Tube Pre-Amps and polarity

kach22i · Sep 26, 2012

When I purchased my GRAAF WFB ONE pre-amp about eight years ago, the seller told me that the output has switched "polarity", and that I should invert my speaker wires or invert my output interconnects (but not both at the same time).

That is to say put R to L and L to R.

However, I have just re-tubed the unit and nothing in the owner's manual mentions reversed polarity.

In fact it says: Connect the input and output pins to the LEFT and RIGHT channels respecting the signal direction. Assure that the connections are good.

Was I given bad information by the stereo shop which sold me my unit, or is the manual a bit neglectful?

Is there a simple way to test the polarity of my unit?

MylesBAstor · Sep 26, 2012

kach22i said:
When I purchased my GRAAF WFB ONE pre-amp about eight years ago, they seller told me that the output has switched "polarity", and that I should invert my speaker wires or invert my output interconnects (but not both at the same time).

That is to say put R to L and L to R.

However, I have just re-tubed the unit and nothing in the owner's manual mentions reversed polarity.

In fact it says: Connect the input and output pins to the LEFT and RIGHT channels respecting the signal direction. Assure that the connections are good.

Was I given bad information by the stereo shop which sold me my unit, or is the manual a bit neglectful?

Is there a simple way to test the polarity of my unit?

The number of gain stages, if you can find out, in the preamp, will tell you. Odd = inverting; even = non-inverting.

I assume that you just reversed L & R at the speaker or amplifier end? Other than that, the only way I know of is listening; sure there must be a test disc somewhere.

kach22i · Sep 26, 2012

MylesBAstor said:
............ a test disc somewhere.

I have a few somewhere.

I'm not going to fry anything with non-inverted polarity, right?

I had the outputs at the pre-amp which go to the amp reversed on purpose. I'm debating on doing it again.

There is a second pair of outputs which I use for my dual voice coil subwoofer, would I want to switch this one too?

microstrip · Sep 26, 2012

kach22i said:
When I purchased my GRAAF WFB ONE pre-amp about eight years ago, they seller told me that the output has switched "polarity", and that I should invert my speaker wires or invert my output interconnects (but not both at the same time).

That is to say put R to L and L to R.

However, I have just re-tubed the unit and nothing in the owner's manual mentions reversed polarity.

In fact it says: Connect the input and output pins to the LEFT and RIGHT channels respecting the signal direction. Assure that the connections are good.

Was I given bad information by the stereo shop which sold me my unit, or is the manual a bit neglectful?

Is there a simple way to test the polarity of my unit?

Polarity is notcompensated reversing right channel with left channel.

Polarity changes the phase of the electrical and the acoustical signal . This means when the speakers are pushing they should be pulling and surely pulling when they should be pushing.

Two inverts will give you normal polarity. If your preamplifier inverts polarity you have to invert again to compensate for it. The easiest way is changing the + and - wires of both speakers (keeping L and R surely) . In order to do it you must be sure your speaker system does not have a common ground, such as some systems with subwoofers.

If you your preamplifier has two sets of RCA outputs one normal and one invert , you can choose the invert for carrying this compensation.

mep · Sep 26, 2012

I must be missing something here or I am tired. Swapping ICs from left to right will have no impact on reversed polarity. You can only correct reversed polarity by switching the + and – at the amp or at the speakers, but never both at the same time or you will still have reversed polarity. Owner’s manuals usually always call for reversing the polarity at the speakers. If you leave the polarity reversed, it won’t hurt anything and some people can’t even hear it. If the polarity is reversed, when your speakers should be moving forward (excursion), they will be moving backwards (rarefaction) instead. Thought of another way, when your speakers should be blowing they are sucking, and when they are sucking they should be blowing.

microstrip · Sep 26, 2012

kach22i said:
I (...) There is a second pair of outputs which I use for my dual voice coil subwoofer, would I want to switch this one too?

Be careful - is it a passive subwoofer with dual coils or an active sub (with filter and amplifiers) that drives a dual coil speaker?

kach22i · Sep 26, 2012

microstrip said:
Polarity is not compensated reversing right channel with left channel.

Correct.

I didn't mean to imply messing with the channels only the + and - of each respective channel.

It looks like I'm not at risk of doing damage operating out of phase should my unit be a phase inverting type.

I'll use a test CD or the Ricky Lee Jones LP I have on hand.

https://groups.google.com/forum/?fromgroups=#!topic/rec.audio.opinion/q4QKKlpHMM8

Get the recording of Rickie Lee Jones first album, called,
appropriately, Rickie Lee Jones. Listen to the track EASY MONEY. With a
system that is correct in absolute phase, she sounds like she is in fornt
of the instruments (naturally!) and when the system inverts, she sounds
like she is behind the insstruments. There are many other recordings
where this effect is easily heard.

