[groovyd]

[size=medium] I love my XM6 with the OPA134 and buffers in it but I was interested in upgrading the op-amp to the best I can get and came across this thread (http://tangentsoft.net/audio/opamps.html) where the guy compares all sorts of op-amps and is pretty convinced OPA627 is the top gun. Price is not a problem for me and power consumption is not important but I was wondering if this op-amp would work in the XM6 and moreover if it is a good op-amp?  If so would I replace the buffers with something better as well that would compliment the 627s?  I use macbook usb or iPod touch line level out to the XM6 and am driving either Beyer T5p headphones at home or Philips L1 at work.[/size]
[size=medium]  [/size]

 

[hma101]

I just got my 627s in the mail yesterday. They sound WAY better than the 134. Better detail, imaging, attack and low end punch. It sounds like the 134 but with more resolution. The only thing I can say about the 134 is that it sounds a little deeper, but again I think that's a result of the "haziness" that I normally find in the amp. Please note that This is only with about 8 hrs of burn in time.
 
Although you're using (relatively) low impedance headphones, I wouldn't mess with the buffers (I'm using JH13 - almost same impedance as t5p). While you would hear less "thickness" in the sound, you wouldn't be able to crank up the volume without distortion. I don't know if there are any better buffers out there, but the 634 seem to be used quite often. 
 
There is an amp just released with the same specs as the rig we're both describing:
 
http://www.headfonia.com/possibly-the-best-the-627/
 
While I totally agree with the reviewer's sound impressions, but please note that this particular amp has three buf634 per channel, while the xm6 has only one. I think they shoved so many in there so it could drive high impedance (i.e. orthos) headphones.
 
But yeah, for $20 on ebay the 627 is definitely worth it and personally recommended.

 

[Pappucho]

Quote:

There is an amp just released with the same specs as the rig we're both describing:
 
http://www.headfonia.com/possibly-the-best-the-627/
 
While I totally agree with the reviewer's sound impressions, but please note that this particular amp has three buf634 per channel, while the xm6 has only one. I think they shoved so many in there so it could drive high impedance (i.e. orthos) headphones.
 
But yeah, for $20 on ebay the 627 is definitely worth it and personally recommended.

 
Actually, the extra buffers help with low impedance headphones where more current is needed, not high impedance headphones (ie orthos).  The amp in that review has two buffers per channel, not three as you noted.  Although, the amp in that review does have three active channels> L, R and an active G (ground) channel which might be where you are a little confused. 
 
The OPA627 is a great opamp although please beware of fakes on Ebay.  I prefer to source my opamps from a reputable source such as Mouser or digikey. 

 

[kramer5150]

I never liked the OP2134. Not that it was bad, it just never really did anything really good, or special whenever I tried it.  I like the OPA627 in my PPA.  Its not an aggressive / forward sounding chip though.  Not sure if it matters but my PPA has the phil larocco discrete diamond current buffer.  Together, LOVE it for my Grados, seems to energize the ends of the spectrum without overcrowding center stage... which is a very populated place with the RS1.  
 
Side note (because I am not sure its compatible in that amp).  Another chip I really like is the OPA2107, really warm sounding with good transient attack/decay.  I modded the analog stage of my DAC with one and I have an 18 volt cmoy with one.  The 2107 I don't think is a "high current" chip though.

 

[hma101]

Quote:

 
Actually, the extra buffers help with low impedance headphones where more current is needed, not high impedance headphones (ie orthos).  The amp in that review has two buffers per channel, not three as you noted.  Although, the amp in that review does have three active channels> L, R and an active G (ground) channel which might be where you are a little confused. 
 
The OPA627 is a great opamp although please beware of fakes on Ebay.  I prefer to source my opamps from a reputable source such as Mouser or digikey. 

Sorry...Thanks for the clarification.

 

[hma101]

Update:
 
I bought another pair of opa627 from newark.com. The chips were more expensive ($70 for two 8pin, out the door price).
 
After listening to both pairs, one purchased from ebay the other from the above dealer, I have to conclude that the ebay pair is a counterfeit.
 
While the dynamics are similar the ones from newark have a much cleaner sound. They also look cleaner:
 
The ones inserted are from newark, the ones sitting on the battery are the ones from ebay. As you can see the printing is "smudgy."
 
I also put the stock 134s into the buffer slots. It seems to tame the bass and midrange, which seem to have given the amp a thicker sound. It also allows it operate at lower volumes. Which is good, since I'm using iems.
 
Is using an opamp in the buffer slot kosher?

 

[groovyd]

Wow! So the 627 do work in the XM6?  I was under the impression the voltages were all off and it could not be used.  Would like to get a pair and give them a try... where do you recommend I get them?

 

[hma101]

I bought mine from Newark.com, just b/c I've bought from them before. Price is $30 each, but like I said before probably around $70 for both out the door. 
 
Here's the link:
 
http://www.newark.com/texas-instruments/opa627bp/ic-op-amp-16mhz-55v-us-dip-8/dp/35C1918?in_merch=Popular%20Products
 
I'm sure there's other places that sell them as well.