Amp Measurement Standards

Discussion in 'Measurement Setups, Systems, and Standards' started by purr1n, Nov 1, 2015.

  1. purr1n

    purr1n Finding his inner redneck

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    Amp Measurement Standards

    Not totally standard, but I feel these sets of measurements provide more information that the ones provided by manufacturers via their published specs. I think a lot of you guys will be surprised at how most manufacturer provided specs of 0.0000x% are bullshit when push comes to shove in more real life applications.

    NECESSARY: Include picture of amp
    NECESSARY: Description of switches
    NECESSARY: Picture of inputs and outputs
    RECOMMENDED: 1kHz distortion spectrum ~33 ohm load TDB
    RECOMMENDED: 20Hz single tone ~33 ohm load TDB
    RECOMMENDED: 50Hz single tone ~33 ohm load TDB
    RECOMMENDED: 600Hz and 1700Hz two tone 1:1 ratio ~33 ohm load (same total power as above: tones should be about -3.0db)
    RECOMMENDED: 50Hz and 7000Hz 2:1 ratio ~33 ohm load (same total power as above: 50Hz should be about -1.0db)
    OPTIONAL: 10Hz square wave (need 'scope) ~33 ohm load TDB
    RECOMMENDED:Frequency response (wide band as much as possible) ~33 ohm load TDB
    OPTIONAL: Vrms to clip ~33 ohm load

    RECOMMENDED: 1kHz distortion spectrum ~ 330 ohm load 0.550 Vrms
    RECOMMENDED: 20Hz single tone ~ 330 ohm load 0.550 Vrms
    RECOMMENDED: 50Hz single tone ~ 330 ohm load 0.550 Vrms
    RECOMMENDED: 600Hz and 1700Hz two tone 1:1 ratio ~ 330 ohm load (same total power as above: tones should be about -3.0db)
    RECOMMENDED: 50Hz and 7000Hz 2:1 ratio ~ 330 ohm load (same total power as above: 50Hz should be about -1.0db)
    OPTIONAL: 10Hz square wave (need 'scope) ~ 330 ohm load 0.550 Vrms
    RECOMMENDED: Frequency response (audio band, wide band, ~ 330 ohm load 0.550 Vrms
    OPTIONAL: Vrms to clip ~33 ohm load

    • NECESSARY: Do at least 33 ohm or 330 ohm. May depend on the type of amp. For example, a tube amp should prioritize on the 330 load. OTL amps we might not bother with 33 ohm load. It's all context. The measurement should be fair and we should note limitations "Didn't bother with orthos as obviously this amp was meant for high Z headphones." For example, measuring DNA Stratus with HE6 would be a nonsensical. It's not necessary to do that.
    • NECESSARY: Group the above CORE measurements together. If you want to do another extra set of measurements, do so in ANOTHER POST. DO NOT DO STREAM OF CONSCIOUSNESS with 25 measurements. No one will understand what is going on. Exceptions may apply of course for amp comparisons.
    • NECESSARY: Document analomies in measurements. Note good performance. Please talk about them.
    • NECESSARY: DO NOT DO RMAA. RMAA IS CLOSE TO USELESS.
    0.550Vrms, as recommended by D. North, is an excellent voltage level for testing. Quite loud on Sennheiser HD650. Note that Ultrabike has used 0.600Vrms in the past.
     
    Last edited: Nov 14, 2015
  2. kapanak

    kapanak Canucklehead - Friend

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    If I may add, please state the instrument/equipment/tools used for the frequency measurements as well in an amp measurement.
     
  3. purr1n

    purr1n Finding his inner redneck

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    That may be variable. Ultrabike is using his Focusrite. I am getting Hands a QA400.
     
  4. firev1

    firev1 Friend

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    Maybe you could request the QA guys for a QA971 while you are at it so Hands has some nice loads to work with.
     
  5. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    I've also wondered how well the EMU 1616m might work. Stated specs and loopback measurements look really nice on it. And apparently it works OK with Windows 8 and 10.

    Either way, that or the QA400, what I could really use are resistive loads for DAC and amp measurements.
     
  6. purr1n

    purr1n Finding his inner redneck

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    See this. I made this from an old Grado headphone cable. You really don't need to solder if you can twist the wires and metal well together. Attach clamp probes where indicated by red arrows.
    IMG_20151114_164335368.jpg
     
    fiddler, firev1 and The Alchemist like this.

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