# Phase inversion Preamps



## sportflyer (May 2, 2010)

If the preamp is phase inverted, then I will need to reverse the speaker connections for 2 ch operation. This becomes a real pain when switching between a non phase inverting Receiver in HT mode and 2 channel listening. Any simple solution ? 

Tks


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## Jungle Jack (Jul 28, 2009)

Hello,
Just to make sure I am clear on this. You are using a 2 Channel Preamp with HT Passthrough that allows you to integrate it into your HT? I know several who have done this very thing allowing them to have a Music focused 2 Channel experience whilst easily switching to 5.1. 

If the Preamp is Inverted, you could always connect it in an opposite manner. Inverting the inversion if you will. That way you would still benefit from the Preamp without having to swap Speaker Cables when watching HT. I know many Integrated 2 Channel Amplifiers also offer HT Passthrough as well where it provides the Amplification for the Mains. Do let me know if I have this scenario mixed up.
Cheers,
JJ


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## drchicago54 (Jun 5, 2012)

I am not sure there is any way to invert polarity at the preamp end. It is the way it is. To my knowledge you can only invert at the speaker terminals either at the power amp or speaker end. Otherwise, you need an inverting power amp much like Conrad Johnson does with some of their new power amps. Good luck. There is a guy at Stereo Unlimited in San Diego name Bruce who would be happy to help you solve this. Give him a ring at 619-223-8151


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## sportflyer (May 2, 2010)

Other components in the chain ie Receiver and power amp are not phase inverted, so I hesitate to buy a phase inverting preamp because the only way I can think of to reinvert the overall phase is to swap connections at the speaker inputs. This then makes switching between Ht and 2 channel a nuisance. I dont think there is a nice solution .


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## phycomp (Jun 19, 2012)

Forgive my ignorance, but why is phase inversion important? I didn't think our ears are sensitive to phase as long as both speakers are in the same phase.:rubeyes:


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## JoeESP9 (Jun 29, 2009)

Read the excerpt below from Clark Johnsen's book. Check the link for a longer excerpt.

http://www.positive-feedback.com/Issue1/cjwoodeffect.htm

Oh, the Wood Effect. Discovered by Charles Wood at the Defense Research Laboratory in 1957, it was first reported in 1962 in the Journal of the Acoustical Society of America. "Wood used as a signal a sinusoid partially clipped during half of each cycle. The resulting sound had a different timbre when the flat-topped portion was presented to the ear as a rarefaction, than it did when leads were reversed and the flat-topped portion was presented as a compression." There you have it, ladies and gentlemen: An asymmetric sinusoidal signal, presented those two dissimilar ways, with no other distortion, was proven to sound very different each way. Let’s see, what else in the sonic realm generates asymmetric signals? Well, ta da! That would be musical instruments! Which explains how polarity permeates our entire audio world, albeit through negligence, because we hear normal and inverted polarity (more accurately, compression and rarefaction) so very dissimilarly, ,yet rarely are they differentiated by us in playback.
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Phase is measured from input to output. Amplifiers and preamplifiers are constructed of amplification stages. Each stage inverts phase. Devices that don't invert phase have an even number of stages.Those that have an uneven number of stages invert phase. The number of stages a device has is not related to it's quality. 

Some can hear the difference in absolute phase, others can't although this may be somewhat system dependent. Try it for yourself by reversing both speaker leads at the same time. They will still be in phase with each other but have different absolute phase.


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## drchicago54 (Jun 5, 2012)

Certain pre and power amps invert phase I assume by the nature of their design. For example I have a Conrad Johnson preamp that is a hybrid of sorts. It's input gain stage is a single tripod tube that by its nature inverts phase. The output stage is FET and does not invert it back so somewhere in the circuit to keep an even number of inversions so the net change is 0 I need to either have a power amp that inverts it back or reverse my speaker leads. My power amp is all tubes and does not invert phase so to keep the sound in phase I switch my speaker leads. I know of no inherent advantage of inverting phase but it seems to happen as a side product of the preamps design


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## JoeESP9 (Jun 29, 2009)

Not to sound "snarky" but, have you listened for yourself as to whether or not a change in absolute phase is audible to you with your present system? You may be trying to solve a problem that doesn't exist. 

IME the ability to hear absolute phase is highly speaker dependent. esl's and single driver systems make it easier to hear as they have no crossovers to alter phase and timing. 

All CJ preamps I'm aware of invert phase. On another thought, which CJ preamp is a hybrid?

If you want to preserve absolute phase you must know what the phase of the source is. There is no standard as to what phase a recording is or should be. Presuming you can hear the difference, it's likely that each recording (sometimes different selections on the same recording) has a different phase than the previous one. This is why many higher end CD players used to include phase reversal switches.


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## drchicago54 (Jun 5, 2012)

You are not being snarky at all. I have no idea if I can hear phase differences in recordings because I don't know which recording was recorded in what phase. My ears are not super discerning.
I have the CJ ET 5 preamp. I do believe most if not all CJ
preamps invert phase


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## sportflyer (May 2, 2010)

Here a link to check how good you are at detecting absolute phase . 

http://www.audiocheck.net/blindtests_abspolarity.php

I failed the test  !


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## JoeESP9 (Jun 29, 2009)

drchicago54 said:


> You are not being snarky at all. I have no idea if I can hear phase differences in recordings because I don't know which recording was recorded in what phase. My ears are not super discerning.
> I have the CJ ET 5 preamp. I do believe most if not all CJ
> preamps invert phase


Why not give things a listen and find out for yourself if you can hear a difference when the absolute phase is changed? That makes more sense than agonizing over something you may not be able to hear.

I've been aware of the Wood effect for quite some time. I set my system up to make those two channel recordings that sound best, sound their best. Most of the other recordings aren't good enough or have too much studio overdubbing and "sweetening" to tell and MC sources are a can of worms I prefer not to open. If it turns out you can hear phase differences you should investigate a quick easy way of changing it. If I were you I'd set my preamp and two channel sources to sound their best. I wouldn't be concerned too much about absolute phase with MC sources going through my surround processor. 

I'll freely admit, were my preamp and/or processor equipped with phase reversal switches I'd probably use them. In their absence I just leave things as they are. It's all to easy to over intellectualize things in this hobby. I much prefer having fun. Much as I hate to say it, because many people who have truly atrocious sounding systems are always saying it, if it sounds good to you then it is. 

Sometimes it's better to just enjoy what you have. This may be my age speaking so I won't be offended if no one listens to me.


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