Help!!!!!!!!!!!

[kha02a]

Ok I'm a newbie to recording and I'm currently working as an intern in a recording studio here in Nashville. My boss the owner/engineer/producer of the studio is really trying to teach me so he's having me write a 2000 word paper about some of the basics.

 

What better way to research than to bounce some of these questions off of you experts?

 

There are quite a few questions here so if you can help me with any (or all) of these topics I would greatly appreciate it.

 

This might also be a good way for other rookies on the forum to learn a thing or two. Here they are:

 

Signal Flow:

 

Define and state differences between line, mic and amped level signals

 

What is resistance?

 

What are ohms?

 

High Z -Low Z?

 

What is high impedance and low impedance?

 

List maximum cable lengths for different signal levels.

 

What is the signal path for a typical live performance set up?

 

What is the signal path for a typical project studio?

 

What is bus?

 

What is pre fader and post fader?

 

What is the difference between bus and VCA (voltage control amplifier) group.

 

Thanks Guys!!

[Kiwiburger]

I don't usually like doing other people's homework for free, but here are a few ideas for what they are worth:

 

Resistance is futile.

 

Ohms are where the little Amps live.

 

You take the Hi Load and i'll take the Low Load.

 

A cable is as long as a piece of cable.

 

Follow the yellow brick road.

 

The path to my studio is made of concrete.

 

Bus, bus - magic bus.

 

Pre-Vader was Anakin Skywalker, Post-Vader was Darth

 

If you have to ask the difference between a bus and a VCA, i'm not going driving with you ...

[kha02a]

Wow that reply might have been the best example of wasted energy ever...not helpful .....not funny.

[Kiwiburger]

Seriously dude - a simple Google would answer all these basic questions.

 

And describing the signal path for a live rig or studio is a huge ask. But Google will still find plenty.

 

I think the reason your boss gave you this exercise was to see what you know, or just how capable you are of finding out. I don't think it helps your learning to just get answers handed to you on a plate.

 

Maybe there are others here with more time and patience - best of luck.

[kha02a]

Who cares how I find out as long as I find out. I don't think research has to be hard to be valuable. What's the difference in reading it and having somebody tell me it if I still went out and got the answers I needed?

[Kiwiburger]

True.

 

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/resis.html

 

http://www.soundonsound.com/sos/Jan02/articles/faq0102.asp

 

http://www.presonus.com/firepod.html#diagrams

 

[kha02a]

Thanks Kiwi

[Kiwiburger]

Your welcome.

 

A bus is an electrical term for a common conductor. They can take the form of a common rail that wire terminate to, or perhaps a long strip of copper on a printed circuit board that various other circuits on the board connect to.

 

Audio mixers connect various channels to a bus for the purpose of mixing. A mixer can have more than one bus - maybe seperate buses for main output, monitor output, effects send and effects return. Basically anywhere more than one channel mixes with another, that's a bus.

 

A typical mixer channel is a mic preamp, followed by eq, followed by the fader, connecting to the main bus.

 

A microphone has a very low output and needs a mic preamp to boost it up to Line level. "Line level" is your basic audio equipment signal level - there are consumer and pro standards for line level - unbalanced -10dbV and balanced +4dbV.

 

Instruments like guitars/bass/electric pianos are somewhere in between mic and line level, so sometimes Instrument level inputs are provided. They are at a slightly lower gain than the mic preamp - and also Hi-Z which is a seperate issue.

 

Mixers have insert points - where you can tap in and insert a compressor or something like that. It's important to know exactly where in the signal chain this insert point is located. It could be Pre-Fader, so changes to the fader won't affect the level coming from the insert point. Or it could be Post-Fader - where the fader setting does change the level at the insert point.

 

Re: "What is the difference between bus and VCA (voltage control amplifier) group." - A VCA is a Voltage Controlled Amplifier. Often found in real analog synthesisers, they are also used in some compressors, and in some mixers - especially if mix automation is involved.

 

I don't really understand this question, as I think it relates specifically to some desk but you haven't said which one. Maybe SSL? Anyway - if it has VCA's, I would expect one per fader. This would be controlled by the fader, or by stored automation data, to change the levels. I would expect this mixer to have various buses for various purposes, and probably each VCA would have it's own specific bus.

 

[where02190]

http://acapella.harmony-central.com/forums/showthread.php?s=&threadid=1032968

 

http://acapella.harmony-central.com/forums/showthread.php?s=&threadid=1032972

 

Perhaps you might consider actually studying, rather than look to others to do your homework for you....

[kha02a]

Wow Where you are so smart. Do you really just search through all the forums looking for opportunities to be a smart ass?

