Go Back   Home > Forums > Member Areas > The Lounge

The Lounge A place to talk about almost anything but politics and religion.

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 2013, 09:09 AM   #10011
diyAudio Member
 
Join Date: Mar 2007
Location: Oxfordshire
I have always suspected that beyond a certain point all we can reliably hear as amplifier upgrades are PSU improvements . As I said earlier it might be possible to contrive a PSU which is just about able to handle the ripple currents and has some surplus voltage to burn off . Suggestion 2 x 10 000 uF with 10 V over voltage to output dumpers ( class B ) . Smooth supply at - 10 V ( +/- ) for class A amp sections ( LTP VAS ) .

Here is the possible benefit apart from price . The amplifier and PSU could be combined . The track length almost zero at the 0V reference point . I have a hunch that making the dumpers first in line would be best . Then simple regulators to VAS etc . If someone says this is speculation , it is . We throw ideas around as money is the only other solution . Proving that speculation would be very expensive . People buying something is the only way ( Carver ) . Even then a victory of hype over reality is not unknown .

My belief is the big cap PSU's are merely giving cleaner VAS supplies . Somewhere in history the imperatives of the cheap amplifier market have become universal . That is CCRR will do miracles so no need to know about clean VAS supply .

An analogy I would like to put forward . I have often wanted an open formula for push rod engines in formula one . That is if you want 10 litre V12 you can have it . This would be to run against 2.4 litre V8 that will end this season . I know it would be a non starter as the 2.4 litre will outperform it . Weight , size and rev ability . The analogy is that mostly we are building 10 litre V12 's in audio . No harm in it and rather marvelous .

Unless genuinely needing 1000 W 1 ohm on peaks I doubt the energy calculations justify the capacitance often used ( me guilty also ) . A suggestion . Build an amp to my recipe ( over voltage dumpers , class B ) . Have VAS emitter at 0R 16 R 47 R . I suspect the VAS emitter resistance will have more effect on punch than adding 47 000 uF per rail . To repeat myself , I am convinced that the VAS base impedance is the slew sound of amps . The numbers far exceed any real requirements . One way to make an amp sound nicer is VAS emitter resistance . The better one is a high gain VAS transistor . For reasons I don't understand I feel a high gain VAS transistor rivals a Darlington . I am sure the Darlington VAS sounds opaque . Cascode seems better .

I beleive Citroen in the late 1920's said 330 cc was an optimum cylinder size ( He came from Voisin as an aero engineer ? ) . The French had a fiscal horse power tax which favoured long stroke engines ( bore = horse power ) . If my memory is correct the 330 cc was for square bore and stroke . Nearly 100 years later that rule is still about right . Amp PSU's are not as well understood . I come from two families of mechanical engineers . I am not one myself . I have worked with them and have had to run projects . The difference I see is mechanical engineers are use to component failure . Mechanical engineers must not have component failure . It simplifies the tasks . Sadly nothing holds the amplifier designer in check . The mechanical engineer is often struggling to meet a weight limit . Over engineering is a luxury that reality will not allow . What the mechanical engineer looks for is a safety margin . That's what an amplifier designer should be doing . They don't have to build it or sell it . They should know it .

A friend is using an amplifier I designed . The PSU is now 5 times larger . I got very upset when someone wanted to double the components in the amplifier . I think the reason was it would do no harm and allow him some design input ( ? ! ). The owner of the amp firmly said no . They put in some new current mirror designs I had suggested . The irony is , it is a FET amp . 5 times the PSU size will not do what converting to bipolar output stage might . That's what I would have done if wanting more punch . Audio Precission test suit available , still didn't let the obvious be seen . My test gear is mostly home made . It get the same test results . Dvv said I design amps by taking out parts until they stop working . Absolutely correct . However I use a double VAS .

Galactron were imported by Goodman's into the UK I think ? Goodman's were and are excellent engineers . The public image was dowdy . Somehow good engineering seldom is enough .

