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

Headphone Systems Everything to do with Headphones

Please technically explain this audible mod
Please technically explain this audible mod
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 July 2017, 05:34 AM   #21
rjm is offline rjm  Japan
Richard Murdey
diyAudio Member
 
rjm's Avatar
 
Join Date: May 2004
Location: Kyoto
Please technically explain this audible mod
Quote:
Originally Posted by Osvaldo de Banfield View Post
Without global NFB, the thermal inaccuracies or runaway of the output stage is uncompensated, and very risky for the earphones live.
The degeneration from the big 10 ohm emitter resistors takes care of that.
__________________
RJM Audio website|blog
  Reply With Quote
Old 14th July 2017, 09:18 AM   #22
voltwide is offline voltwide  Ireland
diyAudio Member
 
Join Date: Jan 2010
And to my knowledge there is no way to control thermal runaway using global feedback
  Reply With Quote
Old 14th July 2017, 12:10 PM   #23
elmura is offline elmura  Australia
diyAudio Member
 
Join Date: Aug 2012
Here's an interesting question:

If I were to bypass the whole opamp stage, ie. run a short from the 10k R13 /C105 low pass filter direct to the other side of R23/R24 to so that only the diamond buffer is active (or if necessary, desolder the necessary bits), would the input impedance be sufficient (10K + BC550 / BC560) considering I'll use most of the attenuator range.

Any problem with this? I don't need gain.
  Reply With Quote
Old 14th July 2017, 12:21 PM   #24
Osvaldo de Banfield is offline Osvaldo de Banfield  Argentina
diyAudio Member
 
Osvaldo de Banfield's Avatar
 
Join Date: Dec 2011
Location: Barrio Garay,Almirante Brown, Buenos Aires, Argentina
Quote:
Originally Posted by rjm View Post
The degeneration from the big 10 ohm emitter resistors takes care of that.
I don't agree. If outputs goes, for example, 10V positive or negative, there is nothing that can counteract this deviation, but can damage earphone“s moving coils.
__________________
Osvaldo F. Zappacosta. Electronic Engineer UTN FRA from 2001.
Argentine Ham Radio LW1DSE since 1987.
  Reply With Quote
Old 14th July 2017, 12:27 PM   #25
mfratus is offline mfratus  United States
diyAudio Member
 
Join Date: Sep 2005
No. The op amp is the driver in this circuit. All this guessing around is futile. What is your goal?

You bought a not-very-good-sounding headphone amp, and you want to gut it out because you don't want to learn anything about design work. It certainly is not done by hacking and cutting.

Read what designers are writing about headphone amp circuits, or buy one that sounds good already.
  Reply With Quote
Old 14th July 2017, 12:59 PM   #26
Osvaldo de Banfield is offline Osvaldo de Banfield  Argentina
diyAudio Member
 
Osvaldo de Banfield's Avatar
 
Join Date: Dec 2011
Location: Barrio Garay,Almirante Brown, Buenos Aires, Argentina
Quote:
Originally Posted by mfratus View Post
It certainly is not done by hacking and cutting.
Unless he is a rich man and can buy dozens of earphones, and when one of them gets burned, simply discard the item and start from zero with another new. Not very "engineering techniques".
__________________
Osvaldo F. Zappacosta. Electronic Engineer UTN FRA from 2001.
Argentine Ham Radio LW1DSE since 1987.
  Reply With Quote
Old 14th July 2017, 01:48 PM   #27
mfratus is offline mfratus  United States
diyAudio Member
 
Join Date: Sep 2005
If you are rich, get a new one. If you are not, then learn something about the technology and improve it. Learning is free, and with the Internet, there is no reasonable limit to learning. But just to cut stuff out of the circuit, rather than studying the problem, is foolish. Has he even read the datasheet of ANY op amp before? It is one of the most foundational parts there is, and this is a fairly standard FET-input op amp. You don't need a college degree, just the interest to learn. It is not a great circuit, but it can be made much better through understanding WHY it is a bad circuit, and WHY it does not sound good.
  Reply With Quote
Old 14th July 2017, 02:04 PM   #28
Osvaldo de Banfield is offline Osvaldo de Banfield  Argentina
diyAudio Member
 
