Mackie 1604VLZ-Pro - are balanced outputs really balanced?

[plz]

Has anyone actually checked this? According to the manual (pg10) & every review I've seen, all outputs are said to be balanced... but I was checking my new studio wiring with a scope and found nothing was coming out of any of the TRS cold (ring) connections except for the Main outputs, i.e. the direct outs, aux sends, subs and the control room outputs all appeared to be unbalanced.
I checked the circuit diagram in the user manual and sure enough, all outputs apart from the main outs only feed the hot output; the cold appears to be connected to earth via a resistor.
Am I missing something or is there some deception going on? 

[RoadRanger]

No deception - just confusion. Those outputs are "impedance balanced" - the theory is that the resistor matches the impedance of the cold output pin to the impedance of the hot output pin, hence a balanced input will work almost as well with it as a true balanced output .

[plz]

Many thanks RoadRanger - it's all becoming clear now. Have heard the term before but never understood how it worked. So the fact that the cold wire can now 'float' means interference noise on the cable will still cancel out at the balanced input end... but you sacrifice the signal-to-noise benefits of the larger voltage swing from two out of phase signals. It's a nice simple trick with one resistor - seems the Allen & Heath mixer does the same thing but the manual uses the terms 'differentially' and 'impedance balanced' so is a lot clearer (although not as humorous as the Mackie ).

This has scuppered my idea of verifying the new wiring by checking the hot & cold levels at the patch panel end - if there's no signal on the cold when it's behaving normally, how can you check it's wired ok? The non-pedants might say who cares; you wouldn't hear any difference and it's only the noise immunity which would suffer, but that's just me

[Greg C.]

So the fact that the cold wire can now 'float' means interference noise on the cable will still cancel out at the balanced input end... but you sacrifice the signal-to-noise benefits of the larger voltage swing from two out of phase signals. It's a nice simple trick with one resistor - seems the Allen & Heath mixer does the same thing but the manual uses the terms 'differentially' and 'impedance balanced' so is a lot clearer (although not as humorous as the Mackie ).

Impedance balanced outputs have been used for decades now to save money and provide comparable CMRR of active balanced outputs. balanced lines are not about having both hot and cold be active, they're about having matched impedance relative to ground. Most people don't need the extra 6dB of gain that active balanced outputs provide. As for degraded S/N, that may not be true. In theory you would lower the noise floor by 6dB with double the voltage swing. However, the active output circuit on the cold line adds some noise, so it's probably a wash.

This has scuppered my idea of verifying the new wiring by checking the hot & cold levels at the patch panel end - if there's no signal on the cold when it's behaving normally, how can you check it's wired ok?

You can measure the resistance from the hot and cold lines relative to ground if you want to make sure your line is balanced. If you want to make sure your point to point polarity and lines are correct, get something like a Rat Sniffer/Sender pack with the appropriate adapters in and out of your patch bays to make sure your wiring is good.

[plz]

Impedance balanced outputs have been used for decades now... ...balanced lines are not about having both hot and cold be active, they're about having matched impedance relative to ground.

Thanks for the clarification Greg. I've used them for years but never fully appreciated them - it was only this recent re-wiring exercise which showed up my lack of knowledge. When the previous layout was wired, a cold connection was missing on an active balanced output - the signal was still there but the level had dropped and I spent ages tracking it down; it was then that I incorrectly presumed all balanced outputs were differential. This time round I tried to be clever by checking all hot & colds first - that'll teach me

You can measure the resistance from the hot and cold lines relative to ground... ...get something like a Rat Sniffer/Sender pack to make sure your wiring is good.

These sound good ideas so I'll get on with the testing.
Thanks to all for your quick help on this - the Mackie is exonerated.
Phil

[WK154]

In case anyone ever cares I was looking at the CR1604 VLZ schematics and found that mains L&R and Mono out are in fact active balanced outputs the rest are impedance matched in the days where the magic # was 120ohms. Cheers.

[Kev tyler]

Does the onyx pre amp in the cheapest mackie  mixer sound the same as the most expensive?
Kev

[Kev tyler]

I think what I am saying is this, I regularly use the 1640i, thought of purchasing the 820i but have now noticed they are flogging the onyx preamp in the guise of vlz, without parametric eq, it's not really the same channel is it?


Sent from my iPad using Tapatalk

[WK154]

The difference is that the 1640i has a 4 band eq vs the 806 3 band Perkins. The older VLZ has fixed Q (3 band) as opposed to the variable Q in the Perkins. The difference on vocals is not that much unless your into distortion and effects so money is better spend on a better mic match to vox than mixer.

[Kev tyler]

Thansk

[Kev tyler]

Sorry

Thanks wk, I have nice mics, I have always been a bit against mic  channels without parametrics as I seem to find these on cheap thin sounding desks, and to be honest I have often ruled out the purchase of more up market desks equally without sweeps due to the often lack of built in fx, which ultimately forces you in to lugging a 2ft and over square case everywhere you go in order to contain the separate 19 inch reverb unit you have to buy.

So I am in a bit of dilemma right now, when I work with my band I use either the large onyx or a midas desk, and the stage is ours, supporting acts have to fit in around us, and that's great, the problem is when I am the solo support act and I roll up with gear that does not either fit in my allocated space or impose a health and safety risk. Hence the constant craving for the non existent products I keep hinting about.

As I said a while back, I think the dl with its secure home for a pad is my best option, despite the bells and whistles of the new x range, only the largest mixer in the  x range is going to offer a safe place to leave a 500 dollar euro pound ipad, and some amount of diy tinkering will be required to ensure the pad is still there when you come back from the toilet etc.

Thanks

Kev

[RoadRanger]

[...] often lack of built in fx, which ultimately forces you in to lugging a 2ft and over square case everywhere you go in order to contain the separate 19 inch reverb unit you have to buy

That's not true - I used a Alesis Picoverb with my 1604. It's tiny and sounds better than the DL's FX IMO.

[WK154]

I'd recommend the Nanoverb 2 since it also has the much desired foot-switch and a ton more effects.

[RoadRanger]

I'd recommend the Nanoverb 2 since it also has the much desired foot-switch and a ton more effects.

Yup - but the Picoverb sounds better (24 bit vs 16 bit) and most just want a simple chorus/reverb.

[WK154]

I'd recommend the Nanoverb 2 since it also has the much desired foot-switch and a ton more effects.

Yup - but the Picoverb sounds better (24 bit vs 16 bit) and most just want a simple chorus/reverb.

Actually it's a 18 bit system and of course the rest is individual opinion and there are lots.