Symetrical schematics are alike plague in Brazil, do you like them? - Page 11 - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 8th April 2010, 10:50 PM   #101
diyAudio Member
 
destroyer X's Avatar
 
Join Date: Feb 2004
Location: Recife - Brasil Northeast
Default Well boys...this is correct Nico Ras..you got the point... i have real strong

appreciation on you Nico.. you know that..also respect for you...also you know that.

Cal Weldon is rigth...thanks God (this is true) we have him here....or i would be punished in a couple of days.... you cannot say someone is retarded or something alike..it is forbiden..so..when you need to send some message, then you use their brain against themselves.

I cannot stand for some guys, this is the reality...they are very few guys, but i really think they are below the minimum line of human quality, despite can be excelent in their profession.... they have humiliated, in the past, Hugh Dean..and i cannot forgive such kind of thing...Hugh is a sweet person.. excelent researcher.... make specially good amplifiers...tuned for his speakers and personnal taste..others may feel need more bass, others may feel need more treble..depending the speaker you use.

I will build my amplifiers..that's what i gonna do...and never will go against Cal Weldon, he is fair, really fair..... i was waiting for him.

For sure, it is my strategy to provocate...sadly my provocations are not considered challenge.... challenge is considered when others goes provocating me..interesting.... something different on me..maybe thick skin or other thing.

I gave my message to the ones are clever....it is enougth to me...build amplifiers is much better than spend my time with some "specially clever guys"

regards all.....back to old Destroyer...destroying transistors.

Carlos
__________________
How speaker generates sound; http://animagraffs.com/loudspeaker/

Last edited by destroyer X; 8th April 2010 at 10:57 PM.
  Reply With Quote
Old 8th April 2010, 11:07 PM   #102
wahab is offline wahab  Algeria
diyAudio Member
 
Join Date: Nov 2009
Location: algeria/france
Quote:
Originally Posted by PMA View Post
Just a simple question - is it OK if you push by an amplifying transistor stage, and pull just by current limited CCS? Is it better than to push and pull by the same principle?? Is it OK to have different limitation, different slewing of push and pull halves??
Intrinsically, the circuit will have a non symetrical transfert function,
which can be summarized as higher bandwith for the half wave that
is pulled by the amplifing device...
The drawback is, among others, a different slew rate for each signal polarity...
  Reply With Quote
Old 8th April 2010, 11:33 PM   #103
Eva is offline Eva  Spain
diyAudio Member
 
Eva's Avatar
 
Join Date: Oct 2003
Location: Near the sea
Send a message via MSN to Eva
Symmetrical LTP and VAS works as two paralleled single ended ones. Slew rate is doubled and becomes symmetrical as both asymmetries add up and cancel. THD can be halved due to higher O/L gain.

Subjective impressions about amplifiers with less than 0.1% THD are b.s. for me, and will always be. Try to hear -60dB of any kind of noise when amplitude modulated by 0dB music. I find these crazy impresions a byproduct of spending too much time at home particularly when listening takes place in a non acoustically conditioned room with junk speakers.

I have repaired many of these fully symmetrical amplifiers, both car-audio, hi-fi and pro-audio. They all exhibited perfectly clean clipping behaviour with no traces of oscillation or sticking to the rails, and clean square wave response, two things that Carlos has not been yet able to achieve. The last oscilloscope videos that I saw demonstrated extremely bad clipping behaviour at least on one of his amplifiers. A funny way to circumvent that is to feel proud of imaginary achievements, but these seem ridiculous to most people except you. Always comparing yourself to less skilled people may also work for you but does not make sense for anybody else. Indulging in self pity does not work with oscilloscopes, they never lie.
__________________
I use to feel like the small child in The Emperor's New Clothes tale

Last edited by Eva; 9th April 2010 at 12:00 AM.
  Reply With Quote
Old 8th April 2010, 11:43 PM   #104
diyAudio Member
 
Join Date: Apr 2007
Quote:
Originally Posted by Eva View Post
Symmetrical LTP and VAS works as two paralleled single ended ones. Slew rate is doubled and becomes symmetrical as both asymmetries add up and cancel. THD can be halved due to higher O/L gain.

