+4dBU or -10dBV

Sorry to add to this a little late but just some points to consider with regards to having a balanced studio, hum and noise etc.

First lets be clear what a DI box is for. Primarily, a DI box allows you to plug stuff into a mic input. In live applications for eg the inputs on stage that go to the monitor desk/foh will be mic inputs. you'll see lots of DI boxes (and splitters) in live apps.

A DI box is usually used in live apps for gear like keyboards etc as they are line output devices that need to go into mic inputs, but in the studio where we have plenty of line inputs it is usually unnecessary. Many DI boxes have evolved into general converter boxes - handy "swiss army knife" gizmos that allow you to convert jacks to XLR, change signal levels, lift earths, provide electrical isolation etc etc. They can be a life saver in some situations. But you only need them if you need them if you know what I mean. I don't have any in my studio now and I don't miss them since I acquired a computer interface with a dedicated "instrument input" for DI-ing guitars and basses.

With regards to balanced lines in the studio...
It is quite common to live with un-balanced lines in the studio as cable runs tend to be much shorter than in live applications - certainly for the average project studio. A balanced line is only useful if there is significant interference to combat. using the standard un-balanced output line from a keyboard is unlikely to cause problems with hiss and hum in a typical project studio, assuming everything else is working well.

One thing I'm concerned about is that you say your mics are unbalanced. this is very unusual unless you have ~very~ cheap mics. If this is the case it is unlikely that a di box will help. you'd be far better buying a better mic(s).

Guitars, basses are never balanced and could well benefit from a di box due to their weak outputs, but then it is still worth trying them out on your system as many modern circuits can now cope with these lines much better than they used too. I also find many guitarists have these Pod thingies that have nice handy line-outputs as well as the great effects and speaker simulations. If I was a guitarist I'd buy one of those before a DI box any day.

If you find you have trouble with hiss and hum there is a good chance that simply getting everything balanced will not be the cure. In an average project studio, I'd say in 99% of the cases, hum is ~not~ due to un-balanced lines. Usually one can trace where the hum or hiss is coming from by unplugging gear one piece at a time - its often one or two bits of gear that is the culprit. Poor electric supplies, bad earthing or dodgy cables and connectors is the major source of hum and hiss. If you ~are~ indeed picking up interference on your non-balanced cabling it might be easier to cure or switch off the source of the interference (eg strip lighting, fridges, old tv's etc). You may well find that if you have gear that is less than "pro" that the interference "gets in" whether your lines are balanced or not.

You might want to check your gain structure too as this can be a major cause of hiss. For eg... your computer's sound card has its output volume (assuming there is one) set low so your monitor amplifier volume needs to be set high to compensate. Answer: turn up your sound card and turn down the monitors. As a rule of thumb most electrical instruments should have their volume controls at (or close to) full - and that include any internal volume settings (in the case of multitimbrel synths)

Before noegplease pounces on me, I am just pointing out that it would be wise, before spending money "balancing your studio", to investigate precisely what is causing your sound problems. You might find that just one new cable or plug is all you need! Perhaps at the least you could ask your dealer if you could try the beringer box to see if it is the answer, before you buy it.

enough waffle already 🙂

Hope that helps a bit.

I agree.

It's just bad when someone shoots down my 11 years of experience with off the wall remarks. I tend to get peeved. Especially since I do try to help those who really need the help.

Audio production is a fun and exciting career,and it is difficult.There are many ways to "skin a cat" in a production.

I do get peeved when physics and electical properties get subjected to varying degrees of misinformation,it only makes for a more confusing environment.Especially for the uninitiated in the science behind the sounds.

So Jeff,do you have any more questions on levels/gain structure? Maybe you can open a new post,instead of continuing this one.

Cheers

Great! Actually, all of my past questions on this topic have been answered. Looking forward to your future posts and also sharing any insight I gain in the future. Take care, Jeff

<It's just bad when someone shoots down my 11 years of experience with off
<the wall remarks


And where did that happen!

I think if there was any "shooting down" going on it was from you and very well aimed at my first post on this thread.

I totally agree with you about "misinformation". My intention was to clarify and help - nothing more. If you found my writing offensive that was not my intention - far from it.

I think some wires must have gotten crossed somewhere.

I think it is also wise to avoid assumptions about posters. Non of us know who we are "talking" to. And those number-of-posts and ratings don't tell you anything about the poster.


here's to a happy forum and help for all.

