Phase Inversion in Preamplifer?

I just bought a used Audible Illusions 2D here on a'gon. This will be my first venture into separates. I've learned that AI preamps have inverted phase, so it's recommended that I switch +/- polarities at the speaker-amp hook-up. OK. But according to AI literature the phono stage of the preamp is NOT inverted, only the output stage is. So, since I listen to both vinyl and CDs, what do I do? Should I reverse speaker wire polarity or not?

Incidentally, the amp I'll be using is an ATI 1502 -- still haven't been able to find out if it inverts polarity or not. But based on my (limited) research thus far it appears that phase inversion is a design of preamplifiers more than power amplifiers. Is that right?

It does appear that the phase inversion issue happens more in preamps than in amps.
I do not believe that it make a great difference at all. My Joule Electra LA 150 preamp inverts phase as well and in my research it really does not matter and is not something to keep you up at night.
Also keep in mind that even within the same CD, the songs can/do flip/flop the phase.
Yes, thanks for the reply, but what about the fact that the phono stage is not inverted while the rest is? Is this anything I need to do anything about?
I have a preamp that allows for inversion of phase by remote control. Yes, one can hear a difference quite readily. But, with most recordings, the difference is subtle, and it is not entirely clear which is the preferred setting (e.g., with one setting the vocals may be more realistic, while the piano becomes unnaturally phasey).

Because recordings seem to be all over the place, there is no reason to really worry about phase if you don't have the means (and will) to switch on a recording-by-recording basis. That kind of switching is only practicable with a phase switch, preferrably, one switch by remote.
The fact that the phono stage does not invert is meaningless. The signal still passes through the line stage after leaving the phono stage, so even when using phono your output will be inverted when leaving the AI, period. You have what is called an integrated preamp, which is similar to an integrated amp. Instead of a preamp and amp in one box, you have a phono stage and line stage in one box. As you become more familiar with seperates, you will realize that the phono stage runs through the line stage and then on to the amp.

Bottom line, everything coming out of your AI will be inverted. The only concern you would have is if the phono stage also inverted, which would then cancel out the line stage's inversion. However, it does not, so you have no worries.

So change the polarity of your speaker cables only once, either at the amp output OR at the speaker input. Note that if you change polarity at both ends you will defeat the purpose.

Hopefully this helps.

I have to say that the whole phase inversion thing leaves a bit to be desired. Much good advice has already been posted. From my perspective, I have a Joule Electra LA-100 MkIII that inverts phase and a Hagerman Trumpet phonostage that has a polarity switch. I recently acquired a passive preamp that does not invert phase. My system is set-up so the digital front end runs through the passive and the analog front-end runs through the Joule. So I don't have to keep swapping the speaker leads back and forth, I just leave them wired + to + and - to -, using the polarity switch on the phonostage to reverse phase to compensate.

The funny thing about all this is that I really can't tell the difference. I have a few test discs, two CD and one LP. Using the voice phase tests swapping the speaker leads made no difference to my ears. However, swapping IC leads did. As for the Rives CD, they use a track with solo piano followed by solo bass. Again, I could not tell the differnece. Although Larri's point about the piano seems to make some sense now that I think back on it. I may have to revisit that test track.
FWIW Jmcgrogan2 is absolutely on point. Most sources that you will attach to your pre-amp won't have "inverted phase". Probably the description arrises out of the fact that tube phono preamps often do invert phase, especially the little one tube cheapies. I have noticed that the inverted phase issue arrises most often in tube equipment with a single tube per side. Perhaps those that use a second tube as a cathode follower correct for the initial inversion. Just a thought.......
Newbee - At least in my experience, the Joule LA-100 MkIII and Cary SLP-98 use cathode (in the Joule's case it is a Mu) followers and both inverted phase.
The line and phono stages of the Audible Illusions Modulus
series are both phase inverting, but since the phono stage
output is always routed through the line stage (unless you
are using the phono stage only through the tape output) the
net result is that your sources input directly to the line
stage will be inverted in polarity while the phono stage
input will be in proper absolute phase. Whether you will be
able to hear the difference is debatable, but the easiest
way to achieve correct phase for all sources is as follows.
Reverse the polarity of both speaker cables at either the
amp end or the speaker end (not at both). Then also change
the polarity of the connections to each channel of your
phono cartridge. This will resolve your absolute phase for
both line level sources as well as your phono playback.
The problem with this whole discussion is Polarity and Phase Inversion can either mean the same thing or something completely different, depending on who's talking and what component they are talking about.
Preamps by Conrad Johnson all invert phase. I could not tell any difference by changing the polarity to my speakers. It is also interesting to know that many recordings are recorded phase inverted. Since your preamp inverts phase some of these recordings should turn out just right if you can hear any difference at all.
Sugarbie - you're correct about phase inversion and polarity. In my case, while it is called a polarity switch on my phonostage, the manufacturer suggests it is used to invert phase.
I just wanted to be sure that when you made the statement
" voice phase tests swapping the speaker leads made no difference to my ears. However, swapping IC leads did"

