[stereocilia]

It turns out that I could have been using my amp with one channel inverted the whole time (like this:
http://www.avahifi.com/root/equipment/bridge/bridge_wiring_single_amp.htm )   

It does sound a little more authoritative, I must say.

How much more power does this actually give, does anybody know?

All this talk of phase inversion and common mode rejection and differential systems, in a different thread, made me remember the old Hafler amplifier null test described in the manual for the XL-280.  From what I understand (I'm no EE) the Hafler test just shows that the distortion at the input looks like the distortion at the output, so it's not such a useful way to evaluate an amp.  Maybe that's why I haven't heard of anybody testing amps this way for a long time. 

[Wayner]

What preamp do you have?

Wayner

[avahifi]

The Hafler 280XL's claim to fame was that its two output channels were supposed to null with the inputs from 20 to 20KHz and thus be really perfect.

Unfortunately the method they used to get the null caused more sonic issues than it was supposed to solve.  They provided a user adjustable trimmer capacitor in the audio circuit feedback loop.  This actually caused a large underdamped resonance at around 80K Hz.  This was to tweak the measured frequency response up to measuring flat up to 20K Hz or so.  Of course this meant your speakers were seeing overemphasized high frequency trash way above the range of human hearing.  This obsolete though was that you can't hear that.  They overlooked the issue that although you cannot hear 80K Hz, your tweeters can.  Case in point, excess high frequency input into your tweeters will melt them.

I have suggested many times that a speaker designer design a low pass filter into his speaker crossover to protect the speakers from out of band high frequency garbage.  My assumption is that the tweeter will get unhappy long before it melts, and that an unhappy tweeter will not sound as good a happy tweeter.  So far, to the best of my knowledge, nobody has tried this.  It would be a simple double blind test of a set of speakers, one with the low pass filter, one stock, to determine if my suggestion has merit.  Oh well.

It is so much easier and more fun to just install a set of exotic speaker cables.  I will be using my Mark Funk supplied wires at the AudioKarma show for sure.  You will be amazed.  Mark better brace himself for a flood of orders, assuming it is possible to find more of the materials with the same sonic quality.

Regards,

Frank Van Alstine

[stereocilia]

Wayner,
I have a Jeff Rowland Consonance.  I purchased it used a few years ago, I like the numeric display and the ability to store and recall settings using the remote for level matching if I want to compare sources.  The remote sensor is in a separate box so it can be located elsewhere.  My only concern is that all the relay clicking as volume is changed reminds me that relays have a finite life span.  I wish it had the phono option, a headphone output, and while we're at it, some tone controls.

You know, wiring the amp with one channel inverted makes me wonder why any audiophile who has a normal/bridged switch on the back of their amp doesn't put the amp in bridge mode, use BOTH inputs, and reverse one set of speaker wires to get the power supply benefit.  Maybe it doesn't work that way, or maybe the stereo amp mode already does this internally on most amps, but it seems like an easy way to make a solid improvement.

I am noticing better imaging; the center image is easier to identify as being in the center.

[Wayner]

I had a Soundcraftsmen preamp with the same normal and inverted outputs. I did run the amp as you are, but really didn't notice much sonic improvement at the time. However, while Soundcraftsmen was some OK stuff, certainly not to the level of JR or AVA. Sound fun.

Wayner