Hi,

<It's just bad when someone shoots down my 11 years
of experience with off
<the wall remarks

And where did that happen!
</div>
<snip>

And I agree as well,we should strive to get the facts correct,for other readers.
Take these three statements from your original response,to let you know how you were in fact misinforming,and why I fired back as a result:

[quote]Your statements completely disregard line impedance conditions >Given the same true RMS conditions on a single ended line and a differential >line and equal, or even nearly equal source and load impedance conditions, >then power transfer will be the same. Frequency response will not be >affected.[/quote]

Using an RMS reference while talking about impedance mismatches is not a good and accurate way to dispel a confusion.The term RMS is about power[u/u],not level imbalances.
Here,I quote directly form my favorite reference book:
Handbook for Sound Engineers,Glen M. Ballou,editor.ISBN #0-240-80331-0
Chapter 31.6.2.1 "Loudspeaker Power Capacity Specifications"
"RMS Power" is another common rating method.Mathematically,there is no such thing as rms power.RMS power is calculated from rms voltage and load resistance.The correct rem should be "average power.However,an rms power rating for a loudspeaker is usualy simiar to a pink noise rating"

[quote]In the studio you will probably find the end result is just a change of > level when miss-matching -10 and +4.[/quote]

There is more to it than just a level drop.When you connect a partial signal to ground,you "shunt" part of the audio signal and lose some of it.Not just make it less loud.This should not be a source of confusion.

Again,a quote from my reference:

Chapter 19 "Attenuators"
page 643

"However,if a low impedance output feeds a long line to a high impedance input, high frequency losses will occur if the line is not terminated with low impedance and preferably matched.

So you see,there is more to it than just a level loss.Please check your facts,sir.

[quote] +4dBu is "louder" signal. Its does not reduce interference. >Interference remains the same but it will be lower in level relative to +4dBu >compared to a -10dBV line level and so the signal to noise ration will >be better for +4dBu (ie the interference will sound less). Please ?>excuse my pedantic point.[/quote]

Please excuse your underlined terms. +4dBu against -10dbV is a completely wrong comparison,because these two terms are very different!
dB u is NOT the same as dB V.You do agree on this? You kept referring to these two different terms as if they were the same.In most of your posts.This is an inaccuracy,I would appreciate it if you also agree that it is.

Here is an excellent read,from one of my favorite references:

Handbook for Sound Engineers,Glen M. Ballou,editor.ISBN #0-240-80331-0
Chapter 31 entitled "Sound System Design"
page 1233,subtitle 31.9 "INTERWIRING".

If you like,I can mail you a copy,it is very interesting reading.Rather long,but interesting,noetheless.

So,in closing I would like to say that I have absolutely nothing against you, I would like to make a peace offering,and move on.I really enjoy being able to help those who need it.And I'm sure you do too.From now on we should both strive to get our facts correct before posting.It is the least we can do to ensure accuracy in the forums.

Cheers

I have to say that this whole thread is a testament to the old adage that a little knowledge is a dangerous thing. There are more inaccuracies, misconceptions, and down right incorrect statements here than I've seen in a long time.

It's no wonder that the state of music production has dropped so low now that anyone can spend a couple of hundred bucks to have their own studio.

My advice (based on 20 years in pro audio) is to get an education. At least go out and get some real books on what you're trying to do. The one that noeqplease mentions is a good start. The Yamaha Sound reinforcement handbook is also an excellent book to have around, even for those who don't venture out of the home studio. Don't rely on the ads and reviews in the latest EQ mag. Get some reference books and learn what the tech side is. Read the manuals that comes with the gear and if there is something in it that you don't understand, then go to you bookshelf and look it up. Try this before you go posting on the web, so that you have a chance of knowing what people are telling you. And if you do decide to post a response to someone else, be sure that you are 100% accurate for what they are asking.

I apologize if this is all a bit headstrong, but there is just so much bad info out in the forums that it's really hard not to point it out.

Z.

Thanks Prophet Zarquon.

Wise words indeed,and not headstrong,at least not to me.

I agree with you in that there is a need for more informed posts,and more informed posters.