 

I'm pretty sure that I've already replied to all your other nonsense in response to my question. But just so you know this forum is not the only way I'm researching these issues. Of course I used google and of course I did other reading

 

I realize that there is a certain amount of work I have to do on my own to figure this stuff out. And I'm doing it. Can you blame me for trying to get some information here to.

 

Geez I apologize. I didn't realize that this forum was off limits to new guys trying to learn something.

[Phil O'Keefe]

A microphone has a very low output and needs a mic preamp to boost it up to Line level. "Line level" is your basic audio equipment signal level - there are consumer and pro standards for line level - unbalanced -10dbV and balanced +4dbV.

 

Well, technically, that should read "-10dBV and +4dBu."

 

You see kha02a, the problem is when you get other people to do your homework for you - even smart people like Where and Kiwi (and I don't want to call myself smart... but I CAN admit to making my share of mistakes ), they sometimes make mistakes... but YOU'LL be the one getting the grade for it.

 

I have no problem with people who are just learning trying to get some help here - I encourage that actually - ask anyone. But do understand why Kiwi and Where think we're doing your homework for you. That's a ton of questions to plop down in a single post! And frankly, with no offense to your instructor, some of these questions are a bit funny / strange... the thought that he's trying to asess your current knowledge level also crossed my mind.

 

Let's look at a few of these questions:

 

What is resistance?

 

Well, Webster's ( www.m-w.com ) defines resistance as "4 a : the opposition offered by a body or substance to the passage through it of a steady electric current.'

 

What are ohms?

 

Again, turning to Webster's, "the practical meter-kilogram-second unit of electric resistance equal to the resistance of a circuit in which a potential difference of one volt produces a current of one ampere."

 

You might want to also do a Google search on "Ohm's Law". But basically I would imagine that your instructor is asking you to tell him that an Ohm is a unit of resistance.

 

High Z - Low Z?

 

"Z" is symbolic of "impedance". IOW High Z = High impedance. Impedance and resistance are quite similar, but there are some differences. You can click on this link for more info regarding impedance vs resistance.

 

What is high impedance and low impedance?

 

Didn't he just ask you that question with the "high Z / Low Z" question?

 

Low impedance might be in the 50 - 600 Ohm range, while high impedance might be in the 10 kOhm (10,000 Ohm) range.

 

List maximum cable lengths for different signal levels.

 

High impedance (instrument cables - such as unbalanced TS - "tip / sleeve" 1/4" cables used for guitars, etc.) should be kept as short as possible - usually under 20'. This is due to a few factors - longer than that and you risk signal loss (especially in the high frequencies, due to cable capacitance) and the increased risk of the cable picking up RF (radio frequency) interference. Balanced cables can usually be run 200' or more without having the same issues.

 

What is the signal path for a typical live performance set up?

 

For what instrument? If this guy wants you to draw a diagram of an entire concert rig, you're on your own - I don't have enough time at the moment.

 

What is the signal path for a typical project studio?

 

Again, this is a kind of open ended question and IMO, not specific enough. Is he looking for a description of a signal path from instrument to amp to mic to cable to mic preamp to processing (compressor and or EQ) to A/D converter? Or does he want a wiring diagram of an entire studio?

 

What is pre fader and post fader?

 

This usually refers to aux busses. The bus can either "tap" (take) the signal from the channel either pre or post fader. With a pre fade aux send, the signal is tapped off the channel BEFORE the channel fader. IOW, changing the level of the channel fader will have no effect on the level being sent out the aux send bus. When you use a post fader aux send, turning down the channel fader will also lower the level being sent out the aux. Pre-fader aux sends are frequently used for things like cue mixes (for headphone feeds to the studio or for stage monitors), while post-fader sends are commonly used for things like effects - reverbs, delays, etc. That way, when you lower the channel fader, the relative amount of reverb or delay decreases porportionally with the decrease in the overall level. But sometimes a pre-fade send is used for reverb... so that if you lower the channel fader, the reverb level DOESN'T change. While not as common, that is sometimes desireable too.

 

I hope that helps you a bit. And please don't hesitate to ask questions here... but OTOH, if you limit those questions to one or two per post or thread, and then maybe ask some follow up questions about things you need further clarification on, you'll be more likely to get better responses with fewer hassles.

[Danny (NS::U)]

"Define and state differences between line, mic and amped level signals"

 

Mic level signal is typically in the millivolts, whereas line level is around the single volts. Amplifiers tend to generate between 1 and 50 volts.

