Simple Symetrical Amplifier - Page 113 - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State
Home Forums Rules Articles The diyAudio Store Gallery Blogs Donations FAQ Calendar Mark Forums Read

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
 
 
Thread Tools
Old 11th October 2011, 07:30 AM  
dadod is offline dadod  Croatia
diyAudio Member
 
dadod's Avatar
 
Join Date: Apr 2006
Location: Zagreb
Quote:
Originally Posted by Esperado View Post
Just a quick look at the Bob Cordell's web site( i was curious) where i read:
Another View of TIM
Audio
February 1980
This article was published in Audio magazine in February, 1980 at the height of the controversy surrounding Transient Intermodulation Distortion and its relationship with negative feedback. The article discusses the origins of TIM and the transient nature of music that can bring it on. It points out that amplifiers with inadequate slew rate margin are the ones prone to TIM."


Who is ridiculous, now, the one witch had not read-it, but knows that since 1970, or the ones who cannot even understand what they read ?
It is EXACTLY what i said, and i had even noticed feedback to be a part of the problem in my first answer to your
disrespectful ones.
Quoting myself about IM: "
When your amp is unable to follow your signal transients, if it uses CR, that's what happens"
forums can be the best (with people like Lazy Cat) and the worse places (Guess who ?) in the same time..


You should read more carefully. Bandwidth and Slew rate are different thing. Inadequate slew rate??? Increase slew rate from 200V/us to 1500V/us and you can hear the difference.
dado
 
Old 11th October 2011, 09:26 AM  
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
This argument seems to have been brought about by an english language problem.

Post1104 seems to show Esp knows little and yet post1118 states he agrees with the norm.

But read 1104 again and be kind enough to insert the correct english words into the text and I believe you will see what he meant but did not write.
__________________
regards Andrew T.
 
Old 11th October 2011, 01:04 PM  
a.wayne is offline a.wayne  United States
Sin Bin
 
Join Date: May 2008
Location: Front Row Center
Quote:
Originally Posted by Esperado View Post
But did i make a mistake, feeling some kind of irony in your question ? Are-you this kind of audiophile thinking there is no salvation without vinyl records, Quad speakers, tube amps and silver plated wires Teflon isolated with cryogenic treatment?
Yes , you did miss it and i'm the type of guy replacing my 20w SET with an SSA V-12 ...Now If you see then have a drink and a smile ...

it's all good............

Quote:
Originally Posted by fredlock View Post
Hi Alex,

Could you create a 4 power output transistor version PCB and also the Power supply if you get a chance? I think there will be more interest on this than the V12 version, which I think so expensive to build.

Thanks and appreciate for sharing your skill/talent on designing PCB in this forum.
Easy Fred, a v-8 cant sound like an V-12 , go for the 4 extra cylinders..
 
Old 11th October 2011, 04:06 PM  
diyAudio Member
 
Join Date: Jan 2008
[/QOUTE] Easy Fred, a v-8 cant sound like an V-12 , go for the 4 extra cylinders..[/QUOTE]

Hi Wayne,

If I have the money, why not. I tried matching hFE the other day and out of 20 pairs, I'm lucky enough to come up with 4 pairs. That means, I need hundred pairs or more for a V12 amp. Right now, economy isn't good so I'm just going for what I can afford.
 
Old 11th October 2011, 04:23 PM  
diyAudio Member
 
Nico Ras's Avatar
 
Join Date: Nov 2005
Location: East Coast of South Africa
I do not want to burst anyone's bubble, but matching components is a little rediculous to say the least.

I had a production run with some 100 amps. I decided I wanted one for myself and to match every pair of transistors perfectly at several values of Ic.

After adjusting off-set and bias it was no different from any of the other 99. Listening to it and measuring it made absolutely no difference at all.

I have since matched nothing apart from making sure the same part number is written on them and they come from the same manufacturer.

Maybe there is an insignificant difference if using zero negative feedback, but I doubt it.
__________________
Kindest regards
Nico

Last edited by Nico Ras; 11th October 2011 at 04:27 PM.
 
Old 11th October 2011, 05:36 PM  
diyAudio Member
 
Esperado's Avatar
 
Join Date: Jul 2011
Location: France
About this speed of amps question, some precisions.

In open loop, bandwitch and slew rate are correlated. CR introduce a kind of artificial increase of the bandwidth, but cannot do nothing regarding slew rate, witch is the ability of your amp to follow transients (fast changes of amplitude).
To give an image, at an average speed of 60miles/h an old VW will be able to follow a Ferrari between two cities. Never to follow his accelerations keeping the same distance.

When we where in analog world for our audio sources (Vinyls) it was not too much a problem: the bandwidth and the slew rate of the signals where limited in the same time and in a linear and correlated way by the inertia of the mechanical grooving heads and their bandwidth filters. Now, we live in a digital world, and signals from CDs can present slew rate more than ten time higher than a linear source with a 20 000hz sinusoidal limit.

