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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
    Some of you may have read this in the LCD-XC thread but it involves the HA-1 as well so I'll re-post it here.


    After my wife took our beagle out for a walk he decided he hadn't had enough excercise so he began to tear around the house at full speed at the same time I took a restroom break from listening to my XC. I heard this horrendous yelping and I thought he had broken his leg or something while being a complete mental case running around. To my horror I rushed out of the bathroom to see my XC cord wrapped around his leg and both dog and headphones were lying on the slate tile floor!!! :eek:

    My HA-1 amp was pulled about 45° from its normal position as the balanced jack didn't pop out and it yanked the unit very hard over.

    I had placed the XC on the seat cushion when I got up and he jumped up on the sofa at full speed where a cord loop had somehow caught his leg, forming an instant noose, and they both went tumbling to the ground. He was more scared than anything and he's just fine.

    My HA-1 is fine and my headphones as well!! I was terrified that the balanced receptacle would be ripped out of the HA-1 or it would play static given that the jack was pulled so hard. This unit is BUILT and everything seems to be working great! :D. I'm quite impressed with the durability of the HA-1, and thankful that it wasn't more serious (for dog, amp and headphone!). Lesson learned!

    This is the culprit





    I love my Head Fi gear, but I love the little jerk even more!

    Apologies for the dog pics in an amplifier thread.
  2. Smarty-pants
    ^Holy moly, good to hear nothing was damaged. I think I would have an actual heart attack if that happened to me.
    Of course you can't blame the pup too much. I used to have one too and he would do the same thing when he wanted to blow off some energy.
    99% of the time he was cool as a cucumber but then he'd start running around like he got a shot of adrenaline and crack or something, lol.
    I do have kids now too and I just make sure my good equipment stays in my theater room or office and they know not to touch what's in there.
    Just gotta be careful and mindful of where you place your stuff, hopefully out of harms way.
  3. tesox
    Unfortunately I have to say that I found a very annoying bug/fault on my HA-1.

    I operate the Ha-1 only with the remote control!
    The reaction time for Volume changing commands is always delayed and not
    as responsive as it is on other full-size amps (inexpensive ones!) I own.
    This is a little upsetting but something I can deal with.
    But there is a strange behaviour of the volume knob in interaction with the volume display if you use the remote.

    Let me explain:

    You can adjust the Volume in 0,5db steps with the remote control, delayed but it works.
    If you tip the button (up or down) equally the knob rotates step by step equally and the
    display shows the corresponding db-level.
    This does not work on my unit when I reach the area between -12,0db to -13,5db.
    The Volume Knob starts to act weird. Most of the time the knob rotates a big step
    from postion 11 o'clock to 1 o'clock. It is nearly impossible to cross that area with
    the same equal steps it does all the other way.
    On top of that the Volume display acts weird as well.
    It shows always another db-level in this area.
    One time -12,5db is at 11 o'clock next time on 12 or 1 o'clock.
    If I move back and forth in that area the displayed volume sometimes don't changes.
    Or if I move up it goes from -12,5 to 13 and than back to 12,5db again.
    Like I said it acts weird.
    I hope you understand what I tried to explain,
    maybe I make a youtube video of that later.

    The most annoying thing is that the knob moves not equally
    and rotates most of the time (95%) this big step I described.
    So it is not possible to easily fine-tune the volume by remote in this area
    and this is my main listening-level area.

    I really don't want to sent my HA-1 back, but I paid 1.500 Euro here in Germany
    for that amp (what is 2.000 US Dollar!) and I think for that I could expect a working remote control.

