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Old 19th January 2015, 08:42 PM   #1
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Default Filterless class d and tweeters

Hello. Could some one help me?
I have a few problems, that i could not find the answers:

1. Can soft dome tweeters be driven of filterless? I dont know what "soft dome" means, thats only info about them. Maybe i need to add output filter?

2. I only have one free pam8403 channel for them, and they make 2 ohm load, while pam8403 designed for 4ohm, could it work with high pass at aprox 6000hz because power is very low that high?
I could add 1.2 ohm resistor to reach 3.2ohm load, it would be still louder than series speakers. Only if its needed of course.

Thanks in advance.
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Old 19th January 2015, 08:50 PM   #2
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Assuming soft dome means moving coil, you should be fine. Don't use a filterless class D to drive piezo tweeters, at least not with some series resistance.

You should be fine driving a 2 ohm load at reduced power - ultimately you're limited by output current, rather than load impedance. If the PAM chip trips off due to overcurrent, then try adding series resistance.

Or put your tweeters in series - it won't be as loud as paralled tweeters plus a resistor, but if it's adequately loud for your setup, hey.
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Old 19th January 2015, 09:33 PM   #3
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If you fit a 22uH choke in series of the output from the amplifier, the amplifier will be more stable and conform to interference and transmission regulations.
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Old 19th January 2015, 10:43 PM   #4
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Quote:
Originally Posted by gmarsh View Post
Assuming soft dome means moving coil, you should be fine. Don't use a filterless class D to drive piezo tweeters, at least not with some series resistance.

You should be fine driving a 2 ohm load at reduced power - ultimately you're limited by output current, rather than load impedance. If the PAM chip trips off due to overcurrent, then try adding series resistance.

Or put your tweeters in series - it won't be as loud as paralled tweeters plus a resistor, but if it's adequately loud for your setup, hey.
Thank you. This is portable speaker.
My setup is like this: 3 x russian paper 4ohm "almostfulranges" (they reach 12.5khz)
Each about 92db sensitivity. And 2 tweeters.
Tweeters box says that they are 94db, but i dont know if it is true.
Series tweeters can't keep up. Will be trying to conect parralel maybe at even 8-9khz crossover.

All was driven by TDA2050. 1.3ohm @ 12V supply + tweeter through caps, in parralel. Sounds good, but i feel like i am pushing it a little
And class d more efficient even with voltage downconversion. And i like idea of regulated supply. TDA2050 had on/of thumps too, so i used relay... Another 15mA without use.

I decided to upgrade to 2x PAM8403 with active crossover. Powered by 5V switching regulator.
3 chanels driving russian speakers. And last chanel tweeters.

Last edited by valtra103; 19th January 2015 at 10:46 PM.
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Old 19th January 2015, 10:50 PM   #5
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Originally Posted by JonSnell Electronic View Post
If you fit a 22uH choke in series of the output from the amplifier, the amplifier will be more stable and conform to interference and transmission regulations.
Since amplifier is BTL, is one choke enough? Or i need one for neg. output, and one for pos. output?

Thanks for helping


EDIT: is chokes like this okay? http://www.evita.lt/smsl1305-220-dro...md?search=22uh

Last edited by valtra103; 19th January 2015 at 10:56 PM.
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Old 22nd January 2015, 10:56 PM   #6
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Even this is okay:
http://www.evita.lt/en/h-dip-22-dros...uh?search=22uh
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Old 22nd January 2015, 10:59 PM   #7
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Even this is okay:
Choke coil 22uH
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Old 23rd January 2015, 12:48 PM   #8
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Originally Posted by doctormord View Post
Even this is okay:
Choke coil 22uH
Thank you
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