Subjective impressions about amplifiers with less than 0.1% THD are b.s. for me, and will always be. I find them a byproduct of spending too much time at home particularly when listening takes place in a non acoustically conditioned room with junk speakers.
Hello Eva

Are you saying that all amps with less than 0.1% THD do sound all same ?

I do not agree.

Btw, low quality loudspeakers could lower the overall sonic quality of a sound system, but a bad or dull sounding amp will kill all the sonic quality.

Bye

Gaetan

Last edited by gaetan8888; 9th April 2010 at 12:04 AM.
  Reply With Quote
Old 9th April 2010, 12:10 AM   #105
Eva is offline Eva  Spain
diyAudio Member
 
Eva's Avatar
 
Join Date: Oct 2003
Location: Near the sea
Send a message via MSN to Eva
I'm saying that nobody can hear -60dB of noise modulated (and frequency related) by 0dB of music. The music is always 1000 times stronger than the noise. It's like feeling the difference between 1000 grams and 1001 grams of weight, or between 2000000 micropascals and 2002000 micropascals of acoustic pressure (that is 100dB music and 100dB music plus 40dB noise). It's something unrealistic, always backed by subjective claims.

And it's around 10 times lower THD than what I was able to hear in controlled 2nd and 3rd harmonic tests. So I'm assuming that the average human has 10 times better hearing than me (and I don't think I have bad hearing at all).

Another example. Try to tell a piece of wire 1000 milimeters long from another 1001 milimeters long just by sight, without measuring them or comparing one against the other.
__________________
I use to feel like the small child in The Emperor's New Clothes tale

Last edited by Eva; 9th April 2010 at 12:18 AM.
  Reply With Quote
Old 9th April 2010, 12:25 AM   #106
wahab is offline wahab  Algeria
diyAudio Member
 
Join Date: Nov 2009
Location: algeria/france
Quote:
Originally Posted by Eva View Post
I'm saying that nobody can hear -60dB of noise modulated (and frequency related) by 0dB of music. The music is always 1000 times stronger than the noise. It's like feeling the difference between 1000 grams and 1001 grams of weight,
You re assuming that the hand weighting a mass and the ear
listening a sound have both the same precision and relative
sensitivity , which is not true..

Think about the ten octaves we can ear, and the single octave
we can see...

Back to the sounds , listen to a pure sine , and then add a second
harmonic at very low level, you ll be surprised by the threshold
of its audibility...
  Reply With Quote
Old 9th April 2010, 12:29 AM   #107
diyAudio Member
 
Join Date: Apr 2007
Quote:
Originally Posted by Eva View Post
I'm saying that nobody can hear -60dB of noise modulated (and frequency related) by 0dB of music. The music is always 1000 times stronger than the noise. It's like feeling the difference between 1000 grams and 1001 grams of weight, or between 2000000 micropascals and 2002000 micropascals of acoustic pressure (that is 100dB music and 100dB music plus 40dB noise). It's something unrealistic, always backed by subjective claims.

And it's around 10 times lower THD than what I was able to hear in controlled 2nd and 3rd harmonic tests. So I'm assuming that the average human has 10 times better hearing than me (and I don't think I have bad hearing at all).

Another example. Try to tell a piece of wire 1000 milimeters long from another 1001 milimeters long just by sight, without measuring them or comparing one against the other.
Hello Eva

Let say we talk now a bit about the brain and ears psycoacoustic.

Our brain/ears system can detect a time delay of few milisecond between our two ears, so we can have a stereo earing, but some of those psycoacoustic qualities of our brain/ears system rely on very low level sounds between 2khz and 6khz who are give us the sense of space and sound stage wen we ear sounds or musics.

So a bad amp with high frequencies harmonics in it's distortion spectrum will kill those low level sounds and we will lost the sense of space and sound stage in a musics listening.

The distortions number are not all, it's the distortions spectrum and which type of distortions who are important.

