Ye olde Op-Amp in Digital gear question again - diyAudio
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Old 19th June 2003, 12:59 PM   #1
Previously: Kuei Yang Wang
 
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Default Ye olde Op-Amp in Digital gear question again

Koinichiwa,

So, here we again. For a SPECIFIC set of application I am trying to find out what peoples experiences have been with replacement Op-Amp's.

The fundamental limitation is that the device must be available as SO8 SMD Dual Op-Amp part, cost is not a concern (within reason).

Applications are twofold:

1) Input Buffer and signal conditioning for Crystal Semiconductor "Delta Sigma" AD Converters (CS5396).

2) Output Filter & Buffer for Crystal Semiconductor "Delat Sigma" DA Converters (CS4396)

Both sections are part of Pro-Audio gear.

Since I found ages ago the LM6172 to be a good choice for such applications times have moved on and there seems to be a new "best" dual OPA every week or two.

I'd appreciate any input, however, the differences in operation and design between for example DS and Multibit DAC's make what is best for one not neccesarily the best for the other.

I admit to having my Eye on the AD8620 (IIRC). Any others?

Sayonara
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Old 19th June 2003, 02:56 PM   #2
RobM is offline RobM  United States
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OPA627?

For my personal applications I use either 627 or 5332, with a class A follower in the feedback loop if it's an output buffer, followed up with a JT-OLI-3 to prevent RF induced oscillations while maintaining a low output impedance.
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Old 19th June 2003, 02:58 PM   #3
RobM is offline RobM  United States
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Oh, you want a dual opamp. So that shoots out the 627. Shame, that's such a nice opamp.
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Old 19th June 2003, 03:02 PM   #4
Previously: Kuei Yang Wang
 
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Koinichiwa,

Quote:
Originally posted by RobM
Oh, you want a dual opamp. So that shoots out the 627. Shame, that's such a nice opamp.
I know. The 627 would be my first choice on the AD input (maybe also output). But as we are dealing with SMD making adapters would be so messy that I might as well redesign the whole PCB, except all i want is to mod the unit... ;-)

So, what Dual, SO8 SMD package Op-Amp sounds like the OPA627 or even better like the 637 except being unity gain stable?

Tough one, I know....

Sayonara
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Old 19th June 2003, 03:19 PM   #5
RobM is offline RobM  United States
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Does the OP270 come in SO8? I know it comes in a DIP8...
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Old 19th June 2003, 05:24 PM   #6
ojg is offline ojg
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My favorite dual op-amp right now: AD8022
Open-loop bandwidth to over 20kHz and open-loop gain at a sensible 80dB. Very low noise (2nV/2pA) and fairly low distortion.
Very high bandwidth/speed but max Vcc of +-13V.

IMHO, the OPA627 is getting a little old and slow.
The AD8620 is a very good "traditional" op-amp.

-ojg
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Old 19th June 2003, 10:23 PM   #7
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Quote:
IMHO, the OPA627 is getting a little old and slow.
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Old 20th June 2003, 06:24 AM   #8
Werner is offline Werner  Europe
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Hi T,

bought a 2496?

W
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Old 20th June 2003, 05:57 PM   #9
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Hi Kuei,

Have you tested the OPA2132?
Well bypassed it's fantastic, and you may not even need an output cap, as DC ooffset is so low (I have 0.2~0.3 mv on my headphone amp, with OPA2132 and BUF634, without any caps in the signal).
The 2134 seams the same, and is cheaper, but I haven't tried it.
I've used the OPA2132 on several CD players and preamps and it's very good.
Audibly much better than the OPA2604.
Well, the OPA627 is the top, but you whant double...
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Old 20th June 2003, 05:59 PM   #10
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Quote:
Originally posted by ojg

IMHO, the OPA627 is getting a little old and slow.
The AD8620 is a very good "traditional" op-amp.
-ojg

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