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So, the Objective2 headphone amp - designed entirely around the measurements? (PLEASE READ RULES BEFORE POSTING)

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  1. khaos974
    Sennheiser demo'ed their HD 800 with a Lehmann BCL which output impedance is 5 ohm though, and I seem to remember that a head-fier emailed them (or was it Beyer?) and Seenheiser recommended a near 0 output impedance.
     
  2. mikeaj
    Quote:


    I'm pretty sure there are comments about most (but not all) of the points you bring up, in the docs...if one were to actually read them all.  Indeed there's a comment about the output resistor option, and coupling caps, and so on.  I'm not going to do all the work for you, but I remembered a few details.
     
    About the channel balance, that's easy to look up so I just did.  Yeah, that's pretty dependent on the pot you get.  But for reference the quoted value of 0.8 dB matching error is for -45 dB on the volume control, at least for the sample benched.  It's better than 0.8 dB above that level and still under 1.0 dB error at -55 dB, so these are pretty realistic levels.
     
    I'm not sure where you're getting the crosstalk figure, but the first article lists -65 dB crosstalk into 15 ohms, -72 dB into 33 ohms, -91 dB into 150 ohms, and -95 dB into 600 ohms (but a few dB worse at half volume, above 1kHz).
     
  3. b0ck3n
    In response to Currawong, RMAA was only suggested to nikongod as he argued that dScope measurements were somehow irrelevant, seeing as only a select few (and, he implied, likely biased) people could verify them.

    I don't quite see the point in arguing something that's 60 dB below the music, especially a non-issue such as crosstalk. Again, assuming that the measurements provided are in fact correct, the design has no audible weakness. As far as subjective listening reviews go, they're completely irrelevant as they'll only adress the sound of the headphones used, or possibly the source.

    I don't mind constructive criticism - input on how to implement features, reducing costs or size etc, without compromising transparancy would be appreciated, undoubtebly by the designer as well. The goal is to put as good a product as possible, at a price as reasonable as possible, in as many hands as possible, and we're offered a chance to chime in and make suggestions for the amp to suit our specific needs. Afaik, it's unprecedented. So, whether the designer rubs you the wrong way or not, let's all give the design a fair shake and let it speak for itself.
     
    c61746961 and sidel like this.
  4. Armaegis
    Anyone taking bets on how long it'll be before a Chinese manufacturer swipes the design and starts selling?
     
  5. khaos974
  6. Maxvla Contributor
    How much output power is this design capable of?
     
  7. c61746961
    Plenty.
     
  8. Willakan
    Nikongod, I actually contacted NwAvGuy regarding channel imbalance (he has since then updated his article to make it clearer)
    Firstly, the channel imbalance in the specs is 0.6, not 0.8db and is very much worse case. 
    Regarding DC coupling caps, that's just standard audiophile BS (OMG CAPS IN THE SIGNAL PATH! THEYLL DEGRADE MY BASSES). He addresses this at length in his articles.
    As for crosstalk, the 65db figure is into into 15 ohms; that's a pretty punishing load. Into 150 ohms it's 91db. Both figures are very respectable into their respective loads.
     
    And @Currawong, after your annoyance at fledgling Sound Science-related conspiracies, it's a bit rich to try to start a conspiracy theory of your own about NwAvGuy ("Do you know who he is? You know what? Nobody does. Not only that, he has gone to extensive effort to hide his identity. Maybe you should wonder why.")
     
    On a slightly more civil note, regarding your requests for square wave measurements, NwAvGuy has done several and they're in the original amp article, near the bottom. Square wave performance, performance into capacitive loads, slew rate and square wave rise time are all discussed. 
     
  9. qusp Contributor


    Quote:

    my head hurts [​IMG]
     
     
  10. Shike


    Quote:

    But that would require hardware that many casual builders don't own!
     
    See: Nikongod's post for context of what I was saying.
     
     
    As for his identity: maybe he works at a larger audio company that would create issues if people knew?  There's plenty of reasons not to give your identity out online, and he certainly isn't obligated to especially when the design should speak for itself.  I can think of people who's identity we know of that are much less trustworthy.
     
  11. nikongod
     
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    I stop reading books after the 450'th page, and articles on DIY amps after the 12'th. 
     
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    Actually a proponent of the amplifier implied that RMAA measurements were somehow irrelevant by excluding them. 
     
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  12. nikongod
     
    Quote:

    I'm not really concerned with the bass - the caps look to be appropriately sized for good bass response. I'm really concerned with the fact that they are there and what their sonic signature will do to the amp. Ewww. 
     
    With very few exceptions, every amp I have removed coupling caps from has sounded better to my ear. The one exception was adding a coupling cap to facilitate grid biasing a tube instead of cathode bias, but thats quite an apples to oranges comparison - it simply shows that cathode biasing a tube is worse than a coupling cap in that case. 
     
  13. svyr

    where'd be those measurements :D ? especially at different loads :) ? (and power output levels :D )... Though I guess the first one is not necessarily necessary, since you could go off the output impedance
     
  14. khaos974

    There are a total of 3 articles on the amp in question, the first detailing the design criteria and whether the final design satisfied them with extensive measurements of the finished product, the second explaining the design choices and the final one about details in the circuit design and construction, with links to the BOM, the PCB schematics...
     
  15. Satellite_6


    Quote:
     

    THD 1 Khz 150 Ohms 0.0017% Excellent      
    THD 1 Khz 15 Ohms 0.0046% Excellent

     
     
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