Cheers

noeqplease,

[quote]Your statements completely disregard line

impedance conditions >Given the same true RMS
conditions on a single ended line and a differential

line and equal, or even nearly equal source and load

impedance conditions, >then power transfer will be
the same. Frequency response will not be

affected.[/quote]

Mr. O'Carroll didn't say this. I did. I still stand by it too. Basic transmission line theory. If voltage conditions are the same and impedance conditions are the same, then power transfer is the same, across the band, regardless of the line being balanced or unbalanced.

Using an RMS reference while talking about impedance
mismatches is not a good and accurate way to dispel a
confusion.The term RMS is about power,not
level imbalances.

RMS is a term commonly applied to AC voltage. It can be used to describe power, but the traditional formulae is only valid in AC circuits when the voltage and current are in phase.

"RMS Power" is another common rating
method.Mathematically,there is no such thing as rms
power.RMS power is calculated from rms voltage and
load resistance.The correct rem should be "average
power.However,an rms power rating for a loudspeaker
is usualy simiar to a pink noise rating"

The author you're quoting is referring to the terminology used and its appropriateness in the context of loudspeaker power rating. With all due respect, I truly fail to see how loudspeaker power ratings and their specification methods are relevant in this discourse.

[quote]In the studio you will probably find the end

result is just a change of > level when miss-matching
-10 and +4.[/quote]

This is Mr. O'Carroll's quote. It is fundamentally correct.

There is more to it than just a level drop.When you
connect a partial signal to ground,you "shunt" part
of the audio signal and lose some of it.

Yes, if the source is balanced and the load is not, (a rare occurence in stage and studio) then there is a voltage drop.

Not just make
it less loud.This should not be a source of
confusion.

The voltage drop translates directly to "less loud".

Again,a quote from my reference:
Chapter 19 "Attenuators"
page 643
"However,if a low impedance output feeds a long line
to a high impedance input,high frequency losses
will occur if the line is not terminated with low
impedance and preferably matched.

True, as it says, in long line applications. This is also only true when there is a huge disparity in impedance, e.g. 150 ohms driving several hundred meg. This is also true regardless of whether the line is balanced or unbalanced. Should I ever run a half mile of audio cable to something, I'll certainly consider terminating it.

Fortunately, typical audio transmission lines are already fairly well impedance matched for us by the manufacturers of our equipment. The one thing that really throws a monkey wrench into it is the instrument level signal. This is such a high source impedance that it acts almost as a pure voltage source. So the DI's transformer converts it to a current source at a low impedance so we can go a bit further with it and drive a mic/line input in a bridged impedance config.

DI's are also usually necessary on a keyboards line out if I want to send it out to the house mix position via the PA snake, or into the snake feeding the remote truck parked down the street. But that's not for impedance matching, only to achieve a balanced, noise immune line.

So you see,there is more to it than just a level
loss.Please check your facts,sir.

[quote]+4dBu is "louder" signal. Its does

not reduce interference. >Interference remains the
same but it will be lower in level relative to +4dBu

compared to a -10dBV line level and so the

signal to noise ration will >be better for
+4dBu (ie the interference will sound less).

Mr. O'Carroll is again fundamentally correct. Even though +4dBu has a 0dB reference of .775 volts and -10 dBV (note the upper case V) has a 0dB reference of 1 volt, +4dBu is still a hotter signal.

There is only a 2.2dB difference between .775 volts and 1 volt.

Please excuse your underlined terms. +4dBu against
-10dbV is a completely wrong comparison,because these
two terms are very different!
dBu is NOT the same as dBV.You do agree
on this? You kept referring to these two different
terms as if they were the same.

<It's just bad when someone shoots down my 11</div>
years

of experience with off
<the wall remarks</div>

I don't think anyone is trying to shoot your 11 years of experience down. It's apparent that you don't yet have a full grasp of these concepts, but you're getting there. In the meantime, relax. Don't be so sensitive when you're challenged, and try to have a bit more patience with old timers like me that have 30+ years of experience in systems engineering for studio, stage and telephony. We enjoy helping too.

So,in closing I would like to say that I have
absolutely nothing against you, I would like to make
a peace offering,and move on.

Peace offering accepted. At least I hope you'd meant that for me too.
Randall

Yes,for you too.

I still hear the difference though,when an unbalanced signal get plugged into a balanced input,and when a balanced line is fed into an unbalanced input.

I know that in "ideal" situations the two types of transmitters are equal.but I have not experienced the joy of this in the real world for a while now.So I match impedances carefully every time.

Maybe my Doctor can help.I'll have him check my ears.

Cheers