Osvaldo de Banfield's Avatar
 
Join Date: Dec 2011
Location: Barrio Garay,Almirante Brown, Buenos Aires, Argentina
+1.
__________________
Osvaldo F. Zappacosta. Electronic Engineer UTN FRA from 2001.
Argentine Ham Radio LW1DSE since 1987.
  Reply With Quote
Old 14th July 2017, 09:23 PM   #29
elmura is offline elmura  Australia
diyAudio Member
 
Join Date: Aug 2012
Quote:
Originally Posted by mfratus View Post
If you are rich, get a new one. If you are not, then learn something about the technology and improve it. Learning is free, and with the Internet, there is no reasonable limit to learning. But just to cut stuff out of the circuit, rather than studying the problem, is foolish. Has he even read the datasheet of ANY op amp before? It is one of the most foundational parts there is, and this is a fairly standard FET-input op amp. You don't need a college degree, just the interest to learn. It is not a great circuit, but it can be made much better through understanding WHY it is a bad circuit, and WHY it does not sound good.
Is this DIYAudio? A place where hobbyists & curious go to ask questions, discuss ideas, discuss audio circuits? Mostly for the intent on IMPROVING sound?

If I were to "buy one that sounds good already" how does that help me learn? How does that help me figure how to make this one better?
Am I asking questions to learn & understand?
Define learning! Is it reading hundreds of pages on a thread to try make sense of one particular circuit?

Nobody put a gun to your head and told you to respond to my thread. There's no need to be condescending.
I have read several op amp data sheets including this one's. They don't answer my questions:
1. Does connecting input grounds immediately affect soundstage depth through cross talk?
2. Can the buffer stand alone in the circuit?
3. Why does it sound the way it does?

Sent from my LG-D855 using Tapatalk
  Reply With Quote
Old 14th July 2017, 09:26 PM   #30
JensH is offline JensH  Denmark
diyAudio Member
 
Join Date: Jul 2009
Please technically explain this audible mod
You have not shown your measurement results. When trying to optimize a design it is important to know what the starting point is. E.g. the noise, is it white noise or is is power supply related hum? The "cure" will depend on whether you are trying to solve one or the other, or both.
You haven't described the type and level of distortion either. So it is difficult to know exactly what to optimize.

Anyway, if it was my amplifier and I wanted to improve it, this is what I would do (others may have other ideas about this of course):

1. I would make a global feedback from the output instead of the op-amp output. Nonlinearities and offset in the output stages would be practically eliminated. It is important to check if this leads to instability (which could be caused by the phase shift of the output stage). If it does, it can probably be solved by small capacitors across the feedback resistors. Or perhaps capacitors from the op-amp output to the inverting inputs.

2. I would reduce the size of R13 and R14 to reduce distortion and noise.

3. I might replace the op-amp with an OPA1642. The OPA2134 does have a relatively high level of distortion with large input resistors. Even if R13 and R14 are reduced in size, there is still the potentiometer, which will have a relatively high resistance, seen from the op-amp, at least at some settings. Since it is a DIL op-amp it would probably be practical to put in a socket if you remove the original op-amp. The bandwidth of the OPA2134 is not extremely high, so I think it would be safe to use a socket.
See this for more information about the distortion from OPA2134 and OPA1642:
http://www.diyaudio.com/forums/vendo...ml#post4636374

4. If hum is an issue, I would look at way the ground is routed.
  Reply With Quote

Reply


Please technically explain this audible modHide 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
Technically Accurate Speakers: Suggestions? Philosophil Multi-Way 57 26th April 2016 12:34 PM
Best pa subwoofer. (Technically) H Burch PA Systems 42 10th October 2013 12:03 PM
One for the technically minded... norman093 PA Systems 14 17th May 2012 05:04 AM
Not DIY Audio ...technically anyway, but..... quasi The Lounge 1 7th July 2007 10:54 PM
What is 'audible'? steve Everything Else 3 13th September 2004 10:56 PM


New To Site? Need Help?

All times are GMT. The time now is 02:32 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki