Phase Alignment

[PeterSt]

All,

Because it was asked elsewhere, here a brief outlay of what Phase Alignment is/does in XXHighEnd.
It should not be used any more.
Right.
(plus I'd think I disabled it per 2.11 - not sure though)

Phase Alignment is dangerous.
Right again.

Phase Alignment is the most wild trick to let your electronics behave better.
Back at the time everybody used it (this is an XXHighEnd-only), BUT it was under control because it was a hot subject. Thus, everybody grew into it, and only one person blew all of his speaker drivers. So that was quite OK.
Right (not).
(and Phasure paid him the new drivers)

Those with a NOS1 were in luck because they could "trim" the Phase Alignment with their DC-Offset meters. That is, in real time. Not doable without such meters, but it could be pre-set as well with a multi-meter.

It is the most complex piece of software in there, and of course only a phool like me could make it.
So ...

So Phase Alignment plays with DC offset.
It anticipates electronics to behave worse with negative voltage than the positive voltage does. N.b.: Negative voltage is always a derivative from the positive "rail"; it is an extra step (with always additional THD). Btw, don't ask me whether some theory exists that negative can be as good as positive after all, but even if it can, nothing tells that this has been applied in ALL of the circuits in pre-amp, power-amp, and in the end also the DAC of course.

The best part of this whole trip is the avoiding of zero crossing.
Now imagine that each self-respecting PCM DAC (in general these are R/2R DACs) has inherent relatively "huge" problems with the voltage crossing zero, impeded by the "digital code" which causes this. Actually the biggest current (!) step is implied because ALL the bit but one, flip. Thus, those poor D/A chips must apply this when zero is crossed :
00000000 00000000 00000001
11111111 11111111 11111111
... thus because all the bits (but one) need to change state, this draws a relative huge amount of current, but only when the voltage crosses zero.
N.b.: The PCM1704 is quite OK with this zero crossing distortion, but still it measured significantly better on the THD. It also sounded better - and still should;

If it is not active any more, I could reactivate it. But the messages will be larger again. Point is : everybody should measure the DC Offset at the speaker input (hence power-amp output). Speakers won't like this ...
But also : I can imagine that not everything is compatrible with it, like for example the new Pause feature (in Unattended). And when something is not compatible, what happens is that the DC jumps (a big bang). This is not nice for your heart ...

Peter

[acg]

Interesting...operating the dac chip like a Class A amplifier.

Surprisingly, I reckon my setup could handle this Peter, because of the unique way the amplifiers are biased they can handle circa 4Vdc at the input without affecting the drivers too much.  But I would hate to test this theory because replacing $15k of drivers/diaphragms has got warts on it.

[PeterSt]

Oh, but it is not *that* bad ! I mean, once you quite carefully measure in advance what the DC offset is, and you test with playback and without speakers connected, you can just see what happens. And mind you, this should NOT be even 1V of offset. It should be the normally accepted value like 20mV - maybe a bit more at the power-amp outputs (all of them !).

Any self-respecting power-amp will reject DC, unless you remove caps yourself.
Normally - but here it gets dangerous, a speaker will reject it too because of the coincidental capacitors in there. But for example, for my own Orelo-II speakers I already don't know it as Bert might say "dunno, but I think it will be OK". So for example (and people should read this carefully) because there's DSP for the woofers there-will-not-be any protective whatsoever in there because it would counteract the DSP. Hence, there is no filter.
Next problem : The speaker is active, so it is far from easy to check the output of the power-amp(s) in there.
.... And this is exactly how Phase Alignment got forgotten ... this is because I myself don't use it any more. No bribing about it - nothing. But it surely sounded better and still should ...

