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O2 AMP + ODAC - Page 351

post #5251 of 5263

Haha, here's no way I'm gonna remove the one next to the TRS socket unless I absolutely have to. I had to remove the spacers and shorten the pins, then stuff it under the cables.

Alternatively I could have gotten Browndog adapters, but I'm not gonna pay 12$ shipping for something that costs 6$ total and weighs close to nothing, lets not mention that it's the slowest possible shipping method.


I found these on ebay from a greek guy, which means fast shipping within the EU (arrived in about a week). I also ordered rounded pins, but I couldn't have shortened those like these ones as they have those thicker parts which are pretty much mandatory spacers. Something to keep in mind if your O2 is as crowded as mine. The OPAs came directly from TI. Packaging was total overkill XD


As for the sound, don't expect much improvement over the 4556s, but it's noticeable.

post #5252 of 5263

Been there done that!! lol...1688's great specs, use these in several amps with great success.....the OP Amp thread on this site and over at DIYaudio....several folks have done this and the TI design engineer frequents the discussion over there for this IC.


Compared to original O2 A/B several times....hard to really tell any difference...bass is solid.


post #5253 of 5263

Note the small boards I got from Mouser, they fit real well and no issues mounting in my O2 at all. Pins worked well,


post #5254 of 5263
Small boards? They are way bigger than mine.
post #5255 of 5263

Yes they are a bit larger, you can file them down a little, but unlike your O2 mine is bone stock except for this minor mod...I have several O2's for comparing etc....I did build a AGDR O2 Booster Board and it to me IMO makes the biggest difference in sound...


For a Desktop version of the O2 that "never" was AGDR has a "ODA" and I built one of these last year, another stellar amp with tons of current for driving most evey can out there..(note "most"). 


AGDR has started a website for those that want to ply around with his mods and designs....he also has a "super" Cmoy with 1688's one single and one with a dual circuit....really inexpensive and fun to build up..


Ok dont mean to hijack this thread!!


Back to the your normal O2 + DAC channel!



post #5256 of 5263

I honestly can't imagine the booster board making a bigger difference than whatever you have for U1. The OPA1688s are hardly noticeable. In some tracks I can't hear any difference, in others I feel slightly more control. The booster board should be no different, if anything I imagine it'd be worse as it defies 2 of the golden rules of designing amps. Yes, I know, you will defend it to the end. Have you even tried anything else other than the stock 2068D?

post #5257 of 5263

I wont defend it to the end...but it works and works well considering. I dont think it hurts anything.

It is an attempt to make thing "better" by using better spec'd parts, more current if needed etc...the engineering side of it vs the esoteric side of my uber blue 8 guage cables are so cool (lol)... 


Statement of Benefits....true or false from the author. 


The O2 Booster Board provides several benefits:

  • Nearly twice the current output capability on peaks, 250mA vs. 140mA per channel on a stock O2 Headphone Amplifier.
  • Why this matters
  • Nearly zero (50 microvolt) DC output offset voltage, vs. typically 3000uV (60x more) for the stock O2.
  • Zero turn-on or turn-off thumps due to an included headphone relay circuit
  • Doubles the slew rate to 6V/uS, and 20V/uS if the NJM2068 gain chip is replaced by 2x LME49990 adapter
  • Power rail clamp diodes.  This is an important O2 ommision - some versions of the 7912 voltage regulator have been
  • known to fail to start up into some load conditions (in general, not just the O2) without a rail clamp diode.
  • Lower input-resistance induced distortion.  Many op-amps have a little-known problem of distortion being caused
  • by higher levels of series resistance on their inputs.  The NJM4556A is believed to have this problem.  
  • The OPA827 and OPA140 FET-input op-amps used in the O2  Booster Board have been desgined by TI to
  • specifically reduce this problem.
  • Adds 2 LEDs that show when the power management mosfets in the O2 are on.  
  • Helps if any O2 troubleshooting is ever required, to see immediately if both power supply rails are OK.
  • Allows for true zero ohm output vs. 0.5 ohm for the stock O2 Headphone Amplifier.  Lower amplifier output
  • resistance means a better damping factor.
  • THD and noise figures of the chips, per the datasheets, slightly beat (better) the O2's stock NJM4556A


I have AB this mod with a stock O2 for many days, I am drawn to the Booster Board version, but I honestly

do not think I can really hear any differences other than the ole it sounds better to me!!




