Looking for a class D amp that goes down to DC or thereabouts....

[Sokel]

Any examples as it was asked?

I think @pma has already demonstrated something like that,here:

PMA-NC252MP power amplifier

I assume the test is on one channel only, so I assume that with both channels running the problem may be more apparent as they share same power supply. Absolutely correct, I have only one "good enough" resistor load rated at 400W so I can test only 1 channel at such high power.

www.audiosciencereview.com

 

[fpitas]

Of course. The caps still get drained between charging pulses. Otherwise how would they get loaded down?

They get very partially drained, maybe by 1V or so, maybe less. But they are substantially charged the whole time the supply is running.

 

[boXem]

Any examples as it was asked?

DC coupled:
https://boxem-audio.eu/en/stereo-amplifiers/10-arthur-4215e2.html

High pass at around 1 Hz:
https://boxem-audio.eu/en/arthur/34-152-arthur-4222e1.html

 

[Doodski]

DC coupling means DC in, DC out.
Short circuit to ground detection is not done based on voltage but on current (too much = SC).
DC is also measured at the output of these amps, not for speaker protection but to diagnose a failure of the output stage where the supply rail would directly go to the speaker. It is considered as a catastrophic failure. So the threshold is quite high (10V if memory serves) to avoid triggering the fail safe protection because these is a bit of DC at the input.

Hmmz... That's pretty good for Ohms of amplifier load versus the voltage output of the PWM power supply. The switching power supplies I've worked with are all large toroidal and drive 2 Ohms so this is very interesting and the new power supply stuff with iron cores is stuff is very cool. Are those iron cores?

 

[Doodski]

They get very partially drained, maybe by 1V or so, maybe less. But they are substantially charged the whole time the supply is running.

Thank you for clarifying that for me. Very good info.

 

[Doodski]

DC coupled:
https://boxem-audio.eu/en/stereo-amplifiers/10-arthur-4215e2.html

High pass at around 1 Hz:
https://boxem-audio.eu/en/arthur/34-152-arthur-4222e1.html

This is very interesting and I have never seen this before.
Frequency response 0 - 60 kHz +0/-3 dB

 

[fpitas]

Thank you for clarifying that for me. Very good info.

Basically that part of the supply has waveforms a lot like a non-switching supply. But with a switcher, past the caps you usually have an LC filter to get rid of most of the high frequency stuff, especially RF.

 

[Doodski]

Basically that part of the supply has waveforms a lot like a non-switching supply. But with a switcher, past the caps you usually have an LC filter to get rid of most of the high frequency stuff, especially RF.

The last PWM switchers I was with where TL494 and 594s. They operated @ pretty low speeds and where for a high current 2 Ohm rated car amp(s). Repairs where often and productive.

 

[sarumbear]

DC coupled:
https://boxem-audio.eu/en/stereo-amplifiers/10-arthur-4215e2.html

High pass at around 1 Hz:
https://boxem-audio.eu/en/arthur/34-152-arthur-4222e1.html

Does those specs mean if I fed in 1VDC input, I will get 28VDC on the output and I can feed 400W continuously into a load of 2Ohms?

 

[Sokel]

Can someone please explain to me if mine can play lower than 20Hz (not that I have a speaker or sub to reproduce it,mine go to 30Hz,just technical curiosity):

 

[Doodski]

Can someone please explain to me if mine can play lower than 20Hz (not that I have a speaker or sub to reproduce it,mine go to 30Hz,just technical curiosity):

View attachment 287169

If 50kHz is the upper amplifier bandwidth what is the PWM switching frequency upper bandwidth and lower too?

 

[boXem]

Does those specs mean if I fed in 1VDC input, I will get 28VDC on the output and I can feed 400W continuously into a load of 2Ohms?

No, because the output stage protection will trigger above 10 V.
But in theory you should be able to get 200 W into 2 Ohm. Never tried tbh. Until thermal protection triggers of course.

 

[Doodski]

No, because the output stage protection will trigger above 10 V.
But in theory you should be able to get 200 W into 2 Ohm. Never tried tbh. Until thermal protection triggers of course.

It's impressive for speed of operation and practicality while being aggressive.

 

[Sokel]

If 50kHz is the upper amplifier bandwidth what is the PWM switching frequency upper bandwidth and lower too?

That's what it states:



What puzzles me is that they state 3Hz at 10 watts (-3db) but 20Hz-25Khz at nominal power.

 

[Doodski]

That's what it states:

View attachment 287171

Nice!

 

[Doodski]

If I saw 50kHz on a PWM amp back in the day I would be happy. LoL.

 

[sarumbear]

No, because the output stage protection will trigger above 10 V.
But in theory you should be able to get 200 W into 2 Ohm. Never tried tbh. Until thermal protection triggers of course.

Then why have DC response if it’s limited? Does the amplifier enters protection at 20kHz?

 

[sarumbear]

It's impressive for speed of operation and practicality while being aggressive.

Speed in the context of DC?

 

[Doodski]

That's what it states:

View attachment 287171

What puzzles me is that they state 3Hz at 10 watts (-3db) but 20Hz-25Khz at nominal power.

Wot's puzzling?

 

[Doodski]

It's impressive for speed of operation and practicality while being aggressive.

Impressive that is it apparently switches between ranges of operation good and bad.