High Efficiency System- Noise Floor Reality Check?


Trying to gauge whether I'm expecting too much quiet with the system at steady state, ie idling, no music playing. System consists of Avantgarde Duos, with the latest version of the Audiopax 88 monos; Steelhead preamp running a single phonoplayer (The TT, arm, cartridge and wire to the preamp will change in about a week).
Everything is plugged into a pair of Shunyata Hydras- two separate units, one for the speaker/amp woofers (Hydra two, with two outlets; the other a Hydra 6, into which the Steelhead and Audiopax amps are plugged). Using fairly high grade Shunyata power cables on everything; the Hydras, in turn, are plugged into a Richard Gray Substation, a 240v step down transformer that has its own line.

What am I hearing?- well, if you put your ear up the tweeter or midrange horn, a soft 'zzzz' type electrical noise, and from the woofers, a muted 60 hz hum. From the listening distance you can't hear it at all. And, when you crank the gain up on the preamp, no music playing, these noises don't get any louder.
Am I hearing the invariable low level noise of electrical equipment through very efficient speakers? I'm not so anal as to believe I can eradicate all system noise on a set up of this type, but I'm concerned that even this low level of residual noise may interfere with the system's musical capabilities. Would love to hear from high efficiency types since this is my first horn based system.
I also have a good electrician who has helped me in the past, but I'm not sure there is anything he could do beyond this to improve the noise factor, is there? Reality check? TIA.
128x128whart

Showing 1 response by douglikesaudio

The 60Hz hum in the subs may be from poorly shielded or oriented power supply transformers in the sub cabinet. I belive the Avantgardes use internal amps for the subs, yes? If they do, have you tried running them straight off the wall socket with no filtering? If you get a similar 60 cycle hum, you've got an inernal noise source--that is, the mains transformer. Opening the speaker (yikes!) and carefully shielding the transformer with ERS cloth (*don't short anything*) or similar could help. A more simple method of banishing such hum from a component builder's perspective is to change the orientation of the transformer. In other words, unmount it from whatever it's attached to and simply turn in from it's origial mounting position and listen for changes.

If the mains transformer is in a separate chassis from the subs, you can try similar things and it's easier since you don't have to open the speaker.

Not sure about the sound from the horn, but it doesn't sound like a tube issue as the volume doesn't increase with settings.

Hope this helps--we all can get a bit neurotic about this. As I recently said to my audio bud, this sometimes seems more like a support group than a hobby group.

Enjoy.