Lowest noise and distortion Chip - 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 June 2006, 12:44 PM   #1
diyAudio Member
 
Join Date: Jun 2006
Default Lowest noise and distortion Chip

Hi,

I need a chip with the lowest possible distortion and noise for an amplifier for measurements. I figured this would be the place to ask... Any suggestions?

It must be capable of delivering at least 10 watt into a load of 8 ohms.
The gain should be easily configured in the range from 20 to 30 dB.

Best regards
- Anders
  Reply With Quote
Old 14th June 2006, 07:13 PM   #2
diyAudio Member
 
DJ Exprice's Avatar
 
Join Date: Mar 2006
Location: San Francisco, California
Send a message via AIM to DJ Exprice Send a message via MSN to DJ Exprice
LM3886 is nice but I don't know what other people say...but it would probably for really well for you.
  Reply With Quote
Old 15th June 2006, 02:08 AM   #3
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
if you only need 10W the LM3886 is a very good choice in the inverting mode --- the LM4780 is a pair of LM3886 dies in one package and here's what it can do:
Click the image to open in full size.
  Reply With Quote
Old 15th June 2006, 03:19 AM   #4
diyAudio Member
 
DJ Exprice's Avatar
 
Join Date: Mar 2006
Location: San Francisco, California
Send a message via AIM to DJ Exprice Send a message via MSN to DJ Exprice
Non-inverting works too. If you're using the amp for very Hi-Fi sound, isn't the non-inverting amp better?
  Reply With Quote
Old 16th June 2006, 06:38 AM   #5
sangram is offline sangram  India
diyAudio Member
 
Join Date: Sep 2002
Location: India
Actually the 3875 has the lowest THD, noise and IMD among the entire range of National's chips (or is it the 1875?).

Also National specifies that inverting configuration may result in better THD+N.

However the input impedance drops in inverting mode so a preamp or buffer is needed, or a capable source.

Gain configuration is simple if the feedback loop consists of a fixed resistor + a variable resistor, with the variable providing a 10dB adjustment. Most of these chips should be able to handle this gain range just fine.

Or if you have a buffer you can set up the buffer for a 0-10dB gain and the chipamp for a fixed 20dB gain.
  Reply With Quote
Old 16th June 2006, 08:22 AM   #6
diyAudio Member
 
Join Date: Apr 2006
Location: Goulburn NSW
I think it is the 1875 that has the lowest figures, but it is a close contest from memory of looking at all the stats with the 2886 chip, I have a pair but I haven't done anything with them.

They will all produce 10 watts easily enough. Bridged chips and NAT Semi have a few including 3 channel versions (though they are not stellar performers) will give the lowest figures but they will not change crossover distortion fugures, but I guess for your implementation this is not an issue anyway.
  Reply With Quote
Old 16th June 2006, 09:18 AM   #7
Bazukaz is offline Bazukaz  Lithuania
diyAudio Member
 
Bazukaz's Avatar
 
Join Date: Nov 2005
Location: Vilnius
Send a message via Skype™ to Bazukaz
Quote:
Originally posted by sangram
Actually the 3875 has the lowest THD, noise and IMD among the entire range of National's chips (or is it the 1875?).
Here are some comparisons of THD+N from national's site. However , if you think about measuring loadspeaker's THD and other parameters , i don't think that amplifier will have much influence.While distortion of these amps is less than 0.1% , THD of loadspeakers may be a few percent.

Regards,
Lukas.
Attached Images
File Type: png untitled.png (64.4 KB, 316 views)
  Reply With Quote
Old 16th June 2006, 10:05 AM   #8
MikeB is offline MikeB  Germany
diyAudio Member
 
MikeB's Avatar
 
Join Date: Apr 2004
Location: GŁtersloh
Quote:
Originally posted by Bazukaz
While distortion of these amps is less than 0.1% , THD of loadspeakers may be a few percent.
I think that's a fairy tale... I did measurings with my speakers (not highend,but diy,visaton,2 x w170s8,1 x g20sc) see attachment.
The spikes are caused by room acoustics, blue is 2nd harmonic and red is 3rd harmonic. Crossover is at 2.5khz, the tweeter has <0.1% 3rd harmonic. Microphones are also distorting, so you see the product of soundcard/amplifier/speaker/microphone/soundcard.
Also, speakers are unlikely to create high order distortions if not defect.
The 3rd harmonics stop at 8khz in this measuring because of limited samplerate of soundcard.

I don't know where this myth originated that speakers have several % of thd...

Mike
Attached Images
File Type: gif speaker_thd.gif (18.9 KB, 302 views)
  Reply With Quote
Old 16th June 2006, 10:45 AM   #9
diyAudio Member
 
Join Date: Jun 2006
Thanks for the suggestions.

From looking at the figures achieved by jackinnj it looks as if the LM5780 is outperforming the other chips you suggest - that is the LM1875 and the LM3875.

In the 1875-datasheet it is said that:
"THD levels at 20 kHz with 10W output to an 8Ŕ load should be less than 0.05%, and less than 0.02% at 1 kHz."

Comparing with jackinnj curves at 1 kHz the THD+Noise for the finished amp is below 0.003%. Almost a factor 10 better. At 20 kHz the THD+Noise is below 0.02% - thats 2,5 times better for the LM4780.

Any comment on this? Can it be due to the inverting design?
  Reply With Quote
Old 16th June 2006, 11:11 AM   #10
Bazukaz is offline Bazukaz  Lithuania
diyAudio Member
 
Bazukaz's Avatar
 
Join Date: Nov 2005
Location: Vilnius
Send a message via Skype™ to Bazukaz
Quote:
Originally posted by MikeB


I think that's a fairy tale... I did measurings with my speakers (not highend,but diy,visaton,2 x w170s8,1 x g20sc) see attachment.
The spikes are caused by room acoustics, blue is 2nd harmonic and red is 3rd harmonic. Crossover is at 2.5khz, the tweeter has <0.1% 3rd harmonic. Microphones are also distorting, so you see the product of soundcard/amplifier/speaker/microphone/soundcard.
Also, speakers are unlikely to create high order distortions if not defect.
The 3rd harmonics stop at 8khz in this measuring because of limited samplerate of soundcard.

I don't know where this myth originated that speakers have several % of thd...

Mike
Hi,
At what output power did you measure THD ? Did you measure IMD ?

Regards,
Lukas.
  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
Which is the lowest noise FET? Young Solid State 10 11th February 2006 04:20 AM
which is lowest noise bipolar? bane_982 Parts 1 4th March 2005 11:45 AM
Lowest noise levels difi Chip Amps 3 3rd March 2004 10:42 PM
What are the lowest distortion cone drivers available? JZatopa Multi-Way 7 7th September 2003 01:10 PM


New To Site? Need Help?

All times are GMT. The time now is 02:07 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