LM1875 schematic... - 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 17th December 2004, 04:19 PM   #1
w00t is offline w00t  Singapore
diyAudio Member
 
Join Date: Aug 2003
Location: Singapore
Default LM1875 schematic...

Hi all,

I would like a LM1875 schematic other than that provided in the first page of the datasheet. Have tried Google but only found those related to that in the datasheet.

I need about 20W-30W to drive my KEF Cresta1. Already have a 18-0-18 300VA trannie. Refraining from LM3875 due to past disappointments with it. (Rebuilt 3 times with boutique parts, and it had probs 3 times... P2P wired...)

Thanks!
  Reply With Quote
Old 18th December 2004, 05:15 PM   #2
PauSim is offline PauSim  Portugal
diyAudio Member
 
PauSim's Avatar
 
Join Date: Jan 2004
Location: Portugal
Quasar Electronics sell an LM1875 kit wich use quite different values from what Ive seen here for the NFL resistors. Check the 25 W mono amp. Its very easy to build. Sometime ago I started two of these kits to drive my KEF Cresta 2s with good results. In the end I returned to the "traditional" configuration, which I believe sounds much, much better.

http://www.electronic-kits-and-projects.com

http://www.electronic-kits-and-proje.../3000/3050.pdf
__________________
Paulo
  Reply With Quote
Old 19th December 2004, 08:15 AM   #3
w00t is offline w00t  Singapore
diyAudio Member
 
Join Date: Aug 2003
Location: Singapore
Quote:
Originally posted by PauSim
Quasar Electronics sell an LM1875 kit wich use quite different values from what Ive seen here for the NFL resistors. Check the 25 W mono amp. Its very easy to build. Sometime ago I started two of these kits to drive my KEF Cresta 2s with good results. In the end I returned to the "traditional" configuration, which I believe sounds much, much better.

http://www.electronic-kits-and-projects.com

http://www.electronic-kits-and-proje.../3000/3050.pdf

Hi,

Thanks for the reply. By "traditional" configuration, I suppose it's the one on the first page of the LM1875 datasheet?

Thanks once again!
  Reply With Quote
Old 19th December 2004, 08:39 AM   #4
diyAudio Member
 
Greg Erskine's Avatar
 
Join Date: Jan 2002
Location: Sydney/Australia
Default Re: LM1875 schematic...

Quote:
Originally posted by w00t
Refraining from LM3875 due to past disappointments with it. (Rebuilt 3 times with boutique parts, and it had probs 3 times... P2P wired...)
I can't see an advantage of using a LM1875 when you weren't happy with the LM3875. I have built a few IGCs with LM1875 and LM3875 using exactly the same circuit and components. Very similiar results except the LM1875 wasn't powerful enough for very inefficient speakers.

What problems did you have with the LM3875 that you think the LM1875 will solve?

Anyway, here's a couple of circuits.

http://sound.westhost.com/project72.htm
http://gainclone.com/inv_gainclone_1.gif
__________________
Greg Erskine
  Reply With Quote
Old 19th December 2004, 09:56 AM   #5
diyAudio Member
 
demogorgon's Avatar
 
Join Date: Jul 2004
Location: Behind you.
Send a message via MSN to demogorgon
I think you'd be better off trying the lm3886 instead of a much less powerfull IC. maby even teh lm4780.

as for alternate scematics: there are only so many ways to use a op-amp to amplify a signal...
  Reply With Quote
Old 19th December 2004, 01:42 PM   #6
w00t is offline w00t  Singapore
diyAudio Member
 
Join Date: Aug 2003
Location: Singapore
Default Re: Re: LM1875 schematic...

Quote:
Originally posted by grege


I can't see an advantage of using a LM1875 when you weren't happy with the LM3875. I have built a few IGCs with LM1875 and LM3875 using exactly the same circuit and components. Very similiar results except the LM1875 wasn't powerful enough for very inefficient speakers.

What problems did you have with the LM3875 that you think the LM1875 will solve?

Anyway, here's a couple of circuits.

http://sound.westhost.com/project72.htm
http://gainclone.com/inv_gainclone_1.gif
Hi,

My LM3875 had no problems and were extremely silent (hear a very very soft radio broadcast with ears right next to the speakers), but once I turned on my tube preamp, it started acting funnily and it can't be tamed after that!!

BTW, for the inverted gainclone you have given me, can I use a 1/4W for the 0.22ohm at the output pin? Thanks!

Cheers!

Quote:
Originally posted by demogorgon
I think you'd be better off trying the lm3886 instead of a much less powerfull IC. maby even teh lm4780.

as for alternate scematics: there are only so many ways to use a op-amp to amplify a signal...
Hi,

The LM3886 has much too much pins to handle (2 pins of one rail IIRC). BTW, If I sub a LM3886 in place of a circuit designed for LM3875, would the power output be higher? (Supposing the same rail voltages for both) Thanks!

Cheers!
  Reply With Quote
Old 19th December 2004, 07:43 PM   #7
PauSim is offline PauSim  Portugal
diyAudio Member
 
PauSim's Avatar
 
Join Date: Jan 2004
Location: Portugal
Hi w00t,

<<...By "traditional" configuration, I suppose it's the one on the first page of the LM1875 datasheet?...>>

Yes

Cheers
__________________
Paulo
  Reply With Quote
Old 20th December 2004, 02:56 PM   #8
diyAudio Member
 
richwalters's Avatar
 
Join Date: Sep 2003
Location: Alps:Tube amp designs over 150W, SMPS guru.
Default LM1875

<I would like a LM1875 schematic other than that provided in the first page of the datasheet. Have tried Google but only found those related to that in the datasheet>

Hi there.......I've tampered with the original National circuit to the extent that What's shown in the data sheet is prettywell optimised. I've attempted altering the gain with poor results.
I use this op-amp for headphone apps because it has a nice low S/N ratio and good B/W. Like all these power op amps, it is layout sensitive and best used with a ground plane. I've even put this chip in a console and everyone remarked how brill the sound was without realising it.

rich
  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
LM1875...how low can you go? Gcollier Chip Amps 7 6th May 2010 03:43 AM
LM1875 based on the LM1876 datasheet schematic?? w00t Chip Amps 2 14th March 2005 08:23 PM
the best PCB design and schematic for the LM1875? lutherblisset Chip Amps 0 29th October 2004 01:40 PM
Lm1875 soundNERD Chip Amps 14 12th October 2003 02:26 AM


New To Site? Need Help?

All times are GMT. The time now is 10:17 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