something with LM4702 and Power FET - 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 14th December 2006, 04:39 PM   #1
diyAudio Member
 
FastEddy's Avatar
 
Join Date: Jun 2006
Location: North Californie
Default something with LM4702 and Power FET

The suggestion is for a new thread for the National LM4702. My choices would be to use power MOSFET or HEXFET drivers, rather than Darlington pairs or other scenarios.

The LM4702 would make a most excellent ~ 4 to 6 watt stereo headphone amplifier from +/- 12 to +/- 20 VDC rails !!

This chip amp can have some really excellent THD specs (as low as 0.0006% !) with careful attention to details, ground loop questions, etc., etc.:

" ... At 10 Volts RMS output, THD+N is about 0.005% across a 20 Hz to 20 KHz bandwidth ... It steadily drops to about 0.0015% at maximum output voltage. ..." (error ?) " ... At very low output voltages the data sheet shows that THD+N rises to over 0.1% ..."

Personally, I am also interested in balanced inputs for "pro audio", better quality connectivity between pre-amps and remotely powered and bi-amped speakers (power supply, EQs and LM4702 + drivers in each speaker), etc..

Some origins:
http://www.diyaudio.com/forums/showt...22#post1081722
Lm4702

Some references:
near the beginning = http://www.diyaudio.com/forums/showt...01#post1079301 ...
http://www.diyaudio.com/forums/showt...06#post1081506 ...

Resources and DIY references:
http://www.national.com/an/AN/AN-1490.pdf &
http://www.diyaudio.com/forums/attac...amp=1165969434
http://www.chip-pcb.cn./ = recent kits & modules
http://www.tech-diy.com/Amplifiers/LM4702_Sanken.htm = very good DIY board
http://www.werple.net.au/~gnb/audio/lm4702.html = indepth w/ pics and suggestions



"Truth is one, paths are many ..." The Dali Lama
  Reply With Quote
Old 14th December 2006, 04:45 PM   #2
AndrewT is online now AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
with just 6V to play with you will be restricted to Lateral Fets. With low Gm you may even run out of drive for these as well.
__________________
regards Andrew T.
  Reply With Quote
Old 14th December 2006, 04:53 PM   #3
diyAudio Member
 
FastEddy's Avatar
 
Join Date: Jun 2006
Location: North Californie
Like these: "Next Generation Hexfet / Lateral MOSFET ..." ( from: http://aussieamplifiers.com/nx150.htm ) ...?

  Reply With Quote
Old 14th December 2006, 06:08 PM   #4
diyAudio Member
 
FastEddy's Avatar
 
Join Date: Jun 2006
Location: North Californie
Default More '4702 DIY references:

Completed group buys and documantation for a very good LM4702 power amp:

Fast GB: LM4702 high power amp test board ;) ... links for group buy of Veteran's '4702 project = looks good! (board layout: http://www.audio.webd.pl/images/lm4702_pcb.gif ) ... power MOSFET drivers ... oh boy!

Partially assembled: http://www.audio.webd.pl/images/lm4780_pcb_5.jpg ... http://www.audio.webd.pl/images/lm4702_pcb.jpg ... http://www.audio.webd.pl/images/lm4702_assemb.jpg ...

" ... I do feel the chip should be on a small heatsink it runs pretty warm. ..." http://www.diyaudio.com/forums/showt...757#post948757

Origins of the National design?: http://www.ampslab.com/c200cfp.htm

Almost complete: http://www.diyaudio.com/forums/showt...514#post950514 ( http://www.audio.webd.pl/images/lm_amp.JPG & http://audio.webd.pl/images/lm4702_amp_test_1.jpg )

Further circuit improvements: http://www.audio.webd.pl/pdf/monster_amp.pdf

Almost there: http://www.diyaudio.com/forums/showt...373#post952373 ... and ... http://www.diyaudio.com/forums/showt...867#post953867

Veteran's Printed Circuit Board Redesign: http://www.diyaudio.com/forums/showt...11#post1030511 ... newer schematic: http://www.unisonus.com/pdf/monster_amp.pdf ( http://www.unisonus.com/projects/lm4702_amp.html ) ... technical results: http://www.diyaudio.com/forums/showt...01#post1058601 = 0.004 THD at >> 70 Watts !! ... good show!

another '4702 DIY builder: http://www.diyaudio.com/forums/showt...00#post1033700 w/ pictures

  Reply With Quote
Old 14th December 2006, 10:12 PM   #5
diyAudio Member
 
Join Date: Apr 2005
Location: In the Wild, Wild West
Read that LM4702 group buy thread by Veteran. I tested his first board and put some info in there about it. Although THD didn't get below 0.005% the stability is very good and the comp caps can probably be reduced for higher slew rate. They were 30pF but may be able to go down to 15pF. It sounds great to me but I am no listening expert so that means little. I am working on a board more like his monster amp schematic, more devices on each side for higher power. I have only use the 1530/201 pair but am going to try the 1058/162 pair also. Biggest contrionutor to THD on the board I tested is the 2nd harmonic. Others are down really low.

For low power I would think the LM4562 with a buffer output stage might be a better ideal. No reason to use at +/-12V when maximum is like +/-75V.

-SL
  Reply With Quote
Old 14th December 2006, 11:36 PM   #6
diyAudio Member
 
FastEddy's Avatar
 
Join Date: Jun 2006
Location: North Californie
" ... No reason to use at +/-12V when maximum is like +/-75V. ..."

Yes, the lower the rail voltage, the poorer specs like THD, etc. My thoughts os this as a headphone amp (only) may be amiss ...
  Reply With Quote
Old 14th December 2006, 11:41 PM   #7
diyAudio Member
 
FastEddy's Avatar
 
Join Date: Jun 2006
Location: North Californie
" ... I am also interested in balanced inputs for "pro audio", better quality connectivity between pre-amps and remotely powered and bi-amped speakers ..."

Anyone have thoughts about this?
  Reply With Quote
Old 16th December 2006, 05:02 PM   #8
diyAudio Member
 
FastEddy's Avatar
 
Join Date: Jun 2006
Location: North Californie
... more ...

http://www.diyaudio.com/forums/showt...43#post1083343

http://www.diyaudio.com/forums/showt...03#post1083403

http://www.diyaudio.com/forums/showt...06#post1083406

  Reply With Quote
Old 17th December 2006, 01:53 AM   #9
diyAudio Member
 
Steve Eddy's Avatar
 
Join Date: Sep 2002
Location: Sacramento, CA
Quote:
Originally posted by FastEddy
" ... I am also interested in balanced inputs for "pro audio", better quality connectivity between pre-amps and remotely powered and bi-amped speakers ..."

Anyone have thoughts about this?
Balanced inputs? One word: Transformers.

se
  Reply With Quote
Old 17th December 2006, 03:20 AM   #10
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
Quote:
Originally posted by AndrewT
Hi,
with just 6V to play with you will be restricted to Lateral Fets. With low Gm you may even run out of drive for these as well.
Transconductance for one Latfet is 1 S.
  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
XDA-1 -- A symmetrical power amp utilizing LM4702 Russ White Chip Amps 35 24th September 2007 09:44 PM
Lm4702 on pure dc power steven344 Chip Amps 1 14th December 2006 02:34 PM
Power supply for LM4702 rtarbell Power Supplies 6 25th June 2006 07:18 PM


New To Site? Need Help?

All times are GMT. The time now is 07:48 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