# AD797 vs OPA627 ?



## Edwood

How does the Analog Devices AD797 OP amp compare to the Burr Brown OPA627?

 -Ed


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## donovansmith

I don't know about compared to that AD opamp, but the OPA627 is a dark-sounding opamp with incredible detail and a very nice soundstage. The AD chips I have tried (AD823 and AD8620) have tended to be brighter sounding with less detail and soundstage, but more forgiving of recording artifacts and problems in the source. The AD chips were also more aggressive sounding compared to the laid-back OPA627 (other Burr-Brown opamps tend to be overall laid-back and somewhat dark sounding). HeadRoom uses the OPA627 in their higher-end amps, btw.


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## guzzler

the AD797 is not a good chip for headphone amplifiers, it's designed for a very high open gain with low noise in curcuits like microphone amp and phono stage amps. If you want to use Analog Devices, use the 806* or 86*0 for starters, although there are many others

 g


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## Edwood

Was thinking of swapping out the OP amp from the analog output stage of my RME digi96/8 PAD like Iron_Dreamer did. (he used AD797's)

 Since I'm using Grace 901+K1000, detailed, open, and not bright would be a good thing.

 So, not for a headphone amp.

 BTW, what OP amp(s) is in the Grace 901?
 What about the AKG SAC K1000 amp?

 -Ed


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## Music Fanatic

Quote:


 _Originally posted by Edwood _
*
 BTW, what OP amp(s) is in the Grace 901?
* 
 

 It appears the amp in the Grace 901 is the Analog Devices AD815AY: http://www.analog.com/UploadedFiles/...262AD815_b.pdf

 Again, an amazing chip for an amazing amp.


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## donovansmith

Quote:


 _Originally posted by Edwood _
*Was thinking of swapping out the OP amp from the analog output stage of my RME digi96/8 PAD like Iron_Dreamer did. (he used AD797's)

 Since I'm using Grace 901+K1000, detailed, open, and not bright would be a good thing.* 
 

 The OPA627 is great for that. The only potential problem is that it needs around 12V or so to work, which may not work on a soundcard unless the opamps are actually being fed 12V (I though soundcards only had 5V). If the gain is at least 5 or more and the analog stage is well designed, the OPA637 is reported to be quite good also, but is more tricky to work with for stability.


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## Glassman

no chance for 637 on soundcards guys.. some soundcard use +/- 12V, others +/- 5V.. personally I don't see any regulators on RME so there should be +/- 12V and thus no problem.. make sure you bias this bitch to Class A with some 2mA per channel 
	

	
	
		
		

		
			





 6k8 resistor from output to -12V rail will do..


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## PinkFloyd

I've got two opa 627 BP's on a browndog in my Chiarra and they are the best I've heard to date. In my amp they sound airy and detailed, certainly not "dark" sounding.

 Pinkie.


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## donovansmith

Well, compared to the AD chips the OPA627 is dark sounding on the level of the OPA2227/OPA2228 which I think are just slightly on the dark side of neutral, but not nearly as dark as the OPA2132 (this chip should be banned from any amp). In my PIMETA they are a little dark, but the BUF634 is helping add to that. Actually, I love the OPA627 and BUF634 pairing in my PIMETA. Those chips have a nice synergy, especially with my HD600s.


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## Sovkiller

Quote:


 _Originally posted by PinkFloyd _
*I've got two opa 627 BP's on a browndog in my Chiarra and they are the best I've heard to date. In my amp they sound airy and detailed, certainly not "dark" sounding.

 Pinkie. * 
 

Well IIRC the 627 is the chip Headroom uses in their amps, along withthe 637 even on the Blockhead.....Pink have you ever tried the 637, is supposed to be a little bit better, but not unity gain stable, I don't know if you may need that for the Chiarra....


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## gpalmer

Quote:


 _Originally posted by guzzler _
*the AD797 is not a good chip for headphone amplifiers, it's designed for a very high open gain with low noise in curcuits like microphone amp and phono stage amps. If you want to use Analog Devices, use the 806* or 86*0 for starters, although there are many others

 g * 
 

Hmmm, seems to work just fine in my HR-2!


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## Edwood

Well, had a fun little RME vs. RME microMeet today with Iron_Dreamer and Ozric today.

 Unless the Blackgates open up with alot more power as they burn in, AD797's are a No No with the Grace 901. There is simply not enough output volume for the Grace. It is already pretty close to maxed out on the stock RME PAD as it is. But with the AD797's in Iron_Dreamer's modified RME PAD, it was at least 3 "clicks" lower in volume compared to the stock RME PAD.

 The modified RME PAD was lacking in dynamics compared to the stock one. It was certainly smoother and less harsh.

 At the next meet, we'll hear for sure how the modded RME Pad stacks up, so the jury's out til then.

 However, interestingly enough, Iron_Dreamer's Modded RME PAD had some pretty nice synergy happening with the AKG SAC K1000 Amp. I guess it has more than enough power to make up for the output loss. 

 -Ed


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## Glassman

there should be NO difference in the output level, if there is, something is wrong!


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## Edwood

Probably Foobar Settings then. 

 -Ed


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## fewtch

Quote:


  Originally Posted by *donovansmith* 
_I don't know about compared to that AD opamp, but the OPA627 is a dark-sounding opamp with incredible detail and a very nice soundstage. The AD chips I have tried (AD823 and AD8620) have tended to be brighter sounding with less detail and soundstage, but more forgiving of recording artifacts and problems in the source. The AD chips were also more aggressive sounding compared to the laid-back OPA627 (other Burr-Brown opamps tend to be overall laid-back and somewhat dark sounding). HeadRoom uses the OPA627 in their higher-end amps, btw._

 

Fwiw I find the OPA627 to be more forgiving of poor sources/recordings than the AD8620 (could be because of the tendency toward midrange focus). I don't find the OPA627 to be "dark" in the usual sense, merely subdued (and sometimes uninvolving... often it fails to keep my attention). I'm tending to listen at lower volumes with the OPA627 and focus on the big picture rather than the details. IMO the 627 is not a very detailed chip, at least compared to the AD86x0... it's more of an "old school" sound, almost tubelike in certain ways.


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## Edwood

LOL, resurrecting an older thread? 
	

	
	
		
		

		
			





 Don't forget class A biasing! 
	

	
	
		
		

		
		
	


	




 -Ed


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## fewtch

Quote:


  Originally Posted by *Edwood* 
_LOL, resurrecting an older thread? 
	

	
	
		
		

		
		
	


	




 Don't forget class A biasing! 
	

	
	
		
		

		
		
	


	




 -Ed_

 

Well, I'm comparing both chips without class A biasing (so is it a fair comparison? 
	

	
	
		
		

		
		
	


	




).


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## ITZBITZ

The AD8620/10 doesn't really change much with class A bias, but the OPA627 certainly does.


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