupling idea for a single-ended output. I think if it worked everyone would be doing it now. Nelson Pass's SuperSymmetry is probably as close as it gets.



JF
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Old 13th December 2003, 10:01 PM   #28
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Quote:
Originally posted by Bernhard
Is NE5532 FET ? What can I do ?

No it's BJT, but still with some unwanted distortion that won't cancel.



JF
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Old 13th December 2003, 10:03 PM   #29
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Hi,

Sorry, but I don't have a link.. I wish I had.. we're gonna have to search the forum for that.. or actually I hope the orgininal auteur will read this thread and reply...

Regards,
Thijs
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Old 13th December 2003, 10:07 PM   #30
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Quote:
Originally posted by johnferrier
hehehe...

I've abandoned my cross-coupling idea for a single-ended output. I think if it worked everyone would be doing it now. Nelson Pass's SuperSymmetry is probably as close as it gets.



JF

Huhu, to where did you cross-couple if it is single-ended ?

By the way, do you mean "not bridged/symmetric" ?

Aleph-X is single ended.
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