Schematic for LM3875 wanted fast, as soon as possible - Page 3 - 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 31st October 2005, 03:33 AM   #21
Jay is offline Jay  Indonesia
diyAudio Member
 
Join Date: Feb 2003
Location: Jakarta
Carlos, prepare yourself to be dissapointed. I found that LM3875 chip quality is not consistent. I guess fake chips are everywhere, especially for the plastic one. But 3886 is consistently good. Now I stop burning my 3886 and 3876. The bad sounding 3875 have taken over the job
  Reply With Quote
Old 31st October 2005, 04:58 AM   #22
diyAudio Member
 
Greg Erskine's Avatar
 
Join Date: Jan 2002
Location: Sydney/Australia
Carlos and Jay,

I can "guarantee" that Carlos's chipamp will sound good, it's just a matter of how "good" compared to his other amps. The LM3875s came from straight from National Semiconductor (or BrianGT) and all the other LM3875 I have used from these batches worked well.

regards
__________________
Greg Erskine
  Reply With Quote
Old 31st October 2005, 06:20 AM   #23
Nordic is offline Nordic  South Africa
diyAudio Member
 
Nordic's Avatar
 
Join Date: Sep 2005
I think a good habit to get into, is to actualy check places like the National Semiconductor site, to see who their distributor in your area is, and then use it. Then you get the real thing from them directly.

In fact, I find it easier now, to order samples directly from these dealers than from National itself. (at least faster, and free)

Destroyer, we would love to hear what you think about the chipamp, I know you will probably be embabrased to admit haveing built one infront of your solid state friends... lol, but you do have a very valued opinion on this site.

Don't need to give us an audiomagazine review, just a simple "I liked it", or" no, I like something else better..."

Cheers
  Reply With Quote
Old 31st October 2005, 08:19 PM   #24
diyAudio Member
 
enzedone's Avatar
 
Join Date: Nov 2004
Location: New Zealand
Angry R1,R2

Hmmmmm, I've just cut my 22k resistor that I put in, as I thought it was in the wrong place. I was following the page three diagram,(but wired it incorrectly, or so I thought). I am making a P2P LM3875. So I take it that the 220R is in front of the 22K then?...........Oh well better to this correct now. Thanks for bringing this up.
__________________
I realized that a major part of my job was to figure out how to use technology control to create economic force, or leverage, such that money and business flowed in Microsoft's direction” — Alex St.John, father of DirectX.
  Reply With Quote
Old 31st October 2005, 08:24 PM   #25
diyAudio Member
 
enzedone's Avatar
 
Join Date: Nov 2004
Location: New Zealand
Default Carlos

Carlos you are on fire, mate. You pump through amps like your life depended upon it.....
It's a struggle for me to get my second one done
Keep up the the good work....you are a machine.....hehe

Brett

__________________
I realized that a major part of my job was to figure out how to use technology control to create economic force, or leverage, such that money and business flowed in Microsoft's direction” — Alex St.John, father of DirectX.
  Reply With Quote
Old 9th November 2005, 06:08 AM   #26
diyAudio Member
 
destroyer X's Avatar
 
Join Date: Feb 2004
Location: Recife - Brasil Northeast
Default I constructed the pretty red board, Brian i think is the one that produces

The wonderfull board....but i found 680 ohms from Pin 8 to ground!

As i am completely neurotic related those things that have not the value....R1, R2 and R3....this turns me so pixel, that i start to dislike deeply the circuit.....my own neurotical, Psichotical, Esquizofrenic problem...i hate those complications....that you have to find a paper to discover what is R1 value...and them to fix in the R1 place that is marked in the board!!!

Why not to put the value directly printed in the board?..... well.... each crazy one with their own crazy things!

So, i found a resistor from Pin 8 to ground..... this is not so nice!..... and may be my problem related those R1, R2, R3....grrrrrrrr!...i hate those things...why complicate so simple things!

And my sound was alike battery radio..... where is the bass?.... i had to increase 20 decibels to perceive the bass....sub bass was impossible to listen.

