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Old 22nd January 2013, 06:58 AM   #71
Mooly is online now Mooly  United Kingdom
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The input impedance is one area where my solution failed too.

If the input impedance in the pass band remains the same as the original then that suggests we should be able to add a 5.9K in series with the source voltage and that the output voltage will reduce by 50% without affecting the response.
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Old 22nd January 2013, 08:54 AM   #72
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By the way did any of you read Castor-Perry's article in Linear Audio?

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Old 22nd January 2013, 10:52 AM   #73
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Quote:
Originally Posted by jan.didden View Post
By the way did any of you read Castor-Perry's article in Linear Audio?

jan
I must confess I haven't...
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Old 22nd January 2013, 07:33 PM   #74
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Something like this...

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Old 22nd January 2013, 09:17 PM   #75
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... or that ...

A single op amp differential amplifier - nothing new ...

Regards, Toni
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Old 23rd January 2013, 01:09 AM   #76
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sidiy:

I mounted breadboard the two options ("standard" and "modified") and measured input impedance in both circuits above 10 KHz. There may be slight discrepancies in the readings but I do not see major differences.

regards



jan.didden:

I'll look for that article. Looks interesting.

Clarified that is not what I'm using.

Thank you very much for the information.

regards

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Old 23rd January 2013, 01:44 AM   #77
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astx:

Those were the two best approximations, until now. Give me some time to analyze them in detail.

I do not see these nonlinearities, as I said occurs in other case.

I have doubts on the input impedance. I think it's 2K4.

As you can see, I use another variant.

The blue curve corresponds to what You have kindly uploaded.

regards

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Old 23rd January 2013, 06:30 AM   #78
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diegomj1973... is that graph of Zin (post #76) for your new circuit configuration ?
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Old 23rd January 2013, 07:18 AM   #79
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Ad post #75 and #77:
IMHO the blue curve seems to be more linear - standard differential amplifier seems to be the better circuit. The input impedance ist indeed 2.4k
Also with matched resistors the CMRR will be very good.
 
Old 23rd January 2013, 01:23 PM   #80
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Mooly:

Yes. These were measured on a real case.

regards



astx:

The blue curve is more linear than red (no doubt). However, in real cases, this nonlinearity does not exceed 0.1 dB. Believe me it is so.

The main intention in my connection is:
Given a common connection, have the possibility to relocate its components, maintaining its current parameters and improve only the low-frequency response (without prejudice to the other parameters). This would allow us to implement it in all that exists, relocating connections only.

While what you have is very interesting, would have to find a way to keep the same input impedance (or something very similar).

regards
 

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