[geom_tol]

I finally decided to try out a bunch of opamps in my meta42 amp tonight.
I used hd580 headphones and a Pioneer pd-54 cd player (a very smooth sounding player unfortunately, it would have been more interesting with a more detailed/clinical player) and kimber pbj interconnects.
My meta42 used el2001 buffers for this. Cause the el2008's don't fit together with the single->dual opamp converters.
And I've got about +/-10V powersupply.

ad8620- fantastic allround
ad825- really close to ad8620, hard pressed to hear a difference.
opa627-more laidback than the ad opamps, not as clear, but really enjoyable to listen to
opa2604- even more laid back than opa627, not as detailed
opa2134- not bad at all, brighter than the two other bb opamps but not as clear as the ad's
ne5534- brightest of the bunch, but not as enjoyble as the ad's or bb's

Conclusion: All opamps sounded damn good in this amp imo.
The best was ad8620.

I got two ad8065's also, but no soic->dip converters left unfortunately.

I really wanted to try those out.

For grins I occasionally plugged in a Grado RA-1 to compare with. My meta42 with any opamp is better than the RA-1.
The RA-1 doesn't sound bad, it sounds better than you would think considering whats in it. Cool.

 

[KurtW]

A very nice comparison, thanks!

 

[kelly]

Thanks for the info, geom. Have you gotten to try the OPA637 at all?

Via KurtW, my Corda HA-1 (Corda Blue) is now running an opa637 that is biased into Class A via a FET. The sound is not similar to the HeadRoom amps family sound (OPA627). While it is very smooth (and in fact smoother than their amps), the texture and high frequency detail really comes out. Of course, the designs of the amps are very dissimilar--which is why I wonder if any of you guys have used the OPA637 with the rest of the variables being fixed. My guess is that not many people have heard it in Class A.

 

[tangent]

kelly: I was able to listen to the 637 briefly (less than an hour) and it has the same sonic character as the 627, but a bit crisper, and a smidge more dynamic. Given that, and the fact that the two chips cost the same, the only reason I can think of to use the 627 is when the gain is low -- as in the Corda HA-1.

geom_tol: Did you have a current source hooked up in this amp, and if so, which variation?

Without a current source, there's a very easy way to tell the 825 from the 8610/20: listen to solo piano (with perhaps some background accompaniment). If the high notes etch a hole in your head, it's the 825.

With a current source in place, the AD825 sounds a lot more like the AD8610/20.

 

[kelly]

tangent
Did you hear the OPA637 in Class A?

 

[tangent]

Yes. It was in a META42 amp with a cascode current source, running at probably less than 2mA.

 

[geom_tol]

Quote:

Originally posted by tangent geom_tol: Did you have a current source hooked up in this amp, and if so, which variation?

Yes, I have the one you suggest on your website, with the two jfets.
And the sound of the ad825 is indeed very similar to the ad8620.