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What does "reverse phase" do???

tubeboob

tubeboob

Super Member
On my Fisher X202B Amplifier there is a "reverse phase" switch.

I push it to the on position and there is a difference in the sound, I'm not sure what the difference is, but there is a distinct difference.

Can someone tell me what this switch was designed for, and why don't we have that as an option on equipment today?

I look forward to the ejumication.:D

Cheers
 
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In essence what the reverse phase switch does is it takes one of the stereo channels and switches the +to the -, and the - to the +. It's as if you reversed one of the leads to your speaker only you're doing it at the amplifier.

This was done because in the very early days of stereo, some stereo records were mistakenly mastered "out of phase" for one reason or another and this was an easy way to correct that for those discs. (Early stereo Capitol LP's were prone to this for some reason.)

That feature lasted until the early 60's on various models of stereo equipment but by 1960 or so the learning curve of stereo recording and mastering was pretty much up to speed, so it became an arcane feature. It helps to have it though if you collect vintage early stereo recordings.
 
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My Pioneer has this also. 1962 make.
Labeled "stereo-norm" and "stereo-rev".
I was thinking it may also have been used for early am-am and am-fm stereo broadcasts. If you had the dials tuned to the wrong channel, you could reverse them with this switch...
Any merit in that idea?

Danny.
 
aussiedan said:
My Pioneer has this also. 1962 make.
Labeled "stereo-norm" and "stereo-rev".
I was thinking it may also have been used for early am-am and am-fm stereo broadcasts. If you had the dials tuned to the wrong channel, you could reverse them with this switch...
Any merit in that idea?

Danny.
Click to expand...

Your "stereo Norm" and "stereo-rev" is different from the phase reverse switch of this gentleman's Fisher. Your switch switches channels meaning whatever is plugged into the left channel will be put into the right channel and whatever is plugged into the right channel wil be put into the left channel. This was useful for those stereo clasical recordings where the orchestra perspective was reversed from what it should be (Strings on the left and brass on the right.)

Phase reversal changes the polarity of one channel; it doesn't reverse the channels like your switch does.

Think of phase like this, when a stereo system is connected "in phase", a mono signal in both speakers will move both left and right speakers in the same direction. If the mono signal is "out of phase," it will cause one speaker to move outward while the other moves inward. It also means you won't get a centered image of the mono signal, it will be diffuse and odd sounding.

Some early stereo discs were mastrered like that. One channel was "out of phase" relative to the other, resulting in a very odd sound. In fact, if you hit the mono switch on one of these recordings, you'll find that any sound common to both channels will cancel out and disappear. The phase reversal switch corrected that for those recordings, making them "right" and listenable with a proper phantom center image.
 
aussiedan said:
My Pioneer has this also. 1962 make.
Labeled "stereo-norm" and "stereo-rev".
Click to expand...

Your switch is different from the phase switch. Your switch just switches the left stereo signal to the right speaker, and the right stereo signal to the left speaker.

The "PHASE" switch just switches one of the speakers + & - wires, at the speaker connection.

EDIT: Ahhhh, ya beat me to it. :yes: I was typing as you were posting! :yes: :D

:music:
 
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My Kenwood KM-8002 Power Amplifier has Phase Switches for each channel.

Here is a picture of it.


MVC-011F.jpg
 
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My bell has the ster / rev / mono switch. In the phono section it has RIAA / LP / EUR.

What records used EUR or LP?
 
A lot of components invert phase. A lot of recordings are done in one phase, some in the other. I've always thought that phase switches made a lot of sense given that there is no standard, and you could be out of phase for any given recording.
 
tshoejohn said:
My bell has the ster / rev / mono switch. In the phono section it has RIAA / LP / EUR.

What records used EUR or LP?
Click to expand...

LP is for early Columbia's up to the stereo era (and beyond...there's a lot of evidence Columbia never fully adopted the RIAA as their standard LP playback curve.)

EUR is for early UK Decca & DG discs. Again, they seemed to hold onto their own curves even after the RIAA became standard.
 
empirelvr said:
Your "stereo Norm" and "stereo-rev" is different from the phase reverse switch of this gentleman's Fisher. Your switch switches channels meaning whatever is plugged into the left channel will be put into the right channel and whatever is plugged into the right channel wil be put into the left channel. This was useful for those stereo clasical recordings where the orchestra perspective was reversed from what it should be (Strings on the left and brass on the right.)

