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The Opamp thread

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  1. qusp Contributor
    umm just calling their company esoteric says it all for me. its a ridiculously overpriced, underspecced part in an outdated package that just happens to use a copper leadframe (worth an extra 40 bucks dont you think?), which will be plugged into a brass dip socket.... its outgunned by opamps designed nearly 20 years ago, but it suits esoteric because they can say its an opamp designed for audio... whatever the hell that means. most 'audio spec' parts are rejects that couldnt make the cut for more demanding industrial/scientific applications.

    just for example, I know they supply a ready made cop-out for this by saying it gives quality that cannot be measured, but

    vs the $5 lme49990

    3 x higher noise (minimum, they dont specify at what frequency they measure 4.5nV/Hz, could be up to 5x higher) actually it is closer to 5x looking at the graphs
    3 x higher input bias current
    4x lower slewrate, you dont want stupid slewrate for audio, but 5v/uS is pretty low
    100x higher THD

    etc etc, now the lme is a great chip, but not known for its low input bias current, something like the opa827 totally pwns the muse in this regard. sorry but having copper leadframe doesnt make up for it, that and the fact they only come in duals... forget it, its marketing. as ive said before, if I want to build for musicality, i'll build a discrete opamp.

    there was nothing to defend about my comments above, for what they are the 5532 are a good chip, but the reason they are used so often is because its a known quantity, bulletproof, pretty stable and cheap.

    as for NOS... hmm you know my feelings on that matter

    Hey Nigel, no worries, i'm sure youve got better itches to scratch mate :D nothing wrong with it, its been used fairly successfully in dac IV stages because of having decent speed, but nothing really unique about it either. yeah the FiQ is a great amp, not getting much airtime with me though, been meaning to send mine back for an update for ages but never get around to it.

    Nigel, this is what i'm using for transportable these days. zilch0md will appreciate the chunky battery that takes up about half the case volume :p
  2. WiR3D
    I dunno about the LME49720, AFAIK even TI admitted its got issues, in the bass regions. Its definitely the consensus over in the STX thread. But it does have one of the best if not the best soundstages. 
    BTW the LME49860 is just a higher voltage spec variant if your interested. I also have 2xLME49710HA metal cap on pcb - not bad, but the AD797 and the THS4032 clobber it in everything with the STX anyway.
  3. SpudHarris Contributor
    Jeremy, that looks mental mate, absolutely mental! Looks like a beast. Available soon?? :D
  4. qusp Contributor
    yeah its a bit mental like its owner... no not available soon, something yes and probably not really that soon (depends on your definition) but not this exactly
  5. SpudHarris Contributor
    Well, remember your old pal over in blighty when you need someone with golden ears to test stuff!
  6. zilch0md
    That's beautiful!    Transportable and then some!
  7. kiteki
    Any examples of that?
    The http://semicon.njr.co.jp/eng/product/opamp/NJM4580.html has 0.0005% THD, the MUSES chips are higher right?  I see people repeat very often we can't hear under 0.01%, so what is your take on that?  I'm just curious.
    That does appear low, here is a discussion on the 2V/uS slew rate in the OPA111 just fyi - http://www.head-fi.org/t/52255/anyone-tried-the-opa-2111/15#post_608042
    I don't think it's marketing, that seems unlikely.  The retailer prices are too high but that's the same story for the OPA627 and balanced-armature driver units as well which cost 5 times more than they're supposed to.  I can get BA parts cheaper by breaking finished IEM's than I can from Mouser.
  8. kiteki
    Spud and Zilch, if I remember correctly you both currently have (or have had) the iBasso Warbler and the iBasso Pelican.
    Can you offer some honest thoughts on how they compare, and if balanced actually has any improvement apart from stereo seperation?  To me I'm wonder if that's worth the hassle?
    I noticed the Pelican has 2500mW output power, does that mean if I adjust the volume in my pocket by accident I could break an IEM?
    Thanks in advance if you feel like answering. =)
  9. zilch0md
    Hi keteki,
    I've never owned nor heard the Warbler, but I still have the iBasso PB2 Pelican.
    If you are using IEMs, there's really no need to get the PB2, in my opinion.  They have jumpers inside that allow you to select one of three gain settings, so you can select low gain for IEMs, but even then, I think it's more power than you need - even if the volume is not excessive.
    Nigel - do you have any experience with the Warbler?
  10. SpudHarris Contributor
    The Warbler is the P4 and is single ended. That said, it is an amazing amp especially for the price. It's one of my few keepers....
    Kiteki, you are spot on when you say about stereo separation being improved by the balanced Pelican (PB-2) but it's not just that. It just seems a little cleaner and tighter (if that's the correct terminology?). Especially with full sized phones like LCD-2..... Going completely balanced (DB-2 > PB-2) offers very little improvement over single ended input into the PB-2. I have A-B'd so many times and each time I convince myself that totally balanced is better but if I am totally honest it is likely placebo.
  11. kiteki
    Thanks, can you explain why you want to keep the P4 when you already have the PB2?  In non-balanced mode are there differences?  I noticed the P4 says something about 3ch/4ch?
  12. SpudHarris Contributor
    They just give something different even with the same opamps, In 4 channel mode the P4 is a very exiting amp to listen to, the PB-2 is probably a more realistic sounding amp and one I transport for vacations etc with a set of balanced cans (D7000 usually). The P4 is a nice form to strap to a classic for an involving on the go listen but not one I use for critical istening. With the right chipset you probably could tune it for any application I just choose to have the two amps for separate uses.
    Hope that helps.
  13. zilch0md
    A voice of reason speaks!   Thank you for helping to debunk the myth.  You're singing my song, here.
    I've blind tested this with the help of a friend, having volume-matched single-ended output from the iBasso DB2 DAC vs. balanced output, using the JL Audio SPL Meter iPhone app with a lapel mic sandwiched between the ear pads of my LCD-2 to deliver 85.0 dB with both of them.  Then, using balanced output to my LCD-2 while playing a white noise WAV file, I've beaten this to death, but can't hear any difference.   
    I've written this elsewhere, but I believe the greatest benefit to be had by using a balanced output DAC to drive a balanced amp is for noise reduction with long cable runs (between DAC and amp).  
  14. WiR3D
    what about using balanced the way Kingwa does? Which AFAIK is for better volume control among other things? (I can't find the article I read that explained why he went balanced)
  15. zilch0md
    Hi WiR3D,
    Interesting.  I'm not familiar with Kingwa's article, but if I'm interpreting your question correctly, the volume control would offer a greater range of control when using the balanced output of a dual DAC rather than using the singled-ended output (using only half of the dual DAC).  The iBasso DB2 balanced dual Wolfson DAC outputs 2.0 Vrms, for example, with balanced output relative to the single-ended output (1.0 Vrms) - because you're using the whole DAC instead of only half the DAC.  
    Using the amp's volume control to match SPLs at the headphones, you would indeed have less headroom when running single-ended from such a DAC, so single-ended is compromising if you have power-hungry headphones that truly need the headroom offered when using the whole DAC instead of half of the DAC (2.0 Vrms instead of 1.0 Vrms).  With more efficient headphones an amp might be able to offer sufficient headroom whether it's fed with 2.0 Vrms or 1.0 Vrms - in which case, the amp's volume control could be set lower with balanced out from the DAC vs. single-ended output, offering a greater range of control, all else being equal.
    BUT:  There are plenty of single-ended DACs out there that can output 2.0 Vrms.  You don't need to buy a balanced output DAC to get more than 1.0 Vrms into your amp.
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