Vintage test equipment

April 10, 2021
 by Paul McGowan

14 comments on “Vintage test equipment”

  1. If those vintage precision analyzers are completely replaced today by computers which high precision power supplies are found in these computers if normal computers are said to have the noisiest power supplies ever? Any recommendations for a noise free computer power supply?

    1. Well, no. They are not replaced by computers. The Audio Precision is controlled and its data is analyzed by a computer, but the measurement unit itself (with the I/Os) is a very expensive analong piece of hardware.

  2. Cool so if the goal is to get the two sine waves to match ie eliminate the negative stuff and accentuate(amplify) the positive. Then messing with mister in between is the realm of the audio market place which sells various products that add distortion in type and volume that the purchaser enjoys listening to. A universal tune we all dance to.

    1. In real-life circuits, distortion is unavoidable in general. Any test equipment which gets rid of all distortion becomes very expensive to produce in order to achieve so. In audio equipment the manufacturer has to work at a certain price point compromise where zeroing distortion absolutely cannot really be accomplished. And then, there’s consonant distortion and dissonant distortion, the latter being strongly objectionable, while the former may be tolerated. Not all kinds of distortion are perceived the same way by the human brain, and distortion should not constitute the yardstick for choosing hi-fi gear, since it is quite elusive and audible correlations are really hard to establish.

  3. Thanks for the history lesson. Never would have ever known the process to decrease distortion . Cool machine. Your are a walking Encyclopedia on HiFi History. Thank You. Now back to the music!!

  4. I’m not sure it’s the most helpful thing to say that an amplifier adds harmonics. Any amplifier is, to some extent, non-linear, meaning that the output is not an exact but larger version of the input. We generally aim to design low distortion amplifiers, where the deviation between input and output waveforms is small. If we test the amplifier using a pure single frequency (in other words a sine wave) as the test input, then the result of the non-linearity is measured at the output as harmonics of the test signal. This is where the HP 333 comes in.

    The fundamental (sic) problem of the amplifier is that it is (to some extent) non-linear. The addition of harmonics to a sine wave is the way that we characterize that non-linearity.

  5. Is waveform creation and analysis in the Audio Precision analyzer digital? If so, presumably we have to accept that the DAC and ADC in the analyzer are beyond reproach. Otherwise, how would we measure performance of a DAC for the use of audiophiles?

    1. Yes they are. Their measured performance should be, and likely is, ten times better than the distortion that they are supposed to measure in order for the results to be accurate.

      These days the digital analysis allows you to separate out the various distortion components for easy analysis. As one example you can look to even order distortion, like second harmonic, and ignore it because it is more tolerable, some say even desirable, to the human ear.

  6. Maybe Paul’s experience is a bit like the excitement of playing records…the tactile process of getting the record out…cleaning…carefully positioning the tone arm…lowing the cue lever…as opposed to loading a cd and pressing a button.

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