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Oppo HA-1 Impressions Thread

Discussion in 'Headphone Amps (full-size)' started by aamefford, May 7, 2014.
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  1. x RELIC x Contributor

    I LOVE the XC / HA-1 pairing. You can read my impressions here.

    My post is a little enthusiastic, but I still feel the same.

    Edit: I'll add to my impressions that nothing I own sounds as good as my XC, but my XC sounds better on the HA-1 than anything I've tried them with. The HA-1 easily reveals the limits of my other headphones if they can't keep up to the unit.
  2. x RELIC x Contributor
    craftyhack looking forward to your insanely detailed impressions / review. :eek:

    Hopefully it won't take all year!! :D
  3. craftyhack
    Nope, most of the time will be acquiring the gear (and most of that time is getting the $ to get the gear :D).  probably another month or two.  Once I have it, I will be going heads down to do the first rounds focusing on the HA-1.  If it is well received, then I will work on going with the same concept with the other gear I have focusing on those pieces instead.
    The hardest ones will be how to figure out double blind with headphones, I can usually tell which ones i am wearing even with my eyes closed :/.  Perhaps I can get some novacaine/lidocaine to locally inject so I can't feel my head and have my wife put them on to do that part :wink:.
  4. x RELIC x Contributor

    ROFL!!! :D
  5. Maxx134
    You don't have to "not" know which headphone is on to tell which one is better (!)
  6. craftyhack
    I think you are just kidding, and I don't think so either(I would like to think of myself as impartial), but the mind is a funny thing, perception is reality... and after reading as many drug trials as I have, the mind is also VERY powerful, basically we barely understand it. During research, when participants have no idea when conditions are different for others than they think they are for themselves... their mind alone causes physical changes in their autonomic systems that aren't possible for that same person to control under typical circumstances.  I believe that the same is the case in any area, especially hi-fi where reviewing is so subjective to begin with.
    When I hold those BEAUTIFUL XC's, my mind is already making judgements on quality and expected performance.  I know they are hand made in the states which makes me like them more for no good reason... we are a global economy now... just IMO, I want to help my fellow humans in commerce no matter their race or locale.  But I still have pride in "Made in the USA", call it rooting for the home team I guess.  I have read 10's of thousands of lines of gushing reviews, and I have already listened and formed my own opinions.  Therefore, I couldn't be more biased, and because of that, subconsciously adjectives used my be changed subtly, where dark becomes rich and smooth, etc. and the over all tone of the review is changed dramatically.
    I will figure out some way to A/B at least a couple of pairs of cans... and then I will review them.  THEN, I will put those away without reading them.  After that I will try the same without being blind, all other conditions equal.  I will check out the differences, probably post to the science forum for other feedback, and see what happens :).  If it turns out you are right and my bias doesn't affect my reviews, then I will save a lot of $ and possible jail time on scoring that novacaine :D.
    Back to the thread though, without being blind, every pair of HP's I have plugged into the HA-1 have so far (in my list above) have been EXCELLENT.  I am assuming either that means that a) the HA-1 is truly transparent, or b) the HA-1 is not exactly transparent, but has been implemented in such a way so as to complement many types of HPs without being to colorful, where bad combo's may occur... at least for what I own so far.
  7. ogodei
    The manual is correct in both generally accepted practices:
    1) with an analog potentiometer (AKA smooth volume knob) you generally want playback volume to be at least in the midrange (9 to 2 O'clock on the dial) to avoid channel imbalances at the low end
    2) with gain, you generally want to use the least gain needed to avoid distortion or channel imbalances at the high end & any problems when using amps with high output impedance
    With the HA 1 at low gain and the SE HD800s, I found I had to crank the volume up very high. Setting the gain to high corrected that without introducing any noticeable distortions.  Thus, best of both worlds.  With the super efficient PM-1s on the balanced output, I set the gain back to low because they don't need the power, although I didn't find any real penalty for leaving it set to high.