 

Mic level is quite low, because it is AC generated by a very small and light-weight source. Whether that source is inductive (dynamic mics) or electrostatic (condensers), the device is quite diminuitive, and (at least partially because of this) unable to produce more than a small amount of current.

 

Line level is the voltage produced by most signal processing equipment in a studio. Whether the output of a mic pre, or the I/O of a compressor, most of the real heavy lifting in a studio is done at line level. The reason why mic pres are so critical is because they must supply a large amount of clean (or at least pleasing sounding) gain in order to get mic level up to line level.

 

Amplifiers tend to be built to accept line level signals, and in turn deliver much larger voltages at their outputs. This relatively large voltage is required because the amplifier is expected to push relatively large and heavy transducers against air. This requires quite a bit of power, and the voltage demand increases accordingly.

 

"What is resistance?"

 

Resistance is simple (that is, usually independent of frequency content) opposition to the flow of current in a circuit.

 

Resistance and impedance are quite similar, though impedance is more complex than resistance (especially in varying according to the frequency of a signal.) Impedance can, however, be boiled down to the same statement of "opposition to current flow."

 

"What are ohms?"

 

Ohms are the unit of measure by which resistances and impedances are quantitatively expressed.

 

"High Z -Low Z?"

 

Z is typically used to denote impedance. A high Z device outputs more voltage than a low Z device, but will tend to suffer more from long signal lines. A high Z device is also easy to "load down," because other devices following it may have inputs with lower impedances than it can effectively drive. A high impedance device is like a narrow pipe, and a low impedance device is like a large one. The narrow pipe may have quite a bit of pressure, but it will have lots of trouble adequately pressurizing the large pipe following it.

 

"What is high impedance and low impedance?"

 

This seems like a trick question. I've always been taught that Z and impedance are the same thing.

 

"List maximum cable lengths for different signal levels."

 

This is my opinion only, but:

 

Unbalanced mic level should be as short as possible, say, 10 feet.

 

Balanced mic level signal can be run for hundreds of feet.

 

Unbalanced line level signal is probably best kept under 20 feet, though I commonly run it over 100 feet with no problems.

 

Balanced line level signal can probably be run thousands of feet without problems.

 

Amp level signal is probably best kept under 50 feet, not because it couldn't go farther, but because long speaker cable runs can do undesirable things like lower the damping factor of the amp. (Damping is the ability of the amp to control a low frequency driver's desire to drive back down the speaker cable.)

 

"What is the signal path for a typical live performance set up?"

 

That's a little hard to say. It depends on what is considered typical. A relatively simple setup would be mic, to pre, to insert processing (dynamics and channel eq), to pre-fader split for monitors (then to dynamics, eq, amplifier and monitor speaker), to fader, to post-fader split for fx (then processor, then line trim on a return channel), to pan, to routing matrix, to selected buss(es), to dynamics/eq, to crossover, to amplifiers, to FOH speakers.

 

"What is the signal path for a typical project studio?"

 

I'd say mic, pre, pre-fader split for cues (then processing, then either an amp and speakers or a headphone amp and phones), fader, pan, routing matrix, selected buss(es), recorder, line trim on return channel, insert processing (dynamics/ eq/ whatever), another pre-fader split for cues, fader, post-fader send for fx (chorus, flange, reverb, delay), pan, routing matrix, selected busses, monitor routing matrix/ selector, volume control, monitor amp, monitors.

 

"What is bus?"

 

A bus (or buss), as described below, is a common signal line. It's a pipe where you can put a lot different things in the flow, and have them mixed together at the end. There are stereo/ main busses, aux busses, matrix busses, multitrack busses...but they're all just lines where you can put a number of signals together.

 

"What is pre fader and post fader?"

 

Pre fader refers to anything which occurs before the (usually) primary channel level control. Pre fader is therefore independent of the fader's position, which is very useful for things like monitor sends. (I can push things up and down in the mix without causing the artists to go nuts.) Post fader sends are affected by the fader, which is important for fx processors (you don't want to pull that vocal track all the way down and still hear the reverb, do you?)

 

"What is the difference between bus and VCA (voltage control amplifier) group."

 

What I think this means in this context is that a buss group is literally summing the outputs of a number of channels together for the sake of controlling a submix (like, say, drums) via only one or two faders. (You can get more drums without having to try to try to figure out how to push all the drum channels up the same amount.) A VCA group is where a number of faders can be controlled proportionately by another fader, but without having to be summed in a different buss. The VCA's respond to a control signal that merely says "up/ down x dB," without having to be routed through another summing stage. (They may still be summed by the stereo buss summing amp, but you are still able to change all the drum levels with a single fader.)

