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

Everything Else Anything related to audio / video / electronics etc) BUT remember- we have many new forums where your thread may now fit! .... Parts, Equipment & Tools, Construction Tips, Software Tools......

What is wrong with op-amps?
What is wrong with op-amps?
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 29th June 2010, 09:59 AM   #11
jacco vermeulen is offline jacco vermeulen  Netherlands
diyAudio Member
 
jacco vermeulen's Avatar
 
Join Date: Oct 2004
Location: At the sea front, Rotterdam or Curaçao
Send a message via Yahoo to jacco vermeulen
Plenty of (used) Ferrari owners who traded in for a Fiat, exact same knobs.
  Reply With Quote
Old 29th June 2010, 10:34 AM   #12
wahab is offline wahab  Algeria
diyAudio Member
 
Join Date: Nov 2009
Location: algeria/france
What is wrong is that some people think that their
ears are accurate enough to measure -100db THD ratios
as soon as an op amp is involved in the sound chain..

Yet, a tube amp that produce 2% of THD will sound
distorsionless for the same pundits..
  Reply With Quote
Old 29th June 2010, 10:46 AM   #13
tiefbassuebertr is offline tiefbassuebertr  Germany
diyAudio Member
 
tiefbassuebertr's Avatar
 
Join Date: Jul 2005
Location: D-55629 Schwarzerden
Quote:
Originally Posted by wahab View Post
What is wrong is that some people think that their
ears are accurate enough to measure -100db THD ratios
as soon as an op amp is involved in the sound chain..
Yet, a tube amp that produce 2% of THD will sound
distorsionless for the same pundits..
Yes, and this is still again to observe in a hifi shop by demonstrations of commercial preamp devices, if classic and acoustical/vocal jazz CD's/records was used. But what is the actually reason therefore?
  Reply With Quote
Old 29th June 2010, 10:51 AM   #14
jan.didden is offline jan.didden  Europe
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Westende Resort, BE coast
Quote:
Originally Posted by tiefbassuebertr View Post
Yes, and this is still again to observe in a hifi shop by demonstrations of commercial preamp devices, if classic and acoustical/vocal jazz CD's/records was used. But what is the actually reason therefore?
The reason I don't know, but the cause is in the way perception works.

jd
__________________
Cable: a potential source of trouble interconnecting two other potential sources of trouble - Erik Margan
Linear Audio pubs and articles . The SilentSwitcher now at diyaudio store SilentSwitcher. Keeping in touch with SY.
  Reply With Quote
Old 29th June 2010, 11:03 AM   #15
wahab is offline wahab  Algeria
diyAudio Member
 
Join Date: Nov 2009
Location: algeria/france
Quote:
Originally Posted by tiefbassuebertr View Post
Yes, and this is still again to observe in a hifi shop by demonstrations of commercial preamp devices, if classic and acoustical/vocal jazz CD's/records was used. But what is the actually reason therefore?
Hi , Tief

As musician , i obseved 20 years ago that using what
was called an Aural Exciter changed a cold digital sound
in something that sounded warm and live , since
the principle of this accessory is to add EVEN harmonics
to the original sound.
A tube amp has almost the same effect, so when one
listen to a transistorized clean sound, he seems to him
that something that was there with a tube audio chain
is suddenly missing.
Of course, adding a tone control to a solid state amp
will not produce the same effect, since the tone control
increase both originals even and odd harmonics.
This, with the fact that a tube amp has a low damping factor,
modifying even more the original sound , is the reason why
some see a superiority of the tube things over the SS siblings !!

That it to say, they prefer an enhanced sound , yet, they
call those wave shapers "Hi fi" items !!...

cheers,

Wahab
  Reply With Quote
Old 29th June 2010, 11:16 AM   #16
jean-paul is offline jean-paul  Netherlands
diyAudio Moderator Emeritus
 
jean-paul's Avatar
 
Join Date: Sep 2002
Location: Germany
Quote:
Originally Posted by tiefbassuebertr View Post
Each OP-Amp type has it's own THD/IM spectrum, strongly independend from the layout and load conditions so as the quality of power supply (mostly the badest solution with 7815/7915 or LM317/337 in use and hence the bad reputation by some music lover's)
For you an good solution could be this discrete and very easy topology:
BF862 Preamp
If you want also deal with various OP-Amps for the aim of compare, prefer the types AD797, OPA604, OPA134, NE5534 oder LME49710. Avoid in all cases dual or quad OP-Amps (no perfect ground management possible) and use for each op-amp a complete independend power supply and independend power supply transformer. This means for a line stage two power supplies and if there is RIAA head amp integrated, six power supplies.
A good power supply solution is that one from the RIAA head amp NAD model PP-2, schema to find anywhere here on the forum.



I agree, especially if there are high parasitic capacitances by large and long signal leads to the power amp. The AD797 and the NE5534 are op amps with highest idle current in the normal DIP-8/SO-8 outline - as I know.
This is also the way I see it except that I would like to add OPA627 and LME49860 (a dual opamp) to the list of good devices. Since most of the commercial gear uses dual opamps the single versions are useless unless one wants to use pink cat adapter PCB's etc. which can make things worse.

