2132PA 2132P & 2132UA
Dec 1, 2008 at 2:51 AM Thread Starter Post #1 of 11

Fred_fred2004

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Can anyone tell me if there is a difference between these three variations? I've ended up with 5 of each and I'm not sure which is the best to use. They are all DIL-8 packs
 
Dec 1, 2008 at 2:54 AM Post #3 of 11

Fred_fred2004

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Got them off eBay they look like old stock still in sealed static bags
 
Dec 2, 2008 at 6:29 AM Post #6 of 11

rembrant

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According to the data sheet. opa2132PA can have an input offset voltage of up to 2mV! compared to the max offset voltage of opa2132P which is .5mV.

To put that into perspective, a (standard) cmoy amp with opa2132P should have a max DC offset of 5.6mV. Fine.
With opa2132PA that would be 22mV. Not fine.
You could drop the gain to 3 and it would be 6mV. That is still higher than the worst 2132P chip and with 8db less amplification.

I only say that because your question had me looking more closely at the data sheet and I had planned to buy some PA chips for exactly that purpose.

How typical is it to get chips with max or near max voltage offset figures? I don't know. Thats where my experience turns to speculation.
 
Dec 2, 2008 at 6:41 AM Post #7 of 11

Fred_fred2004

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I'll plug them in and see if there is any smoke/flames or even funny noises,
 
Dec 2, 2008 at 6:45 AM Post #8 of 11

rembrant

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I would check the DC offset before plugging anything into the amp. Perhaps change R3 to 5k to be safe. The amp it self will be fine. It's your headphones you should be worried about.
 
Dec 2, 2008 at 7:21 AM Post #9 of 11

Fred_fred2004

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I tried them both before I read your last post, and everything survived. I can't tell any differance in any way and I just found this on Tangent's site

he says
As for the OPA2132P, it's about twice the price of the 2132PA, and I can't hear a difference relative to the 2132PA. This isn't surprising, since the only specs that are different between the two chips are the DC specs, and there is no DC in audio.

But I'm now out of my league
 
Dec 2, 2008 at 8:41 AM Post #11 of 11

rembrant

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You really need to read this.
Working with Cranky Op-Amps
and get familiar with the offset calculator
Electronics Calculators

Especially, if you decide to go rolling opamps. The guys around here typically make it seam like all you have to do is change the opamp. That is not true. You have to change the entire resistor network as well. If you use an input cap you are pretty much stuck with R2 and you can really only change R3 and R4. Considering the lowest pot you can get is 10k your stuck with r2 anyway.

For instance, if you decided to try lets say a LM4562 you would need to change r3 to 5k and r4 to 50k and even then your DC offset would be 18mV with the typical lm4562. That is way to close to the margin(20mV). So your left with reducing the gain or increasing the caps again and there are downsides to both.
If that chip is even a bit out of spec your boned.
Considering the maximum allowable input voltage offset of that chip which is .7mV. The typical is .1mV
The input current offset is 11nA typical and 65nA max.
The input bias current is 10nA typical and 75nA max.
Your chances of getting a perfect Opamp here are pretty slim.
 

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