[audiofil]

 
Quote:

 Anyone who finds the 627 class-a too warm or dark sounding is not going to be impressed with the 2134 IMO.

I agree, OPA2134 is a lesser performer.
 
 
Quote:

Originally Posted by AlfBaxter 

For me the OPA627 in class-a is much brighter and more open than the OPA2134.

 
I agree about the openness.
But I disagree about the brightness. I just wouldn't put "OPA627" and "bright" in the same sentence.
 
In my system the M-stage (1st version) is quite a bit warmer and bassier with OPA627 vs. OPA2134 (both biased in class A).
The OPA2134 without the bias resistor is quite a bit brighter and has a weaker bass response.
 
 
Now, given the wide range of excellent opamps today I really believe there are much better choices for HD650 than OPA627.
 
 
 
 

 

[AlfBaxter]

Quote:

I agree, OPA2134 is a lesser performer.
 
 
 
I agree about the openness.
But I disagree about the brightness. I just wouldn't put "OPA627" and "bright" in the same sentence.
 
In my system the M-stage (1st version) is quite a bit warmer and bassier with OPA627 vs. OPA2134 (both biased in class A).
The OPA2134 without the bias resistor is quite a bit brighter and has a weaker bass response.
 
 
Now, given the wide range of excellent opamps today I really believe there are much better choices for HD650 than OPA627.
 
 
 
 

Interesting - your experience is the exact opposite of mine. You say that in your experience, the OPA2134 is (i) at its brightest and least bassy without the class-a bias mod, (ii) is brighter and less bassy in class-a than the OPA627 in class-a. I have only ever used the 2134 without the class-a mod, and in my experience (with M-Stage V2, I might add) things are exactly - and quite clearly - the other way around. The 627 with class-a is significantly brighter, and much, much less warm and bassy, than the 2134 without. I can even hear details in the top end with the 627 class-a that go missing in a pretty overwhelming lower midrange and bass on the 2134.
 
It's really a night and day difference for me - the OPA627 in class-a sounds closer to the LM4562 (which I found too bright, bordering on painfully so) than it does to the opa2134 stock. Where did you get your OPA627? I bought mine from Cimarron, so am pretty sure it's genuine. If you picked your up very cheaply (not suggesting you did!) then it may not be genuine. Or it may be that different versions of the same model chip respond differently to class-a biasing.

 

[audiofil]

I'm using 2 x OPA627AP on a Browndog adapter and 3.3 kohm Vishay resistors.
I use the same resistor values for OPA2134, but they're Muticomp instead of Vishay.
Digikey/Farnell are my regular suppliers for components.
 
Just for the sake of argument:
- This is not the first time I use OPA627. Some time ago I used to modify TDA1541 based cd-players into NOS cd-players and OPA627 has been my top choice for many years, precisely for the sound signature I've described previously.
- I'm using at the moment "bright" sounding headphones (AKG and Grado) with the M-stage, so we may perceive things differently. I prefer warmer sounding opamps like OPA2107 and OPA627 with them.
 
If I were to use HD6x0, however, my personal choice would be different -  LME49720 HA (which echoes my initial statement - avoiding opa627 for dark headphones)

 

[stephenguoo]

I was considering the m stage, but i'm getting a Gilmore lite. I hope this is going to be better than the m stage. I will be using it with the hd650, so I hope they can couple up nicely.

 

[sluker]

Just got mine from HLLY 300 shipped with a HLLY TAMP-20 (25w/ch amp) included. Delivery took 7 days from order time, but zero communication other than from e-bay.
A quick question for all those who have had theirs for a while. 
How long for burn-in? How many hours for the most significant change?

 

[purrin]

Quote:

It's really a night and day difference for me - the OPA627 in class-a sounds closer to the LM4562 (which I found too bright, bordering on painfully so) than it does to the opa2134 stock. Where did you get your OPA627? I bought mine from Cimarron, so am pretty sure it's genuine. If you picked your up very cheaply (not suggesting you did!) then it may not be genuine. Or it may be that different versions of the same model chip respond differently to class-a biasing.

