opa 2134 vs 2 opa627

[jacco vermeulen]

Here is an example from a diyaudio member.
( calling herself a geek chick on headphone forums )

 

[lucpes]

I'm no specialist, but here's what I think is a good read on decoupling/grounding OPAs:

http://www.analog.com/UploadedFiles/Application_Notes/135208865AN-202.pdf

IMO, or at least based on my ears, additional capacitance from V- to V+ does indeed make a positive difference sound quality wise, I usually use 10nF COG ceramic with good results (my ears/my preferences/my equipment) in this position - OPA V+/ V- pins. I think that good HF behaviour in this position is more important than raw capacitance (electolytic) - at least for high bandwith opamps, as long as you have decent decoupling on both rails.

This (from my master tinkerer POV) might also yield improvements SQ wise (using 4.7 nF silvered mica for rail-to-rail decoupling right on top of SMD OPAs).

 

[analogrules]

Does anyone know where i can pick up 4 opa627 and what would I expect to pay? Also what others would you rec amend to replace opa2134 with? I already have the adapters! This is for a Music Hall CD 25.2 player.

Thanks!

 

[jcx]

you are asking to be scammed searching for lower cost ebay sellers - just go to mainstream official distributors - easily found on TI.com opa627 product page

Digikey http://www.digikey.com/?curr=USD product search: opa627

opa827 is newer, cheaper presuably aimed to replace 627

opa1642 certainly betters most opa2134 specs

 

[analogrules]

Thanks, That seems to be a good call. Do you know if the 827 sounds any better the 627 and is a single channel chip? I here that 627 sounds much better then the opa2134. What do think?

 

[highendguy]

Exactly to the point, iamwhoiam !
That test showed no difference between AP and BP versions, difference only being the DC values.
I got the BP versions at the same cost as the AP's, a lot of them.
I have been forcing opamps in class A for ages, because of the distinct difference in sound when fets are driven in class A.
Maybe a reason why, imho, the difference between B's and A's exists.
20years ago i started using the Burr Brown OP27, in those days people who favored OP27 over 5534's already were exotic.
Telling others that BBOP27's sounded much different than PMI OP27's gave you the look, BB OP27 were very hard to come by in those days.
Now people say OP27's are no good, 5534's are trash.
It has not been that long ago when i still saw $3000 preamps running on 5534/5532's.
imo, the proper way to drive fets is in class A.
Still, the majority seems to keep running their opamps in normal mode.
Carlos is very keen on the OPA627, so am i, i am very fond of the BurrBrown sound.
I havent tried by-passing on the pins yet, but if i do i dont think i need a scope to tell the difference.
Still, it would no hurt if an existing difference could be quantified.

Sorry, but I stumbling on your old post I couldn't resist to correct
First of all the OPA627 is a FET opamp by it's input stage, which is always in class A, and not by it's output stage which is BJT based.
The measured the output stage for my purpose, and it (the output stage, and so the whole opamp) IS class A at least to 1Veff @ 400R.

 

[Hugh Jazz]

Update in 2018 - OPA1622 is awesome in headphone-op amp circuits but unfortunately is not in SOIC or DIP packages, so it needs skills such as this:

An externally hosted image should be here but it was not working when we last tested it.