My WiiM Amp tests, chapter 2
- Thread starter onlyoneme
- Start date
IMO it looks fine, but someone else might confirm or deny it. @harkpabst ?
@onlyoneme,
Are LPF and HPF both -18db/oct?
And was the cause of the noise a steep slope?
Thank you so much.
Filter steepness is definitely different, telling from your own measurements. With the current firmware it appears to be a 4th order Linkwitz-Riley filter now (which is much more common and most probably favourable over an 8th order filter).
Since my replacement amp was delivered just yesterday (PCB_version 5) I didn't spend time for measurements, yet. But I will at some point I'm the near future. I didn't measure anything on the previous unit (PCB_version 4).
Once again, great work! Thanks a lot!
PS:
The slopes look good to me. The slight rise above 5 kHz is absolutely negligible. It's still down by ~80 dB at 20 kHz and no sub will play that high, anyway.
Since my replacement amp was delivered just yesterday (PCB_version 5) I didn't spend time for measurements, yet. But I will at some point I'm the near future. I didn't measure anything on the previous unit (PCB_version 4).
Once again, great work! Thanks a lot!
PS:
The slopes look good to me. The slight rise above 5 kHz is absolutely negligible. It's still down by ~80 dB at 20 kHz and no sub will play that high, anyway.
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It's rather -24 dB/oct I think.
I can't see well with presbyopia
Glasses are my best friends tooI can't see well with presbyopia
Hi all, first post here I have been looking at PCB versions mentioned on here and the various issues people are having. I got my amp on new year's eve from Amazon UK. It has PCB version 4 and there is an obvious high pitch continual whine from the unit itself but so far it only seems to be audible to me with my ear close to the unit. I haven't experienced any other unwanted sounds so far. It would be amazing to hear of any known differences between PCB 5 and version 4. These tests are really interesting so thanks for your efforts.
Completely understand and I am grateful for what you have shared. I just wanted to comment for others who have PCB 4 in case they are curious about any known issues or have any other input to this. For info my RCA inputs are reversed like your PCB 5 version but I have no class ll mark.
@onlyoneme, I’m glad to see you posting measurements. I haven’t seen you posting here in a while. I had ver 2 but return it and purchase again and got ver 5. No hum unlike the first one.
in the case of using this type of amplifier it is still interesting to observe the effective impedance curve of the speakers concerned.....
the situations when going up in frequencies are so variable...
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This is typical of entry level Class D. However, PFFB will be integrated into new amplifiers by Aiyima and Fosi Audio. I hope that WiiM incorporates PFFB into the next version of the Amp to eliminate load dependency.in the case of using this type of amplifier it is still interesting to observe the effective impedance curve of the speakers concerned.....
the situations when going up in frequencies are so variable...
The rise into 8 ohms load is less than 2 dB at 20 kHz (edit: closer to 1 dB, I think). Not nice for sure, but also not reason for too many concerns.in the case of using this type of amplifier it is still interesting to observe the effective impedance curve of the speakers concerned.....
the situations when going up in frequencies are so variable...
Implementing the TPA3255 with post-filter feedback would have improved on that noticeably.
It's important to understand that these measurements are taken with a purely resistive load. Just from looking at this one graph you cannot say for sure what's going to happen with inductive (or even capacitive) load.
In other words: Just because a loudspeaker is sold as being nominally 8 ohms or even because the impedance trace shows an absolute value of 8 ohms at high frequencies doesn't necessarily mean the rise in SPL will be as seen in this graph.
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