Last edited by nigel pearson; 14th July 2013 at 09:35 AM.
  Reply With Quote
Old 14th July 2013, 10:48 AM   #10012
dvv is offline dvv  Serbia
diyAudio Member
 
Join Date: Sep 2004
Location: Belgrade, Serbia
My experience says a Darlington VAS will sound warmer and somehow more powerful than a cascode VAS, but the cascode VAS tends to be somehow cleaner and better defined, with more detail.

Where a cascode VAS beats the pants off almost any other VAS configuration is the fact that it can be configured for exceptionally short settling times very easily, no particular pain, just 2 components (a fast diode and a resistor) over the standard fare. Those two components can shorten the settling time by a factor of 10:1, which is no joke. And if you wonder can we really hear that, the answer is yes, we can, the sound simply becomes better defined without turning into a shriek or some such. Sort of snaps into better focus.
__________________
Such is life, baby! Ета жизњ, бејби!
  Reply With Quote
Old 14th July 2013, 12:18 PM   #10013
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
@Tom

The CircuitCalculator.com Blog PCB Trace Resistance Calculator

I get about 12 m-ohm/in for a 2mm trace. With thicker (1 oz) copper, that drops to 6. So for two 1" long traces to the cap, we're somewhere around 12-25 m-ohm.

So, in this case, it seems to be somewhere between us, but a bit closer to you.
__________________
"It is difficult to get a man to understand something, when his salary depends upon his not understanding it." Upton Sinclair
  Reply With Quote
Old 14th July 2013, 07:00 PM   #10014
a.wayne is offline a.wayne  United States
diyAudio Member
 
a.wayne's Avatar
 
Join Date: May 2008
Location: Front Row Center
Quote:
Originally Posted by nigel pearson View Post



Unless genuinely needing 1000 W 1 ohm on peaks I doubt the energy calculations justify the capacitance often used ( me guilty also ) . A suggestion . Build an amp to my recipe ( over voltage dumpers , class B ) . Have VAS emitter at 0R 16 R 47 R . I suspect the VAS emitter resistance will have more effect on punch than adding 47 000 uF per rail . To repeat myself , I am convinced that the VAS base impedance is the slew sound of amps . The numbers far exceed any real requirements . One way to make an amp sound nicer is VAS emitter resistance . The better one is a high gain VAS transistor . For reasons I don't understand I feel a high gain VAS transistor rivals a Darlington . I am sure the Darlington VAS sounds opaque . Cascode seems better .



.
Why are you guys always singling me out .......
__________________
On the floor looking at the great ones and drooling ..... :
  Reply With Quote
Old 14th July 2013, 07:43 PM   #10015
diyAudio Member
 
Join Date: Mar 2007
Location: Oxfordshire
Quote:
Originally Posted by a.wayne View Post
Why are you guys always singling me out .......
No way am I . It is like having a 155 MPH car . It gives confidence . When forced to have 110 MPH make if feel like it would be 155 . Mine is like that . The engine is good for that . I have the base model and is limited . A simple remap and it will go from 90 to 168 BHP . Mine was higher . As I service it myself the computer defaults to standard mode if not having the computer reboot link . I still have the confidence it is there for the asking . My mate has a full mapped engine .

I am tempted to draw my minimal PSU concept just in case it wasn't understood . Looking at TO3 I would hook my 10 000 uF directly to the collectors using a conductive plate cum heat sink to maximize conductivity . The spare cap terminals to the ground plane directly ( GP ) . A single rectifier bridge to each collector on the heat sink . The spare terminal to the GP . This is to minimize losses ( one rectifier would be OK , two is easier ) . A dropper resistor to the next stage with capacitor and perhaps zener ( VAS ) . The TO3's 10 V higher than VAS . The 10 000 uf arranged at 90 degrees to minimize heat pick up . I would predict the amp would be a kicker and super sweet . The transformer wires would be usual length going almost directly to the TO3's . The TO3 terminal it's shape and extended for soldering . The 1 ohm stuff is possible if the caps can take it . 22 000 uF might still work . My speakers are 4 ohms on a good day . I often hear the current limiters working ( nothing nasty , just a gulp ) .

