GS User Question - Audio Cables

This question will get a million responses, each claiming that they have/know the best audio cable.

The most important quality of a cable is the size, within reason. Then it comes down to quality of the component parts and the connections used.

I'd go with something here:

RCA Audio Patch Cables at Crutchfield.com

The most important feature is actually the capacitance per foot, then the effectiveness of the shield.

Cable capacitance directly impacts where the high end frequency rolls off based on the input impedance of the component you are driving. The longer the run the higher the capacitance and the more high frequency loss you get.

Oh, come on!

Bigger is always better. And, if it's gold plated it must be the best!

Must be why the one guy named "Monster" does so well. :)

I'll defer to you.

Being in a band (in my mis-spent youth) and later, being director of engineering for a noise cancellation company don't necessarily qualify me to recommend recording studio cabling.

Besides that was a lifetime ago. I can't hear well enough to be a music critic any more.

I ran sound for local bands while in college, and continued for a few years.

Your question is incomplete.

Are you running sound in a studio or are you mixing for a stage?

You would have to look at both the mixing console and the amp.

Do they both have RCA connections?

Do they both have XLR connections?

RCA is unbalanced XLR could be either balanced or unbalanced.

Makes a big difference in quality of sound over long runs.

Also could be an Amphenol AP connection, I suppose....

Need more info.

It sounds like a pro application and most pro equipment uses balanced line XLR connector or balanced line stereo 1/4 plugs.

Consumer goods use RCA connections.

The better cable to use is from Blue Jeans.

For balanced line cables use Belden 1800F

For single conductor cable use LC-1 or Belden 1505F

Both cables have very low capacitance per foot, which is critical for longer runs and high input impedance where the potential for high frequency rolloff is prone.

Blue Jeans Cable will make the cables specifically to your needs or you can order the raw wire. I have had excellent service with them and their prices are very fair.

The only thing I recommend from the sparse information is to use cables composed of material with and without free valence electrons (conductor and insulator). The cables composed of just free valence material are typically used only for mechanical support (suspended speaker).

Now depending on how far apart the mixing console is from the amplifier, how frequently they will be disconnected from each other, the electrical interface circuitry these cables will carry, environmental exposure (salt water spray, alcoholic beverages, direct sun light, insects, etc.) then some sound advice (pun intended) could be provided. It would also be nice to know the sonic application: local bar band sound reinforcement, traveling stage show production, wedding DJ, fixed basement recording studio and family surround sound theater.

If you want some really nice cables, check out: http://gothamaudiousa.com/

They will even send you a sample.

Nice stuff.

re:- "What kind of cable"..?

The type of cable used to connect line level signals would be a 2 Core Shielded cable similar to almost ANY Mic Cable you would buy from a Music Store/Proffessional Sound Equipment outlet.

Loss & High Frequency roll off are really non-issues (unless you are running 100s of yards), as you will adjust the output gain & EQ the output to sound how you want anyway (thus compensating for any minor losses).

We run a proffesional audio system in a 350 seat auditorium, where we have approx 30yds between the Mixing Desk & the Power amps. We are only using a "multicore" cable to send many outputs to a number of amps, & this cable would be significantly smaller in gauge than a single mic lead. We have no issuse with signal, gain or freq response.

You can buy these as either XLR or Balanced 1/4" jack Plugs/Sockets. If you require any other fitting you can get adaptors to suit (RCA-XLR, RCA-Jack, Stereo Jack-XLR...)

Ah, do you think so?

The formula for calculating high frequency cable loss is as follows:

Now, average mic cable has a capacitance of about 100 pF/meter.

For a simple 10 meter run of that cable with a source impedance of 10,000 Ω, you get a -3 dB rolloff at 15,915 Hz. Not what you want if you are spending a lot of money on audio equipment, but losing your precious high end to a $20 cable.

Your 27.4 meter run with the same cable and source impedance would give you a corner frequency of 5,800 Hz.

Fortunately, pro equipment source impedance is typically much lower than 10 kΩ; more lime 600 Ω, which avoids the problem for you.

However, for consumer HiFi the source impedances are much higher and cable length and capacitance become a much more critical factor.

Since when has consumer audio output impedances been as high as 10k. The input impedance of consumer devices is 10k, not the output. As the wiki article points out this along with cable lengths allows the impedance bridging principle to be used that you almost describe. (Oh, where is L in your circuit description? By adding a second reactive component you should get a second order polynomial. Depending on where this inductor gets place will determine the transfer function. This is much more complicated than you make it with this equation. If C→0 this properly becomes an infinite frequency low pass filter. If L→0 then this does not make sense. For a two pole filter ω0 should be (LC)^-0.5. R only effects the dampening or Q of the filter.)

Using your equation with L removed from the equation and with Zo<1000 then with your 30 meter run the corner frequency is greater than 50kHz. A bat might notice the missing ultrasound .

I agree. Inductance is not factored in, but I don't think it is a primary consideration with this scenario (line level audio cable) because of the voltage to current ratio is so much higher (unlike speaker cable).

L in the equation is length in meters and yes, when the source impedance drops the corner frequency goes up. This is one reason why pro equipment uses 600 Ω balanced lines.

As for high output impedance devices, my stereo preamp is such a device and required the addition of a DRV134 chip to drive a balanced line out. The line length between my preamp and the power amp is just a little too long to run unbalanced due to the placement of the power amp.

OK, the nomenclature I'm familiar with would then make C→C' and L→l (that should be a script lower case l but with only one font...). I'm stunned that any audio preamplifier would have such a poor output impedance. Now many a low end audio equipment will not be capable of producing a large line level output voltage. A more common problem will be a poor driver feedback design that renders the output sensitive to capacitive loading and can cause an oscillation.