This way i search the National aplications and i perceive that they cutted the bass because of the case size....impossible to dissipate continuous 50 watts of power... so i understood why the small condenser into the feedback line, the inverted input, that is the same as the second differential transistor in a standard discrete amplifier.

Well....i changed values, as i was having 2 watts when the amplifier was reproducing 15 hertz!!!

Now i have 25 watts in this frequency...and will increase the 1000uf condenser to have a completely flat amplifier from 5 hertz to 20 Kilohertz.

Negative!,the amplifier is not bassy now, it is flat!....having bass entering, it reproduces, without increase nothing or decrease the treble...it is nice,but cannot face some discrete!...sorry!...no chance!

Now, the Chip is sounding alike a big amplifier...do not know if will survive, as National made that not for mistake....hehe....they are avoiding that we send the unit to space!

Try if you want guys...i do not recomend, in the reality, my modifications are a foolish, but the sound result is not!

Now amplifier is flat!...the chip is LM3875, with metal case, with negative voltage there!

It is early in the morning, i cannot play too much loud, it may appear problems related the maximum current protection, and this i will check tomorrow!....but sounding as a battery radio, with that damn mid ranges and trebles only, is too much for my ears!...aaaaagh!

regards,

Carlos
Attached Images
File Type: jpg full bandwidth.jpg (47.3 KB, 390 views)
__________________
These words sounds alike English..but they are not.. these are words without meaning, just sounds made by humans; https://www.youtube.com/watch?v=_X_7iMHugXM
  Reply With Quote
Old 9th November 2005, 01:15 PM   #27
Banned
 
Join Date: Mar 2003
Location: Lisbon, Portugal
Carlos, that low capacitance (1,000uf) is ridiculous, it doesn't work with most speakers.
Contact me, i'll send you a PSU schematic that will turn that amp into a real thing.
  Reply With Quote
Old 9th November 2005, 01:32 PM   #28
diyAudio Member
 
destroyer X's Avatar
 
Join Date: Feb 2004
Location: Recife - Brasil Northeast
Default Let it be...ridiculous...with a Jaca fruit and a Watermellow around the neck

With monokini....and dancing shaking the hum.

ahahahaha.... be happy man...it is sounding in those ridiculous speaker in my ridiculous house playing ridiculous musics in a ridiculous volume.

I am watching 1 cicle per second moving my speaker...ridiculous movement that is turning me ridiculously happy!

All right my..........friend!


ahahahahhaa!


Carlos
__________________
These words sounds alike English..but they are not.. these are words without meaning, just sounds made by humans; https://www.youtube.com/watch?v=_X_7iMHugXM
  Reply With Quote
Old 9th November 2005, 02:42 PM   #29
Banned
 
Join Date: Mar 2003
Location: Lisbon, Portugal
Carlos, 1,000~1500uf is a trend introduced by the original 25W Gaincard, and the typical 'gainclone' is a copy of that.
What I meant is that this capacitance is anywhere near enough to move most speakers, and then the amp sounds bad.
I was referring to the ridiculous capacitance (1,000uf), nothing more.
  Reply With Quote
Old 9th November 2005, 02:59 PM   #30
diyAudio Member
 
Ouroboros's Avatar
 
Join Date: Dec 2003
Location: Nottingham UK
But Carlos's circuit schematic shows 4700uF, so where's the 1000uF coming from?
  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
Wanted Mordaunt-short MSW20 Schematic Wanted simon dart Subwoofers 0 22nd May 2009 08:19 AM
Wanted Lm3875 Nuuk Swap Meet 2 5th March 2009 08:02 PM
Wanted Lm3875 Kit BigBill6778 Swap Meet 5 4th February 2009 03:01 AM
I would like to have LM3875 bridged, do you have schematic? destroyer X Chip Amps 7 15th September 2006 07:24 AM
Non-Buffered Non-Inverted Gainclone (LM3875) fpr 47K Pot Circuit Wanted krishu Chip Amps 42 5th January 2004 12:14 PM


New To Site? Need Help?

All times are GMT. The time now is 11:30 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