Steve Williams · Sep 26, 2012

kach22i said:
When I purchased my GRAAF WFB ONE pre-amp about eight years ago, the seller told me that the output has switched "polarity", and that I should invert my speaker wires or invert my output interconnects (but not both at the same time).

That is to say put R to L and L to R.

However, I have just re-tubed the unit and nothing in the owner's manual mentions reversed polarity.

In fact it says: Connect the input and output pins to the LEFT and RIGHT channels respecting the signal direction. Assure that the connections are good.

Was I given bad information by the stereo shop which sold me my unit, or is the manual a bit neglectful?

Is there a simple way to test the polarity of my unit?

My preamp is also an inverting preamp

All I do is reverse the speaker cable leads at the outputs of my amp

I also have a pair of subs coming out of the preamp and I reverse the speaker cables as well to the subs

LL21 · Sep 26, 2012

Steve Williams said:
My preamp is also an inverting preamp

All I do is reverse the speaker cable leads at the outputs of my amp

I also have a pair of subs coming out of the preamp and I reverse the speaker cables as well to the subs

ditto.

Steve Williams · Sep 26, 2012

It's pretty simple

mep · Sep 26, 2012

Steve Williams said:
It's pretty simple

Unless you have multiple source components and one of them inverts phase. This is most common with tube phono stages and mixing with a CD player for instance.

microstrip · Sep 26, 2012

mep said:
Unless you have multiple source components and one of them inverts phase. This is most common with tube phono stages and mixing with a CD player for instance.

Still very easy - you just swap the + and - at the cartridge!

I hope you do not have a tuner that inverts the phase - then we could have a problem.

kach22i · Sep 27, 2012

mep said:
Unless you have multiple source components and one of them inverts phase..................

My mind started to go in this direction while I was back there, then I felt a certain audio madness start to set in.

Thanks to everyone, I had just replaced the tubes in my pre-amp but not the ones in the phono section, and I have the same problem I had before (inverted polarity aside).

Guess it wasn't the tubes gone bad after all.

I'm getting sound out of the left speaker only, the balance control seems to have no effect (some volume fluctuation). When I turn it all the way to the right, sound still only comes out of the left.

I'm guessing it could be the balance potentiometer, but really don't have an idea, just guessing.

I'll double check any possible physical or mechanical linkages which may or may not exist between the channels.

Looks like the pre-amp is going to the shop with the in need of repair tube power amp I have.

I'll be getting my old Carver CT-17 pre-amp/processor/tuner out of the basement next. I really hate that thing after hearing a true non-mid-fi pre-amp in my system.

DonH50 · Sep 27, 2012

I used to be fairly religious about absolute polarity, but over time discovered (a) it was almost impossible to hear if it was reversed (though easy to mesaure), and (b) a number of recordings had reversed or random polarity so it didn't really matter anyway.

mep · Sep 27, 2012

DonH50 said:
I used to be fairly religious about absolute polarity, but over time discovered (a) it was almost impossible to hear if it was reversed (though easy to mesaure), and (b) a number of recordings had reversed or random polarity so it didn't really matter anyway.

But if you know it's reversed, it will drive you crazy. Otherwise, you have to turn your audiophile card in and listen to Bose.

jazdoc · Sep 27, 2012

If polarity (phase) is wrong, you will know it. When compared to correct phase, bass output is markedly decreased and soundstage becomes indistinct and wavering. If you have any question, use a mono LP and try hooking up your speakers both ways...it's really easy to hear the difference and tell which is correct.

mep · Sep 27, 2012

jazdoc said:
If polarity (phase) is wrong, you will know it. When compared to correct phase, bass output is markedly decreased and soundstage becomes indistinct and wavering. If you have any question, use a mono LP and try hooking up your speakers both ways...it's really easy to hear the difference and tell which is correct.

Doc-Are you sure you aren't talking about "out of phase" vice reversed phase? What you just described is what "out of phase" sounds like and not reversed phase.

DonH50 · Sep 27, 2012

mep said:
But if you know it's reversed, it will drive you crazy. Otherwise, you have to turn your audiophile card in and listen to Bose.

It's a short drive...

DonH50 · Sep 27, 2012

jazdoc said:
If polarity (phase) is wrong, you will know it. When compared to correct phase, bass output is markedly decreased and soundstage becomes indistinct and wavering. If you have any question, use a mono LP and try hooking up your speakers both ways...it's really easy to hear the difference and tell which is correct.

What mep said. If the phase of both channels are inverted there is no cancellation. If one channel is reversed and the other not, you will cancel the sound from the speakers at the listening position. If everything was perfect you'd hear nothing; in practice, the most cancellation occurs in the bass.

jazdoc · Sep 27, 2012

mep said:
Doc-Are you sure you aren't talking about "out of phase" vice reversed phase? What you just described is what "out of phase" sounds like and not reversed phase.

Yep, my bad

Tube Pre-Amps and polarity

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