    Don't get me wrong, I love this amp but I'm disappointet and hope for an answer/reaction
    from Oppo like that this issue could be fixed by a firmware update.
  4. jonstatt
    I think your unit is faulty unfortunately. You have uncovered a design issue which I will talk about in a moment. But in terms of the jumping behaviour you are seeing, mine does not do this. Everytime I press up and down on the remote, I get exactly 0.5 step. It is slower to change this 0.5 step at around -13 because the volume knob seems to move more between each step around there. But I have consistent behaviour of 0.5 steps...no jumps whether I use the remote or the knob itself...no problems.
    Now to the design issue! There is something really weird about the spacing of the volume steps around 12 o'clock! The area that -13dB covers for example is much bigger than any other dB level. So if you turn the knob slowly from about -18dB you will see it steadily goes 17.5, 17, 16.5, 16 etc then for some reason around 13dB it suddenly spaces out a lot more....and then as you get past about 1 o'clock the spacing gets closer again. VERY weird! It makes no sense because the volume control is an analogue device not a digital one so I suspect this means the dB levels are also not right at all.....
    You asked why it is so slow? Probably because its a real precision analogue volume control and NOT a digital one like all the cheaper units would likely be or an AV amplifier.
  5. efeist
    I would agree that tesox may have a defective unit and should return it to OPPO.  
    With regards to the "design issue" jonstatt, its probably more of a design compromise related to the construction of the potentiometer.  The potentiometer taper can be linear or logarithmic depending on the application.  For audio amplifiers, it is usually logarithmic (audio taper) which is very difficult to construct so an approximation of a logarithmic taper is the result.  If the oppo didn't provide a digital volume display, your ears probably couldn't "hear" the variability in taper that you describe.  My guess is that the dB level indicated is correct because it is a measured reading of voltage and not the position of the potentiometer.
    I hope this information is useful.  
    Maxx134 and Smarty-pants like this.
  6. jonstatt
    Thanks for the reply. I understand what you mean about the taper on the potentiometer. I would understand therefore if the gaps got bigger and bigger as you turned the volume more. But what happens is that its stretched out in the middle (around the 12 o'clock point), and compressed at both ends (although it moves fastest at the low end). I don't think you would expect the middle to be the widest spaced (in dB terms) whether the pot was logarithmic or linear....
  7. efeist
    Finer resolution near the mid point of the potentiometer is a desirable design goal.  In addition, the construction of logarithmic pots usually requires overlapping 2 resistive elements with the overlap at the mid point.
    I checked my OPPO and it is consistent with you comments.
  8. craftyhack
    Mine behaves in the same way.  I would assume that an analog volume control could be designed to have a different precision depending on the position of the knob, where the contact planes for each level of resistance could be made variable.  A design like that (this?) would make sense(be welcomed IMO) in the expected sweet spot to make it easier to adjust within that area of db level, given one doesn't have to twist in mm increments to find their preferred listening level :).  I can't tell looking at the internals of the HA-1 online (and I don't really want to take mine apart :D), but the volume control housing is pretty big, so *something* is going on in there.  Or... the reported db steppings could be wrong, and/or have nothing to do with volume knowb position, read on :D.  Considering the time and effort that went into the design and given the beta program where I am assuming at least one participant had OCD traits (I see that a lot with engineers... like me :D), it is hard to imagine something like this getting through to production broken, but something weird is definitely going on, so I did some rough measuring to determine behavior, mainly to observe consistency (or lack there-of, I see both happening...).
    Regarding the remote control behavior, I see similar and reproducible behavior regarding inconsistencies of knob position relative to level, and it is different on whether I am increasing level or decreasing level, and positions aren't even consistent across runs.  First, I think you hit the nail on the head regarding delay, the changes seem more delayed in the areas where you have to move the knob more to change level, probably because the unit waits until the knob is in the new position before indicating the new level, that is how mine behaves anyway.  Regarding inconsistent positions... here are my rough measurements.
    Gain is on Normal (if that matters, I didn't have time to check High to see).  Starting at -18db, measured in degrees where 12 o'clock=360/0 degrees, printed from here(http://www.blocklayer.com/protractor-printeng.aspx) given the awesome scaling function to print one the same inner diameter as the knob, and using a piece of lead from mechanical pencil as the "needle" aligned with the volume value indicator on the knob... as I assume mech pencil lead is pretty straight (enough), although it doesn't matter.  Note that parallax error is terrible, so I recorded measurements from same perspective without moving with each volume step.  While the absolute values may be off, they are consistently off, so the data should still be good enough:
    Increasing volume:
    -12db=15 ("the jump")
    Decreasing Volume from -10db above:
    -10.5db=42 (huge difference from -10.5db above)
    -13db=345 ("the jump", but different db step...)
    Before I moved, I adjusted from -10->-18 and back a few times, they always landed on 43 and 305 respectively.  So... consistent there.
    I do plan on doing this again, I am intrigued!!  Basically I cannot see any algorithms going on here, at least none that I remember from EE and NukeE schooling... but this is a piece of electronics so there HAS to be some underlying logic here!
    Anyway, I have to assume that knob position is just not an absolute indicator of level in any way, otherwise something is indeed broken... I have ways to make this data *much* more precise, and I want to do this several times in a row, after a complete power off, again with High gain, different loads (low vs. high impedance headphones, bal vs. SE), etc. and then graph it all and look for patterns... but that would take more time than what I have before getting to work.  Honestly, for me it doesn't matter as I have no problems finding good listening levels (at least so far), and it sounds great regardless, but this is fun in an OCD way :D.
    P.S. I realized that I was being stupid, there was no load for these measurements, I could have been listening to some tunes while doing this dang it!!
    P.P.S. These measurements should be taken with a grain of salt given the parallax problem.  I only had one eye open to do this to reduce the issue, but moving my head in any dimension by perhaps a mm or two (up, do, either side, back and forth) caused the perceived measurement to change by a degree or two.  If I can get that needle ON the paper, then this will be MUCH more precise.  Even with a precision of +- 2 degrees though, the jump inconsistencies from one step to the next are just plain weird and they certainly are not linear/graduated, considering 1+-2 degrees in the sweet spot area surrounded by 5-10+-2 degrees, and then that weird 26 +-2 degree jump in the -12.5 db area.
  9. craftyhack
    Totally agree with your first point.  Your second point is something I need to go read about, sounds interesting and relevant here perhaps, thanks for the info!!  I remember that volume measurement in db is logarithmic, and I haven't mess with logarithms since college (15+ years ago) so brushing up on logs and volume measurement will hopefully help me understand WTH it is I am see here :D.
  10. efeist
    And I thought I had OCD bad.  :)  (Also and engineer, EE)
  11. craftyhack
    LOL, you should meet some of the guys I work with!!  BTW, here is a pic of my setup.
    jonstatt likes this.
  12. efeist
    Love it!
  13. jonstatt
    In terms of consistency, I have noticed something now.
    If you go upwards in volume, step by step using the remote....the volume makes a big clockwise shift from -13.0 to -12.5...but when you go back downwards, -12.5 to -13 is a small shift, and then -13 to -13.5 is a big shift!
  14. craftyhack
    Different for me, when increasing, jump is -12.5->-12db, when decreasing it is -12.5->-13db.
  15. HiFiAudio

    That is the mid point or flat point of the precision wire-wound potentiometer range.   Firmware won't do anything.   You not dealing with a linear digital application, this is true analog implementation, and when used with the remote you will always notice a bit of jumping of volume level as displayed when turning the motorized potentiometer in the flat point.
    Does this help?
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