Sunday, 24 February 2013

MEASUREMENTS: "Slim Devices" Squeezebox 3 [Updated June 25, 2013]

Next up - my classic "Slim Devices" Squeezebox 3 (I believe this is one of the "first run" units; I was on a wait list at introduction):
- Internal DAC chip: TI/BB PCM1748E


Setup: i7 computer system with the analogue outputs of SB3 --> E-MU 0404USB. Details for this setup is same as Essence One tests.

Here's the oscilloscope plot of a 1kHz square wave at 0dBFS off the analogue outputs. Square wave have a slight downward slant. Peak voltage 2.64V. Nice channel balance (yellow = right, blue = left).

Standard linear phase digital reconstruction filter.

RESULTS:

First 2 columns are the stock SB3+stock wallwart connected to my basement music server by WiFi. Notice that 24-bit data does result in dropping of the noise floor by ~6dB. It looks like the good ol' SB3 internal DAC is capable of about 17-bit resolution when fed with 24-bits. Note that the old Stereophile review from 2006 did not measure 24-bit performance.

Second 2 columns are the same setup but with the ethernet (hooked up to my DLink gigabit switch 6 feet away). Essentially no difference compared to the WiFi.

Final column is with the SB3 over WiFi but the *SB Touch wallwart*. I see folks here talking about the crappy wallwart (true, the UNIFIVE wallwart looks and feels nasty compared to the one that came with the Touch!). I fed the 24-bit data and the result is essentially the same as the UNIFIVE. Based on these measurements, I don't see any evidence that the Touch wallwart would improve the stock SB3 performace.

Frequency Response:


Decent - obviously not as flat as Essence One from 20Hz-20kHz...

Noise Floor:


16-bit data obviously not as good as 24-bits. No difference between the WiFi vs. Ethernet groups.

THD Graph:


Dunn J-Test:
16-bit (16/44) -



24-bit (24/48) - 

CONCLUSION:

1. The SB3 can benefit from 24-bit "hi-res" audio. Whether you can hear the extra 5-6dB is your problem :-)
2. I see no evidence that a Touch wallwart would improve the performance over the cheap stock power supply. Who know is the multi-hundred $$$ or linear power supplies make a difference...
3. No evidence that running in WiFi mode will add any noise to the SB3 output.
4. The Dunn J-Test is demonstrating minimal jitter.

2 comments:

  1. Squeezebox 3 has production flaw, electrolytic capacitors between DAC and OpAmp are turned wrong way. As they are inversly polarized, they deteriorate with time, causing noticable degradation of audio quality.

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