Bandwidth Limitations Of Class D Amps??

Most Class D amplifier designs require a filter at the output to remove the high frequency switching noise that is present in the signal. Various designs use different types of filters with varying cutoff frequencies. I doubt that any are designed to remove frequencies under 20KHz, but Class D amps are generally more frequency limited at the high end than conventional output stages can be. Whether this is audible can be a subjective question. Some engineers feel that in order to avoid introducing any phase shift to the audible high frequencies requires an amp to have a flat bandwidth response extending to many multiples beyond the audible frequency limit.

My Gilmore Raptors are -3db at 60khz
Alan

"My Gilmore Raptors are -3db at 60khz"

Arh, are those Class D amps an end to end proprietary design by the maker or do they incorporate another company's Class D amp modules?

ANything more to back up the published specs?

-3db means there will be phase shift problems all the way down to 10khz.
Why some say the upper mids and top end is hard could mean the the filtering is too high and letting the nasty switching noise intrude.
Why some say the upper mids and top end is bland and opaque could mean the filtering is too low and effecting the harmonic content of the upper mids and highs.

This is why you'll see class d manufactures bringing out different versions or mk 1 2 or 3 They change the filtering to the above to either or a combo of both, which I think sounds the worst.
Once technology get more advanced and they invent components whith much higher switching frequencies so they then can use the filter so the effects and phase shifts of them are well out of the audible range then Class D will compete with the good of linear amps, until then it is comprimised, but great for subwoofers.

Cheers George

GEorge,

You might be correct regarding the theoretical weak aspects of Class D but my experience is that they ARE competitive with other amps, not just good for subwoofers. Many users and reputable reviewers would agree.

All designs have flaws/imperfections, switching and otherwise. Gotta look at the whole picture, not just one aspect of one particular design.

It's like when Ralph from Atmasphere focuses on downside of negative feedback and says it can never sound like music. Many SS (and tube) amp owners might disagree, though his theoretical argument seems sound. One aspect of design theory only tells a part of the story though. THere are many factors that go into a good design. Most engineers think their way is best, and few do everything exactly the same, so I do not hold that against a good engineer that has done their homework.

Switching frequency just makes that aspect of Class D design very straightforward to quantify in comparison to many design aspects of non switching amps.

That is an advantage I would say in terms of being able to clearly identify an actual performance bottleneck specification with CLass D, similar to how sampling resolution defines limits of digital media.

Do non switching amps have any parameter that is similarly definitive? Not sure. That make comparisons hard and more subjective, not necessarily a good thing!

I do agree that as switching frequencies get higher, issues will diminish further. That bodes even better for the future of CLass D and seems to be happening already with newer Class D modules I have read about, like Abletec for example, however I have not seen any reviews from pubs or individuals on those yet, so the story is still out.