Bye

Gaetan

Last edited by gaetan8888; 9th April 2010 at 12:34 AM.
  Reply With Quote
Old 9th April 2010, 12:59 AM   #108
Eva is offline Eva  Spain
diyAudio Member
 
Eva's Avatar
 
Join Date: Oct 2003
Location: Near the sea
Send a message via MSN to Eva
I agree that very high harmonics are much easier to hear because there is much less chance of these frequencies happening strong enough in the recording to mask the distortion products, but we are considering electronic systems with 4th and higher harmonics well below 0.1% (like 0.01%), thus usually below the noise floor, only 2nd and 3rd reach strong levels.

When THD is below 0.1% things such as output impedance become more important. The usual frequency-dependent output impedance figures can yield more than 0.2dB tonal unbalance due to frequency-dependent speaker impedance.

Note that 0.1% is more or less the same as 0.087dB

For example, in my three-way PA setup I can clearly hear differences in tweeter level as low as 0.2dB. I use a 24-bit digital crossover with controls in 0.1dB steps. We are very sensitive to tonal balance changes involving wide frequency bands, particularly at high SPL like 110dB-120dB where tone balance becomes critical, and changes as low as 0.5dB may turn pleasant into quite unpleasant listening. I routinely use a prototype speaker system capable of these SPL in my living room. In the past few years I have probably played with crossover filters and equalization and delays for a few thousand hours, so I think I have a good sense of what things we are sensitive to and what things we aren't.

Output impedance is seldom taken in consideration in class AB amplifiers. It's usually low in the range of .020 ohms up to 1Khz, rising smoothly to .2 ohms at 20khz. This changes with topology, transistor choice, frequency compensation, resistor values, etc. Many circuit changes result in unexpected changes in output impedance. People is doing that kind of changes on their circuits every day and claiming better or worse sound by means of unknown phenomena.

Consider the .02 ohm to 0.2 ohm rise in output impedance alone, with a 8 ohm load this already implies a 0.2dB tonal unbalance (from 1Khz to 10khz). Consider variable speaker impedance and tonal unbalance may worsen by another 0.2dB. This *can* be heard (and measured), but nobody talks about it. Is measuring these things too complex?

I design my class D amplifiers to have as low output impedance as possible across the whole audio band. In my latest design a 2.8 ohm load makes less than 0.1dB difference in frequency response across the whole audio band, in comparison with no load. THD is below 0.1% up to insane power levels. In my opinion this is what results in neutral sound.
__________________
I use to feel like the small child in The Emperor's New Clothes tale

Last edited by Eva; 9th April 2010 at 01:19 AM.
  Reply With Quote
Old 9th April 2010, 02:15 AM   #109
Eva is offline Eva  Spain
diyAudio Member
 
Eva's Avatar
 
Join Date: Oct 2003
Location: Near the sea
Send a message via MSN to Eva
The .02 and 0.2 ohm figures are the result of a 400 LF damping factor falling to 40 at 10khz. These are good figures, since most circuits may have only 100 or 200 at LF falling to 10 or 20 at 10Khz, thus resulting in 0.8dB or 0.4dB of tonal unbalance.

Then factor in the typical output coil, 2uH gives an additional 0.1dB of tonal unbalance. 4uH gives 0.2dB. 8uH gives 0.4dB. Some circuits use a coil, others doesn't. The inductance of these coils is not well controlled, almost nobody measures them.

And all this being speaker dependent.
__________________
I use to feel like the small child in The Emperor's New Clothes tale
  Reply With Quote
Old 9th April 2010, 01:52 PM   #110
wahab is offline wahab  Algeria
diyAudio Member
 
Join Date: Nov 2009
Location: algeria/france
Thanks for the infos, Eva , it s well explained..
Personaly, i dont like those LR filters at the output,
but to stay in the cautious side, i implement them,
but no more than 1uH//1R.
  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
Symetrical out low Zout karsten21 Tubes / Valves 5 1st February 2010 11:19 PM
Sale: Some fostex's and alike Piek Swap Meet 0 21st July 2008 01:17 PM
going balanced/symetrical - what benefits? weissi Solid State 15 20th October 2007 09:06 AM
Symetrical field, is this? Raka Multi-Way 6 14th September 2003 02:21 PM
Non-symetrical SMPS output cm961 Parts 4 21st August 2003 11:27 PM


New To Site? Need Help?

All times are GMT. The time now is 09:22 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