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Old 3rd November 2009, 11:22 AM   #1
Havoc08 is offline Havoc08  Denmark
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Default Changing the std. opamp of active x-over

Hi all,
I would like to know if anyone can tell me whether I can change the TI-81/82 opamps in my 24dB active crossover to the TI-NE5532 opamp without problems.

Operational Amplifiers - Standard Linear Amplifiers - TL081 - TI.com

Operational Amplifiers - Standard Linear Amplifiers - NE5532 - TI.com

The reason I want to change is that I read that the TI-81 are mediocre at best and the NE5532 is a cheap upgrade.
As the crossover has about 8 opamps, more expensive ones like opa627 is out of the question, but feel free to propose other mid-end opamps with better sound than the TI-81.
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Old 3rd November 2009, 01:31 PM   #2
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Hi Havoc !
Are you able to post a circuit diagram ?
Your circuit may be sensitive to DC offset. In that case i whould not use the NE5532.
The NE is bipolar and has no bias cancelation. On the other hand Douglas Self is saying (he has a lot of experience with the NE) that the DC offset of that chip is not that bad in praxis.
By the way the NE5532 is a double OP and the TL081 is a single so you should use the NE5534. The NE5534 may need compensation though. It depends on the gain and topology of the circuit.
The NE5534 is an upgrade in terms of distortion and noise and a very good value.
Another option is the OPA134. This is a Fet device with low offset and resonably inexpensive.
There are many other options but those i mentioned are the most popular and i have a lot of experience with them.
Soundwise the NE5534 has a neutral "matter of fact" sound.
The OPA134 is liked by many peole for it`s "musicality".
In my setups it sounds a little more fullbodied and rounded although it has higher distortion in the treble especially when you load it lower then 2kOhms.
It certainly is a popuar chip and i see it in many expensive gear.
There are also some "tricks" you can do to an opamp stage to make it sound better.
One is to bias it in class a and one is to buffer it. Of cause you can do both.
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Old 3rd November 2009, 04:51 PM   #3
Havoc08 is offline Havoc08  Denmark
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Thank you for your reply Joachim.
I must confess that I bought the x-over as it was very cheap.
It is a reckhorn F1 active crossover.
http://www.reckhorn.com/graphics/f1/...putVoltage.jpg
Please note that the circuit shows some resistor modifications to alter the output voltage. Also the diagram shows the 4558 opamp I think. I'm quite sure that is not what is in mine.

I can't remember whether it was the TI 81 or 82... I'll open it up and check. It is of course important for you to comment on opamp choice.

As my amp is sort of full bodied in it's sound, I think a neutral sounding xover is preferable.
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