spacealf
Then you get into Sound System Engineering - like football stadiums and such and line voltages and other factors to consider or with extra-large concerts and places like Carnegie Hall and other sound system venues.
All different and engineered with respect to that.

Hmmm... not at all actually! The fundamentals for a proper sound system design change very little from critical listening system to small club to large arena.
 
1) Clean power and a cleaner ground system
2) Proper interconnection - and at the risk of being run out of town, there is only one proper interconnection scheme - a balanced source (does not have to be symmetrical) driving a balanced input, with the shield properly terminated on both ends.
3) Quality cable - not esoteric cable, quality cable, meaning sized properly, and without a drain wire. There are debates about Reussen vs braided shields, but both work well.
4) Proper gain structure - as pointed out earlier, 60 dB of gain is not uncommon in a microphone preamplifier. That's a 1000:1 ratio, so every little noise is going to be boosted 1000 times - that's a challenge! Proper equipment design plays a large role, but even the best design can be brought to its knees if gain is not applied well.
 
It really is that simple... but of course the devil is in the details.
 
Specific Answers:

davdud101I know that every connection in the signal chain add a little bit of noise to the signal...

That's mostly an old wives tale - passive components do not have a noise figure, and do not add noise to a system. Really bad interconnections, however, can do all sorts of bad things, from adding noise to rectifying the signal. Use good connectors and this is a non-issue.
 

davdud101But I've heard that longer cables tend to [do something malevolent that don't remember and am not quite sure of

Another old wives tale - sorta! For a high Z source, especially driving a high Z input, cable capacitance can be a factor. For modern, voltage transfer designs you have a source Z of very nearly zero, driving an input impedance of no more than 20 times that. Long cables are not a problem.
 

davdud101 So with that in mind, is it better to use longer cables (in the case that they're needed, for space and stuff) with fewer splits in the chain, or... what? 

It depends! There is no right answer.
 

davdud101Why are my preamps so noisy?

Can't answer that. Some preamplifiers, even well thought of models, can be noisy.
 

davdud101what difference does a preamp make? 

Noise, distortion, timbre, you name it. No two preamplifier designs will sound identical.
 

davdud101Why are some preferred over others (mostly in high-end pres)?

A lot of it, ok, well to be fair some of it is pure snobbishness. The truth is, an API preamplifier sounds different than a Neve, or a Urei or a Millenia Media or a Grace or a Hardy or a Great River or a...
 
It is largely a matter of taste, and experience. In general, I think I can hear the difference between a low cost preamplifier and one that commands a higher price.
 
Real world differences do exist, chief amongst them are headroom, quality of the power supply, and of course topology.
 

davdud101I know that last question is pretty stupid

Geez I am such a buzz-kill... but again, no, there are really no stupid questions!
 
All that said - it is quite possible to make a really good recording with modest gear. It is all about learning to use what you have to the best of its capabilities. And you learn that by asking (dumb??) questions here.

"Then you get into Sound System Engineering - like football stadiums and such and line voltages and other factors to consider or with extra-large concerts and places like Carnegie Hall and other sound system venues.
All different and engineered with respect to that.

Hmmm... not at all actually! The fundamentals for a proper sound system design change very little from critical listening system to small club to large arena."
 
Well, yes it does in a football stadium and arena type stadium.
There are books on Sound System Engineering, and college courses to become a Sound Engineer and measurements in places like Carnegie Hall and other places like that. They just do not hire the hook up a band in a night club people, they hire Professionals in those places.
 
And they do not use balanced cables, they use line-voltage cables with 26,400 whatever watts to run it all plus anything else they need. I do have a book on it, and even the formulas used are quite extensive.

http://www2.jblpro.com/products/installed/

http://www2.jblpro.com/index.html
 
http://www2.jblpro.com/catalog/general/Installations/Default.aspx
 
Now in your local small type church you may get by with it, but if they want it done like some people want it done, they pay, pay, and pay for professionals to figure it all out before giving them a price and doing the work.
Lest you be 40 feet up hooking up those speakers to cover an area in a church or any place like that.

 
But nowadays I suppose a lot of people think they are a recording engineer (except only in their own brain and those they can convince). Will it be done by people like that, well yes, but still the person is going to have to know something about any of it.
(and still convince others to spend the bucks on it).
 
 

Bill made a real good point.
 
When I was speaking of "low impedance" connections I forgot that it is 2014, and as Bill explained, impedance bridging rather than impedance matching has become the norm. That means my explanation about "low impedance" is dated and not really an explanation of what you are most likely to encounter now a days.
 
I got schooled again. Happy to have it happen! Thanks for being gentle. :-)
 
 
edit grammar

Hi Spacealf,
 It seems as if you are speaking about constant voltage sound systems. That's a technology for playing back or presenting sound through arrays of loud speakers spaced throughout a facility.
 
