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Old 1st October 2006, 04:31 PM   #1
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Default Ultra Low Hz below 15 Hz

Hi.. Folks..

I am going to make some machine (massage) with class-D amp.

And it needs class-D module which can play between 1 ~ 50 Hz with 200 W rms sine wave output.

I didn't make a detail search. But, I found UM10155 runs from 20 Hz, too high.

I wonder UM10155 cannot play below 20 Hz, or just have much THD.

Any recommendation would be appreciated..

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Old 1st October 2006, 07:36 PM   #2
Pafi is offline Pafi  Hungary
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Almost any classd amp can work at 0 Hz, if you bridge 2 of them, and remove coupler capacitor. However in this case (UcD) you must limit output voltage to ~95% of power supply voltage.
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Old 2nd October 2006, 06:56 AM   #3
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Thank you Pafi.

Then, would you recommend some amp modules or circuits for this use?

Output : 300 W RMS
Range : 1 ~ 50 Hz
Clock Fr: 500 Hz under (for effectiveness)

No sound quality is required, only cost and output effective.

Of course good endurance is required.
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Old 2nd October 2006, 07:10 AM   #4
Pano is offline Pano  United States
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Wow , this is an interesting application. Very clever.

Years ago I designed some interface circuits for motion control in the theater. Moving scenery and such. We used some very nice controllers made be Citroen, of all people. =)

They output 3 phase variable frequency 220V to run motors. If you don't find class-d modules that meet your needs, you might look in that direction.
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Old 2nd October 2006, 09:55 PM   #5
Gorilla is offline Gorilla  United Kingdom
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Don't forget a higher switching frequency will reduce the size (and thus cost) of your passive components.

Also have you considered using a micro (such as an Atmel or PIC)?
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Old 5th October 2006, 08:25 PM   #6
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Take a look at the Buttkicker amp.
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Old 6th October 2006, 04:48 PM   #7
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Most Class D amps don't care about running down to low frequency. I don't know enough about the UcD to know why it is limited but the other Class D amps I have seen are limited by an input capacitor. I have actually run some Class D down to 10Hz with a ultrasonic carrier frequency of only about 50kHz. Pretty slow but it gives the highest efficiency and less EMI with a slow carrier. The draw back being that most of the audio frequencies have horrible THD. But you won't be worried much about THD and at 50Hz will be fine anyway. Check out something easy to work with like a T-amp from Tripath. I thinking finding something to do the power and at the carrier (clock?) frequency you want will be harder than getting it to run nicely at 1 - 50Hz.

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