[PinkFloyd]

Anyone tried the LM4562 audio opamps as yet and, if so, what do you think of it? If you've got a spare dip8 version I wouldn't mind a try of it.

Chip details here: http://www.national.com/ds/LM/LM4562.pdf

 

[Clutz]

Funny you should ask... I've just been reading about it myself. I wish they made a single channel version, cause I'd like to try dropping it into my PPA, though I'd have to lower the gain to get the ultra low distortion and IMD - but I could easily live with that.

 

[Polaris111688]

It looks pretty impressive. A PSRR of 120dB, and low distortion.

Clutz, I was just thinking about my current PPA project with that opamp too.

 

[Filburt]

I will be testing this chip probably next week when they arrive. If you want, I can talk about the results although I don't have the equipment here to do scientific measurements; will have to do that during the winter break if I can. It looks like a good replacement for the NE5532; perhaps better than the AD8599 as the 8599/797 is difficult to work with in terms of actually obtaining the advertised performance.

 

[Iron_Dreamer]

Wow, the specs on this thing look sick. It'll be interesting to hear your findings, Filburt.

 

[Filburt]

Quote:

Originally Posted by Clutz Funny you should ask... I've just been reading about it myself. I wish they made a single channel version, cause I'd like to try dropping it into my PPA, though I'd have to lower the gain to get the ultra low distortion and IMD - but I could easily live with that.

You'd also need to balance bias currents and whatnot, if you haven't already done so. The "typical" Ib on it is 10nA, which is 2000 times the max rated Ib of the OPA627 (5pA), for example. We've been successful in using a 500nA chip (AD8058) in the PPAS project, so presumably 10nA is doable

Quote:

Originally Posted by Iron_Dreamer Wow, the specs on this thing look sick. It'll be interesting to hear your findings, Filburt.

Sure, no problem

. I wish this came in single package as well, since I could then test it in the buffer stage of my DAC, but oh well. It will be interesting how it does against some of the other high performance audio op-amps.

 

[JahJahBinks]

Please see:

http://www6.head-fi.org/forums/showthread.php?t=202491

It's interesting to see how people react differently in the thread I started compare to this one.

 

[Clutz]

I saw the previous thread, but I didn't comment cause I hadn't read much about the opamp yet. I have done some reading on it now, and I think it seems promising. Now, I'm not an EE, nor do I have much background in electronics, but I disagree with ATAT in his assessment that PSRR doesn't matter for audio applications. According to Tube CAD, "PSRR refers to the ratio of a circuit's change at its output relative to the disturbance at the power supply that caused it." Hence, a high PSRR improves how resistant a circuit is to power supply noise. I agree that it's current output capabilities are nothing to write home about, and it's slew rate isn't that fantastic - but the OPA627's slew rate is only 55uV/S - granted, that's over twice the slew rate of this new opamp, but I think that demonstrates that there are other factors that are important to having a good sounding opamp than just slew rate.

Anyway, there has been quite a discussion of this opamp over at diyaudio, and they seem to like it. A lot of people have said it's made big improvements in their system. That is interesting, but it doesn't necessarily say much - people can hear improvements if they want to. Still, it suggests that we shouldn't write this opamp so quickly. If they made a single channel version, I'd buy a pair and pop them into my ppa.

 

[JahJahBinks]

The best thing to do is to get one and listen. Because we have agreed in the past that you can't determine its sonic signature based on electrical specs.

 

[ATAT]

I saw the DIYaudio thead, and it looks interesting, I have a few here I'll try them at some point. PSRR for audio seems not as important as other characteristics since audio power rails are obsessively clean of ripples..

ATAT.

 

[splaz]

Couldn't you cut pins off and jumper them around etc. to just use one channel or is there some reason that wouldn't work ?

 

[Clutz]

Quote:

Originally Posted by ATAT I saw the DIYaudio thead, and it looks interesting, I have a few here I'll try them at some point. PSRR for audio seems not as important as other characteristics since audio power rails are obsessively clean of ripples.. ATAT.

I agree, there are other characteristics are more important - particularly as power supplies get better - that said, if given the choice, I'd rather have greater PSSR all else being equal. Anyway, the THD+N and IMD specs on that puppy are really impressive, and those are two things I would care about for audio. All in all, I agree with JahJahBinks - let's listen to it. Hell, it might be a good cmoy opamp to use with a high impedance headphone - at least for testing. I should think HD580s would be fine with them. 300 ohms instead of 600 - still, not bad though.

What do you think?

 

[PinkFloyd]

So, is anyone going to send me one of these buggers? I'll either pay or swap for something (chips etc.) NS don't want to send me samples

 

[ezkcdude]

Quote:

Originally Posted by Filburt Sure, no problem . I wish this came in single package as well, since I could then test it in the buffer stage of my DAC, but oh well. It will be interesting how it does against some of the other high performance audio op-amps.

I read that single and quad versions will be available in early 2007.

 

[ozshadow]

I honestly do not put much faith in spec sheets but choose to rely more on hearing the actual opamp. Take the 2107 opamp. Spec-wise, you would not think much of it, but everyone that listens to it enjoys it. AD8620/10's compete with OPA627's and are in the same ballpark spec-wise, but sound completely different. Maybe these specs matter more for alternative applications other than audio amplifiers, but for audio amps, just get it and listen then decide. It's like opening Christmas presents, no matter how big the box is or how nice it's wrapped, you never know what you are gonna get til you open it !