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Old 23rd February 2011, 02:58 PM   #1
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Default op amp

Hi and thanks for taking the time to read this post.

I have purchased a nice dac which uses an Burr Brown opa2604 opamp.

Can anyone suggest a good upgrade. I was thinking of the ever popular BB opa627ap but have been told this is quite old and should really consider a modern one.

Can anyone please advise, something which works well in the opa2604's current environment (voltage, current, etc)

Many thanks in advance. John.
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Old 23rd February 2011, 03:46 PM   #2
AndrewT is offline AndrewT  Scotland
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Some Members on this Forum say that the opa2604 is a good opamp for audio.

Do you realise you will have to develop the PCB and components to suit a different opamp?
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Old 23rd February 2011, 03:55 PM   #3
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by AndrewT View Post
Some Members on this Forum say that the opa2604 is a good opamp for audio.
Me for one

You could always try the LM4562, as long as it is OK with regard to it not having FET inputs... and for 98% of applications it should be OK.

Have you a circuit for the DAC ?
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Old 23rd February 2011, 04:42 PM   #4
jcx is offline jcx  United States
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you really need to know some things about the circuit - the 2604 is unusual in running from higher supply V than most standard op amps, and for rolling with modern chips many new processes have even lower than the older "standard" +/-18 V supply limits

there are newer fet input op amps seemingly aimed at the opa626/7 niche: ad8610/20, ada4627, opa826

some faster op amps will not be happy in layouts that work for slower chips
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Old 24th February 2011, 05:46 PM   #5
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Hi. Many thanks for the replies.

OOps!! i did not know the entire circuit board had to be redesigned. I read this review Op-Amp review page
and it appears this guy was just dropping chips into the socket, he did not say anything about redesigning.

So just popping the opa2604 out of my dac and fitting in a higher spec chip is not possible?

I contacted the manufacturer be he declined giving me a circuit diagram.
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Old 25th February 2011, 11:46 AM   #6
Mooly is offline Mooly  United Kingdom
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[QUOTE=goodsguys;2481604] So just popping the opa2604 out of my dac and fitting in a higher spec chip is not possible?
QUOTE]

Virtually any dual opamp will work. To get the absolute best results requires optimisation... something 99% of folk just swapping devices never consider.

Just try the devices you are interested in, and have a look at my posts here,

The best sounding audio integrated opamps
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Old 26th February 2011, 08:28 AM   #7
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Hi And many thanks for the reply.

Is there a drop in replacement for the tlo72cp and the opa2604 as an upgrade. A few forum members are reporting excellent results by using the lme49720 and opa 2134 as replacements for the tl072cp, the opa2227 as a replacement for the opa2604.

Best wishes. John.
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Old 26th February 2011, 08:54 AM   #8
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The circuit board probably doesn't have to be reworked. What could be important is decoupling caps in close proximity to the opamp's power pins if you replace OPA2604 with a faster opamp. If needed, such caps could be hardwired.

What's the risk of too high voltage for eg LM4562 in a DAC? What's the risk of not enough current?

Some bipolar opamps have high input bias currents and maybe tweaking has to be done to get it right.

Op-Amp review page This is an OLD review and I wouldn't trust it. To my ears AD823 is awful and he gives it 9/10.

There are lots and lots of reviews here and at Head-fi.org The Best Sounding DUAL opamps

Happy opamp rolling! Don't go for expensive and exotic opamps. The standard opamps to try is LME49720 (the same as LM4562), OPA2134 and NE5532 (this one has high input current so you have to check for DC offset before connecting it to headphones or the amp/speakers if your DAC is without output capacitors). They all sound quite different and are cheap.
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Old 26th February 2011, 09:02 AM   #9
Mooly is offline Mooly  United Kingdom
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You may not "improve" on the performance of what you have... you are just going to have to try and see. The 2604 is great as an I/V converter in DAC's if that's what it's being used as.

The LM4562 might be worth trying... it's not a FET device but has low input bias currents so should minimise any potential DC offset issues. Same goes for the LM49720.

Only you can decide if others are subjectively "better" or provide the kind of sound you are after.
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Old 26th February 2011, 09:05 AM   #10
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Thread moved to more appropriate area.
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