This is a review and detailed measurements of the vintage Panasonic SA-XR57 multichannel Audio/Video Receiver (AVR). It is on kind loan from a member. It originally cost US $400. I don't know when it came out but I remember the Panasonic advertisement about it with their tall speakers.
The SA-XR57 is a switching amplifier and it shows from its weight. It is incredibly light despite its large size:
It has some unusual features like automatic speaker selection which I used and it correctly detected I had two speakers. It kept saying they were biwired though which they were not. I connected my speakers to the front left bank (A):
The video features are of course long obsolete.
The interest here was to see how an early sample of switching amplifier performed so let's get into it.
Amplifier Audio Measurements
As usual, we start with our dashboard view of 1 kHz tone into 4 ohm load at 5 watts:
As you see, the above is with analog input. Results with analog input was just a hair worse so doesn't look like digital input helps it any.
SINAD is dominated by high fifth harmonic at nearly -70 dB. Add a bit of noise to it and you get the SINAD of 68 dB as indicated. Here is the total ranking:
So unfortunately not good (above is using analog input).
Signal to noise ratio is nothing to write home about:
Frequency response is good:
The peaking is well above audio band.
Multitone shows what we already know:
Using analog input, we get this into 4 ohm:
Very strange ups and downs in the graph as different non-linearities kick in and dominate. Switching to digital input doesn't cure it:
Here is the outcome with 8 ohm and analog input:
Thermal Stability
The results here were "curious:"
While the trend is toward lower distortion, there is some mechanism that is producing those correlated sinusoidal variations in THD+N.
Conclusions
Panasonic has certainly achieved the efficiency goal in designing this receiver. Alas, it has rather strange response which I think is indicative of less than perfectly engineered amplifier. I suspect you can pick these up for a song so in that regard, it may not be a bad purchase if you want a cool and light amplifier. Otherwise, I can't recommend it.
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As always, questions, comments, recommendations, etc. are welcome.
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Never is used for hifi or more than stereo on TV sound. Sounds good enough I suppose. I can vouch for its longevity, although it never gets pushed, it gets annoyingly cranked to shouting levels because the old man is mostly deaf. Runs cool, low power draw, all on an UPS to prevent power issues, expecting that's added to the longevity. Never a hiccup. Knock on wood. No reason to think it will quit working in the foreseeable future. Whatever. Just amazed Amir felt like spending the time measuring it when it's nothing but trivial information.
