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Old 5th May 2013, 05:54 PM   #11
Mooly is offline Mooly  United Kingdom
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There's more to substituting what is already a good opamp, than just picking myriad device numbers from the well known standards we use today.

For starters the OP27 accepts supplies of up to 44 volts so that limits the possible alternatives substantially. Is that a reason why the OP27 was specified originally ?

If the OP27 is being used in a noise critical application then the surrounding circuitry is almost certainly designed to capitalise on that and substituting a FET device would probably degrade the overall noise performance.
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Old 5th May 2013, 06:38 PM   #12
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I remember OP-27 as being a very good low offset moderate speed amp used for things like DC precision reference buffers. The OP-37 was the faster non-unity-gain-stable version. Other than the high supply voltage they wouldn't be my first choice for audio, but that doesn't mean you couldn't build a decent audio circuit with them. They offered very low offset for their time, but time has marched on.
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Old 5th May 2013, 08:02 PM   #13
M Gregg is offline M Gregg  United Kingdom
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Quote:
Originally Posted by Mooly View Post

For starters the OP27 accepts supplies of up to 44 volts so that limits the possible alternatives substantially. Is that a reason why the OP27 was specified originally ?

.
Thank's

For the heads up on the voltage....Its OK its just +/- 15...

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Old 6th May 2013, 07:29 AM   #14
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by M Gregg View Post
Thank's

For the heads up on the voltage....Its OK its just +/- 15...

Regards
M. Gregg
Here's what I would do. Your curious to hear what difference swapping the OP27 is going to make. We've all said why you should be cautious and what some of the problems could be.

So with that in mind just try a few different devices. I would certainly put the OPA604 on the list despite it being a FET amp. Why. Because for a DAC output at line level noise isn't an issue. Its also one of the best sonically. And perhaps something like the LME49990 too.
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Old 6th May 2013, 09:31 AM   #15
AndrewT is offline AndrewT  Scotland
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Originally Posted by godfrey View Post
Try LM741. Nevermind what the meter-readers tell you, you may be surprised at the subjective performance. I'll almost guarantee you'll hear a difference.
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Originally Posted by Rundmaus View Post
We're using the 741 Op-amp in the lab course for physics students: It's a quite old design with less-than-perfect performance that makes it easier to measure some of the imperfections and limitations of 'real world' Op-amps compared to 'ideal' theoretical ones.

I would seriously doubt that a 741 type will be an improvement.
but would he hear a "difference".
Would he like the difference?
Would he be surprised at the level of difference?
Each of those questions and answers will educate him, whether he is capable of measuring any "improvement".
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Old 6th May 2013, 11:06 AM   #16
JMFahey is offline JMFahey  Argentina
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I very much doubt there will be any difference; even less an "improvement".
By the way, neither we, nor the OP, have the slightest clue as to what that Op Amp is actually doing.
Care to share a schematic at least?
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Old 10th May 2013, 11:31 AM   #17
M Gregg is offline M Gregg  United Kingdom
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Well,

Just to update...the past history I updated this chip many years ago fom NE5534 to OP27..so thats why I was wondering if there was a better OPamp...

So I tried the others and guess what the OP27..which is an analogue devices chip blows them all way..and I did not do any measurements because it was night and day difference...

The OPA134 was sort of "dark" and "closed in" to listen to in comparison..

The OP27 compared to the NE5534 is much better I tried just to see if it was "me" in the past and the OP27 blows it away..

Tried the OPA604 similar sounding to the OPA134..so the OP27 is back in..

I bought some new OP27 AD and used them..even though they were 3 times the price of the opa134..

The amp is in the driver output stage of a meridian DAC..so what do the specs mean...well I know if the circuit was optimised etc then maybe..but in this application its moot..

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Old 10th May 2013, 12:15 PM   #18
M Gregg is offline M Gregg  United Kingdom
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So,

I put the meridian on the digital out of a pure i20 ipod dock and its pretty good..
I'm comparing to a cyrus CD..

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Old 10th May 2013, 12:25 PM   #19
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Originally Posted by cliffforrest View Post
"beat OP27" at what??
From post #2.

If you cannot identify what you are looking for you will never know when it is achieved.
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Old 10th May 2013, 12:53 PM   #20
Mihkus is online now Mihkus  Estonia
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A new and modern preamp/headphone amp...
TDA1308 sounded pretty sweet to my ears used it as headphone amp with PCM2706
Not sure why but compared to my PC sound card it is an wonderful little device or set of 2.

NE5534 is a bit too bassy
OP27 left my hands dirty but i still like it the most.

More likely the sound depends on the source as i have used many "Hi-Fi" and 2 "Audiophile" sound cards they are total bs, for that price, design your own dac
Waste as much time you can on design and look for the best, i mean the one you like the most.
Some say, choose the one you like, not the one others like.

Good luck.
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