That you understand that swaping speaker cables chage polarity in each individual channel, while swapping Interconnects just swaps channels r l
Autio, re-reading my post I did not make myslef clear. Swapping the speaker leads at the amp binding posts (+ to - on each channel) I could hear no difference, meaning the voice on the test CD stayed centered and was well imaged. However, with the speaker leads wired correctly, swapping the RCA leads at the amp inputs so that L from preamp output goes to R amp input and R preamp output goes to L amp input, I could hear a difference. The voice on the test CD was not centered, instead appearing as if it were coming from different areas.
If a system is out of phase you are more likely to hear differences at the frequency extremes, not in the center midrange like vocals. Affects the bass the most in my experience.

I would think having the right channel out the left and vise-versa would ruin the focus/image. Assuming the singer is in the center....
The voice would normally be to the left of the right channel microphones and to the right of the left channel microphone.
Switching the channels puts the sound of the voice on the outside of both channels instead of in the center.
Then a test CD that uses a voice to do phase testing seems to be flawed. Something like the Rives CD where piano and bass are used would be more accurate. Correct? On that CD the bass was fine in both tests. However, I think Larryi may still be on to something with the piano, and I'm going to revisit that.
When both speakers are not wired in phase this will of course effect the sound, more noticeably the bass. But if all minus & plus connections between your amp & speakers are correct, and you insert a phase inverting preamp, at this point it will take a very good ear to hear the differences because some recordings are phase inverted (as mentioned above). Personally I would not be too worried over a phase inverting preamp & making corrections. I was told that in order to manufacture a phase correct preamp it will require additional sound degrading circuitry.
Clio09, a test CD to make phase corrections is a very good investment. If there are no other components in your system inverting phase other than the preamp than reversing polarity on both of your speakers will correct this. I am just saying it is difficult to hear the difference if this is the case. Good deal.
If your system is phase correct, playing music recorded out of phase will not change the phase of your system. If not a mistake, they may have recorded it out of phase to create the sound they wanted when you play it back, that is all. Grooves on an LP or digital code on a plastic CD cannot invert the electrical signal going through your system or add a gain stage to your preamp. You are playing the sound of something out of phase on a system in phase, that is all.

If your CD player has a polarity switch, not sure if it really corrects it or just makes it something else. I have such a CD player and that owners manual says it reverses polarity, NOT to be confused with inverting the phase.

A way to have fun with phase is to play the same signal through both speakers (use bookshelf speakers). Reverse the speaker wires on only one speaker. Now place the two speakers together face to face. It won't be a perfect seal, but if perfect the sound volume would go away (or in your case it would be greatly reduced). This is because the two speakers are playing the same sound 180 degrees out of phase with each other. They will cancel each other out creating silence.

This is similar to the experiments they do to try to make luxury automobiles quieter. They play the frequencies of road noise out of phase to cancel out the actual road noise, making it quieter inside the automobile.
The way it was explained to me is if the preamp is inverted one must switch speaker leads + - at either amp end or speaker end. But because of the possiblity of the amp being inverted one must try both ways. Taking some tracks with good vocals, the proper way will show more Depth on the vocals. I was able to notice this but it wasn't a big difference but it was there. In this hobby it is about getting the small gains and not costing anything is a Bonus.