 
LOL, maybe you have sub-spec or wierd OPA2134? On M-Stage, I've found OPA2134 a little bit brighter (with tubbier bass) than LM4562 (warmer) and OPA627 (tho never tested this chip on M-Stage, but I'm speaking in general on other amps I've built).  OPA627 without class A biasing was extremely laid back, but with class A biasing, OPA627 comes to life. In regards to going class A, LM4562 gets warmer and BB chips mentioned above get brighter, except OPA2134 where I found sound signature doesn't change that much.

 

[AlfBaxter]

Quote:

 
LOL, maybe you have sub-spec or wierd OPA2134? On M-Stage, I've found OPA2134 a little bit brighter (with tubbier bass) than LM4562 (warmer) and OPA627 (tho never tested this chip on M-Stage, but I'm speaking in general on other amps I've built).  OPA627 without class A biasing was extremely laid back, but with class A biasing, OPA627 comes to life. In regards to going class A, LM4562 gets warmer and BB chips mentioned above get brighter, except OPA2134 where I found sound signature doesn't change that much.

Yeah something's definitely different in the chips I have, given my setup. No way LM4562 is warmer than OPA2134 - my girlfriend listened to some music when I had the LM4562 in and without any prompting from me said it hurt her ears after prolonged listening, due to the emphasis at the top end. I have switched them many times, trying to decide which I liked more - I always went back to OPA2134, which, despite comparative lack of detail in the treble and excess lower mid and bass, was always more pleasant for extended listening. My LM4562 was positively harsh in comparison to the OPA2134.
 
For what it's worth, the LM4562 is a pull from an Auzen prelude, and the OPA2134 is the stock one from the M-Stage. Also without prompting, gf said that the OPA627 in class-a had all the detail she heard in the LM4562 without any of the fatiguing treble. This is exactly what I had independently concluded.
 
I would suspect that we don't mean the same thing by terms like 'bright' were it not for the fact that I agree with you entirely that the OPA627 is laid back when not in class-A, but gets brighter and - as you say - comes to life with the mod.

 

[AlfBaxter]

Quote:

 
If I were to use HD6x0, however, my personal choice would be different -  LME49720 HA (which echoes my initial statement - avoiding opa627 for dark headphones)

I agree about that. Maybe we have had different experiences with HD6x0. Mine are the revised version (silver baffle) and while they are not short on bass, they are certainly not dark sounding. I do think the Burr-Brown opamps are generally on the warm side, and so wouldn't advise anyone to pair them with headphones that lack top end - but like I say, I have never found my HD650 to be dark. In any case, I can certainly recommend M-Stage with OPA627 to those who have later versions of the HD650 - but maybe not for those who have the original versions that suffer from the Senn 'veil'.

 

[ninjikiran]

True story, the LM4562 from the prelude seems a bit more amplified on the high end compared to the Lm4562 I bought from digikey and LME49720 I got from purrin.
 
It might just be something awkward with the batch Auzentech got.  While it might not make a noticeable difference for me, I have been thinking of trying the HA model of the LME49720(metal can).  I wonder if I can just stick the pin into a standard dip8 without conversion.  The cost to risk ratio is close to nothing and it'll quell my curiosity.  It wouldn't go into my M-Stage though, it'll go in my DAC which is using the plastic variant.

 

[Mad Max]

Sure you can stick the metal can in just like that (after carefully trimming the leads), but it is not good for the long run, I'm told.  You should solder the opamp into an appropriate adapter first.

 

[sluker]

OK 
This is dissapointing, after three hours of use the right channel cut out. I have tried both inputs and different cans as well as letting it sit idle for a half hour but it is still not working. One interesting observation is that when I turn it off for the fraction of a second that the power is still there the right channel comes back.
Has anyone experienced this? Is there a quick fix?
I would hate to send this thing back to China after three hours of use.

 

[Mad Max]

Have you contacted coolfungadget about it?

 

[sluker]

Actually I bought it from HLLY, and yes I sent them an e-mail. No response yet. 
Edit:
I just got a response from David Gao (quick) and he suggested that I open it up and make sure the op-amp is secure. Otherwise he said I should send it back. 
Does anyone know if HLLY covers shipping for warranty? Normally I wouldn't complain but I have had this thing all of six hours and shipping to China ain't cheap (so much for a good deal).
By the way, how do I know which is the op-amp

 

[Mad Max]

Right there.
 

 

[sluker]

Thanks
While I am in there is there anything else I should check which could be causing this?