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Re: Few highend preamps in my experience have invert switches nt

Hi Mark.

To me, 'phase' & 'polarity' is terminlogy difference in its practical sense.

According Rob Karsten, designer of Atma-Sphere Music Systems, the 'inverse' switch on the front panels of its MP-1 MK2 & MP-3
pre-amp, is to ensure "absolute system phase" is in line with the
correct phase in which the music was recorded.

Unfortunately, many music performances were unintentionally recorded out of phase or wrong polarity, thanks to those recording engineers' 'great' job. This inversed polarity or phase sonic effect
will render individual instruments sound 'tarnished' & lack of 'attacks' or 'bites'.

However, such inverse sonic effect will not be so noticeable unless the recordings are acoustical performances, e.g. classical, jazz &
non-electronic-type music, & were recorded with basically, two microphones, where reversed phase or polarity is crucial.

For thode modern music, heavily electronic & recorded in muli-miking & multi-tracking format, the sonic importance of polarity or phasing
is out of consideration. One just can't detect the difference.

To ensure the rig is reproducing music recordings of the correct polarity or phasing, one can always reverse the polarity of speaker terminals, of BOTH channels, i.e. (+) switched to (-), according to
Rob Karsten. Then, listen to any sonic improvement. If it does sound better, it means the rig is now in "absoluate system phase". Otherwsie, undo what one just did.

However, it will surely be a pain if for every recording one got to carry out testing by reversing speaker terminals, in order to get the best sound effect. Here comes the 'inverse' switch, so that such hassle can be eliminated for good.

However, there is one technically issue here. To reverse the phase
of the amp circuit, it needs a phase or polariity inverter. An active
one, usually with some gain, will introduce unwanted distortion.
The better topology is to employ differential input circuitry, so that
the signal can be directed to other reversed phase input with a simple
passive switching method, without adding unwanted distorition.

Some hi-end amp with differential input driving stages will do polarity or phase reversing properly, e.g. Atma-Sphere.

More on this issue next time.

Good listening.

cheap-Jack
Aug 25, 2003.


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  • Re: Few highend preamps in my experience have invert switches nt - cheap-Jack 13:58:32 08/25/03 (0)


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