Audio Experts advice on LM4780 PCB - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

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 26th October 2010, 05:34 AM   #1
diyAudio Member
 
Join Date: Apr 2005
Location: India
Default Audio Experts advice on LM4780 PCB

Hi,
My friends have purchased few LM4780 ICs and he want a 7.1 amp with it. So asked me to make a very compact PCB for this IC.

So i have made on with single layer PCB. PSU is on different PCB with 2x10000uf caps.

All resistance (except Zobel ones) are surface-mount on the bottom of the PCB.

Please have a look and give your advice for any improvement.

This is a stereo PCB for all 7 channels and i am working for one parallel for subwoofer.

Thanks

Rakesh Sharma
Attached Images
File Type: jpg Part LM4780 Stereo.jpg (232.6 KB, 469 views)
File Type: jpg LM4780 Stereo.jpg (264.2 KB, 452 views)
  Reply With Quote
Old 26th October 2010, 05:47 AM   #2
diyAudio Member
 
Join Date: Apr 2005
Location: India
Parallel PCB
Attached Images
File Type: jpg LM4780 Mono.jpg (257.6 KB, 430 views)
File Type: jpg PartsLM4780 Mono.jpg (222.6 KB, 408 views)
  Reply With Quote
Old 26th October 2010, 07:41 PM   #3
diyAudio Member
 
Join Date: May 2008
- Seems the Rin are missing on the stereo PCB.
- On both PCBs there are no smoothing caps.
- It is always recommended to avoid rectangular traces. Curves or 45 angles are better.
__________________
If you've always done it like that, then it's probably wrong. (Henry Ford)
  Reply With Quote
Old 27th October 2010, 12:17 AM   #4
diyAudio Member
 
abraxalito's Avatar
 
Join Date: Sep 2007
Location: Hangzhou - Marco Polo's 'most beautiful city'. 700yrs is a long time though...
Blog Entries: 109
Send a message via MSN to abraxalito Send a message via Yahoo to abraxalito Send a message via Skype™ to abraxalito
Is the ground from the PSU PCB the unmarked point near your name? If so, that's probably one of the worst places it could be for sound quality For optimum sound, I suggest your power supply doesn't use a centre-tapped transformer - two (separately rectified) secondaries would be better.
__________________
Seek not the favour of the multitude...rather the testimony of few. And number not voices, but weigh them. - Kant
The capacity for impartial observation is commonly called 'cynicism' by those who lack it.
  Reply With Quote
Old 27th October 2010, 08:19 AM   #5
Piggy is offline Piggy  Hong Kong
diyAudio Member
 
Join Date: Nov 2009
It seems OK to use a ground bus for the small signals, but do not connect the dirty grounds (speaker return, zobel and decoupler ground return) to that bus. Make the pads bigger to increase the adhesive if you are going to solder the wires directly to the PCB. Take a look of the LM4780 datasheet, the grounding topology is more or less like that.
  Reply With Quote
Old 27th October 2010, 09:30 AM   #6
ampimp is offline ampimp  United Kingdom
Banned
 
Join Date: Sep 2009
Location: coventry
Default decoupling o.1Uf

Try to get those 0.1Uf decoupling caps as near to the ic as possible.
I have just done so and i can report it was well worth the extra effort.
Regards Ian
  Reply With Quote
Old 27th October 2010, 12:59 PM   #7
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Quote:
Originally Posted by ampimp View Post
.....I have just done so and i can report it was well worth the extra effort.
that is useful information that we rarely see.

Similarly, reports on efforts that do not work are equally useful.
__________________
regards Andrew T.
  Reply With Quote
Old 27th October 2010, 06:21 PM   #8
ampimp is offline ampimp  United Kingdom
Banned
 
Join Date: Sep 2009
Location: coventry
Smile Thanks to Andrew T

My last post was from imformation Andrew T posted to another newbie.
Thanks Andrew i managed to fit 2.5 mm caps with only 15 mm length of wide track to main ground . So far Im thinking most anyone can get a chipamp to work but with a little more effort and lots of reading you can turn it into somthing i would say quite special sounding and with the lm3886 lack of bass naa lack of boom wow i can hear textures and timbres and most of all emotion in my music. and belive me if there is deep powerfull base in a track you will hear it . Right thats it from me as you can tell im buzzing not the amp lol.
  Reply With Quote
Old 28th October 2010, 09:54 AM   #9
diyAudio Member
 
Join Date: Apr 2005
Location: India
Woow... Thank you all for your kind views. As a newbie in DIY Audio amp hobbie this is a super push.

My Psu was a Center tapped type PSU with one bridge, but now i will change it with two seprate rectification section and yes ground track is the bottom one (under my name "RAKESH")


As per the grounding topology and moving 0.1uf cap closer, this is a difficult task, since i have to make the circuit PCB as small as possible.

Can i shift Zobel from PCB to Speaker socket terminials ?

The finished amp will be used as 7.1 amp, placed on the back plate of a subwoofer. Making a subwoofer with 7.1 output.
Amp will be running with 20v +- and 4ohms load, powered by a 10amp transfromer for front, side ,rear and center channel and another 4 amp transformer for Sub amp only.

Any more possibilities for improvement.... please suggest.

Thanking
Rakesh Sharma.
  Reply With Quote
Old 28th October 2010, 10:28 AM   #10
diyAudio Member
 
Join Date: Oct 2010
Quote:
Originally Posted by pacificblue View Post
- It is always recommended to avoid rectangular traces. Curves or 45 angles are better.

Why?

(I think I know the answer, just want to hear what you have to say...)
  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
Need advice from the experts echosystm Multi-Way 3 4th September 2009 12:14 PM
2x60W/1x120W audio amplifier PCB (LM4780/4732) veteran Group Buys 238 20th December 2007 10:55 PM
advice from the experts notaclue Multi-Way 6 11th July 2006 11:24 PM
FET experts advice needed bostjancek Solid State 4 24th November 2005 02:52 AM


New To Site? Need Help?

All times are GMT. The time now is 03:54 AM.


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