 Large venues routinely use balanced interconnections for low level signal communications. I work in football stadiums and on golf courses as a sound technician frequently. At golf tournaments we lay down many miles of line level balanced cable so that the microphones strewn around the course can be pott'd up when the director cuts the camera shots to the various locations. Football stadiums are similar. Some permanent installations have adopted digital interconnection over stuff like Cat5 cables too.
 
 best regards,
mike
 
 

what Mike said - Constant Voltage (High Impedance) loudspeaker systems are used to minimize the I*R losses in the loudspeaker wiring.
 
you wrote:

And they do not use balanced cables, they use line-voltage cables with 26,400 whatever watts to run it all plus anything else they need. I do have a book on it, and even the formulas used are quite extensive.

 
The wattage is determined by the transformer taps and the voice coil impedance, the current is a function of the system resistance and the impressed voltage, and the nominal impressed voltage is 70V. Please re-read the JBL documents, I am very familiar with them, and they do not say what you quoted.
 
70V lines can be balanced or single ended.
 
AND, you would NEVER want to use a 70V loudspeaker in a critical listening environment - the transformers cause all sorts of problems! (I did install 70V sub-woofers in a very high end hotel ballroom. It sounded a lot better than I expected, but the size, weight, and cost of those subs was ridiculous, still don't know why they did that.)
 
That said, I have designed some very large systems (one is the largest CobraNet system in the USA), and more than a couple recording studios, a handful of broadcast facilities, and even a couple houses of worship and nightclubs. The fundamental principles I mentioned above apply to ALL of these projects. And sticking to these basics saved my bacon on several occasions!
 
Sometimes they do hire the "hook up the band" guy for medium sized projects - this often works to their disadvantage<G>! For the bigger projects they do hire guys with degrees and 30 years experience, not because the fundamentals are different, but because the complexity is mind blowing. Especially when the loudspeaker count reaches into five digits... I haven't tackled anything like that yet, but it would be fun.
 
My point, which clearly I did not make, is that all you need to do is learn the basics, and then you can apply them to any audio system. You might stumble around in the dark for a bit on a larger design (heaven knows I did), but you'll get there!

Dang. this is some dense information... The way I understand it, impedance is the amount of power needed to raise the signal to line level? If not, could someone explain that?
 
And MY GOODNESS, I see it. The preamps found in my BOSS BR-532 are very clean, enough that I cannot hear noise when monitoring thru them! I mean in comparison to the toy, it's like night and day! And I still get a nice signal, not too quiet. This proves the degree to which I need to purchase a USB interface REALLY soon...

davdud101
Dang. this is some dense information... The way I understand it, impedance is the amount of power needed to raise the signal to line level? If not, could someone explain that?

 
Impedance is the opposition to alternating current flow (measured in ohms and frequency dependent)
Resistance is the opposition to direct current flow (measured in ohms)
Voltage is the potential difference between two points (e.g. in a circuit, across a battery), measured in volts
Current is the flow of electrical charge through a circuit, measured in Amperes (columbs/second)
Power is the rate of doing work, measured in Watts (Joules/second)
Energy is the ability to do work, measured in Joules
 
You can, to a degree, ignore Energy and Charge, but it is a good idea to get a grasp of power, voltage, current, and resistance/impedance... and especially the relationships between them:
Voltage = Current * Resistance (or impedance)
Power = Voltage * Current
 
Have fun!

Well, its been years since that book and I took something else but had taken calculus and such in college way back.
It's way beyond usually what is perhaps the usual home setup. And yes speaker connections and mic hookups yes are different or can be even down to the gauge of wire used to hook up your speaker system at home depending.
 
I think a lot of home studios are usually at the low end of the totem pole so to speak with equipment that can be used to make a recording or anything else in the recording field, unless one has thousands of dollars to put into it, then it probably would not be used for home personal recording use, but have to be a business.
 
Things will change that is for sure.
 
It's not like I going to have this type of studio anytime soon or ever. Sardines in a can. (a little humor). (and where is the cello at). Well, that studio has been brought up before here. It will never happen for me.
 
http://www.youtube.com/watch?v=exQRfHbSwn0
 

Yeah impedance is just another name for resistance in most cases.  The difference between line levels and mic levels is really just voltage and the impedance standards for each allow the current to flow reliably from interface to interface.  
 
Bridged connections mean the receiving end has a resistance of ideally 10x the source.  220ohm to 2200ohm for mic level and 1000ohm to 10khm for line level.  This is to maximize the voltage which is what modern transistors rely on.  Matched impedance with the same input and output resistance are for maximizing power (watt) transfer for devices like radio transmitters or older tube electronics.  

And yes I just realized last night I quoted instrument cable instead of line level impedance, which usually has an output impedance of 100 to 440+ ohms and an input impedance of around 10,000 ohms in some cases.