Phono Preamp Measurements from ASR

Discussion in 'Audio Hardware' started by patient_ot, Apr 10, 2019.

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  1. patient_ot

    patient_ot Senior Member Thread Starter

    Location:
    USA
    Thought this might be of some interest here. The site is mainly DAD/HP amp oriented but has started measuring phono stages.

    Review and Measurements of Lounge LCR MKIII Phono Amp

    Review and Measurements of eXemplar Exception Phono Amp

    Review and Measurements of Cambridge Audio Duo Phono Preamp

    Review and Measurements of u-turn Pluto and ART DJPRE II Phono Preamps

    Please no "measurements don't matter" posts in this thread. Also, if you have specific critique of something technical, take it up with ASR, not me.
     
    clercqie, JohnO and gumsrave like this.
  2. vinylontubes

    vinylontubes Forum Resident

    Location:
    Katy, TX
    Why was he using an 8.8 mV signal on the Lounge? States he wants 1 V output. But both outputs are out of spec for most phono applications. What cartridge outside of a ceramic outputs anything near 8.8mV?
     
  3. patient_ot

    patient_ot Senior Member Thread Starter

    Location:
    USA
    You should really take it up there. FWIW two fairly popular cartridges, the Ortofon 2M Bronze and 2M Black measured at 7.9mV and 8.6mV respectively.

    Ortofon 2M Bronze 2M Black
     
  4. mikeburns

    mikeburns Forum Resident

    Wow they tested a class d audio amplifier there. Seems like it has a fair bit of distortion too. My one sounds so good (SDS470C). Maybe I like distortion? I suppose I need to ask myself what level of distortion is actually audible? It certainly sounds a lot better than my old Rotel thats for sure.
     
  5. harby

    harby Forum Resident

    Location:
    Portland, OR, USA
    Generally about 1% is where we can definitely hear harmonic distortion. It is cumulative, though - an amp rated 0.9%, along with a turntable that can never get below 0.5%, and tube phono pre, then your speakers, all starts to add up.

    With a Class D amp, however, much of the distortion is an inaudible function of the PWM modulation, even the part that can't be filtered electronically is filtered by the ear. Analysis needs to include a passband limiter to get a number related to our perception.

    What it looks like when you have a 24 bit 2Mhz ADC to analyze it:



    The reference level is not like digital's 0dB, where nothing can be higher. It is just a reference, like -10dBu signals being 0VU on the meter. Like with an analog tape recorder, where you can go higher in recording until the tape saturates and high frequencies are lost, the levels on vinyl are purely up to the mastering engineer, and if not limited by the groove spacing or inner groove distortion, such as on a 12" single, the levels can be increased significantly to overcome surface noise, electrical noise, and reject feedback.

    The review came to the same conclusion I did about the ART DJPreII, that, while flat, it has lower headroom than others, and high level input signals can't drive my pro ADC to 0dB before it starts to distort. He does seem to be using 1/3 or 1/6 octave tones zoomed out too far, instead of the sweep/chirp mode which would give a continuous frequency plot. Ideally, one would input RIAA-compensated sweeps or a signal with a similar volume/frequency envelope.
     
    Last edited: Apr 14, 2019
    mikeburns likes this.
  6. sublemon

    sublemon Forum Resident

    ASR is Stereo Review for the 21st century apparently. The guy who runs it seems to be a bit on the spectrum, it's not clear if he actually listens to anything, and he doesn;t think sound can be characterized. Personally I am more of the objective side of the debate as far as audiophilia, but it doesn't take a genius to understand that because everyone's hearing curve is different (the rub being everyone needs to listen for themselves because of this). As far as measuring well equating to good sound, there are plenty of cases where this is proven to be incorrect (harmonic distortion, minimum phase digital filters etc).
     
    mikeburns likes this.
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