Lme49600 headphone amp - 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 19th May 2010, 04:35 AM   #21
diyAudio Member
 
benchtester's Avatar
 
Join Date: Apr 2007
Location: Oakland, Calif.
Quote:
Originally Posted by theAnonymous1 View Post
Hmmm, I'm curious now to know how much, if any, oscillation is taking place with my board.

Anyone here interested in putting in under their scope? You can keep it when your done.

jcx?
What an offer. I'll test it for oscillation if you like (and it is still available). I'll send you a PM with my address.
  Reply With Quote
Old 19th May 2010, 04:41 AM   #22
T in AZ is offline T in AZ  United States
diyAudio Member
 
Join Date: Jul 2009
Quote:
Originally Posted by theAnonymous1 View Post
Hmmm, I'm curious now to know how much, if any, oscillation is taking place with my board.
jcx?
I was wondering if you tied the BW pin to V- or let it float?
  Reply With Quote
Old 19th May 2010, 06:44 AM   #23
diyAudio Member
 
Join Date: Jun 2004
Location: the Netherlands
Quote:
Originally Posted by T in AZ View Post
I was wondering if you tied the BW pin to V- or let it float?
Dear,

I would not let if float. With tying the BW pin to V- you put the buffer in Class A, a feature u don't want to skip. Besides, even if you limit the bandwidth of the buffer, the driver still has a high open-loop bandwidth. Even though you don't find oscillations, the total bandwidth for audio is way to high, So I would use at least a 47p from driver output to negative input as indicated in my schematic anyway. Even with 100p you still have a band-with till over 200Khz.

With kind regards,
Bas
  Reply With Quote
Old 19th May 2010, 07:06 AM   #24
T in AZ is offline T in AZ  United States
diyAudio Member
 
Join Date: Jul 2009
Thanks, I'll be putting a few of these together.
  Reply With Quote
Old 19th May 2010, 08:28 AM   #25
diyAudio Member
 
theAnonymous1's Avatar
 
Join Date: Feb 2004
Location: Anonymityville
Quote:
Originally Posted by benchtester View Post
What an offer. I'll test it for oscillation if you like (and it is still available). I'll send you a PM with my address.
PM received.

If you could possibly get some scope shots of the output and post them here that would be great.

Like I mentioned, the board works perfectly and sounds great. I'm just curious now to see if there is any nasty stuff going on that, if there is, I can obviously live with.

The 47pf cap suggested by Sebastian is probably a good idea anyway and something I will include if I build another board.

Quote:
Originally Posted by T in AZ View Post
I was wondering if you tied the BW pin to V- or let it float?
It's tied to V- just like the schematic.
  Reply With Quote
Old 19th May 2010, 08:41 AM   #26
diyAudio Member
 
benchtester's Avatar
 
Join Date: Apr 2007
Location: Oakland, Calif.
Quote:
Originally Posted by theAnonymous1 View Post
PM received.

If you could possibly get some scope shots of the output and post them here that would be great.
No problem. They will be genuine scope shots, i.e. digital photos of the phosphorous screen.

I've been playing with speakers for the last couple of years; but about 10 years ago I took the moniker "benchtester" when I was designing high bandwidth power amps. I get a kick out of seeing how fast I can tune an amp before oscillations become a problem (fail to decay).
  Reply With Quote
Old 19th May 2010, 09:07 AM   #27
diyAudio Member
 
Join Date: Jun 2004
Location: the Netherlands
Quote:
Originally Posted by benchtester View Post
No problem. They will be genuine scope shots, i.e. digital photos of the phosphorous screen.

I've been playing with speakers for the last couple of years; but about 10 years ago I took the moniker "benchtester" when I was designing high bandwidth power amps. I get a kick out of seeing how fast I can tune an amp before oscillations become a problem (fail to decay).
How many flames and smoke you went through?
  Reply With Quote
Old 19th May 2010, 10:05 AM   #28
diyAudio Member
 
benchtester's Avatar
 
Join Date: Apr 2007
Location: Oakland, Calif.
Quote:
Originally Posted by Sebastiaan View Post
How many flames and smoke you went through?
Not a lot. The secret is to start with high impedance loads ~100 ohms, then low impedance but low input, and finally full power after you are confident in the circuit.

I only remember two war stories: first was when a carbon resistor flamed due to oscillations. It looked just like a burning match inside my amp. I threw out every carbon resistor in my inventory after that, and I only use flameproof metal film resistors now. BTW my local DIY event is called "Burning Amp"; I qualify .

Second was not an oscillation issue. I moved a power op amp (PA05) circuit board with power on it and apparently shorted something. It fried a $300 multichip module. No way around it: that hurt!
  Reply With Quote
Old 13th June 2010, 01:45 AM   #29
diyAudio Member
 
benchtester's Avatar
 
Join Date: Apr 2007
Location: Oakland, Calif.
Quote:
Originally Posted by theAnonymous1 View Post
PM received.

If you could possibly get some scope shots of the output and post them here that would be great.
Sickness and work have been getting in the way, but I did complete one simple test which looks pretty good.

The lower trace is a 1 MHz square wave in (~.5 volts in p-p) and the upper trace is the output (~1.5 volts out p-p) without any load besides the oscilloscope.

One can see some ringing at 10 MHz, but it decays nicely. I think this circuit is pretty good just the way it is. I will try to follow-up with more tests such as capacitive loading, but it may be a week or two before I get some more hobby time.
Attached Images
File Type: jpg 06-11-10_1648.jpg (284.0 KB, 660 views)
  Reply With Quote
Old 13th June 2010, 03:36 AM   #30
diyAudio Member
 
Join Date: Apr 2009
Thank you! It is very encouraging to have your comments. I am thinking of adding capacitor at input. Any suggestions? Thanks again!
  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
What's the difference Between LME49600 and LME49610? bashenan4455 Chip Amps 4 20th September 2011 05:30 AM
WTB: LME49600 preamp-board from ebay Nisbeth Swap Meet 5 6th April 2010 04:46 PM
Compound OpAmp w LME49600 jackinnj Parts 1 25th February 2010 06:36 PM
What's the difference Between LME49600 and LME49610? bashenan4455 Chip Amps 3 14th February 2010 01:22 PM
LME49600/LME49740 Headphome Amp theAnonymous1 Solid State 28 31st January 2010 04:25 AM


New To Site? Need Help?

All times are GMT. The time now is 09:27 PM.


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