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Class D Switching Power Amplifiers and Power D/A conversion

New Breeeze Audio TPA3116 2.0 100W dual chip
New Breeeze Audio TPA3116 2.0 100W dual chip
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Old 12th July 2019, 04:41 PM   #101
carlmart is offline carlmart  Brazil
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Finding the case and assembling it inside might not be that easy.
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Old 12th July 2019, 05:11 PM   #102
chermann is offline chermann  Austria
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Originally Posted by carlmart View Post
Finding the case and assembling it inside might not be that easy.

thats DIY
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Old 29th July 2019, 05:32 PM   #103
chermann is offline chermann  Austria
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Hi i am back.....


pump it up......at post 78

any expert to answer this??
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Old 29th July 2019, 06:02 PM   #104
FauxFrench is offline FauxFrench  France
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The question must be this one:
at the tpa3116 i have "just" 1,5db?....is the TPA3116 not sensitive of impedance-missmatch because of this frequency adaptation that ICG wrote in post 24?

Before the experts arrive, I will give it a shot.
The speaker impedance acts as damping of the output filter resonance. When the damping is reduced with a higher speaker impedance, the frequency plot will show a rise near the resonance frequency. That may affect the high treble a little.
The audible range is below this resonance and the carrier frequency is solidly above the resonance frequency. ICG has divulged statements that the carrier frequency is not fully fixed but varies in order to reduce distortion. Perhaps from the same principles as class T (Tripath). But, for EMI reasons, I doubt that the frequency variations from the 400KHz nominal carrier are large. It is rather a spectrum that is spread-out a bit around the 400KHz. As the 400KHz is already well above the filter resonance frequency, I doubt you will notice any practical influence from this variation of frequency on the response of the filter resonance.

Now we are all awaiting The Doctor, ICG and voltwide among other.

Last edited by FauxFrench; 29th July 2019 at 06:08 PM.
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Old 29th July 2019, 07:15 PM   #105
chermann is offline chermann  Austria
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Thank you!



lets wait...
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Old 30th July 2019, 02:20 AM   #106
ICG is offline ICG  Germany
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Quote:
Originally Posted by FauxFrench View Post
The audible range is below this resonance and the carrier frequency is solidly above the resonance frequency. ICG has divulged statements that the carrier frequency is not fully fixed but varies in order to reduce distortion. Perhaps from the same principles as class T (Tripath). But, for EMI reasons, I doubt that the frequency variations from the 400KHz nominal carrier are large. It is rather a spectrum that is spread-out a bit around the 400KHz. As the 400KHz is already well above the filter resonance frequency, I doubt you will notice any practical influence from this variation of frequency on the response of the filter resonance.

Now we are all awaiting The Doctor, ICG and voltwide among other.
I am no Doctor. But there's an important point. The thing you're flatout ignoring is the impedance rise on a lot of speakers. Many dome tweeters aren't a problem and AMTs or most ribbons laugh about that but the impedance of a horn tweeter isn't that flat. But it gets really bad if you look at the impedance plot of fullrange drivers. A lot of these got ~30 Ohm at 15 or 20k and that's by no means trivial anymore, we're talking about ~5dB at some amps here! So, you can in many cases disregard that, but for some folks it is actually very important. As always, it depends on what you're actually doing. I do not try to scare anyone off of class D amps, I try to rise awareness of the problem. No more, no less than that.
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Old 31st July 2019, 06:21 AM   #107
chermann is offline chermann  Austria
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Hi

I checked the TPA3116 datasheet and compared it with the others e.g. TPA3251. i cannot find in the block diagramm the automatic by TPA3116 with the "regulation" of this osc. frequency.

the effect that the filter mismatch in higher frequencies was alwasy checked by my board mods - but i never tried to split the amps in low and high.

so if i think about what ICG wrote -and that trough for lot of spekaers- then the logical consequence is to split the amps in a first step in low and high = bi amping with an adaptation of the "tweeter" ouput filter - correct?

i try this at the filter designer (i use the setup which i learnt at my TPA3255 board and feeback by the specialists)

so for an impedance of t 20 ohm we need a coil of 50H

chris
Attached Files
File Type: pdf Class-D LC Filter Designer_tweeter high impedance.pdf (192.4 KB, 8 views)

Last edited by chermann; 31st July 2019 at 06:23 AM.
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Old 31st July 2019, 07:39 AM   #108
FauxFrench is offline FauxFrench  France
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Quote:
Originally Posted by chermann View Post
Hi
I checked the TPA3116 datasheet and compared it with the others e.g. TPA3251. i cannot find in the block diagramm the automatic by TPA3116 with the "regulation" of this osc. frequency.
the effect that the filter mismatch in higher frequencies was alwasy checked by my board mods - but i never tried to split the amps in low and high.
so if i think about what ICG wrote -and that trough for lot of spekaers- then the logical consequence is to split the amps in a first step in low and high = bi amping with an adaptation of the "tweeter" ouput filter - correct?
i try this at the filter designer (i use the setup which i learnt at my TPA3255 board and feeback by the specialists)
so for an impedance of t 20 ohm we need a coil of 50H
chris
Hi Chris,

I understand ICG's reply such that the problem relates to the impedance variation of certain speaker drivers with frequency. Actually, it is not the carrier frequency changes of the TPA3116 that is the problem.
Apparently, some horn speakers (I assume conical treble horns) and in particular full range drivers may have highly variable impedance with frequency.

For a pure treble driver, we could in principle put an electronic high-pass filter before the class D amplifier and use an adapted output filter for the higher treble driver impedance. It is then a matter of how constant this treble driver impedance actually is.
The big problem seems to be with full-range drivers having a varying impedance becoming some 30 Ohm in the top. There the output filter is about right for most of the frequencies while at the top the filter is poorly damped due to the increase in impedance. For such full-range drivers, we cannot filter out a part of the frequency range and we cannot make a dynamically adaptable output filter with varying properties for different frequencies. At least it will be very complex.

The conclusion I draw from ICG's qualified analysis is that class D, due to the output filter, is less suited for full-range drivers because of their varying impedance. Impedance variations with frequency is much better handled by class AB amplifiers having a low output impedance in the full audio range.

50uH for 20 Ohm sounds about right.

Last edited by FauxFrench; 31st July 2019 at 07:46 AM.
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Old 31st July 2019, 07:59 AM   #109
chermann is offline chermann  Austria
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Hmmm..

practical a coil with 30H TDK Epcos - 495-75392-6-ND - with about 8 Amps must be the better solution..will not fit in this TPA3116 dual amp
gives enough current availability at low frequencies and fits for the high impedance speakers.
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Old 31st July 2019, 08:09 AM   #110
chermann is offline chermann  Austria
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Hi FF
Thanks for your feedback..
Yes the frequency response of speakers is normal - real - i know.

as a look and read a lot in this forum and i recognizes at stronger amps (apex, hypex, ICE moduls) big fat coils and if i remember right such values about 30H or so. now it looks more logical for me because of the higher Z at high frequencies
so my conclusion is like the post before...big value for the "tweeter" but with higher current avalibitlity (low DC -bigger coil) to push some current at the bass chassis.

so do not understand me wrong - at all my modification (FX502spro, TPA3255 YJ) i keep still the recommendations and i am happy with this low cost Class D amps sound wise.

chris

Last edited by chermann; 31st July 2019 at 08:28 AM.
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