If the heat sink is internal and split it will be a conductor in both senses .

About ground planes . Is it true if of low resistance no need to do anything else ? I guess PSU , and speakers close to the rectifier end ? Signal in as far away as possible ? To stress it would have no star or bus-bar ground .

Last edited by nigel pearson; 14th July 2013 at 07:54 PM.
  Reply With Quote
Old 14th July 2013, 07:52 PM   #10016
diyAudio Member
 
Join Date: Mar 2007
Location: Oxfordshire
Quote:
Originally Posted by dvv View Post
My experience says a Darlington VAS will sound warmer and somehow more powerful than a cascode VAS, but the cascode VAS tends to be somehow cleaner and better defined, with more detail.

Where a cascode VAS beats the pants off almost any other VAS configuration is the fact that it can be configured for exceptionally short settling times very easily, no particular pain, just 2 components (a fast diode and a resistor) over the standard fare. Those two components can shorten the settling time by a factor of 10:1, which is no joke. And if you wonder can we really hear that, the answer is yes, we can, the sound simply becomes better defined without turning into a shriek or some such. Sort of snaps into better focus.

Great point . Another is we get a dream transistor at low cost and using plentiful parts . I built a transistor valve cascode after loosing faith in all valve cascodes . It was incredible ( BC 550 C + ECC 82 I think ? ) . I didn't use it as the guys wouldn't like it . I used a pentode . The cascode said what I needed .
  Reply With Quote
Old 14th July 2013, 07:52 PM   #10017
a.wayne is offline a.wayne  United States
diyAudio Member
 
a.wayne's Avatar
 
Join Date: May 2008
Location: Front Row Center
please , 1000W@1ohm peak works for me , feel free to discuss ....
__________________
On the floor looking at the great ones and drooling ..... :
  Reply With Quote
Old 14th July 2013, 08:17 PM   #10018
dvv is offline dvv  Serbia
diyAudio Member
 
Join Date: Sep 2004
Location: Belgrade, Serbia
The Current Surfer speaketh ...
__________________
Such is life, baby! Ета жизњ, бејби!
  Reply With Quote
Old 14th July 2013, 08:52 PM   #10019
diyAudio Member
 
Join Date: Mar 2007
Location: Oxfordshire
I was very surprised to find there is no practical use in going above 10 000 uF . If wanting a big amp I would use 6 x 10 000 uF offering 30 A ripple current .

This component seems optimum . 100 V devices fit my most interesting model . Often 100 V devices sound faster and less dark . The dialectic is better to resit flash-over .
ALS30A103KE100 - BHC COMPONENTS - CAPACITOR, 10000UF, 100V | Farnell United Kingdom
  Reply With Quote
Old 14th July 2013, 09:26 PM   #10020
a.wayne is offline a.wayne  United States
diyAudio Member
 
a.wayne's Avatar
 
Join Date: May 2008
Location: Front Row Center
Not by Tom's calculations , 200K would be a min .......
__________________
On the floor looking at the great ones and drooling ..... :
  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
Sound Card for Measurements Marik Solid State 2 2nd January 2012 08:59 PM
Sound Card Recommendations (For Audio Measurements) dchisholm Equipment & Tools 5 16th July 2011 09:40 AM
How to protect sound card during amp measurements? okapi Everything Else 13 2nd September 2008 03:06 PM
Quality Control differences = variations in sound quality? KT Class D 0 14th November 2004 06:51 AM
Sound cards - test and measurements jackinnj Everything Else 2 5th July 2003 03:02 PM


New To Site? Need Help?

All times are GMT. The time now is 05:45 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