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Tested the STM mixer,mono inputs with control room sine.Tested channel 1 and 2 with every other channel.Phase inverting,and everone was ok.
I the tried mono sin into stereo channels:
Sine into L of channel one
Sine ino R of channel two,
I then inverted each but no phase cancellation.
Is there a pan law to stereo construction?

Also added stereo wave to both,then inverted one side,and that cancelled sound.
Interesting
Amyone?

Was the mixer's "Latency compensation" switch activated?

Where were the signals originating from? (ASIO, Wav, ADAT etc).

Note:
I've noticed that my ADAT connections will have phase issues (edit> meaning that a stereo pair will not remain in phase entering into the SFP environment). Oddly enough simply sticking the Phasefix module inline on a stereo pair corrects it WITHOUT needing to adjust the left/right delay values on the Phasefix module itself.

<font size=-1>[ This Message was edited by: valis on 2004-11-18 01:08 ]</font>

I did did some phase tests too. Connected mono ASIO Source to both inputs of a channel. Inverted one side and Mono-ed the Mix, there was no phase calcellation. The shifting could be then either in the channel, or on the Mix or the transfer there too.
So I connected phasefix to the Channel's Direct output. Total cancellation - so the error wasn't on the channel, but on the Mix strip!?

This asks for some more testing eh.

Yes
My tests were with internal Sine wave(control room of Sfp).
I haven't tried external source yet.Will do tonight.
Could anyone explain architecture of Stereo channel.Is there a pan Law?Thing is if I have sine wave entering Right,of each stereo channel,then I invert one there should be a phase cancellation,but there isn't.
Testing this because I seem to lose my Guitars when checking in Mono.These are panned.
Thanks

Tried the same in a fresh project, and phase is coherent now. So DSP load does matter -the previous testing project was kinda full and recycled for a bit. Phase Compensation didn't matter, since it makes for phase coherence of different channels, not L/R... I guess this phase issue is why a couple of people I know refuse to use other then Micro- or Dynamicmixers.

Could anyone explain architecture of Stereo channel.Is there a pan Law?

As you move panning to one side, opposite side fades out. There is 100% channel separation, something fed on one side doesn't leak on the other.

100% phase coherency and 0% crosstalk. two things that never happened with hardware.....

Could anyone explain architecture of Stereo channel.Is there a pan Law?

As you move panning to one side, opposite side fades out. There is 100% channel separation, something fed on one side doesn't leak on the other.

[/quote]

No,pan is centre.I just feed signal into either Left or Right in each channel,then phase.It doesn't cancel it.I thought Stereo would be 2 mono signals.

On 2004-11-18 17:18, at0m|c wrote:
... I guess this phase issue is why a couple of people I know refuse to use other then Micro- or Dynamicmixers...

it won't save them - I observed the exact same behaviour as above with both of them
but there was no general pattern to detect - under some circumstances SFP seems to just screw things. A reload fixed it in my case.

cheers, tom

You test it wrong, because you do not understand the way a channel is panned. I will try and explain.

When you enter a signal in 1L and nothing in 1R, it will never be panned center. You are being fooled, because you have an identical signal in 2R. Mute 2R, and you will realise, that the pan on Ch1 only turns up the left side (panning left) or turns it down (panning right). This is normal mixer behavior. If you want another kind of panning, use Shane White's panning utillity.

So what you get is 1L in your let speaker and 2R in your right speaker. This way, you will only percieve a cancellation if you where deaf on one ear and sat in an anechoic chamber, and if your hearing ear was perfectly centered - or shifted by any amount of full frequency lenghts.

If you want to test phase stability between L and R channels, use my mono summer utillity at the ourput of your mixer. This gives true mono - not just L spread over both channels, as normal SFP procedure is.

One thing more: You may need to double click the fader, because even when looking as if in zero position, it may be sligthly off.

On 2004-11-22 05:52, Immanuel wrote:
...This gives true mono - not just L spread over both channels, as normal SFP procedure is.

Is that true?

I believe so.

Isn't that mono summing of L/R that the Mono button does? Panning on the channel was perfect center, hence the cancellation on Dir output...

Sorry. I was not specific enough.
When you set a channel to mono, it does indeed work in mono. What I was refering to (though it was far from obvious from my writing) was, that if you have 1L and 2R and you want to check for phase issues, you need to mix the two channels IE by using MONO channels on a micro mixer. You can not use a stereo-effect set to mono, because it will only output the left input in both outputs.

I see, that I left too much unsaid in my previous writing.

You haven't tried test properly:

If you try my test and put same signal(mono) in R of 1,and R of 2.Then phase it doesn't cancel.This is why I've asked for architecture of stereo channel strip in STM mixer.
If you have same signal in both channels why aren't they cancelling when phased in one?
If you have same stereo signal in both then phase either L or R it will cancel other channels respective.

Thanks for help

that was my observation, too - and it was not reproducable reliably.
Most times my project worked as intended and the 2 signals phased out each other, but there WERE situations when this didn't work.

I've used the same mono signal on 2 channels.
There can be a delay (of a few samples) between channels if they are processed on different (physical) DSP chips and the afformentioned button on the mixer is to compensate this.
Unfortunately it's not totally reliable, so one has to check if this occurs on a 'critical' signal.

Don't bash the system too much on this annoyance (which it undoubtly is) - imho it's a side effect of the extremely dynamic (and economic) allocation of DSP resources.

And what is phase accurate anyway these days (?) of cheapo players and speakers

cheers, Tom

Have you tried forcing channels to same DSP card?

no, I reloaded the project and it was okay again.
My projects are rather simply structured - in a more complicated setup there could indeed remain some hidden garbage causing such effects.
On the other hand I wouldn't bother just for the sake of 'but it is there...', unless that part of the mix really needs it.

cheers, Tom