As usual a non-technical opinion from me: in all cases where I replaced already tweaked opamp circuits (with even very good types) for an open loop discrete design with all its disadvantages it still sounded better. And no I did not listen to added distortion. The standard disadvantages with discrete circuits are :high offset/drift, channel differences etc. in a way larger magnitude than with opamps.

My experiences are with I/V converters in DACs and preamps. But it often is poor implementation of the opamps in question that defines the results. Proper decoupling the power supply lines is such an example where things go wrong.

Opamps are quite easy to work with when you know their limitations but a simple discrete circuit often sounds better but only so after a lot more work.

Despite all excellent explanations from true experts I simplified matters by avoiding designs around opamps as I think the feedback is what causes the disadvantages.

Yeah, "I think" is not the best of reasoning. And I too leave opamp circuits sometimes as they are and replace the devices for better types and decouple them as it is far less work than redesigning. The point is to think carefully especially with high speed high bandwidth opamps. An input filter around 100 khz can be a good remedy when it picks up high frequency signals.

BTW the original power supply of NAD PP-2 is an example of how not to do it !!
__________________
It's only audio. Member of the non modular PCB design committee

Last edited by jean-paul; 29th June 2010 at 11:40 AM.
  Reply With Quote
Old 29th June 2010, 11:18 AM   #17
analog_sa is offline analog_sa  Europe
diyAudio Member
 
analog_sa's Avatar
 
Join Date: Aug 2002
Location: Cascais
What is wrong with op-amps?
Quote:
Originally Posted by wahab View Post
Yet, a tube amp that produce 2% of THD will sound
distorsionless for the same pundits..

I would never defend or use any type of amplification with thd above 0.1%. If for no other reason, then at least because it's so easy to achieve.

Otoh, if 2% sounds distorlionless to someone it may simply mean they are not sensitive to what is quite likely a dominant 2nd harmonic. Is steady state thd, unless totally gross, at all relevant to music?
  Reply With Quote
Old 29th June 2010, 11:49 AM   #18
kstagger is offline kstagger  United States
diyAudio Member
 
kstagger's Avatar
 
Join Date: Dec 2003
Location: Grand Rapids
I've come from the 'tube' only camp and after years of that, recently got into solid-state (thank you Mr. Pass). Just last week I finished building an Audio Sector Phono Stage using OPA627 op-amps. Honestly, it is the most revealing, quiet and cleanest phono preamps I've ever heard. It has certainly changed my mind about op-amps! Like any other active device, if they are done right then the results will be good.
  Reply With Quote
Old 29th June 2010, 11:52 AM   #19
suntechnik is offline suntechnik  Russian Federation
diyAudio Member
 
Join Date: Jun 2010
Location: St. Petersburg
Quote:
Originally Posted by wahab View Post
EVEN harmonics to the original sound
Even or odd just a pure math that comes from FFT. I've heard nice sound that comes from an organ or a grand piano but never directly from a spectrum analyzer.

Quote:
a transistorized clean sound
It means that all transistor gear sounds exactly the same equally perfect, iPOD+LM3886 = MarkLevinson=TV set

However in real life every sample of audiogear has it own sound signature. Otherwise one clean (perfect) sounding opamp would be sufficient for the entire audio market forever.
  Reply With Quote
Old 29th June 2010, 12:28 PM   #20
wahab is offline wahab  Algeria
diyAudio Member
 
Join Date: Nov 2009
Location: algeria/france
[QUOTE=suntechnik;2230300]Even or odd just a pure math that comes from FFT. I've heard nice sound that comes from an organ or a grand piano but never directly from a spectrum analyzer.

QUOTE]


Not at all....

musically speaking :

H2 is an octave and doesn tchange the harmony of the music
H3 is a fifth one octave higher and can be dissonnat if a chord
is played with an altered fifth.
H4 is the same as the fundamental, but two octave higher.
H5 is a major third, and can be dissonant if the musical piece
is played in minor mode.
H6 is a fifth again.
H7 is dissonnant musically speaking, having no relevance with
the musical scales.
H8 is the fundamental three octave higher.

So it s not about some FFT analysis, but about
musicality of the distorsions.

About the rest of your sayings, you are strtching my words
to fit your own sayings.
Did i said that a ipod + clone amp is perfect ?..
With such an imagination , you should have guessed
that i was talking about properly designed transistorized
items...and yes, a gainclone can be a good amp !!
For the ipod, it s another story, of course.
  Reply With Quote

Reply


What is wrong with op-amps?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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Op Amps ... Borat Solid State 44 7th September 2009 03:23 PM
Op Amps MrGuitardeath Instruments and Amps 61 4th May 2005 11:37 PM
FS PA02 Power op-amps +/- 18v, 5 amps modifry Swap Meet 0 11th August 2004 07:45 PM
Op Amps in Solid State Guitar Amps MrGuitardeath Instruments and Amps 1 11th February 2004 07:43 PM
What are the things that may go wrong with amps. downhere Solid State 1 9th December 2001 07:28 PM


New To Site? Need Help?

All times are GMT. The time now is 10:13 AM.


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