Tube preamps and inverted outputs

[Crimson]

Quite a few (if not all) of the tubed preamps available today invert thier outputs. Some of them include polarity switches, whereas others simply ask that you hook up your speakers out of phase. In the instance where there is no polarity switch, do you tend to hook up your speakers out of phase or not? And if so what kind of speakers do you have? The reason why I ask is because with my choise of speaker (Magnepan), its very difficult to hear a difference between when they are wired in or out of phase.




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[MichaelW]

Crimson,

I use the Cary SLP-98L tube preamp in my system. This preamp also ends up inverting the final output signal. The funny thing about this preamp is that there are three different verions of the circuit for the preamp, one that is a low gain and no feedback, one that is low gain and has some added feedback and a high gain version. The first two low gain versions have a extra run in the circuit designed so that the final output signal is non-inverted whereas the high-gain version does not. Hence, the high gain version has a far simplier circuit. I have heard all three circuit versions and own the high-gain version. When I was comparing the low gain versions (the one that non-inverts the final output signal) to the high-gain version (the one that ends up inverting the final output signal) I noticed that the high-gain version did not sound somehow *correct* compared to the low-gain version. The bass sounded boomy and the soundstage was compressed. Switching the speaker leads, to my Joseph Audio RM50si speakers, solved this for me. Keep in mind that in my system, I also use a tube amp. I have not tried my Cary SLP-98L with a solid state amp so I can't comment what the final sound combo was with the speakers leads switched or left as is.

[Crimson]

Thanks for the info! I have the Cary SLP-50B feeding Bryston monos (which I've had for several months now) but only read the manual this past weekend! Not knowing that the output signal was inverted, I had the speakers hooked up in phase. After reading the manual, I hooked them up out of phase and could not hear a difference. Methinks it may have to do with the fact that I'm driving Maggies which probably don't care either way, plus the fact that they have 6' of breathing room behind them (the soundstage depth reamined the same).




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