Deigning amps, the good practice is to set each stage speed faster than the one preceding. And to design them for they limit they speed/bandwidth in a linear way. That where Output Fets presents an advantage against bipolar: they are faster, and more linear at high frequencies.
The Current feed back is a way to get better slew rate, with negative feedback, because the correction signal (CR) will not across a slow and non linear input stage, introducing an additional delay before to be subtract to the the original input signal. CR can present high levels at transients, and generate distortion if they are applied in a non linear way. Reason why CR had a bad reputation during some times.

Cascodes are too good practices to get rid of distortions at Hfs. That where Lazy Cat is accurate all the way in his designs, and why everyone find his designs are sounding "easy".

The way to limit the TIM is trivial, in a sense: never apply a signal with edges the amp cannot follow. So, build the fastest (slew rate =open loop bandwidth) amp you can, and limit the max slew rate of the incoming signals in the input, in a linear way -means by a low pass filter- above the amp open loop capabilities.

I believe that, for preamps, 50V/µs is a good value, according to the 1V level ( it needs much more in DACs output stages before filtering) and a perfect amp have to follow this speed by its gain: My SSA have 30 gain factor, and a 1500Vµs of slew rate: i'm at least in the rails.
I reduce the bandwidth in the input stage by a low pass filter at 1Mhz, to get a near flat phase response curve up to 10 000hz.

About Class D, by design, the slew rate is very hight, as the power stages are using a high clock square waves frequency: They present in theory a good match to Digital sources.

Some friends of mine (in witch i believe too ) just changed his high end previous amps for such D amps in his active system, and report sound is even better, and said mr Hiraga was astonished by his set. That why i want to try, i do not believe in fashion. I believe direct comparison with my actual SSA/Crescendo amps will be a difficult challenge for my future D amps. Will see witch will be the winner. I do not believe in "thin" sounding or any bad reputation of class D (coming from cheap PA amps) witch are those kind of audiophiles rumors i do not care about. And i believe that, some times, reducing distortion give the feeling of "simplifying" the signal. A better amp can sound "thiner" if some agreeable distortion is removed. I believe in "transparency", not agreeable sounding amps, i'm not an "audiophile".

SSA amp is very transparent and easy, not "agreeable".
__________________
Ultimate Protection and more.The Only Source of Knowledge is experience, everything else is just information” ©A. Einstein

Last edited by Esperado; 11th October 2011 at 05:42 PM.
 
Old 11th October 2011, 07:22 PM  
a.wayne is offline a.wayne  United States
Sin Bin
 
Join Date: May 2008
Location: Front Row Center
Quote:
Originally Posted by fredlock View Post
[/QOUTE] Easy Fred, a v-8 cant sound like an V-12 , go for the 4 extra cylinders..
Hi Wayne,

If I have the money, why not. I tried matching hFE the other day and out of 20 pairs, I'm lucky enough to come up with 4 pairs. That means, I need hundred pairs or more for a V12 amp. Right now, economy isn't good so I'm just going for what I can afford. [/QUOTE]

Yikes ......

Quote:
Originally Posted by Nico Ras View Post
I do not want to burst anyone's bubble, but matching components is a little rediculous to say the least.

I had a production run with some 100 amps. I decided I wanted one for myself and to match every pair of transistors perfectly at several values of Ic.

After adjusting off-set and bias it was no different from any of the other 99. Listening to it and measuring it made absolutely no difference at all.

I have since matched nothing apart from making sure the same part number is written on them and they come from the same manufacturer.

Maybe there is an insignificant difference if using zero negative feedback, but I doubt it.
OK... this is in contrast to conventional wisdom, now will apply to the SSA also, or does this design call for matching outputs.....

Quote:
Originally Posted by Esperado View Post
About this speed of amps question, some precisions.

In open loop, bandwitch and slew rate are correlated. CR introduce a kind of artificial increase of the bandwidth, but cannot do nothing regarding slew rate, witch is the ability of your amp to follow transients (fast changes of amplitude).
To give an image, at an average speed of 60miles/h an old VW will be able to follow a Ferrari between two cities. Never to follow his accelerations keeping the same distance.

When we where in analog world for our audio sources (Vinyls) it was not too much a problem: the bandwidth and the slew rate of the signals where limited in the same time and in a linear and correlated way by the inertia of the mechanical grooving heads and their bandwidth filters. Now, we live in a digital world, and signals from CDs can present slew rate more than ten time higher than a linear source with a 20 000hz sinusoidal limit.

