I know from a technical perspective, balanced vs unbalanced shouldn't make a difference with wire runs under 25'. If everything is properly grounded you shouldn't get any humm, but in practice I have found balanced interconnects are quieter and the closer you get to a fully balanced system, the quieter the system gets.

I have never been able eliminate the ground loop type humm in any system I have had without using XLR connections. Technically, I know you can do it with RCA connections. I have made sure everything is plugged into the same power strip. I have used a line conditioner. I have bought expensive cables. I have never been able to completely get rid of that humm without using XLRs. i still have a little bit of airiness if I get close to the speakers but no humm in my current systems. Plus, there are technical reasons that make a lot sense to me that justify expensive RCA cables. I see no technical reason to spend a lot on XLRs, and as a result I don't.

For systems, I have one which is a Marantz Pre/Pro and power amp and the other is an Ayre Preamp and Rogue audio power amp. The Ayre/Rogue system is extremely quiet. If the volume is at 50%, I need to get within about 1ft of the speakers to hear the airiness. If I ever get fully balanced sources I think I will get extremely close to complete quiet. The Marantz system isn't as quiet. With volume up at 50%, I need to get within about 2' of the speakers. In both cases, I have connected the systems using RCAs and I get a humm. Also, I had a Carver system that lacked XLRs and I could never get rid of the humm.

Again, I know there is no technical reason for my experience. Maybe I am completely inept. I can say for certain, I am lazy and cheap. Thus, I buy balanced equipment now and use XLR connections.

pentode wrote:

How common are audio systems without any audible hum, even when listening for it right at the speaker? I've yet to have one, myself, but know they exist.

Power amplifiers often have hum of their own, but the level is usually so low that it is not usually noticeable. Preamps or voltage amp stages in integrated amps can be a source of hum on occasion, especially when a noisy tube is the culprit.

If you want to get technical, the hum that might come from a balanced interconnect calculates out theoretically to the order of 10,000 times less than with a unbalanced interconnect, but keeping the unbalanced interconnect away from sources of hum can help to keep it under control and avoid any real problems.

As far as unbalanced interconnects are concerned, i would never recommend running one more than 2 meters, not only because of potential hum problems, but general degradation of signal quality.

Balanced interconnects are virtually immune to any sort of hum or interference. I keep my system all-balanced, except for a couple of places where balanced is not an option.

I have seen balanced interconnects used with microphones, which generate a very tiny signal voltage, run over 100 feet in symphony hall recording venues where they go very close to high-power AC cables for lighting, and there isn't a whisper of hum. Try that with an unbalanced interconnect!

I do not get any humm in my system, but I do get a faint hiss when I put my ear relatively close to the speaker if no music is playing. The hiss becomes louder when the volume is raised on my amp, but it's never a concern at my listening levels.

I'm too much of a noob to know if this is typical, what's causing it, or if it can be fixed. I assume that it isn't related to a humm that may be caused by a ground loop, and chalk it up to a line noise that my amp produces. It's not anything that affects playback, and like I said it's only noticeable when no music is playing and my ear is close to the speaker.

Since the induced magnetic field associated it's current traveling through a conductor is radiated perpendicular to the direction of the current flow you can usually reduce hum and noise in the system by ensuring that no cable or power cord is adjacent to another cord or cable. If such topologies are unavoidable make sure that cables or cords are placed such that they're not running parallel to each other, rather are perpendicular to each other. Separation by say a foot or two is also desirable for situations when parallel runs are unavoidable as the intensity of the induced magnetic field falls off at a rate proportional to the square of the distance from the conductor. It goes without saying this stategy is especially important for low signal level cables such as tonearm wiring.

Geoff Kait
Machina Dynamica

pentode wrote:

How common are audio systems without any audible hum, even when listening for it right at the speaker? I've yet to have one, myself, but know they exist.

Always be sure to keep cables from a turntable as short as possible. The signal from the cartridge is very small and any hum that is picked up there is going to be amplified a lot along with the cartridge signal, so that is a critical area.

If you have to go a long distance from the turntable to the amplifier, you should put a separate phono preamp close to the turntable and then the cables from the phono preamp to the amplifier can be longer without any problems.

Another reason turntable cables must be kept short is that the cables that are directly connected to the cartridge place a capacitive load on the cartridge, which can affect its sound quality. Keeping the cables as short as possible minimizes the problem.

I'm not sure what the hiss is that is sometimes present when putting your ear close to the speaker with volume knob at say 4 but without music playing. Most likely that is the background noise of the preamp and amplifier. And you're amplifying only the noise. While some military and audiophile electronics are designed to have heroic Signal to Noise ratios, you know, things like strategic nuclear submarine receivers for underwater operation and the Blowtorch preamp which have super high SNR. You will NOT hear any HISS in those systems.

If you can hear HISS when the volume knob is at 0 something else going on that is more mysterious. In that case most likely what you're hearing is the Cosmic Background Radiation from the Big Bang. If you can hear the ocean you're in real trouble.

Geoff Kait
Machina Dramatica

All:

With my Creek Evolution 50A amp and creek internal DAC, there is absolute silence (when no music is currently playing of course, lol) on all digital content. In fact, digital by design is supposed to work this way. I would contend if anyone is hearing any kind of noise with digital content they are having cabling or other technical issues or defective equipment.

Having said that, I do experience a very very faint "hum" with a rega turntable, but I think that is also normal.

Respectfully,

Ron

Ps. As my amp is actually all integrated with internal DAC, there are no cables to deal with. I will say when I first installed the DAC I did experience a rather bothersome but very low level hum, after re-inspecting the installation of the card, I noticed a ribbon cable was making direct contact with the backside of the printed circuit board. Merely re-locating the cable completely resolved the issue.