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Old 24th January 2008, 03:20 PM   #1
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Default slew rate adjustment...

Hi, I am a complete newbie. I have what i think is a very simple question. I have honestly spent the last 3 days searching thru this forum and cannot get a clear cut answer. maybe there isnt one...

but here goes

i would like to change opamps in a box i have.

the original opamps slew rate is 13 and 8 respectively
the opamps i want to switch over to rate is 20.

is it absolutely necessary to change capacitors to adjust for the new rate?

since i am new to this, I would like to avoid unnecesary steps.

thanx in advance for any help!
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Old 24th January 2008, 03:38 PM   #2
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Faster slew rate does not always mean better sound.

Putting faster op-amps in may mean decoupling requirements are more fussy and/or compensation capacitors (if present) need to be changed.

What is the "box", what chips are in it and what do you want to put in?
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Old 24th January 2008, 03:43 PM   #3
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This is sort of like asking:
I need new tires for my automobile the ones I have now are rated at 100 MPH, I would like ones rated at 120 MPH, what should I get?

Op-amps have many parameters, slew-rate is just one.
Some parameters:
Supply voltage
Supply current
Pin out
Gain
Frequency range
Input impedance
Output impedance/load

And the list goes on.
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Old 24th January 2008, 03:52 PM   #4
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there are tl072's and ne 5532's in there right now.

my thought was to change the 072's to opa2134 and the ne5532's to opa2227.

Its just a cheap compressor i have around.
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Old 24th January 2008, 07:37 PM   #5
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I know that there are other factors to consider.

I was just trying to ask the most basic question i could.

so with those opamps I have listed, does anybody see any potential problem with the changes i want to make? All of those opamps are dual aren't they?
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Old 25th January 2008, 07:37 AM   #6
h_a is offline h_a  Europe
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Actually I think you won't come far just by changing opamps without knowing what properties are needed in a specific position.

I know it's probably not what you want to hear, but I would recommend to reengineer the box first, draw a schematic and try to understand how things work. You are of course highly welcome to post the schematic here and discuss it with others which may help you to understand it.

I'm sure you get then far better suggestions to improve it than now, with the added bonus that you learnt something interesting.

All the best, Hannes
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Old 25th January 2008, 09:36 AM   #7
AndrewT is online now AndrewT  Scotland
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Quote:
Originally posted by richie00boy
Putting faster op-amps in may mean decoupling requirements are more fussy and/or compensation capacitors (if present) need to be changed.
agreed
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Old 25th January 2008, 10:01 AM   #8
Nordic is offline Nordic  South Africa
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OPA2227 may be tricky.... normaly needs a bit special treatment...

Opa 2132 is a bit of a step up in some regards but a step down in others, like noise rejection....
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