Deigning amps, the good practice is to set each stage speed faster than the one preceding. And to design them for they limit they speed/bandwidth in a linear way. That where Output Fets presents an advantage against bipolar: they are faster, and more linear at high frequencies.
The Current feed back is a way to get better slew rate, with negative feedback, because the correction signal (CR) will not across a slow and non linear input stage, introducing an additional delay before to be subtract to the the original input signal. CR can present high levels at transients, and generate distortion if they are applied in a non linear way. Reason why CR had a bad reputation during some times.

Cascodes are too good practices to get rid of distortions at Hfs. That where Lazy Cat is accurate all the way in his designs, and why everyone find his designs are sounding "easy".

The way to limit the TIM is trivial, in a sense: never apply a signal with edges the amp cannot follow. So, build the fastest (slew rate =open loop bandwidth) amp you can, and limit the max slew rate of the incoming signals in the input, in a linear way -means by a low pass filter- above the amp open loop capabilities.

I believe that, for preamps, 50V/µs is a good value, according to the 1V level ( it needs much more in DACs output stages before filtering) and a perfect amp have to follow this speed by its gain: My SSA have 30 gain factor, and a 1500Vµs of slew rate: i'm at least in the rails.
I reduce the bandwidth in the input stage by a low pass filter at 1Mhz, to get a near flat phase response curve up to 10 000hz.

About Class D, by design, the slew rate is very hight, as the power stages are using a high clock square waves frequency: They present in theory a good match to Digital sources.

Some friends of mine (in witch i believe too ) just changed his high end previous amps for such D amps in his active system, and report sound is even better, and said mr Hiraga was astonished by his set. That why i want to try, i do not believe in fashion. I believe direct comparison with my actual SSA/Crescendo amps will be a difficult challenge for my future D amps. Will see witch will be the winner. I do not believe in "thin" sounding or any bad reputation of class D (coming from cheap PA amps) witch are those kind of audiophiles rumors i do not care about. And i believe that, some times, reducing distortion give the feeling of "simplifying" the signal. A better amp can sound "thiner" if some agreeable distortion is removed. I believe in "transparency", not agreeable sounding amps, i'm not an "audiophile".

SSA amp is very transparent and easy, not "agreeable".
You wield an interesting double edge sword ESP..

So your friend and Mr Hiraga like the agreeable sound of added class-d distortion, but you will not accept the opinions of audiophiles, because of the removal of said agreeable distortion ......
 
Old 11th October 2011, 07:46 PM  
diyAudio Member
 
Nico Ras's Avatar
 
Join Date: Nov 2005
Location: East Coast of South Africa
Hi A.Wayne, I did not match anything in my SSA, nor are the transistors even in close proximity to each other and I cannot complain about stability nor listening pleasure. But I am not an audiophile, I listen to the music not the equipment.
__________________
Kindest regards
Nico
 
Old 11th October 2011, 07:54 PM  
a.wayne is offline a.wayne  United States
Sin Bin
 
Join Date: May 2008
Location: Front Row Center
Quote:
Originally Posted by Nico Ras View Post
Hi A.Wayne, I did not match anything in my SSA, nor are the transistors even in close proximity to each other and I cannot complain about stability nor listening pleasure. But I am not an audiophile, I listen to the music not the equipment.
Thanks Nico, you just saved Fred and i a bundle ..... Fred have enuff outputs for two V12's.....and

"Audiophiles prefer to listen to music at a quality level that is as close to the original performance as possible using high fidelity components"...Wiki


See music .. wahlah ... your an audiophile .....




...

Last edited by a.wayne; 11th October 2011 at 08:00 PM.
 
Old 11th October 2011, 08:43 PM  
diyAudio Member
 
Nico Ras's Avatar
 
Join Date: Nov 2005
Location: East Coast of South Africa
I am sorry but I differ with the statement. Audiophiles listen to snippets of impressive sounding stuff and they use irrelevant adjectives like speed, slam wham and after the two second snippet sound follows it with another snippet of another impressive sounding passage. I have yet to meet an audiophile that will sit and enjoy an entire performance. Two seconds into a performance he is already thinking what he wants to hear next,

By The way Christophe, my SSA earlier tonight I could measure 368V/uS slew and by carefully optimizing all components I ended up with 1378V/uS SR - but I must say very honestly it did not move me anymore than before, the music still sounded exactly like before.
__________________
Kindest regards
Nico
 

 

Hide this!Advertise here!
Thread Tools

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 schematics are alike plague in Brazil, do you like them? destroyer X Solid State 151 1st July 2010 02:09 PM
Symetrical out low Zout karsten21 Tubes / Valves 5 1st February 2010 10:19 PM
going balanced/symetrical - what benefits? weissi Solid State 15 20th October 2007 08:06 AM
Symetrical field, is this? Raka Multi-Way 6 14th September 2003 01:21 PM
Non-symetrical SMPS output cm961 Parts 4 21st August 2003 10:27 PM


New To Site? Need Help?

All times are GMT. The time now is 08:02 AM.


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