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

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  1. SpaceTimeMorph


     
    Quote:

    However, 2 Vrms is not the standard for portable line input voltages.  Most portable players are ~1 Vrms, some significantly lower at around .5 Vrms.  2 Vrms is more likely for home usage.  Speaking of home usage, the power supply while running off of AC line voltage is rated for 24 Vpp.  Even accounting for .5V drop across the Schottky's you are dealing with 23.5 Vpp, which is 8.3 Vrms.  With a gain of 2x through the opamp that leaves you with a 4.15 Vrms input.  These leaves you with about 4% headroom here, which is cutting it awefully close.  However, the specified 4 Vrms max input was a design rating for input voltage, not a typical value.  With a 2 Vrms input and 3.1x gain you are dealing with 6.2 Vrms, which leaves you with a 33.9% headroom here; more than enough.  So, in short, you cannot compare the max output level of this for portable usage with a home source.  This is actually all explained within his articles.  Correct me if I'm wrong, but are there normal sources out there that would put out 4 Vrms or higher?
     
    Here is a link to the datasheet for the NJM2068.  I'm not sure what the performance of the 2608 is, but since it isn't used in his design...
    http://www.datasheetarchive.com/NJM2068%2A-datasheet.html#datasheets

     
     
     
  2. The Monkey Contributor
    Is this a portable or a desktop amp?
     
  3. khaos974
    Portable, but still able to output 0.5W on battery (33 ohm load, 1 kHz, inferior to 0.01% THD+N), on AC it has maybe 15% more power, it should be able to drive the HE-6 at 110 dB.

    Still waiting for independent confirmation of the measures.
     
  4. Steve Eddy


    Quote:

    This needs to be modified to include no links to threads on other forums not directly maintained by him but where he may address critiques of the design (a link I posted previously to such a thread was subsequently deleted).
     
    Allowing a thread for the discussion and critiquing of a particular individual's design without that individual being able to respond to any of it is eminently unfair in my opinion and to that end I think this thread should be removed.
     
    se
     
     
    maverickronin, Nom de Plume and sidel like this.
  5. odigg


    Quote:

    While I do agree that it's unfair that NvAwGuy cannot post in this thread, I don't think deleting this thread is the answer as Head-Fi is a popular site.  Many people who have the engineering know-how to comprehensively review and critique the O2 are on Head-Fi, not on the other mainstream forums.  Average Joe types (like me) are not on audio engineering forums and don't care to be since we can't much all that much sense of what is said.  Head-Fi is probably one of the few sites (that I know of) where the average Joe can make some sense of stuff said in the DIY section.
     
    Maybe NvAwGuy should be allowed back onto Head-Fi with the restriction that he can only post in this thread?  That makes the most sense to me as I'd like to hear what he has to say about critiques of his amp design.
     
    Anyway, I know I'm not supposed to discuss bans and what not so I'll leave it at that.
     
     
  6. Steve Eddy


    Quote:
     
    So you agree that it's unfair, but that's ok because HeadFi is... popular? Really?
     
    Quote:
     
    And it's also ok because some people here aren't on other forums? Really?
     
    Quote:
     
    How 'bout just sticking to the rules as posted?
     
    "No links to NwAvGuy's website, or resources maintained directly by him."
     
    The link I posted was not to his website or to any resources maintained directly by him.
     
    Edit: I posted the link in response to another post which was also deleted suggesting that the thread be moved to someplace where NwAvGuy could respond.
     
    se
     
  7. khaos974

    Actually, it's no links direct or indirect to nwvaguy, so let's stick to the design.
     
  8. fishski13
    Steve,
    while i have plans to build this amp for someone, i have to agree.  he's been banned here and elsewhere.  he has his own blog and diyaudio.com where anyone is free to join in on the discussion. 
     
  9. kevin gilmore
    Lets assume that the amp is running on AC power, the voltage drop across the diodes and fets is zero and the
    input amplifier is rail to rail. At least according to the schematic, the voltage gains are 3.1 and 7.17
    So  1.2 VRMS is the maximum input voltage at a gain of 7.17 where the input amp is already clipping.
    And 2.76 VRMS is the maximum input voltage at a gain of 3.1 where the input amp is already clipping.
     
    Run it off of fully charged batteries and you get
    .83 VRMS at a gain of 7.17  and
    1.93 VRMS t a gain of 3.1
     
    practically after the diode and pass fet and the fact that the opamp is not rail to rail take
    about 20% off of those numbers.
     
    Over the years many manufacturers put the pot in the middle after the gain stage.
    Lots easier on tube gear where the power supply rails are in the hundreds of volts.
    The benefit is slightly lower noise. While its unlikely that this amp is going to be
    used with a cd player with a tube output stage, those typically put out well in excess
    of 5 VRMS.
     
    The pass fets and comparators are not a power supply, they are a under voltage
    kickout circuit. The pass fets are either very hard ON, or very hard OFF.
     
     
     
  10. Steve Eddy


    Quote:

    That's not what the posted rule states.
     
    Quote:
     
    You say "the design" almost as if it somehow materialized out of thin air. But it didn't. It was designed by someone. So I don't see how the design can be discussed without it having implications for the person who designed it.
     
    se
     
     
  11. Steve Eddy


    Quote:

    Yes, but the point is, he's not free to join in on the discussion here. And as I said above, you can't really separate the design from its designer.
     
    se
     
     
  12. Anaxilus


    Quote:

    You must be kidding, it's done here all the time.  This is not unique.  If I had a dollar for everytime Spritzer went to town on Rudistor I'd have a 009 by now.  [​IMG]
     
    I'm also not sure I'd agree the designer isn't or can't be represented here.  I see quite the contrary tbh.  To ask the thread to be removed on your grounds is over the top and unprecedented IMHO. 
     
     
  13. fishski13

     
    Quote:

    i agree, but he made his bed with his petulant behavior and refusing to desist.  he has a blog where he is free to act in any way he feels like and discuss whatever he wants.  i am surprised HF allowed this thread in the first place.
     
     
  14. Shike


    Quote:

     
    Two sides to every story.
     
     
    Either way, you can say he's rude but it doesn't change the fact that his measurements and design are good for the community.
     
  15. fishski13

     
    Quote:
     
    good for the SS community, fine, but i would disagree wholeheartedly for the DIY community.      
     
     
     
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