    The dB volume readouts on amps usually are set by reference to some nominal, 'reference' set of speakers or cans.   Meaning, when you plugged that reference set of speakers in and tweaked  the amp volume to where it reads '0 dB', you would get 80dB or 100dB or some set volume as measured at some set distance to the speaker drivers.  Once that level is determined, the engineers can attenuate the amp circuit before the volume control to make that reference point get reached anywhere along the range of the control they want.
    In short, 1) a '0dB' reading has no real mechanical reference to any specific spot on the volume knob (unlike say a '10' on 1 to 10 scale), and 2) without some sophisticated maths, there is little way of predicting the actual measured level of sound output you will get with a given set of phones and the volume control set to '0dB'.   The engineers could theoretically set it very low in the range so you can need to keep cranking up the volume way past '0' to hear anything.   In practice it's usually set somewhere pretty high up on the dial and produces a volume that would destroy your hearing if you listened to it with a reasonable set of speakers or headphones.
  8. jonstatt
    In relation to an AV processor / amplifier, the 0dB has a genuine meaning as long as its a calibrated system. Most modern AV processors include a mic and an automated calibration routine. So as you correctly said, 0dB corresponds to a specific output level for a disc that has been encoded according to specific parameters (like a THX certified disc). 0dB therefore corresponds to reference listening levels.
    In the case of the headphone amplifier, this is craziness to have anything greater than 0dB because as you pointed out, every headphone model is different in how loud it will be at any specific volume level. In the case of the headphone amplifier, the volume control is nothing more than an attenuator, so you should only ever see a range from 0 (no attenuation), to various negative numbers indicating the level of signal attenuation!
    I think Oppo should change this!
  9. Maxx134
    One way may be to buy another can that "feels" the same on your head to the expensive one..
  10. ogodei
    I get it, tying the dB level back to the physical attenuator.  It would be very cool to go the other way though:  With each amp, include a foam head with a built in SPL meter that plugs into your amp.  Plug in your cans, put the cans on the foam head so the SPL meter picks up the sound, then the amp adjusts itself so 0dB is some reference level SPL as played back by your specific cans.   Now that would be cool (if people could ever get past arguing what the reference level should be, and how the head-related transfer function is really boosting some freqs. so the SPL meter is wrong, etc., etc.)
    But going back to a -80 to 0 scale would also work.  I want it to be software configurable though, so I can make mine go to +1.  [​IMG]
  11. craftyhack
    Nah mate, it's gotta go to 11!
  12. twicehelix
    Hello HasturtheYellow-
    Wondering if the stereo XLR outputs on the back of the HA-1 are also fed by a Class A amplifier like what is offered for the headphone output? 
    I've been thoroughly enjoying my HA-1.
  13. HasturTheYellow
    The XLR outputs are not amplified, so they are not a part of the Class A design. The integration is very similar to how we designed the BDP-95/105/105D's analog output stages.
  14. twicehelix
    Neat! Does this analog output use opamps, or discrete devices? (Or does my question make no sense?) I'm not an electrical engineer, nor am I familiar with the BDP units, except knowing that they are highly regarded. I can imagine some "buffering stage (s)" coming from the DAC chip and its associated devices, leading to the XLR analog outputs. I can also imagine that you folks have engineered a great power supply (I see a large toroidal transformer and many fat capacitors) that may also grace these XLR outputs? My apologies for being so inquisitive-- I guess being a scientist I'm trying to understand why the HA-1 sounds so fantastic.
    Benchmark and Mytek, I believe, use 4 Sabre DACs in their units; Oppo uses one. Interesting to understand the trade-offs given a digital section (1-4) DAC chips, interfaces and analog sections (discrete and complex) vs. opamps. I realize that a unit is really the sum of its parts convolved by its design which takes into account how parts interact. A SYSTEM. No one component defines....
  15. HasturTheYellow
    We use op-amps, but the manufacturer and model numbers are not available at the top of my head. For the BDP-95 and the BDP-105 we used Texas Instruments LM4562/LME49720 op-amps, so it is very likely that we are using similar chips in the HA-1.
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