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Old 15th December 2007, 06:00 AM   #1
xephon is offline xephon  Australia
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Default Replacement opamps for active crossover?

I've got here a Tru Technology (car audio) 3-way active crossover with TL072CP opamps. Model No. F-1B

I've been searching these forums and have a few possible candidates.

OPA627
AD845
OPA2134PA
NE5532AP
NE5532P

I need 11 of these things for a complete swapout, so cost is a concern (virtually ruling out the top two).
I'll be driving a set of Dynaudio System 320 speakers through Tru Tech amps.


Any suggestions? I can get all the above through RS Components.
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Old 15th December 2007, 09:43 AM   #2
Calvin is offline Calvin  Germany
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Hi,

OPA2134 or OPA2604 are very ok for this application. They are both dual-OPs and JFET-input-devices. They don´t cost much and work quite flawlessly as direct replacemants.
OPA627 and Ad 845 are single types and costly.
The NE-Types are bipolar devices which I wouldn´t use in Filter apps. Besides the ´claimed to be the best of´ NE 5534 from Philips (if I remember correctly) are no longer in Production.

jauu
Calvin
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Old 15th December 2007, 10:08 AM   #3
AndrewT is offline AndrewT  Scotland
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Hi,
the BJT input of the 5532 will probably change the crossover too much.
The 627 will need substantial additions to the PCB to get them to work properly. This may also apply to the 845.

The 2134 FET input should be fine for the filters and will probably do for the input buffers and output drivers as well. Be prepared to add some on pin decoupling to get the best out of them.
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Old 15th December 2007, 10:58 AM   #4
xephon is offline xephon  Australia
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Well, the OPA2134PA or OPA2604AP seem the go then. I can get the 2134 for around AU$6 and the 2604 for around AU$8 or so each from RS Components. Is this a reasonable price?

What's the difference between the two? I noticed the slew rate of the 2604 is 25mS, whereas the 2134 is only 15mS.


The decoupling you describe, that's just a cap between +Vcc and GND on each chip yea?
I reckon I can handle that. What value is recommended?

Thanks.
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Old 15th December 2007, 12:02 PM   #5
AndrewT is offline AndrewT  Scotland
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Quote:
Originally posted by xephon
What's the difference between the two? I noticed the slew rate of the 2604 is 25mS, whereas the 2134 is only 15mS.


The decoupling you describe, that's just a cap between +Vcc and GND on each chip yea?
I reckon I can handle that. What value is recommended?
slew rate >=10V/uS is probably OK for all audio crossovers.
Look at the manufacturer's datasheet for recommendations.
Or search for Carlosfm's advice on decoupling.
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