Even loading of both supply rails... by inverting one channel

wwenze · 16th February 2010, 05:42 AM

Since quite a bit of the same sound exist in both channels especially bass, both channels more or less draw similar amount of current from the positive or negative rails at the same time.

What if, one channel is inverted so it outputs negative while the unaltered channel outputs positive, so both rails are more evenly loaded. The inverted output isn't an issue with speakers where all that's needed is some rewiring.

This could improve performance slightly and be a bit easier on virtual ground circuits, but I haven't seen this being done for some reason?

analog_sa · 16th February 2010, 07:54 AM

A very old idea. At the time of the NAD3020 a popular tweak was to invert one channel of the phono cartridge and the corresponding speaker. This changed the sound quite substantially as the power supply was indeed marginal. Don't mean to say the sound actually became better, just different, with a wider sound stage and a whole in the center.

wwenze · 16th February 2010, 09:32 AM

I c... the transformer of 3020 is indeed very small compared to its later revisions.

Enzo · 16th February 2010, 11:20 PM

And there are commercial professional audio power amps made that way as well.

Steerpike · 17th February 2010, 12:04 AM

Sony do this on their car amplifiers too.

Corax · 17th February 2010, 08:44 AM

This is also often done in Class-D amplifiers with single-enden output stages. These are known to suffer from rail-voltage pumping effects while energy is going back to the power-supply bulk caps and therefore will rise the rail voltages - sometimes to the maximum voltage level of the driving chips or the switching transistors. Definately something you don't want if you consider reliability of the design.
With bridged Class-D amplifier this will not happen because the energy will not go back to the rails but (through the rails) to the other inverted driving output - completely avoiding the rail voltage pumping effect.
This effect, by the way, will be worse with mono signals being present in the audio signal. And this is usually the low frequency region with the high power bass signals compared to the mid or high frequency region.
Similar is the effect on analog power amplifiers, except that the rail voltage pumping effect does not happen.
If you compare the scheme for a bridged amplifier with your modified stereo amplifier you'll see that this is exactly the same hardware configuration. One channel is inverted and the output of the inverted channel goes to the (-) pole of the speaker. The only difference is the usage of two speakers instead of one for the bridged mode.

16th February 2010, 05:42 AM	#1
wwenze diyAudio Member Join Date: Mar 2008	Even loading of both supply rails... by inverting one channel Since quite a bit of the same sound exist in both channels especially bass, both channels more or less draw similar amount of current from the positive or negative rails at the same time. What if, one channel is inverted so it outputs negative while the unaltered channel outputs positive, so both rails are more evenly loaded. The inverted output isn't an issue with speakers where all that's needed is some rewiring. This could improve performance slightly and be a bit easier on virtual ground circuits, but I haven't seen this being done for some reason?

17th February 2010, 12:04 AM	#5
Steerpike diyAudio Member Join Date: Jan 2006 Location: Johannesburg, South Africa	Sony do this on their car amplifiers too. __________________ Steerpike's Toybox

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Many question about Threshold S/** supply rails	ANADIGIT	Pass Labs	9	25th June 2009 01:45 AM
Phase inverting one half of a push-pull parrallel channel before recombining?	Test Electrix	Power Supplies	3	23rd March 2009 07:04 PM
Supply rails vs output	smithy666	Solid State	7	16th July 2008 01:54 AM
Gain / supply rails query	Khron	Chip Amps	3	10th June 2006 10:47 AM
Power supply inverting	sL!	Car Audio	6	13th April 2004 02:47 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	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

16th February 2010, 07:54 AM	#2
analog_sa diyAudio Member Join Date: Aug 2002 Location: Sofia	A very old idea. At the time of the NAD3020 a popular tweak was to invert one channel of the phono cartridge and the corresponding speaker. This changed the sound quite substantially as the power supply was indeed marginal. Don't mean to say the sound actually became better, just different, with a wider sound stage and a whole in the center.

16th February 2010, 09:32 AM	#3
wwenze diyAudio Member Join Date: Mar 2008	I c... the transformer of 3020 is indeed very small compared to its later revisions.

16th February 2010, 11:20 PM	#4
Enzo diyAudio Member Join Date: Sep 2004 Location: Lansing, Michigan	And there are commercial professional audio power amps made that way as well.

17th February 2010, 08:44 AM	#6
Corax diyAudio Member Join Date: Feb 2005 Location: south of lower saxon	This is also often done in Class-D amplifiers with single-enden output stages. These are known to suffer from rail-voltage pumping effects while energy is going back to the power-supply bulk caps and therefore will rise the rail voltages - sometimes to the maximum voltage level of the driving chips or the switching transistors. Definately something you don't want if you consider reliability of the design. With bridged Class-D amplifier this will not happen because the energy will not go back to the rails but (through the rails) to the other inverted driving output - completely avoiding the rail voltage pumping effect. This effect, by the way, will be worse with mono signals being present in the audio signal. And this is usually the low frequency region with the high power bass signals compared to the mid or high frequency region. Similar is the effect on analog power amplifiers, except that the rail voltage pumping effect does not happen. If you compare the scheme for a bridged amplifier with your modified stereo amplifier you'll see that this is exactly the same hardware configuration. One channel is inverted and the output of the inverted channel goes to the (-) pole of the speaker. The only difference is the usage of two speakers instead of one for the bridged mode.