O2 Op Amp Rolling

Discussion in 'Modifications and Tweaks' started by rtaylor76, May 18, 2016.

  1. purr1n

    purr1n Finding his inner redneck

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    Don't want to be mean, but you guys are killing me with the opamp rolling on a mediocre amp. A CMOY / CHA47 running on +/- 12V rails beats the crap out of the O2.
     
  2. rtaylor76

    rtaylor76 Can't wipe his tag

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    I'll have to check that out Marv. But you need a 12V battery for that. Got any that will fit in an Altoids tin?

    At least the 12v power rails in the O2 are pretty stable. And the O2 provides gain before the buffer and has a double buffer at that.

    And besides, no one is pretending it is anything but a mediocre amp. It does matter what op amps you use. Just trying to make the mediocre not as mediocre.

    You really hear the OPA2107. Completely changes personality in pretty much everything I've used it in. I am only guessing the OPA602 is even better (single channel version, it has to be).

    Of course I've been too busy mess with op amps as I've been building, and compiling linux for Raspberry Pi's lately.
     
  3. Cspirou

    Cspirou They call me Sparky

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    @rtaylor76 - 12v doesn't have to mean 12V battery, it can just as well be any bipolar power supply.

    The best example I can think of what Marvey is talking about would be the Apex Butte by Pete Millett. It has regulated +/-12V powering a single opamp.
     
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  4. purr1n

    purr1n Finding his inner redneck

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    I've heard and used every single opamp mentioned in this thread and many more. I've also breadboarded many variants of the CMOY CHA47 MINT PPA and even a design like the O2 with paralleled opamps buffer stage. None of this shit is new to me.

    The O2 has a few issues that immediately limits its potential:
    1. The limited gain (because of the pot after gain stage and limited voltage rails). Higher gain can sound better
    2. The capacitor between the gain and buffer stages.
    Yes, different opamps change the sound, and make O2 slighty better. But not better enough that elevates it from high school baseball league to AAA pros. Just different shades of mediocre.
     
    Last edited: Nov 25, 2017
  5. Poleepkwa

    Poleepkwa Friend

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    The Butte is much better sounding than the O2.
    Only place it loses out on is the rather high gain for sensitive headphones using the stock opamps.
     
  6. rtaylor76

    rtaylor76 Can't wipe his tag

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    O2 has +/- 12V power rails without having to be a three channel amp like the CMOY.

    And Marv, I know what you say. I hear you. No need to repeat. My whole purpose for starting this thread is op amp swapping in the O2 and performance differences...to alter the mindset that one is stuck with the stock sound based on "objective" measurements. I think I succeeded my goal.

    I've come to pretty much the same conclusion as you and frankly only use my O2 in testing stuff. I barely remember where it is half the time. No reason to be a snob about it. Some of us can't afford carp and have to deal with the carp we have or can improve on. An upgrades Civic can also be fun and quick, but it's no Porsche - so we all know this...well established. But some of us have to upgrade our Civic's unfortunately.

    I'm interested in building a Butte. One day. When I have more bandwidth when I am done changing kids diapers. Only a couple of years away.
     
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  7. Cspirou

    Cspirou They call me Sparky

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    Cmoy is not a three channel amp, you are thinking of the Mini3 by AMB. Cmoy is a single dual opamp.
     
  8. purr1n

    purr1n Finding his inner redneck

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    Not being a snob. My headphone setups circa 2009-2010 consisted of a AMB Gamma 2 / Sony X as sources, and breadboarded amps. Had two toddlers then so I too couldn't afford nice stuff. Just encouraging you to DIY because you going to get much better results than treating opamps in the O2 like wine vintages.
     
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  9. trl

    trl Acquaintance

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    Hi,

    Not sure I fully understand that, sorry. AFAIK O2 has 2.2uF caps on audio-input and Butte has non, which could be an advantage for Butte if there's no DC on the DAC/Line-Out feeding it; otherwise this could be a small disadvantage I'd say, as the DC-in could get on the headphones output plug.

    Besides the DIY projects and mid-fi devices there are not many others out there with DIP8 sockets to roll opamps, Marvey. :)

    However, I found ASUS Essence One and Burson Play as being very good devices to test opamps (all I/V, LPF and VA stages). I've also DIY the 2-opamps amplifier from LME49720/LME49600/BUF634 datasheets and I've also tested opamps with this one too. With the last one is good if you build 2 identical amplifiers and do a proper A/B test between both with different opamps.

    Best,
    Raul.
     
  10. rtaylor76

    rtaylor76 Can't wipe his tag

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    Some say the input DC blocking coupling caps on the input are redundant since most output devices are already blocking DC in some way by DC or AC coupling.

    And yes, on the Butte, there is no AC or DC coupling on input or output, so if DC is on the input, it will show on the output amplified. It may actually contribute to the good sound of this amp. That, and the fact the DC rails are well designed. Life without good voltage regulators must have been hard.

    The O2 after all is some cheapo amp that has many design flaws. @Marvey is right and the Butte is much better designed all around albeit a less powerful amp.

    And on your other comments, an op amp to do I/V will behave and sound much differently than as a buffer or as an input drive or in a filter circuit.

    In thinking about it the O2 is kind is a silly product now. Not to mention the negative aspects of nwavguy brings along, which is a good thing he's not around anymore (although I have my suspicions about Archmicio in being the same guy). Sorry, didn't want to preach to the choir.
     
  11. trl

    trl Acquaintance

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    Indeed, most DACs already have output caps to block DC.

    Cheap and extremely low noise, basically it's very low noise and neutrality combined with the DYI purchase kit attracted me most some years ago. :)
     
  12. Grattle

    Grattle Acquaintance

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    Like grilling steaks - half of the fun is in the making, and the drinking of the beer.

    Ok, well maybe not half...
     

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