Basic knowledge about I/Os

zezappa · Post by **zezappa** » Mon Feb 16, 2004 7:13 pm

Sorry for this basic question but I get no other (neither better) place to ask.
I'd like to understand the diferent levels I get using balanced or unbalanced ins and outs, tho not in much technical explanation which I can't understand.

When I use balanced outs I get better level than with unbalanced ones and no matter to where I send them to. I think this is correct.

What's concerning me is when I use the unbalanced In of my LunaII(with an unbalanced source) I get upper recording level than with the balanced In of pulsarII+ (even sending from balanced outs to it).

Is this a normal behaviour or shall I think that there's something wrong with the pulsar+ and/or its I/O plate?
I'd thank for some help.

Post by **garyb** » Mon Feb 16, 2004 10:52 pm

bal standard: +4db
unbal standard: -10db or -20db

valis · Post by **valis** » Tue Feb 17, 2004 12:52 am

Honestly it gets even more confusing

Balanced is +4 dBu
Unbalanced is -10 dBV

dBV represents the level compared to 1 Volt RMS with no reference to impedance (0dBV = 1V)

dBu represents the level compared to 0.775 Volts RMS with an unloaded, open circuit, source (u = unloaded).

Analog devices has a nice calculator here:
http://www.analog.com/Analog_Root/stati ... nvert.html

+4 dBu = +1.782 dBV

-10 dBV = -7.782 dBu

zezappa · Post by **zezappa** » Tue Feb 17, 2004 1:13 am

I can see that on my mixer but what does it mean to the recording volume I can get?
I haven't felt my doubt clarified, or shall I understand that as: -yes, pulsar In is damaged?

Sorry, I think of what I am afraid is true. I'll try to explain better but...

I plug my bass, or a mic, to the preamp, and with the following connections I got this example:

unbalanced pre lineout » mixer line in = volume -10
balanced pre xlr » mixer mic in = +4

unbalanced pre lineout » luna/stm16 = volume -3.4
balanced pre xlr » pulsar+/stm16 = volume -21.4

tho the above values were arbitrary, the input volume of pulsar+ is always near 18db below luna.

Sorry valis, you posted while I was writing this and thanks, I'll try to understand how the meaning of your explanation translate to "practic" values, which for me are volume values and it seems difficult to learn electronic matter by this way. Thanks folks.

<font size=-1>[ This Message was edited by: zezappa on 2004-02-17 01:25 ]</font>

Shayne White · Post by **Shayne White** » Tue Feb 17, 2004 1:22 am

On my Alesis AI3 I/O box, I can switch between +4dBU and -10dBV. I found that +4dBU was about 11dB softer than -10dBV, so...I hope that helps clarify things a bit. I don't know the technical ins and outs of what that all means, but I'm just reporting my findings.

Shayne

zezappa · Post by **zezappa** » Tue Feb 17, 2004 1:35 am

thanks shayne, your point took me some hope to keep working as till now, 'cos the balanced Ins seems smoother even attending I must put the external sources louder to get good recording levels.

my lack of knowledge..., I hate it.

Post by **garyb** » Tue Feb 17, 2004 1:50 am

thanks for the correction,Shayne.
of course the point is."yes the balanced i/o is referenced to a hotter 'zero'". therefore,it is normal to have to add gain when going from unbalanced to balanced and reduce gain when going from balanced to unbalanced.
this is normal and relatively standardised....

peace.

valis · Post by **valis** » Tue Feb 17, 2004 5:58 am

...and that extra gain lowers your noise floor and increases dynamic range.

zezappa · Post by **zezappa** » Tue Feb 17, 2004 10:01 am

Thanks guys...
I feel very much happier now as it seems there's nothing damaged

So, I'll keep on using balanced I/O's on all my routings.

Immanuel · Post by **Immanuel** » Tue Feb 17, 2004 11:56 am

Or a car analogy:

-10 is like the speed limit on the streets in a city
+4 is like the speed limit on the high ways

If you drive -10 on the high way, you can not keep up, and the signal gets too low.

If you drive +4 in the city, you will chrash (distort).

*********************************************

Therefor, if going from -10 to +4, you will have to run you outputs realy hot to use the full headroom of the +4 device (very like impossible in this situation without saturating (distorting) the -10 output - it's like trying to go 100MPH on a bulldoozer).

On the other hand, if you go from +4 to -10, you will have to lift your foot a bit from the speed pedal. This way, your Ferrari will not colide with all the busses in the city.

*********************************************

Was this of any use?

jabney · Post by **jabney** » Tue Feb 17, 2004 12:46 pm

Cool link Valis. Thanks!

Zezappa, to add even further to the confusion, sometimes balanced can be better, but not always. The way in which a hardware manufacturer/designer balances a signal has an impact on how it sounds. As always, use those measuring devices located on the sides of your head

to make the final call.

Oh, and for mixing balanced and unbalanced, try to avoid it in hardware if you can. If not, Rane note 110 at http://www.rane.com/note110.html originally written in 1985, remains the standard reference for a lot of folks.

john

Immanuel · Post by **Immanuel** » Tue Feb 17, 2004 1:50 pm

balanced <-> unbalanced

If you go from balanced to unbalanced, you loose 6dB signal.

Post by **hubird** » Tue Feb 17, 2004 9:20 pm

nice thread, thanks guys

zezappa · Post by **zezappa** » Tue Feb 17, 2004 9:38 pm

I'm still a bit confused with all this traffic, ...but as I love strong emotion I'll keep driving my Ferrari on the highway

Immanuel · Post by **Immanuel** » Wed Feb 18, 2004 7:05 am

That'll be connecting +4 with +4