How do you know if your preamp has inverted the phase?

[duderduderini]

Its monday and I feel like asking a dumb question.
I read somewhere that out of phase stages in a preamp can cause some loss of listening pleasure.
So the dumb question is I have 2 stages in my preamp for phono (Ixys current reg on each anode with output of 1st stage off anode into grid on stage 2 (which also has an Ixys reg on it) feeding into an srpp line stage?
So what is the rule of thumb here?
Thanks
Nick

[ray_moth]

Rule of thumb is a grounded cathode stage inverts the phase; grounded grid and cathode follower do not. SRPP counts as a grounded cathode, so your preamp inverts phase twice (once in each stage), the net effect being no inversion.

If you believe it's possible to enjoy music more without inversion, this is good news for the preamp but what about the main amp?

[duderduderini]

Hi Ray_moth
I have 2 stages in the phono section. They each have an ixys current
reg on them. They are grounded cathode. So thats 2 and phase is inverted twice. The third stage (line stage) counts as a grounded cathode as well so shouldnt the preamp be out of phase when I am playing records. Come to think of it it should be out of phase when i am just using the line stage.
Does being out of phase mater?
I am using one preamp to feed a ss power amp and the other feeds my pp 6550 power amp.
Can anyone enlighten me on the relative merits of phase reversal and what if anything can be done to ameliorate it?
Thanks

[oshifis]

Originally posted by duderduderini
Does being out of phase mater?

The answer is easy: listen to your system for a while (I suppose it's done already). Reverse the speaker cable polarity and listen again. Compare.
It is good to know that virtually every CD player having a single inverting opamp analog stage does reverse polarity.

[ray_moth]

The third stage (line stage) counts as a grounded cathode as well so shouldnt the preamp be out of phase when I am playing records.

Ah, there's a third stage! From your description I thought there were only two. In that case, when using all three stages, yes, it will produce an inverted output. Whether this will be audible is outside my experience but, as I said before, if you don't know whether your power amp inverts then all bets are off!

P.S. I'm a skeptic. I suspect it only matters if you think it does, like some people can imagine themselves a toothache

[duderduderini]

Hi Guys
I did the listening tests and found this
1. On my phono section with the polarity reversed on the speaker outputs, it suddenly becomes , to me anyway, a LOT more listenable.
BUT
2. The cd player sounds better with the polarity switched the other way
This ties in with the opamp stage in the cd inverting the signal and my 6sn7 srpp inverting to normal phase.
So given this, I really need either a new phono stage which remains inverted so that the srpp can invert it again OR I need two line stages. One which inverts and vice versa.
The phono stage i built uses 2 stages with e280f with an ixys current reg as i mentioned. the output comes off the anode of each stage. I really like this phono stage and would be loathe to change it. I figure a 3rd stage- perhaps a cathode follower might help. Is it right that a cathode follower is unity gain?
What suggestions do you guys have?
Or maybe i could just change the speaker wires over between cd's and vinyl
By all means speak your mind but go easy on me.. i dont have the tube guru minds of most here. No doubt some or all of my theory is flawed
Thanks
Nick

[dnsey]

You'll probably be able to swap the 'hot' and 'ground' connections at your phono cartridge.
True, some carts have a shield connected to the ground pins, and others have their grounds commoned, but there's no harm in trying!

[duderduderini]

Hey!!
that sounds brilliant. i will try this and get back to you
Its the simplest solutions that possess the most beauty
thanks
Nick

[oshifis]

I use 3 stages in the phono, the passive RIAA eq is divided between them (bass boost between 1st and 2nd, treble cut between 2nd and 3rd). This arrangement is inverting, and the line stage is also inverting. So does the I/V converter after the DAC. I don't care about the tape and tuner inputs.

But how can we be sure that the correct polarity is maintained during the disc cut or CD mastering on every recording?

[EC8010]

Originally posted by oshifis
But how can we be sure that the correct polarity is maintained during the disc cut or CD mastering on every recording?

You can't and it probably isn't. Suppose you had a snare drum, would you put the microphone above or below? (They're opposite polarities.) What's actually done is to mix both with one inverted. But which one? What about direct injection from an electronic instrument? Or the difference between a pressure microphone and a velocity microphone?

I believe absolute polarity is a function of asymmetric distortion in small loudspeakers, so one way round sounds better than the other, depending on track.