LM1876

pra3718 · 4th November 2012, 12:01 PM

I have already 2 chips in my drawer. So I wish to build Bi-Amp. Pls find attached file.

AndrewT · 4th November 2012, 11:29 PM

Do we get to see the schematic?

Have a look at the route the fast transient currents must follow into and out of the HF decoupling as they pass from Output PIN to output Zobel and back again.
With a route that long, can any fast transients pass around the loops?

pra3718 · 5th November 2012, 05:27 AM

Quote:

Do we get to see the schematic?

Input Cap not added, assume can be fitted at crossover output.
Zobel not added.

AndrewT · 09:49 AM

The schematic shows Cs.
You have placed the four Cs capacitors on the PCB, but in the wrong place.
The fast film or ceramic parts of Cs must be at the power pins and must be connected together in the shortest loop possible. The junction so formed is then connected to the corresponding junction of the electrolytic Cs. This common junction for all four Cs caps must be close to the OUTPUT PIN of the amplifier. Now connect the XZobel from OUT to Cs.
That is the ONLY way to allow the very fast rising and falling transients to pass around the Cs decoupling routes. Your decoupling route goes around the outside perimeter of the PCB and is about 10 (ten) times too long to be effective. The added inductance very effectively prevents the fast transients getting to their destination. In addition you have enclosed all the low level signal traces and components INSIDE the loops carrying those output currents. That makes for a good transmitter and receiver of unwanted distortions.

Start again.

pra3718 · 5th November 2012, 12:55 PM

I tried my level best.

AndrewT · 6th November 2012, 08:14 AM

There are many Threads where Members ask how to layout amplifiers.
Go and read and if you agree then adopt the ideas that suit you.

pra3718 · 7th November 2012, 01:20 PM

One more try

AndrewT · 7th November 2012, 01:51 PM

You still have the decoupling capacitors connected by a long route that passes around the whole PCB. That route can never be short !!!!!!!!!!!!

pra3718 · 8th November 2012, 03:15 PM

Infact, Post # 4 is well descriptive, I read several times to understand what you want to say. Being not an electronics man, I understood few of them.

I tried to copy the style of "LM4780 SS Pcb" which appreciated by many members. My layout may be looks like pinkmouse's pcb but may not technically similar or correct.

But, if I remember "That route can never be short !!!!!!!!!!!!" I should concentrate to another layout.

Best Regards.

"YOUR DREAM DOESN'T HAVE AN EXPIRATION DATE. TAKE A DEEP BREATH, AND TRY AGAIN."

Pls just look pdf for my todays job.

palstanturhin · 8th November 2012, 04:53 PM

Must the LM1876 have both pins 2 and 15 connected?

5th November 2012, 09:47 AM	#4
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	The schematic shows Cs. You have placed the four Cs capacitors on the PCB, but in the wrong place. The fast film or ceramic parts of Cs must be at the power pins and must be connected together in the shortest loop possible. The junction so formed is then connected to the corresponding junction of the electrolytic Cs. This common junction for all four Cs caps must be close to the OUTPUT PIN of the amplifier. Now connect the XZobel from OUT to Cs. That is the ONLY way to allow the very fast rising and falling transients to pass around the Cs decoupling routes. Your decoupling route goes around the outside perimeter of the PCB and is about 10 (ten) times too long to be effective. The added inductance very effectively prevents the fast transients getting to their destination. In addition you have enclosed all the low level signal traces and components INSIDE the loops carrying those output currents. That makes for a good transmitter and receiver of unwanted distortions. Start again. Last edited by AndrewT; 5th November 2012 at 09:49 AM.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
LM1876 Eagle file	Audio Bliss	Chip Amps	2	20th September 2011 10:16 AM
Lm1876	Bone	Chip Amps	8	18th February 2011 02:32 PM
LM1876 shematic	hamedfazelm	Chip Amps	4	26th May 2010 12:59 PM
LM1876 power amplifier	JozzaG	Chip Amps	3	4th February 2010 01:23 PM
lm1876	fabpri	Chip Amps	4	15th January 2004 12:22 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	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

4th November 2012, 11:29 PM	#2
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Do we get to see the schematic? Have a look at the route the fast transient currents must follow into and out of the HF decoupling as they pass from Output PIN to output Zobel and back again. With a route that long, can any fast transients pass around the loops?

6th November 2012, 08:14 AM	#6
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	There are many Threads where Members ask how to layout amplifiers. Go and read and if you agree then adopt the ideas that suit you.

7th November 2012, 01:51 PM	#8
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	You still have the decoupling capacitors connected by a long route that passes around the whole PCB. That route can never be short !!!!!!!!!!!!

8th November 2012, 04:53 PM	#10
palstanturhin diyAudio Member Join Date: Jun 2011	Must the LM1876 have both pins 2 and 15 connected?