A new unit is with me. Because new device is too cold to be powered, I can focus on external differences. Both units are almost undistinguishable.
One difference is reversed channels on RCA inputs. Second one is a class II power supply mark printed on the bottom.
I've seen units with reversed RCA plugs in some recent YouTube movies, so this change was probably applied in the meantime.
There are also subtle differences between outside boxes, like the mentioned class II mark. Another one are black and white icons of the music services vs colorful ones for the box of old unit.
First things first, as the full set of measurements and tests takes a lot of time, I will verify known issues at the very beginning.
PSU noise - absent, it's (almost) deadly silent. I can hear something only when my ear touches the chassis directly. Well, I know it could be pretty risky idea...
PCB_version - 5.
HF switching signal on sub out - absent.
Low frequencies / multitone bad performance - seems to be greatly improved in my quick and dirty measurements. I will provide more details tomorrow.
SMPTE, 5W:
Multitone, 5W:
Differences are huge.
Another example of improvement, this time for THD+N vs level at 100 Hz, 4 ohm load as before:
An old unit starts to distort much earlier.
THD+N vs level measurements at different frequencies finally look like for other TPA3255 implementations, 4 ohm:
Below the same measurements but for V1 unit:
Yet another comparison vs old unit, for multitone measurement at different load levels:
THD at 5W/4ohm load, related to frequency, for both units:
Surprisingly slightly worse performance for higher frequencies in case of the new model.
It can be also seen for lower 1W load:
Measurements - optical in to speakers out
All tests here were made with an external LPF. More details: https://forum.wiimhome.com/threads/my-wiim-amp-tests.1873/
Although the new revision is a clear improvement over an old one, the most basic SINAD measurement for 1 kHz sine signal will not reflect it at all in case of 4 ohm load.
4 ohm / 5 W, an old unit:
And the new one:
For 8 ohm load there is a measurable improvement.
8 ohm / 5 W, an old unit:
And the new one:
Nothing has changed in case of the load dependency:
Crosstalk, left to right and right to left, 4 ohm / 5 W:
THD+N vs output voltage, for 4 ohm and 8 ohm load:
And details for different frequencies, 4 ohm:
and 8 ohm:
THD vs frequency, for 4 ohm and 8 ohm:
Measurements - optical in to sub out
I've use 200 Hz crossover frequency and 100 Hz test sine signal again. As the output is no longer affected by the HF switching signal, there was no need to use an external LPF.
Pure performance for 0 dBFS input signal improved a lot, although a sign of clipping is visible:
It can be seen in the stepped THD test:
Performance is slightly similar to the Pro which shouldn't surprise, as the Amp probably uses Pro's DAC for its sub out.
Multitone controversy
Erin reported in his review ( https://www.erinsaudiocorner.com/electronics/wiim_amp/ ) that the Amp is loosing some power when complex signal is used for testing. I tried to reproduce it ( https://forum.wiimhome.com/threads/review-of-wiim-amp-by-asr.2891/post-41093 ) but without success. I've decided to repeat these tests once again recently, but I still couldn't observe the mentioned effect.
I suspect that the proper crest factor is important here as if it's not minimized in the multitone test signal, then RMS level can be much lower than peak to peak level, and it affects the output power.
Stay tuned.
One difference is reversed channels on RCA inputs. Second one is a class II power supply mark printed on the bottom.
I've seen units with reversed RCA plugs in some recent YouTube movies, so this change was probably applied in the meantime.
There are also subtle differences between outside boxes, like the mentioned class II mark. Another one are black and white icons of the music services vs colorful ones for the box of old unit.
First things first, as the full set of measurements and tests takes a lot of time, I will verify known issues at the very beginning.
PSU noise - absent, it's (almost) deadly silent. I can hear something only when my ear touches the chassis directly. Well, I know it could be pretty risky idea...
PCB_version - 5.
HF switching signal on sub out - absent.
Low frequencies / multitone bad performance - seems to be greatly improved in my quick and dirty measurements. I will provide more details tomorrow.
SMPTE, 5W:
Multitone, 5W:
Differences are huge.
Another example of improvement, this time for THD+N vs level at 100 Hz, 4 ohm load as before:
An old unit starts to distort much earlier.
THD+N vs level measurements at different frequencies finally look like for other TPA3255 implementations, 4 ohm:
Below the same measurements but for V1 unit:
Yet another comparison vs old unit, for multitone measurement at different load levels:
THD at 5W/4ohm load, related to frequency, for both units:
Surprisingly slightly worse performance for higher frequencies in case of the new model.
It can be also seen for lower 1W load:
Measurements - optical in to speakers out
All tests here were made with an external LPF. More details: https://forum.wiimhome.com/threads/my-wiim-amp-tests.1873/
Although the new revision is a clear improvement over an old one, the most basic SINAD measurement for 1 kHz sine signal will not reflect it at all in case of 4 ohm load.
4 ohm / 5 W, an old unit:
And the new one:
For 8 ohm load there is a measurable improvement.
8 ohm / 5 W, an old unit:
And the new one:
Nothing has changed in case of the load dependency:
Crosstalk, left to right and right to left, 4 ohm / 5 W:
THD+N vs output voltage, for 4 ohm and 8 ohm load:
And details for different frequencies, 4 ohm:
and 8 ohm:
THD vs frequency, for 4 ohm and 8 ohm:
Measurements - optical in to sub out
I've use 200 Hz crossover frequency and 100 Hz test sine signal again. As the output is no longer affected by the HF switching signal, there was no need to use an external LPF.
Pure performance for 0 dBFS input signal improved a lot, although a sign of clipping is visible:
It can be seen in the stepped THD test:
Performance is slightly similar to the Pro which shouldn't surprise, as the Amp probably uses Pro's DAC for its sub out.
Multitone controversy
Erin reported in his review ( https://www.erinsaudiocorner.com/electronics/wiim_amp/ ) that the Amp is loosing some power when complex signal is used for testing. I tried to reproduce it ( https://forum.wiimhome.com/threads/review-of-wiim-amp-by-asr.2891/post-41093 ) but without success. I've decided to repeat these tests once again recently, but I still couldn't observe the mentioned effect.
I suspect that the proper crest factor is important here as if it's not minimized in the multitone test signal, then RMS level can be much lower than peak to peak level, and it affects the output power.
Stay tuned.
Last edited:
For all and especially those with "older" items I highly recommend checking with a multimeter or similar. It COULD be dangerous with more than a little prickling on the fingertips.