PS: The one item I do like is the ability to have a true zero ohm for those that want to try.....

Edited by adydula - Yesterday at 7:26 am
post #5258 of 5263

Why do you keep copy/pasting that? I think everyone who's interested in the O2 knows about it, and you probably posted it no further than 2 pages back. Anyways, the OPAs should do roughly the same thing sound wise as the booster board for literally peanuts (otherwise I wouldn't have bothered with it), on top of that it won't increase thermal noise, nor the amount of components. I think I already said it, but I'll say it again: the booster board is too damn expensive for what it does. It's a definite no for me.


You still didn't answer my question: did you even try to replace U1? It's the one that can make a hell of a difference.

post #5259 of 5263

Gee Duke I didint know I was under interrrogation! Sorry about pasting the above "stuff" once again...some folks dont back browse. If the booster board is too expensive for you great...for many of us we like to play and the cost of this mod is not that expensive....but hey its YOUR money,.


There are alot of theoritical benefits of the booster board, whether you agree or disagee or hear anything at all...


oh and YES I have changed U1


Ok back to my cave....have a nice Merry Christmas!!



post #5260 of 5263

Oh, no you don't! No going back to your cave for you, Mister! :D It's not expensive for me, it's expensive for what you get: audibly close to nothing. I've spent a lot of money on various upgrades, for example the Burson and Sparkos opamps, but they are worth it, especially the Sparkos. I've spent 98€ on a power supply + 38$ (which is really cheap) on a custom made silver plated and teflon coated Y cable for my ODAC... money well spent. Spending money on something that may or may not improve (or worse may decrease) SQ is not really my thing.


Back to the interrogation: what opamps did you try?

post #5261 of 5263

Muse...only 78x more expensive that the original 2068.....worth it?? You decide.


Heck u can build a booster board for the cost people spend on Burson and other ooompa loomp goodies....parts listed on agdrs cost spreadsheet is $57....not that expensive. But if it doesnt do anything for you then i understand where your coming from....


another post just for the kiddies:



Replace the U1 gain chip witth the ($47!) MUSES02 chip. The NJM2068 gain chip that NwAvGuy used in the O2 headphone amp is really pretty good, as he showed by tests in his blog. Good enough that relatively few chips would yield any substantial improvements in measured numbers.   One chip to consider is also made by that same company, New Japan Radio, the MUSES02 available at Mouser as part #513-MUSES02 for a whopping $47 vs. just $0.60 for the original chip. There really is nothing in the MUSES01 datasheet numbers that jumps out at being a big significant improvement over the NJM2068, certainly not worth 78x the cost. The slew rate is 5V/uS but again with the NJM4556A output chips in place you still won't exceed 3V/uS. The MUSES02 is written up by NJR as their "flagship" audio chip with "excellent sound". I've read one posted review of the chip (an amp other than the O2) where the person was claiming a noticable sonic improvement. So there you go - for the "how it sounds vs. measurements" audiophiles out there, here is a chip to try and see what you personally think. :)


all the best, this was written from deep inside my cave...."echo, echo...."



post #5262 of 5263

Last time you said 40$ for the booster board if you solder it yourself in reply to my ~100$ (not including shipping to Europe and customs). As for the opamp I trust my gut feeling and it tells me to stay away from the MUSES0X. The Burson and Sparkos opamps on the other hand use topologies that have proven themselves. There are a lot of really great solid state amps on diyaudio with the same or similar designs. I'm gonna stick to the Sparkos, it has cleaner bass and sounds so damn realistic and natural. The Burson is a bit more musical, almost as if it was a tiny bit V shaped, but there's listening fatigue on the long run, in the O2 at least.

post #5263 of 5263

Inflation....and  I got a GREAT deal on parts!!


Its too bad your in a different part of the world,,,I would like to sit you down and do a blind test with you to see how

well those op amp derivatives really work...many a man has been humbled.



Edited by adydula - Yesterday at 12:41 pm
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