Variable impedance - what's the audible impact

[tmtomh]

It is interesting that the measurements of Class D amplifiers are made with additional filtering.
To measure Class D amplifiers the APx555 requires additional HF filtering to get stable meaningful numbers. Does that additional filtering remove anything audible?

If there is a purgatory where ASR members go in the afterlife, it must be a place where every thread is just this question over and over, and no one agrees on the answer.

 

[DualTriode]

If there is a purgatory where ASR members go in the afterlife, it must be a place where every thread is just this question over and over, and no one agrees on the answer.

If you know please share.

 

[tmtomh]

If you know please share.

I wasn’t blaming you - it’s just that this question gets raised over and over (sometimes with very dire and poorly supported claims about the sonic or operational consequences), and it seems that no matter what answers Amir and other knowledgeable folks provide, the answers are not considered sufficient.

I’m not an expert myself so my answer would be partial, and I wouldn’t recommend anyone take my word for it anyway. But there are folks here who can answer it.

 

[DualTriode]

I wasn’t blaming you - it’s just that this question gets raised over and over (sometimes with very dire and poorly supported claims about the sonic or operational consequences), and it seems that no matter what answers Amir and other knowledgeable folks provide, the answers are not considered sufficient.

I’m not an expert myself so my answer would be partial, and I wouldn’t recommend anyone take my word for it anyway. But there are folks here who can answer it.

hello All,

I search for AUX040 / @amirm on ASR and get only one hit:
https://www.audiosciencereview.com/...5-review-amplifier.28512/page-61#post-1000707

I have a APx555 on my bench and a AUX040 in the cage. I have yet to measure more than one amplifier/speaker combo for anything acoustic with and without the AUX040 added filter.

Big picture it seems to me that the added AUX 040 should not make any acoustic difference. The stuff that the filter would remove is well above the output of most any tweeter let alone what we can hear when we are 10 years old.

If anyone has acoustic measurements with and without the AUX 040 say 22kHz and less I would like to see them.

Thanks DT

 

[tmtomh]

hello All,

I search for AUX040 / @amirm on ASR and get only one hit:
https://www.audiosciencereview.com/...5-review-amplifier.28512/page-61#post-1000707

I have a APx555 on my bench and a AUX040 in the cage. I have yet to measure more than one amplifier/speaker combo for anything acoustic with and without the AUX040 added filter.

Big picture it seems to me that the added AUX 040 should not make any acoustic difference. The stuff that the filter would remove is well above the output of most any tweeter let alone what we can hear when we are 10 years old.

If anyone has acoustic measurements with and without the AUX 040 say 22kHz and less I would like to see them.

Thanks DT

Thanks! I think additional results are "hiding" here on the forum because (if memory serves) "AUX040" was not actually mentioned in those other discussions. The issue often comes up when one member here in particular starts a new thread, as he periodically does, with a new torture test of a Class D amp and then makes ominous claims about the problems of Class D design topologies. Then folks usually chime in describing the aspects of the torture test that do not resemble actual musical signals, and the aspects of the torture test that are designed to exploit design aspects of Class D and are not actually flaws of Class D. Then the endless back and forth ensues.

Regardless, your "big picture" conclusion/supposition is indeed the most reasonable one, IMHO and in the opinion of many others here who are more knowledgeable than I am. And no, no one has chimed in with any results or evidence, acoustic or otherwise, that your big picture view on this is wrong.

 

[valerianf]

Let us take a practical example: the Onkyo RZ50.
Amir has tested it and very well explained the problem with its power stage.
If someone has a speaker with low impedance in the low frequencies area, at a high-level volume, it will trigger the nannies.
As there is no indicator that the nannies are engaged, the Onkyo will limit its output to around 20W.
Thus there will be a large amount of distorsion when cranking up the volume.
Yes the massive distorsion will be audible.
CQFD.

 

[KSTR]

I have a APx555 on my bench and a AUX040 in the cage. I have yet to measure more than one amplifier/speaker combo for anything acoustic with and without the AUX040 added filter.

Don't run a speaker (or whatever) load through the AUX020/040. It's intended to filter/protect the analyzer input, representing a high impedance load.