Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Chip Amps Amplifiers based on integrated circuits

The best sounding audio integrated opamps
The best sounding audio integrated opamps
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 11th November 2013, 08:09 PM   #2111
audioman54 is offline audioman54  United States
diyAudio Member
 
audioman54's Avatar
 
Join Date: Jun 2008
Default LME Answers

Carl,
Unfortunately there are unions for engineers allowed in Silicon Valley...and no engineers over 55!

Mooly,
Talking about and working on audio “Stuff” always cheers me up.

CFT,
Bob Pease was able to hear the difference between the LME49710' and 713's in the sound room at National and was shocked that he could do that at 67 years old. We used identical D/A preamps for the listening tests. (I designed, and hand built, 10 of these as demo units to show off the LME parts and my Avatar is a pic of that preamp. Please check out the attached pic of an AP2 Cascade 192 THD+N plot of that preamp before and after a power supply change Bob Pease suggested. We actually presented that change to my LME base power supply regulator circuits at AES in SF several years ago.)

One unit had all metal can LME Opamps and the other one had all plastic dip LME Opamps. We matched the output levels of both D/A preamps to within 1dB and then sealed up the units and labeled them A and B. I then switched out the externally identical units and Bob listened to them in our sound room at National. (That sound room, which is closed up now, had Wilson Watt Puppies driven by the LME49811 power amps that I designed – See TI/National AP Note AN-1490 which is the LM4702 version of the same demo power amp. The LM4702 was the first part made on the new Vertical High Voltage process that made all the rest of the LME series of parts) Switching out the two identical units in this way resulted in a true double blind test... without having to use those poorly designed double blind switch boxes that always screw up double blind tests because they degrade the sound in the switch box.

When we were done with the listening tests we opened the units up to see if unit A or unit B had the cans or plastic parts the results were…(Insert suspenseful pause here) ..Bob chose the metal cans over the dips every time we did the test! (We did it twice as I recall.) Bob thought the metal can unit "Just Sounded Better" and was shocked that he could hear the difference. That led to some investigations about why...but Bob then had his terrible auto accident going to the wake for another IC industry legend Jim Williams and passed away before we got a chance to finish the tests.

(Analog engineering legend Bob Pease killed in car crash | EDN

Bob thought the reasons for the better sound with the metal cans might have been:

A. The plastic package is constraining to the layers of the chips which could cause problems with mechanical heat stress inside the die layers during thermal events...
B. The shielding of the can... (Only electrostatic though not magnetic which is usually a bigger problem)
C. The slightly larger round legs on the can
D. The thermal dissipation of the can
E. The exposed die mounted on a ceramic substrate inside the metal could handle the thermal transients "better"
F. Insert your guess here

But sadly we never got the chance to check out any of these possibilities together.

I hope some of you are enjoying listening to our LME Opamps! A ton of work (5+years), millions of $’s and some luck (and prayers) went into getting the LME series of parts produced.

Best LME Audio Regards,

Audioman54 / Mark
Attached Images
File Type: jpg D-A FFT Noise Before After Bob Pease Power Supply mod.JPG (49.8 KB, 484 views)
  Reply With Quote
Old 11th November 2013, 08:10 PM   #2112
audioman54 is offline audioman54  United States
diyAudio Member
 
audioman54's Avatar
 
Join Date: Jun 2008
Carl,
Unfortunately there are "NO" unions for engineers allowed in Silicon Valley...and no engineers over 55!
  Reply With Quote
Old 11th November 2013, 08:28 PM   #2113
SY is offline SY  United States
On Hiatus
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
The best sounding audio integrated opamps
Oddly enough, I've been getting recruited left and right, despite also being vintage 1954. Helps to be a scientist instead of an engineer, perhaps. Companies seem to need a grown-up in charge, just to keep the whiz kids focused.

Best of luck, I wish I could do something to help.
__________________
"You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is."
  Reply With Quote
Old 11th November 2013, 08:45 PM   #2114
Carl_Huff is offline Carl_Huff  United States
diyAudio Member
 
Join Date: Dec 2004
Location: Bakersfield, CA
" ... Please check out the attached pic of an AP2 Cascade 192 THD+N plot of that preamp before and after a power supply change Bob Pease suggested. We actually presented that change to my LME base power supply regulator circuits at AES in SF several years ago.) ..."

Mark,

Would this be the LME49600 based power supply that we have chatted about in the past?

