Go Back   Home > Forums > Design & Build > Software Tools

Software Tools SPICE, PCB CAD, speaker design and measurement software, calculators

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 20th June 2012, 03:31 PM   #11
diyAudio Member
 
Join Date: Feb 2012
Location: Michigan
Oh boy... That looks like a nightmare with AB amps. Before I get too involved, do they make any small audio transformers (no larger than 12mm in any dimension) with good frequency response in the range of 20 hertz to 20K hertz? The power output would be from 10mW to 500mW. I wouldn't mind using small transformers if I could find decent ones. All the ones I've found have really bad quality outside of like 500~10K hertz
  Reply With Quote
Old 20th June 2012, 08:26 PM   #12
diyAudio Member
 
Join Date: Feb 2008
Location: Jackson,michigan
Yes, I have seen them but they are not cheap!
Jensen is one company that comes to mind.
Lundahl is another.

JENSEN TRANSFORMERS, INC. - ISO-MAX® Audio Isolator Products

Lundahl Transformers, audio transformer and tube amplifier transformer manufacturer

Here is a search page from Mouser that may help you,

Transformers Audio & Signal | Mouser

Here is just an example of one of the Jensen transformers,

http://www.jensen-transformers.com/d...s/din2lofl.pdf

And also Sowter,

SOWTER AUDIO TRANSFORMERS

SOWTER PRE AMP/ LINE AMP TRANSFORMERS

Just to name a few.

Jer
  Reply With Quote
Old 20th June 2012, 11:34 PM   #13
diyAudio Member
 
Join Date: Feb 2008
Location: Jackson,michigan
Quote:
Originally Posted by Nubcakes View Post
Oh boy... That looks like a nightmare with AB amps. Before I get too involved, do they make any small audio transformers (no larger than 12mm in any dimension) with good frequency response in the range of 20 hertz to 20K hertz? The power output would be from 10mW to 500mW. I wouldn't mind using small transformers if I could find decent ones. All the ones I've found have really bad quality outside of like 500~10K hertz
It shouldn't be any more of a problem then your typical BTL configuration except for the higher current handling of the VGamp in which would be just a matter doubling (paralleled) of the output devices.

Also running the VGamp in a Class A mode might be a good idea as well in fact running all three in a Class A mode may not be as efficient but it would guarantee the possibly of a higher sound quality.

FWIW

jer
  Reply With Quote
Old 21st June 2012, 04:16 PM   #14
macboy is offline macboy  Canada
diyAudio Member
 
Join Date: Oct 2003
Location: Ottawa, Canada
"guarantee the possib[ilit]y of a higher sound quality"
That sounds like audiophile marketing speak... just shy of making an actual specific claim (by adding wording like "possibility of" to the claim) so that it doesn't need to be proven to be true.
  Reply With Quote
Old 21st June 2012, 05:00 PM   #15
diyAudio Member
 
Join Date: Feb 2012
Location: Michigan
Quote:
Originally Posted by macboy View Post
"guarantee the possib[ilit]y of a higher sound quality"
That sounds like audiophile marketing speak... just shy of making an actual specific claim (by adding wording like "possibility of" to the claim) so that it doesn't need to be proven to be true.
Well from my understanding Class A Amps are the rolls royce of Audio Amplifiers. They provide pretty much supreme quality at the dreaded cost of efficiency. I think I read somewhere that the efficiency could be good if you were driving a signal close to the limit of the amplifier continuously. Otherwise your efficiency will be proportional to the limit of the amp since Class A amps are fully "on" all the time.
  Reply With Quote
Old 22nd June 2012, 03:50 PM   #16
diyAudio Member
 
Join Date: Feb 2008
Location: Jackson,michigan
I uses the word "possibility" as the term "theoretically".
We already know what Class A mode is and has already been proven to be what it is.

This doesn't mean the a class AB mode amplifier can not produce a good sound quality.

In fact the class AB pushpull amps as in the schematic are already running in a Class A mode as long as the peak current flowing into the load is not more than the quiescent current flowing through the output devices.
If the peak load current exceeds the quiescent current of the output devices then it is considered to be in a Class AB mode unlike Class B because the output devices are never ever in an off state.

The efficiency of a Class A amplifier is quite low typicaly around 10% to 15% and no more than 25%.
But in a push pull Class A or a BTL Class A configuration the efficiency can be as high as 50%.

I suggested that the Virtual ground amp to be running in a Class A mode to help eliminate any crossover switching distortion because it will be spending must of its time near the zero crossing point.

This type of circuit also works with opamps and even they typical have a Class AB output stage.

It has been highly debated in many threads as to whether or not they (opamps) have Class A ,Class AB or Class B output stages and is irrelevant to the overall function of the circuit.

jer

Last edited by geraldfryjr; 22nd June 2012 at 03:57 PM.
  Reply With Quote
Old 25th June 2012, 01:18 PM   #17
macboy is offline macboy  Canada
diyAudio Member
 
Join Date: Oct 2003
Location: Ottawa, Canada
Quote:
Originally Posted by Nubcakes View Post
Well from my understanding Class A Amps are the rolls royce of Audio Amplifiers. They provide pretty much supreme quality at the dreaded cost of efficiency. I think I read somewhere that the efficiency could be good if you were driving a signal close to the limit of the amplifier continuously. Otherwise your efficiency will be proportional to the limit of the amp since Class A amps are fully "on" all the time.
I didn't mean to question the statement about class-A amps itself, rather, I was just poking fun at the snake-oil-marketting-like wording that you had used.
  Reply With Quote
Old 1st October 2012, 12:08 AM   #18
diyAudio Member
 
Join Date: Feb 2012
Location: Michigan
Time for some thread necromancy! Click the image to open in full size.

So the project that I needed the amp for got OK'd and I've been adjusting the amp design a lot. I've think I got it optimized as much as I can while maintaining minimal cross over distortion.

There is something that has been bothering me though. When I build the amplifier on bread board and test it, I can't draw much more than 630mW of power before the signal starts clipping at both peaks (regardless of load). LT spice shows that I should be able to get around 1284mW (using a 4 Ohm Load in place of the 8 Ohm one) before it starts clipping. I obviously don't expect to get as high as LT spice says I can, but I'd like to at least get 750mW.

The signal going into the AB-amplifiers doesn't drop much or clip with a 4 Ohm load connected, but for some reason the signal is getting lost/reduced and clipped coming out of the AB-stage transistors. I ran through the equations for it several times and it's not matching up with what I am actually seeing.

Any ideas I could try?

Click the image to open in full size.
  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
My new design of differential buffer I/O board for fully balanced design alant4321 Solid State 28 28th July 2011 09:53 AM
Differential push-pull design question Tyimo Tubes / Valves 4 15th January 2010 07:05 PM
Differential filter circuit: biasing problem Alex M Tubes / Valves 4 5th May 2009 09:44 AM
Differential to differential amplifier Cauhtemoc Solid State 3 15th August 2007 07:39 AM
differential amplifier Thomas Giz Digital Source 1 23rd March 2003 08:07 PM


New To Site? Need Help?

All times are GMT. The time now is 04:58 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