Phase reversal changes the polarity of one channel; it doesn't reverse the channels like your switch does.

Think of phase like this, when a stereo system is connected "in phase", a mono signal in both speakers will move both left and right speakers in the same direction. If the mono signal is "out of phase," it will cause one speaker to move outward while the other moves inward. It also means you won't get a centered image of the mono signal, it will be diffuse and odd sounding.

Some early stereo discs were mastrered like that. One channel was "out of phase" relative to the other, resulting in a very odd sound. In fact, if you hit the mono switch on one of these recordings, you'll find that any sound common to both channels will cancel out and disappear. The phase reversal switch corrected that for those recordings, making them "right" and listenable with a proper phantom center image.
Click to expand...

Thanks for saving me from making a fool of myself any further.
It is interesting how the makers of audio gear had to cater for the recording industry.
I guess not all that much has changed.
 
Not sure I saw it in the previous replies... but it's mentioned in the H/K A500 manual that this switch was there to phase the speakers properly back in the 60's. It was then common to have unlabeled (black-red or anything) speaker wires, thus you just had to flip the switch to correct it.

Patrice
 
Accuphase Inverted Phase from 2010

My Accuphase has an Inverted Phase button and the unit is from from 2010. Why would such a new unit require this?.

When playing a record with the button off I notice the woofer speaker reverberates and when it is off it doesn't. I also have a 10Hz button which makes no difference.
 
SX-950SX-980 said:
My Accuphase has an Inverted Phase button and the unit is from from 2010. Why would such a new unit require this?.

When playing a record with the button off I notice the woofer speaker reverberates and when it is off it doesn't. I also have a 10Hz button which makes no difference.
Click to expand...

For the first question- many CD players output in inverted phase, for whatever technical reasons. It's more common than many would think!

For the second question- you're changing the phase between speaker and cartridge. Rumble-feedback from the speaker to the phono cartridge is in-phase in one position (hence, the speaker 'reacts' more to ultra-low frequency feedback, since it's like positive feedback), and is out-of-phase in the other position (the woofer doesn't react nearly as much to ULF feedback, since it's acting as negative feedback- it cancels out, in essence).

As for why the early amps had one-channel phase invert- it was primarily because of the existence, in the early stereo days, of vertically-modulated stereo, vs. horizontally-modulated stereo, on LP records.

Some early stereo records were vertically modulated- the channels were out-of-phase, so the needle would go 'up and down" quite a lot in the groove. This was hard on many stylus/cartridge/arm combinations, so the standardization was made, later to ONLY doing horizontal modulation.

The main difference, is that for vertical modulation, one channel is OUT of phase (in relation to a mono recording). Whereas, with horizontal modulation, they're IN phase, when recorded. So, to play those few vertically-modulated records, you had to invert one channel.

BTW: These vertically-modulated records are also the ones, that say "NOT for playback on MONO systems". You would virtually hear NOTHING from the output, since the information common to the channels, would cause the stylus to go UP and DOWN, whereas mono cartridges read SIDE-to-SIDE. In contrast, horizontally-modulated stereo is OK for mono cartridges- the common information is side-to-side, and ONLY the difference (the things that makes one channel different from the other) are vertical).

But, in short, that's the main reason why we have those single-channel phase-invert switches... for those odd early stereo records, made with the short-lived vertical modulation format...

Regards,
Gordon.
 
A lot has been covered here but not all ways of changing the phase are the
same on all this equipment, some change phase on 1 channel, and some will
do it on both channels.

To go along with Gordons first response, if the cd-player is off on "absolute"
phase then swapping both channels on an amp/whatever would be a way to
put the music back in phase.

Also as said many recordings differ in there absolute phase which can screw
up imaging when not played back as intended so having a switch to throw on
to change both channels can be a good thing otherwise swapping the speaker
cables on both speakers would be your only way to accomplish it.

Also amps/preamps, and other devices may invert absolute phase just from the
design of there circuits so swapping both speaker cables is a way to get it back.

So when talking phase it's proper to figure channel to channel phase an absolute.
(they are 2 completely different things)
 
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