So Anthony, and others, if you'd be able to engage Phase Alignment (which I don't know at this time) speakers not connected  !!!, set the values as the ToolTips will teach you, and check with the multi meter for DC (for the NOS1, just read out the meters so you can see the applied DC is operative - for other DAC's measure the output of the DAC with the multimeter). No DC at the output of the Poweramp(s) ? then go for it. Connect your speakers and listen. Mind you please, THIS can not go wrong, as long as you measured and deem it OK.
Nothing can go wrong. However :

What can go wrong is the by now possibly unsupported new functionality which causes a Stop of playback and which does not gradually remove the Offset. Starting - same thing. Thus, it is this complexity which makes it, well, complex. Mind you, how strange it may come across to some, this is a pure software function.

The Offset will never be more than 1V at the DAC-input (this is software settable and relates to the volume you play at). So, 1V only. Yes, but when this is "set" in one go, your windows will shake seriously, because it will be half of the max volume you normally apply to the speakers, with instant "rise". This is where the bang comes from.
And yes, with normal Absolute Phase Polarity, your driver will jump forward (and back). ... And when the Stop Playback is not supported somewhere, the driver will go backward (and back). Invert the Phase in XXHighEnd and it will go the other way around (but somewhere at the back of my mind I recall that Inverted Phase is not allowed together with Phase Alignment.

Oh, the Wallpaper Coverart shows what's going on for these settings (the top between the front and back cover).
Where normally you see (below) the _~_, and where Inverted Phase will show _I_, with Phase Alignment active it will show *~* (and theoretically with Inverted Phase *I*).

Now I am curious whether someone will enter this by now again next level. It really will be !
Peter

[briefremarks]

Peter,

Does the XXHE Phase Alignment require the NOS DAC or can this be tried with any DAC?

Ramesh

[acg]

Any self-respecting power-amp will reject DC, unless you remove caps yourself.

No input caps in my power amps but it runs both positive and negative bias and manages to eat the DC regardless.  A nice design that eliminates the input coupling cap.

No caps in the speakers either.  Not anything there because the amps are direct connected to their respective transducer.  All electronic filters are passive line level at the input to the amps but the only caps in series are for the HF channel which is 10kHz+.  There is an single ended output transformer for each channel though, which should also be useful for sorting out DC that does make its way through the amplifiers.

At the moment the preamp is cap output coupled, which should also sort out DC.

So Anthony, and others, if you'd be able to engage Phase Alignment (which I don't know at this time) speakers not connected  !!!, set the values as the ToolTips will teach you, and check with the multi meter for DC (for the NOS1, just read out the meters so you can see the applied DC is operative - for other DAC's measure the output of the DAC with the multimeter). No DC at the output of the Poweramp(s) ? then go for it. Connect your speakers and listen. Mind you please, THIS can not go wrong, as long as you measured and deem it OK.
Nothing can go wrong.

My speakers are active too, but six ways each side, and how to check that for DC?  First off I could check the output of the preamp to see if DC gets through there, which should be impossible.  Then set up dummy loads on the 6 channels of one side and set up 6 multimeters.

I'm very tempted Peter, but the possible loss of software functionality has me a little worried.  Then there is the issue of my MachII randomly getting hot and turning itself off during the day...not sure how this involuntary reboot would affect what DC is pushed into the system.  At the moment you cannot tell when the MII shuts down (no noise) but occasionally when windows reboots there is a soft thump through the speakers...not all the time.

Anthony

[PeterSt]

Does the XXHE Phase Alignment require the NOS DAC or can this be tried with any DAC?

Hi Ramesh,

Can be any DAC.

Peter

[PeterSt]

At the moment you cannot tell when the MII shuts down (no noise) but occasionally when windows reboots there is a soft thump through the speakers...not all the time.

Hi Anthony,

When you do not use the Alt-E Pause feature in Unattended, there is no way that XXHighEnd could impose DC offset during silence (and with Alt-E I just don't know, but my estimate is that this is unsupported, so do not use it !).

Then set up dummy loads on the 6 channels of one side and set up 6 multimeters.

There is no need to set up a dummy load. Just measure the output of each power-amp when XXHighEnd is playing ...
And indeed, when the output of the pre-amp does not show DC already (XXHighEnd playing, no need to measure each power-amp.

Best regards,
Peter