[Danny (NS::U)]

Man, I have to start typing faster than Phil!

 

[Phil O'Keefe]

That's okay Danny, you posted a lot of good stuff, and probably explained things better than I did - at least you gave a different perspective and descriptions of the same things, and that might help people understand things better. Good job!

[kha02a]

Danny and Phil -

 

Thanks so much for your help. I really didn't expect anyone to feel like they had to answer all of those questions. But your help is much appreciated

 

I actually ran into most of those answers in my other research but alot of what you said I hadn't seen yet or you put it in a way I now understand. At any rate your help is useful and greatly appreciated.

[where02190]

 

Originally posted by kha02a But just so you know this forum is not the only way I'm researching these issues. Of course I used google and of course I did other reading

 

 

If that's the case then why do you need us to provide answers for you?

 

Reading is fundamental, cut and paste is IMHO cheating.

[ArrMatey]

 

Originally posted by where02190 If that's the case then why do you need us to provide answers for you? Reading is fundamental, cut and paste is IMHO cheating.

 

that's true but one thing I did find myself is that some reading material you find online isn't always the most friendly towards first readers. I know that after taking class, some texts make a lot more sense now.

That's just the feeling I got...but your point is still perfectly valid.

[Danny (NS::U)]

 

Originally posted by where02190 If that's the case then why do you need us to provide answers for you? Reading is fundamental, cut and paste is IMHO cheating.

 

 

That's true, Where, but the more I think about this, the more I think this forum is actually a distanced, text version of the old "master/ apprentice" relationship.

 

The apprentice asks his questions, and the masters (or, in my case, a more experienced apprentice) answer. We wouldn't be miffed if he asked these same questions verbally while we were sitting in a studio after a session, so why be irritated now?

 

All we really ought to ask is that he credit his sources.

[kha02a]

Yes!! That is exactly how I view this forum and that was my approach when asking these questions. Perhaps I should have posed my question a little differently and made it clear that I wasn't going to just take the answers I got here and plug them directly into my paper. Rather, I was just trying to get information from as many sources as possible and then try and make sense of all the information from here and other sources on my own.

[Phil O'Keefe]

Those last two posts were excellent!

 

 

We're here to talk about recording and everything that pertains to it.... and as I've frequently said, I strongly encourage participation from people of all experience and knowledge levels, and hope / expect the more experienced among us to "pay it forward" to those who are just getting started. If people wish to consider that a sort of onlne extension of the "master/ apprentice" relationship thing, then that's cool with me... not that I have any claims to the title of "master", but I do what I can, when I can... and we do have a few true masters around these parts from time to time.

 

kha02a, if this is just a [part of your research and studying, and you're not just "cutting and pasting" your answers (which might actually backfire on someone anyway - you never know, but your instructor might be a "lurker" and see this thread ), then I commend you for researching as much as possible... that sort of drive for knowledge, sought from as many sources as possible (and cross-checked with reference books and other good sources for accuracy) is one of the things that makes a difference between students who are likely to succeed and those who are just going through the motions and who normally have little chance of going anywhere in this business.

 

Please let us know how you do with your assignment.

 

Heck HERE'S a homework assignment for you:

 

When you finish your research, I would like for you to post YOUR answers to the above questions in this thread - let's see the answers in your own words... and there may be a test, with some follow up questions, to see if you've got a good handle on the concepts...

 

BTW, don't feel bad - this isn't the first time I've handed out homework assignments to people on my forum.

[kha02a]

Phil -

 

Great idea. I'll be happy to post my answers. And follow up questions are more than welcome. Anything that helps me learn is alright in my book even if it is homework. Should have my paper finished this weekend. Then I'll post it or an abbreviated version of it since its supposed to be 2000 words.

[Dave Martin]

Originally posted by kha02a Phil - Great idea. I'll be happy to post my answers. And follow up questions are more than welcome. Anything that helps me learn is alright in my book even if it is homework. Should have my paper finished this weekend. Then I'll post it or an abbreviated version of it since its supposed to be 2000 words.

 

Nope - post the whole 2000 words - or at least a link to the piece. Some of us might want to see what your other research looked like. And some of us who have made these types of assignments before might like to see how much you've simply cut and pasted from this thread...

 

Curiosity makes me ask, where are you interning?

[kha02a]

Ok I can do that. I'm not sure how to post a link to it though. I'm sure somebody can tell me.

 

To answer your question, I'm interning at The Park Studio with Donnie Boutwell. Its on Hawkins off of 12th Ave S. He's an independent producer that works with a ton of independent artists. His website is in my sig. Take a look.