Click the image to open in full size.
__________________
Best Regards,
Carl Huff
  Reply With Quote
Old 11th November 2013, 08:45 PM   #2115
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
The best sounding audio integrated opamps
Quote:
Originally Posted by SY View Post
Oddly enough, I've been getting recruited left and right, despite also being vintage 1954. Helps to be a scientist instead of an engineer, perhaps. Companies seem to need a grown-up in charge, just to keep the whiz kids focused.

Best of luck, I wish I could do something to help.
I'm just a few years younger than SY and getting offers of potential employment in audio/consumer electronics regularly - which I've abandoned for the time being for medical electronics. Make sure your linkedin profile is up to date, and good luck.

I have a few of the metal op-amps, still figuring out what to do with them, IIRC there are pair in the I/V converters of my SACD player, otherwise I'm a tube guy at home.
__________________
"To argue with a person who has renounced the use of reason is like administering medicine to the dead." - Thomas Paine
  Reply With Quote
Old 11th November 2013, 10:59 PM   #2116
audioman54 is offline audioman54  United States
diyAudio Member
 
audioman54's Avatar
 
Join Date: Jun 2008
Hi Kevinkr,
I am surprised those are in your SACD player. Which player is it? Which LME opamp did they use? LME49710's or 713's? Are they the metal can HA parts? Also, please ping me if you hear of any audio jobs in the SF/SJ Bay area.

SY,
Are the jobs you are seeing located in the SF Bay Area?

Carl,
That is the published circuit for the power supply in the headphone AP Note for the LME 49720's but my (& Bob's) changes are different...a bit better as reflected the graph of the output of my D/A preamp with all LME parts. To bad AES lost the video of our power supply presentation. I could have posted it for everyone. Bob would have liked that.

Audioman54 / Mark
  Reply With Quote
Old 11th November 2013, 11:09 PM   #2117
SY is offline SY  United States
On Hiatus
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
The best sounding audio integrated opamps
Quote:
Originally Posted by audioman54 View Post

SY,
Are the jobs you are seeing located in the SF Bay Area?
Not so much. Face it, California has done a wonderful job of driving out businesses that actually make things. I left the Bay Area in late 2008 and never looked back. You may have to consider doing the same.
__________________
"You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is."
  Reply With Quote
Old 11th November 2013, 11:13 PM   #2118
Carl_Huff is offline Carl_Huff  United States
diyAudio Member
 
Join Date: Dec 2004
Location: Bakersfield, CA
"... That is the published circuit for the power supply in the headphone AP Note for the LME 49720's but my (& Bob's) changes are different...a bit better as reflected the graph of the output of my D/A preamp with all LME parts. To bad AES lost the video of our power supply presentation. I could have posted it for everyone. Bob would have liked that. "

Can you share the schematic and details?
__________________
Best Regards,
Carl Huff
  Reply With Quote
Old 11th November 2013, 11:37 PM   #2119
audioman54 is offline audioman54  United States
diyAudio Member
 
audioman54's Avatar
 
Join Date: Jun 2008
Hi Carl,

Not quite ready to publish those changes yet...but if anyone can find the video of the AES presentation in SF with Bob and I that we gave together on Sat Oct 4th 2008, that presentation has 95% of the changes in that video. Let the hunt for the video begin!

Was anyone from DIY at that presentation? I thought you were there Carl?

Audioman54 / Mark
  Reply With Quote
Old 11th November 2013, 11:49 PM   #2120
Carl_Huff is offline Carl_Huff  United States
diyAudio Member
 
Join Date: Dec 2004
Location: Bakersfield, CA
" ... I thought you were there Carl?"

Nope, missed that one. I wish that I had been tho.

Mark, I suggest that you drop a line to Jan Didden and publish your power supply and/ or DAC in his Linear Audio magazine.
__________________
Best Regards,
Carl Huff

Last edited by Carl_Huff; 12th November 2013 at 12:02 AM.
  Reply With Quote

Reply


The best sounding audio integrated opampsHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
The Best Sounding DUAL opamps mudihan Chip Amps 372 2nd October 2016 02:14 AM
-: Best audio OpAmps :- audioPT Parts 62 9th April 2013 12:44 PM
best sounding Tx for sub 10watt class A audio amp? mondogenerator Solid State 2 2nd October 2009 06:21 AM
Help the Idiot: Simple, Great-Sounding Integrated Amp Designs SRMcGee Tubes / Valves 7 15th September 2005 07:43 PM


New To Site? Need Help?

All times are GMT. The time now is 05:16 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio
Wiki