Edit: I notice this post is still frequently visited today. This post was written by me a while ago and it does not meet the standard I require my posts to have now. I'll be frank - to the me of today (2011, but I noticed the situation in 2010, possibly even earlier), this post is full of bull. Just as non-controlled-tested subjective reviews are. More-significant uncontrolled variables swamp any potential difference from the device being tested, and differences heard are wrongly attributed to the device. And I'm not even talking about placebo yet, which many open-minded believers somehow do not believe in its effects.
But I know there are those of you who want to read this review. So I have left the original post untouched below. I just want to make clear the issues with such a review. Subjective reviews are fine, but only if the mentioned differences are tested to reliably exist. And most subjective reviews never test that.
So I got a pair of LM4562 op-amp for my Zhaolu DAC three days ago. This is the most important mod in the series of possible mods because it's like everyone on the net with a Zhaolu is saying that this is a very good upgrade, the others being OPA2107, OPA2134 (or 2132, both not as good as the rest though), LT1469, the king of op-amps (and overly expensive) OPA627, and discreet op-amp stages like the Zapfilter.
(I don't think AD was mentioned because of the nature of the sound and that of Zhaolu, both being very cold)
I chose this because it's almost on the same level as OPA2107 (and some say OPA627) and LT1469, and most importantly it costs the cheapest at $13+ for a pair. This amount can only get you at most one of the cheaper alternatives and less than half of an OPA627 set. And why people would want to spend so much on 4 OPA627s or even a Zapfilter on such a cheap DAC beats me.
Now now, while we're on this topic I might as well talk about why sometimes somebody (or rather a whole group of people) will say that certain op-amp is good while in other applications the said op-amp is crap.
Firstly, op-amps are not perfect and they change the sound signature (which some may like) i.e. different (brands of) op-amps sound different. Different brands of DAC chips sound different also. Different components/implementations sound different too. So a good balance and combination of components that can work in harmony is needed.
Furthermore, different op-amps will perform differently for different uses. In many cases we're talking about voltage buffer, or more commonly known as output/preamp stage. Then there's op-amps for headphones, and op-amps in the power circuitary.
Ok, back to the LM4562, how will this fast and "fast sounding" - what the heck is that? op-amp change the sound of my system?
It sounds... bad. The bass is greatly reduced, the trebles are too bright and sharp. Somebody played with the tone controls here?
However, the trebles are indeed clearer and cleaner and I can hear a bit more instruments. But this induces ear fatigue and I also don't like the loss in bass power. Dynamics is seriously lacking.
Soundstage is slightly wider as mentioned on the web, the notes are clearer but they sound more tonal and I cannot hear the rest of the instruments like impact sound and harmonics. Even my brother is saying that it sounds fake.
That's a lot of sacrifice just for that bit of more musical and "faster" details. And I can't say that it sounds more musical either, since the instruments now sound fake.
After a few days and a few hours of burn-in:
After I came back from camp I listened and was like huh, was this that LM4562 I've just installed yesterday? Or have my ears gotten used to the sound already? The fakeness and harshness is gone and now I'm listening to something that sounds much more normal. The treble has reduced in volume, but the details are still there and clear as ever. The high-frequency hitting sounds are now like free-of-charge, and the bass has more power. Not to be confused with the darker/warmer sound-signature of the Burr-Browns, this LM4562 has an interesting sound; lots of dynamics cannot explain it all - when it's supposed to be loud it's loud, when it's supposed to be soft it's soft. So in some songs the bass (and mid-bass) is just powerful as needed, while in others the amount is just right. At the same time the bass does not sound muffled at all but instead it's punchy, tight, and full of details; I can clearly hear the distortion of the guitar.
So that's the meaning of a "fast" op-amp. Responsive and detailed is a better and more accurate term to describe it.
I love this sound signature, since I'm of a "detail" and "purist", or "natural" person when it comes to frequency response. Don't give me something that's too dark all the time, I'll hate it. Although you can give me as big as soundstage as possible. This, is one part, I'll admit that I'm totally not pure. :)
This may also be the reason why the LM4562 is called "too-dark" in certain applications, for example the Zero DAC, which is said to be very warm in the first place. If the LM4562 decides to amplify that warmness, then whoops, you got a very dark sound.
However, in the case of Zhaolu, LM4562 is less warm than the OPA2604 and other Burr-Brown chips, and sounds more natural.
And still the best part about the LM4562 is the tonality, which was the only thing that was good before the burn-in. Except now it's even better. The chords are in full harmony, the usually obscured notes especially the high ones are now heard. And yet it doesn't sound any noiser but cleaner instead. It's hard to explain except for hearing it yourself.
Oh ya, and now I can hear the individual notes more clearly too. I guess some people actually hate that, especially when it makes the bass more "one-note", but as a musician I like that.
This is a very good upgrade for $13.80, which is less than 10% of the DAC's cost. I used to be a disbeliever of op-amps, now I stand by them, after knowing how big a difference they can make.
W A R N I N G !
W A R N I N G !
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