Filterless subwoofer Class-D amp - diyAudio
Go Back   Home > Forums > Amplifiers > Class D

Class D Switching Power Amplifiers and Power D/A conversion

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 31st December 2003, 03:08 AM   #1
diyAudio Member
 
Workhorse's Avatar
 
Join Date: Dec 2004
Default Filterless subwoofer Class-D amp

I want to know that anyone here with experience with filterless designs or so?
As the self Inductance of SUBWOOFER IS quite high which can act as a filter to switching frequency
  Reply With Quote
Old 31st December 2003, 04:06 AM   #2
MWP is offline MWP  Australia
diyAudio Member
 
Join Date: Oct 2002
Location: Adelaide, South Australia
The filters are there to stop the speaker cables becoming rather powerful antennas....
Not there to stop the HF switching getting to the speaker,
  Reply With Quote
Old 31st December 2003, 07:01 AM   #3
diyAudio Member
 
Join Date: May 2002
Location: Switzerland
Quote:
The filters are there to stop the speaker cables becoming rather powerful antennas....

That one depends on the design goal. For a subwoofer less carrier supression is needed than for driving a full-range speaker and the stetement above has indeed some truth. But take into account that speaker voice-coils can seldom be regarded as lossless inductors at high switching frequencies.
OTOH it is easier to take feedback from the filter output if it's cutoff frequency isn't too low.

Regards

Charles
  Reply With Quote
Old 31st December 2003, 10:22 AM   #4
diyAudio Member
 
Workhorse's Avatar
 
Join Date: Dec 2004
Arrow REPLY

My project amp has switching frequency of around 2~5KHz
and is meant to be installed in the subwoofer cabinet i.e. very close to the driver unit.Therefore aac to me the wires wont make antennas. Some more suggestion requiredPLZ Help
  Reply With Quote
Old 31st December 2003, 11:10 AM   #5
IVX is offline IVX  Russian Federation
diyAudio Member
 
IVX's Avatar
 
Join Date: Jul 2003
Location: Everywhere (Buddhist's context)
2-5khz NO CHANCE..
__________________
Best regards,
E1.
  Reply With Quote
Old 31st December 2003, 12:37 PM   #6
diyAudio Member
 
Join Date: Dec 2003
Location: Munich
2-5khZ is alright from shanon theory...
BUT you will hear the 2-5kHz signal REALLY loud!!!!!! And it might also burn your voice coil, as at 5 kHz the speakers impedance typically will still allow a lot of current....
I would propose to shift the switching frequency above what you can hear.
2..5kHz you will always hear, even with a filter.
  Reply With Quote
Old 31st December 2003, 03:22 PM   #7
diyAudio Member
 
Workhorse's Avatar
 
Join Date: Dec 2004
Arrow REPLY

Thanx for the suggestions to everyone!
I have raised the switching frequency to 5KHz and used the
4th order low pass AIR CORE filter @ -3dB @300Hzto suppress switching components and they are rejected to -74dB
  Reply With Quote
Old 31st December 2003, 04:57 PM   #8
diyAudio Member
 
Join Date: Dec 2003
Location: Munich
...this sounds more reasonable.
for disco or entertainment applications or PA you can probably accept the remaining 5kHz-Signal noise......
  Reply With Quote
Old 31st December 2003, 09:18 PM   #9
subwo1 is offline subwo1  United States
diyAudio Member
 
subwo1's Avatar
 
Join Date: Jan 2002
Location: North American Continent
Default Filterless Class D

Filterless class D technique usually refers to circuitry where the PWM carrier cancels at zero net output level, which should also occur when the net input signal is zero. This approach has not been not very practical for DIY circuits because the amount of needed circuitry is approximately doubled, and the amplitude of the output switching components increase in proportion to the audio signal carried by the PWM. The second drawback could result in an AM transmitter if the outgoing and return audio paths to the speaker are not kept very close together, as in a twisted pair. As the switching frequency increases, a shorter non-canceling output loop to a speaker will tend to radiate more. But since the PWM output of a filterless amp would be a square wave, the EMI never really approaches zero, especially if the square waves have quick rise and fall times rich in high frequency harmonics.

amp_man_1, your proposed circuit does not produce sharp-edged square waves, and with the filtering you have suggested, EMI could be quite low. Your low switching frequency of 5khz reduces EMI 20dB lower than if the frequency were 500khz. Hope I did not mistake anything.
__________________
USMPS
http://groups.yahoo.com/group/switchmode/
  Reply With Quote
Old 31st December 2003, 10:04 PM   #10
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
As a practical matter, you should get the switching frequency
up above (ordinary) human hearing, say 30 KHz, or you'll
always end up hearing the noise coming from something.

30 KHz is no big challenge to switching electronics, so there's
no real advantage to going lower.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Filterless Class D gpapag Class D 37 21st October 2013 10:47 PM
filterless Peltier PWM star882 Power Supplies 14 28th June 2007 01:38 AM
I guess filterless non-OS is a bad idea regal Digital Source 8 16th September 2006 08:00 PM
Filterless DAC - pros and cons? mr_push_pull Digital Source 1 11th August 2004 03:56 PM


New To Site? Need Help?

All times are GMT. The time now is 05:04 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2