My high power LM3886TF

senicz · 22nd February 2006, 12:29 PM

Best sound, best power, super low price.

PierreG · 22nd February 2006, 01:00 PM

Very intersting.
Did you try it?

zafira1981 · 22nd February 2006, 02:50 PM

I tried the same output stage but with a lm1875. I had lot of oscillation problems, but I made it work.

What I couldnt make work was the same but bridged.

the output transistors were 2n3055 / mj2955

good luck!!

Bazukaz · 22nd February 2006, 03:06 PM

What is the reason to do this ? You won't be able to use > +-40V rails anyway.Using two LMs in parralel would give better reliability / easier to build.
Also i think that 2SA1491 have too low power dissipation for reliable operation.

senicz · 23rd February 2006, 11:27 AM

I made this project exlusively for Hi-End speakers manufacturer "EDYTON".
For the high power output you should use 2X2SA1491/2SC2580.

Tim__x · 24th February 2006, 05:31 AM

Are those darlingtons? If not your bias current is going to be very high, Iq(3886)*Hfe(Q2).

steven344 · 24th February 2006, 01:33 PM

Have you ever tried this circuit

zafira1981 · 24th February 2006, 01:39 PM

Quote:

Originally posted by steven344
Have you ever tried this circuit

wow.. that's a strange circuit... do you have the explanation of how it works? I cant figure out..

thanks

steven344 · 24th February 2006, 01:54 PM

This is right from the national lm12 app notes,The zeners set up a regulated power supply to the lm12 as the audio increases the series pass transistors increase the voltage to to lm12,there is always no more then 39 volts between what the lm12 is putting out and the power supply rails feeding it ,its a tracking power supply,I have not tried it yet but I wonder if it would work with lm3875 or lm3886.As an example if the lm12 was putting out + 30 volt peak the + supply would increase to approx 69 volts and the negitive supply would decrease to about -9 keeping the lm12 within soa

steven344 · 24th February 2006, 01:56 PM

http://www.national.com/an/AN/AN-446.pdf

24th February 2006, 01:54 PM	#9
steven344 diyAudio Member Join Date: Jun 2005 Location: ohio	tracking power supplies This is right from the national lm12 app notes,The zeners set up a regulated power supply to the lm12 as the audio increases the series pass transistors increase the voltage to to lm12,there is always no more then 39 volts between what the lm12 is putting out and the power supply rails feeding it ,its a tracking power supply,I have not tried it yet but I wonder if it would work with lm3875 or lm3886.As an example if the lm12 was putting out + 30 volt peak the + supply would increase to approx 69 volts and the negitive supply would decrease to about -9 keeping the lm12 within soa

24th February 2006, 01:56 PM	#10
steven344 diyAudio Member Join Date: Jun 2005 Location: ohio	tracking http://www.national.com/an/AN/AN-446.pdf

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22nd February 2006, 01:00 PM	#2
PierreG diyAudio Member Join Date: Oct 2004	Very intersting. Did you try it?

22nd February 2006, 02:50 PM	#3
zafira1981 diyAudio Member Join Date: Jan 2005 Location: Argentina	I tried the same output stage but with a lm1875. I had lot of oscillation problems, but I made it work. What I couldnt make work was the same but bridged. the output transistors were 2n3055 / mj2955 good luck!!

22nd February 2006, 03:06 PM	#4
Bazukaz diyAudio Member Join Date: Nov 2005 Location: Vilnius	What is the reason to do this ? You won't be able to use > +-40V rails anyway.Using two LMs in parralel would give better reliability / easier to build. Also i think that 2SA1491 have too low power dissipation for reliable operation.

23rd February 2006, 11:27 AM	#5
senicz diyAudio Member Join Date: Jan 2005 Location: Warsaw	I made this project exlusively for Hi-End speakers manufacturer "EDYTON". For the high power output you should use 2X2SA1491/2SC2580.

24th February 2006, 05:31 AM	#6
Tim__x diyAudio Member Join Date: Jun 2004 Location: Edmonton area, Alberta	Are those darlingtons? If not your bias current is going to be very high, Iq(3886)*Hfe(Q2).

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