[LordCloud]

invert phase.  As I bought this unit used and I can't find any info on it, I was wondering as a rule do tubed units usually invert phase or not?  And is there some way I would be able to find out?  Thanks all.

[hmen]

My AES AE-3 pre also inverts phase. I don't think it's very common but some tube pre's do invert phase. AES also makes a couple of amps that invert phase so if you the amp and pre together you don't have to invert the wires.

[JohnR]

Hm, the standard gain configuration for a single tube ("common cathode") inverts phase. I would think there most tube preamps would invert phase unless they are unity gain, or have two gain stages and loads of feedback.

As for how to tell, you could get an oscilloscope, or trace out the circuit. But instead, try this! Swap the polarity of the speaker leads and see which sounds best. Leave it that way. If you can't tell any difference, then the polarity doesn't matter  

[Carlman]

My AI tube pre inverts phase.  If I hook up the speakers without swapping leads, the highs get rolled off and the bass gets kind of thin or less detailed.

I think Sonic Frontiers SF1 lets you invert phase?  I may be wrong... My old Melos tube pre inverted phase but, I didn't know it until after I sold it... Doh!

I've only seen about 5 or 6 tube preamps and all of them inverted phase.  Plus, I agree with JohnR's assessment.... it makes sense from an elecronics standpoint...

[hmen]

JohnR - Thanks for the explanation. I couldn't figure out why they did that. I've only seen a couple of tube preamps and the other ones I saw didn't invert phase but did use feedback.

[BikeWNC]

Thanks for this thread.  After moving equipment around and auditioning speakers, I accidently   connected my speaker wires incorrectly, forgeting about the inverted polarity.  It's amazing how the system sounds so much more full with better bass impact when everything is hooked up right.

[Jay S]

This may be late but... my Joule tube pre inverts phase as well.  The designer claims that it allows him to eliminate an extra gain stage - less is better.

[Ron D]

My Rogue 99 preamp inverts phase

[Tonto Yoder]

I have a BAT VK-3i tube pre that does NOT invert phase (so the website says) though I don't know why that's the case.

[eico1]

What's interesting is does the phase of the recording have any effect on which way the system sounds best wired? I hear it's a 50/50 chance that a recording is what we expect. If you have ever done a recording you would know why!

steve

[doug s.]

eico, i'm w/you on this one.  unless ya have one channels' phase different from the other, i don't really think it matters.  my melos pre has a phase inwersion switch, which basically gets left alone.  i've played w/it occasionally, to no really noticeable effect.  tho i love that pre, the phase switch is pretty useless, imo.  the fact is phase on recordings is completely random, changing from recording to recording, even on the same album or cd.  which would make that phase switch really nice for some obsessive-compulsive golden-eared folk, i guess!    

doug s.

[Tonto Yoder]

What's interesting is does the phase of the recording have any effect on which way the system sounds best wired? I hear it's a 50/50 chance that a recording is what we expect. If you have ever done a recording you would know why!

steve

Silent Running (the isolation platforms) list record labels & their predominant phase.  About half are zero, other half are reversed.

http://www.silentrunningaudio.com/PhaseChart.htm

You can download the list, but they now require a name & e-mail.

[nathanm]

Some absolute polarity stuff