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Review: NwAvGuy's O2 DIY Amplifier

Discussion in 'Sound Science' started by shike, Aug 25, 2011.
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  1. wje


    Quote:

    The following issues were encountered in under a 4-month period of time:
     
    • My Triad power supply died within the two-month mark.
    • My metal case would emit a spark when my metal iPod housing came in contact with it.  (There was not ground established from the input jack to the case screw.)
    • The amp started to get quite warm and distort.  It turns out one of the two power regulators had not been fully seated prior to soldering in place, so it sat up a bit over 1/4".  This meant that 1/4" of the metal tab, that works to absorb head from the chip was not capable of proper functionality.
    • The 4 resistors just behind the input jack were not trimmed close enough to the circuit board -- meaning that they had enough length and enough of a slight bend to come in contact with the internal rail of the case.
    • One of my 9V rechargeable batteries started to blister and malform a bit from its original shape - suggesting that possible the power regulators not operating correctly, could have been oversupplying a voltage to the batteries during the charging state.
     
    I understand that issues can happen.  Nothing we ban can be 100% perfect.  However, I do expect some level of reliability and being that the number of issues kept mounting, I needed to contact the seller so this could be resolved.
     

     
     
     
  2. Willakan

     
    Quote:


    Point 2 would not be caused by failing to ground the amplifier to the case. The only reason grounding is recommended is because otherwise you get hum when you use it with sources with a high output impedance AFAIK. The sparks likely came from some resistors touching the screw rail (as you mentioned happened also.)
     
    As regards point 3, was the regulator's metal tab actually touching the case?
     
    This wasn't one of the 2 big builders, was it? Seems like a pretty impressive list of errors...for the batteries to be damaged something would have to be seriously wrong IMHO: would have thought stuff like that would be caught in build testing.
     
     
  3. wje


    Quote:

    To answer the items in bold:
     
    1) The regulator tab wasn't touching the case.  It had just been snipped in half so that it was the same height as the correctly mounted reglator right next to it.
     
    2) It wasn't one of the big builders at all.  I believe it was just an individual who built a few here and there to earn a few extra bucks. 
     
    My purchase was made on this amp before JDS Labs had released their offering.  If that had been the case, I would have easily gone with JDS, spent about $15.00 more and not had these hassles.
     
     
     
  4. 2000impreza


    Quote:



    Sounds like first time builder mistakes. Can't go wrong with a JDS labs built O2. I recently ordered one from JDS labs as well along with a extra PCB and front plate. Could not decide to build one myself or go pre-assembled so I did both.
     
  5. wje


    Quote:

    My JDS Labs version is lovely.  Then, this past weekend when I learned the builder of my first O2 was providing a full refund, I went a bit nuts.  I found a builder (with an electrical engineer background) to build the amp (board and components) and I also ordered a bamboo front panel for an extra $3.00.  I'll put everything into the proper case from Allied, which is already in waiting as well as 2 power supplies that I ordered, to have a spare on hand.
     
     
     
     
  6. silversurfer616
    As I have an O2 from JDSLabs I am not really interested in all the technical details and specs everybody is going on about.Would like to read a bit more about how the amp sounds like.
    Considering that the designer said it doesn't need" burning in" I am slightly underwhelmed by this amp(but then again I only have it running for ca.30 hours and maybe a little burning in does help).Even my Little Dot MK III was better but maybe I am just a "tube"guy!
    Music has clarity,separation and a good soundstage but for me it is not engaging,not warm enough,not enough ambiance....too clinical!
    I must be a "tube"guy!
     
  7. mikeaj
    Quote:

    No, the sound doesn't change from any burn in.  Unless you no longer have the Little Dot MK III, there's nothing preventing you from going back to using that, so maybe that's for the best.  You can also try running the output of the Little Dot to the O2 and plugging the headphones into the O2:  if some of the "character" of the Little Dot's sound is from  the stages prior to the output rather than just peculiarities dealing with driving low impedance loads, this could be another option to try as well.  So-called double-amping is not really an actual issue, so don't let that stop you.
     
    edit: by "output" of the Little Dot, I was talking about the headphone output, not the RCA jacks out back, though that's also a possibility.  Are the RCA jack outputs just an input passthrough (in this case, going through the RCA would not do anything), or are they amplified with the pre-gain or otherwise run through part of the amp?
     
  8. Shike
    I saw in another thread the MKIII Is tube only (not hybrid) with a higher output impedance.  If this is true both amps will sound different as the MKIII will effect frequency response of the headphones.
     
  9. palmfish


    Quote:

    The Grados have very steady impedance across the frequency band. They might not be significantly affected by a high output impedance.
     
     
  10. Head Injury
    Quote:

    That depends on the output impedance. If it's 75 ohms, for example, there will be a 1.6 dB increase in the mid-bass, which would definitely be audible.
     
  11. palmfish
    Audible, but subtle. Many listeners might consider it an improvement.
     
  12. Shike


    Quote:


    Is he only using Grado's?
     
  13. Head Injury
    Quote:

    No one said he'd have to dislike it. It's still coloration. And 1.6 dB increase in such a critical part of the audible spectrum isn't going to be all that subtle. I wouldn't want anything over 1 dB to be safe.
     
  14. palmfish
    LOL!
     
    I just realized he never said what kind of headphones he's using. I was confusing him with someone in another thread.
     
    I hope he doesn't have Sennheiser HD5XX's. They have a huge impedance bump at 80-100 Hz.
     
  15. wje
    I love the O2 amp.  However, last evening, I had been using my HifiMAN EF-2A for about an hour and getting acclimated to the sound - with my Fostex T50RPs.  I then took the headphones up to bed, so I could go to sleep.  I noticed quite a difference in the sound signature.  Considering the O2 is an amp designed to not color the sound (as is the intent of most amps), I realized that some color can be good.  In that case, the HifiMAN had me quite impressed for a hybrid.  I need to run it this weekend with my HifiMAN headphones and see how it compares to the O2.  I still won't pull my O2 amps from use, though.  They do a great job, too.
     
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