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Absolute phase inversion

R

rashers10

pfm Member
Have just bought an XTC Pre-1 to use with existing power amp.
Manual says this is an absolute phase inverting product and speaker connections need to be reversed at the power amp end.
I am not in the least bit technical! What does this mean and should I do it?
All help most welcome!
Also, remote not available but uses RC5 interface. What remotes are likely to work with this preamp?
Cheers all.
 
Reverse Red (posititve) and black (negative) on one end only of your speaker cables (amp end or speaker end, it doesn't matter.) Just make sure you switch red and black on both left and right speaker cables or you'll have an out-of-phase condition.

Try googling "RC5 universal remotes"
 
re phase inversion, this means at the speaker end only of the speaker cables, connect the postive cable to the negative terminal, and vice versa, ie connect the black plug to red socket and red plug to black socket (if you're using bananas) - you get the idea.


cheers
Matt
 
+ve volts at the loudspeaker input ought to cause the driver(s) to move forwards, this is standard practice.

A non-inverting preamp will take +ve at its input and give +ve on its output, which a non-inverting power stage will pass through as +ve to its output, and the speaker driver will move out of the box and "compress" the air in the room.

If you have a component anywhere in the chain that inverts then the driver will be forced back into the box, creating a rarefaction in the room. This might sound a bit different, depending on various factors. If you have two inverting components then their effects cancel, no need to change anything.

It shouldn't matter which end of the loudspeaker cable you reverse - either do it at the speaker inputs or at the amplifier outputs.

Some power amplifiers have one inverted channel - my NADs for example, which allows them easily to be run in bridged mode. :)
 
Sure you will - but make sure you switch the amp off before swapping speaker cables around...
 
Of course, XTC could have avoided the whole issue just by wiring the output sockets differently - I wonder why they didn't (perhaps the matching power amp also inverts the phase)?
 
rashers10 said:
....Manual says this is an absolute phase inverting product and speaker connections need to be reversed at the power amp end...
QUOTE]

Nothing of this does matter, if only the left and right speaker cables are connected the same way to get both speakers in-phase. Why? Any unit used in the recording/production process may be inverting or non-inverting: The microphone, every amplifier or buffer stage, you name it.*
Among sound engineers it is traditionally established as a fact that nobody can hear any difference anyway, so they do not care if the piece they put into the chain is inverting the signal or not.

This means that the typical record collection which contains records from several labels, of different vintage etc will contain just as many inverted as non-inverted recordings, statistically. Therefore an inverting playback set-up may in half the cases actually give a non-inverted final result, and vice versa.

It probably. would be a sensation if a person could prove beyond doubt the he could detect a difference. Even a sound like hand-clapping which is very simple and should make the mic membrane moved inwards at each clap and -ideally- a loudspeaker membrane move outwards,
(assuming no further distortion in the time domain), will sound essentially the same to the human ear if inverted. (to feel sure myself about this, I have experimented a lot with my own recordings and a physically working switch).

Now let us say that someone in the tiny group of audiophiles who claim that they can hear the difference, owned (or bothered about) only one single record and the recording was made from one mic (or a single set set of identical mics, and no other fundamental distortion in the time domain was introduced, say in the speaker x-over), then one could understand that he wanted to get it right anyway/just in case.( But if this was non-acoustic or a multi-mic production, it would probably contain both inverted an non-inverted material, and make the task even more hopeless).
Sorry for my English, it is probably far from correct, and I hope I have not inverted the truth. Cheers,Z



*The two leads coming from the mic will give a positive or negative signal for a single soundwave hitting its membrane, depending how you connect them to the nest stage, it just like a loudspeaker in reverse.
Click to expand...
 
Bit of an old thread this but after doing a bit of searching thought I'd post here...

Was hunting round on t'web last night and discovered that the Chord DAC64 is also phase inverting (on the phonos outputs anyway which I use - not sure about balanced outputs). Actually I think I did find this out before but had forgotten about it - I vaguely remember trying swapping cables a couple of years ago and didn't notice any obvious improvement.

Anyway the system's moved on a bit since than and my current room is a LOT better acoustically, so I swapped the speaker cables last night to give the correct phase - well I have to say I reckon i heard a worthwhile improvement. I won't go into detail yet as to what improvement I've heard but just wondered on those that have heard a difference, what the difference was they heard so I can compare my findings?

needless to say it's a bit of a pain as my other main source is an FM tuner with the correct phase and i reckon it's enough of a difference to warrant swapping back if I'm doing some serious radio listening...
 
YNWOAN said:
Of course, XTC could have avoided the whole issue just by wiring the output sockets differently - I wonder why they didn't (perhaps the matching power amp also inverts the phase)?
Click to expand...
Can anyone tell me why any amp (pre or power) should invert phase when all they have to do is what YNWOAN suggests? It seems so simple and obvious.
 
Some circuit topologies simply invert phase, as it's inconsequential to how hifi sounds why should designers add extra circuit to flip it back again.
 
On a similar note why can I hear "something wrong" if I inadvertantly connect a Record Deck or CD player Stereo Opposite, i.e. Left to Right and Right to Left between the player and Pre..even if I have never heard the music sample before. I notice this more on commercial pop, Jazz and even some Classical stuff..it drives me nuts and sounds off side to Left or Right until I re-connect the right way.:confused:
 
barrymidd said:
They could simply wire the +ve output to the -ve terminal and vice versa. No extra circuit needed.
Click to expand...

Not on a single-ended preamp.

You could do that on a single-ended power amp output, but with the risk that sooner or later a punter ties the speaker '-' to real ground.
 
Because you are prone to flights of audio fancy.

Or both your cd player and deck have faults in their design that afflict only one channel and your pre or power amps similarly have the same which either exacerbates the fault or ameliorates it.


Which do you think most likely.
 
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