[RafaPolit]

Friends,

There is now several threads spread throughout the circle of people claiming that the ST-10 outputs are really inverted in phase, according to the some 'just because that is how they do it in Asia' (not the most compelling argument),  according to others because that is what their room DSP equipment is telling them (this is now a more credible source).

As I said before, this is not trivial: yes, absolute phase is (most likely, but there is debate) not detectable.  True enough!  But some people add sub-woofers, other speakers, do bi-amping, etc., etc., etc.  So there are dozens of situations where knowing the absolute phase is crucial!!!

Jason replied (very succinctly): I recommend you stick to specs.

Probably good advice, but it takes very little equipment (for those who have it) to actually prove or disprove this: is the absolute phase inverted or non-inverted on the ST-10 outputs?

Please, if anyone has or can get a hold of the equipment, help us run some tests.  If not, lets figure this out!  Lets try and hook some PC distortion software and input back the output to the computer, obviously making sure the output is low enough to not blow the computer inputs.  This probably requires some signal attenuation or some other intermediate device?

Ideally, would NuPrime (which I'm sure not only have all the equipment, but probably knows this already) help measure this out and give us a technically definitive answer (perhaps even nice graph charts, I don't know, something other than: stick to specs), specially now that there are several diagnostic equipment that are claiming inverting phase on the AMP.

Thanks a lot, best regards,
Rafa.

[Genez]

 I have used about five different preamps with my ST10.  The polarity of my system also stayed consistent even with the other amps I have used. 

The only time I have noticed a polarity reversal is with my new tube preamp.  Tube preamps tend to reverse polarity because they do not want to add a second gain stage for purer sound.   Its no big deal.  Just reverse your speaker connections on both speakers.  Most digital recordings that are on CD's are reversed polarity to begin with.   My DAC has a polarity button.  Its easy to check that way.   

This may help...    https://www.youtube.com/watch?v=HJKshrTGPtI

[rustydoglim]

I confirmed with R&D.
ST-10 and ST-10M designs evolved from the NuForce reference amps and they are all inverting amplifiers.
All other NuPrime amps Evolution One, STA-9, STA-6, ....and integrated are non inverting amps.

I will update the product page for ST-10 and 10M. 

The issue with this is that unless you have measuring equipment to test the devices in your chain, you don't really know if it is necessary to reverse the +/- inputs that go into the amp.

[Genez]

I confirmed with R&D.
ST-10 and ST-10M designs evolved from the NuForce reference amps and they are all inverting amplifiers.
All other NuPrime amps Evolution One, STA-9, STA-6, ....and integrated are non inverting amps.

I will update the product page for ST-10 and 10M. 

The issue with this is that unless you have measuring equipment to test the devices in your chain, you don't really know if it is necessary to reverse the +/- inputs that go into the amp.

Its all a matter of our ears then.  If you can detect inversion.  It just so happens most CD's are inverted.   So, they will sound restored with an amp that inverts.  If nothing else in your chain does not invert as well.   At least,  that was the result of some extensive testing made with CD's a while back by an alleged expert.  I simply go by my ears and listen to what sounds the most natural. It turns out that the ST-10 is not alone with inversion.  Other amps do it as well that are even AB.  At least to the consistency in what I can hear when playing music.

I just got a tube preamp that are known to invert polarity.  And, I found I do not now use my polarity button on my DAC like I had with my solid state preamps... What ever it is?  Only if you can hear the difference should it matter.   The closer you get to realistic sound the more important it can be.

If its any comfort to those just learning about this factor... I found that its only a very few times is it needed to change polarity for critical listening.  For, once you have determined what polarity you prefer, by reversing - or leaving alone - how the speaker wires connect, only a few recordings will need flipping.  But,  some recordings I have listened to on CD's can have tracks reversing one from another. That is when having a polarity switch on one of your components comes in very handy.  Especially if you are the type that becomes engrossed in your listening time.

[Chris_33]

For people, like me, who are using the ST-10 in a multi-speaker system (to power my front speakers) this is such an information!

That was well explained by Rafa.

Indeed, even if the phase problem has been detected by the receiver, most of them are saying to not change the polarity if you are sure of your wiring :  https://denon-uk.custhelp.com/app/answers/detail/a_id/1075/~/phase-error-when-running-auto-setup

That will make you having a system with phase incoherence and weird sound issue like I had.

Thank you for the confirmation by NuPrime

Indeed, it should be well explained in the documentation.

[Spenav]

Thanks Rusty for the confirmation.  That should put this issue to rest.  The thing with Audyssey or ARC or any other measuring device is that they don't know what equipment you are using so they tell you what the electric signal is telling them, without passion or prejudice.  In my system, I have 14 channels of amplification (an 8-channel amp plus 4 amplified subs) so coherence is important to me and I can hear the difference. So inverting my ST-10 wires was a no-brainer.  As I alluded to in my previous post on the matter, if it doesn't make any difference in your system or you are too lazy to do it (takes a minute), by all means do nothing.  I dare predict that in a two-channel set up, it probably won't matter. You enjoyment is the ultimate goal. Now with Rusty's post we know the history of it.

[RafaPolit]

Thanks Jason.  This is, indeed, a good thing to know.

I recently bought a Sub Woofer and I was surprised that, in the normal phase setting, the bass seemed diminished. As I said, there are other scenarios that will benefit from this information.

Thanks again,
Rafa.

[Spenav]

Not to start a new debate, I just would like to expend a little bit for the sake of clarity.  What Genez and Rafa are talking about, while closely related are different. If a recording is inverted in terms of polarity you will be hard press to hear any difference unless you can compare it to the original performance and even them only the absolute timing will be off.  In other words, there is not much you can do that will make a difference.  When Rafa talks about his sub performance being altered by the inverted polarity of his ST-10, he is talking about the timing of his lower frequency notes being out of phase with his main L + R speakers in HIS system.  Now there will be audible differences when the system is in phase (adding) or out of phase (subtracting).  Whether the recording itself is inverted or not, he will experience the same issue.  So one is a global issue (Genez), the other a local one (Rafa).  If everything is inverted, you would be hard press to tell but if only one thing is, you should be able to tell.  For the latter, the proper correction is at the source of the problem (reverting the wires in the ST-10) although altering the phase of the sub by 180 degree or inverting the wires of the L + R speakers will bring the same relief.  I hope that helps.