Hiss and buzz in active monitors! Please advise!

[Loopagator]

Mac Powerbook G4 1.5 Ghz
2GB Ram
OS 10.3.4
PT 6.4
DIGI 002
Joe Malone Preamps
Presonus Digimax LT Adat Preamps
Exernal 19" Mitsubishi Monitor
3 x Lacie external hard drives drives (only one used for audio)
Yamaha HS80M active monitors with balanced to XLR connectors


I have just purchased Yamaha HS50M active monitors that sound great, except:

1. Both speaker have a soft hiss, regardless of volume at rear or monitor level at the 002

2. When I turn on the monitor, a ramping-up frequency sounds on the monitors and remains faintly in the background.

The low-level buzzing STOPS when I either: turn off the monitor, or remove the firewire cable from the computer or 002. It begs the assumption that there is an electrical loop between computer, monitor, and 002. Are the monitors just broadcasting the frequecy? Moving the speakers away from the monitor has no effect.

I have upgraded from passive speakers with an old rotel amplifier where the same sound was present, but at an almost imperceptible level. When the amp was cranked, this sound was extreme, but I only monitored at less than 1/4 volume, so it wasn't as noticable.

Both sounds are distracting, but do not appear to go to disk.

I have just called my sparky to investigate any earth/loop issues and whether I am simply overloading the plug. Yet to confirm anything there.

I have tried a dozen potential solutions, mostly plugging things in and out, but to no avail. I have also tried plugging in the laptop to other mains plugs.

The hissing is more consistent and concerning.

Please advise.

[OddsAre]

are you using Balanced connectors? either TRS 1/4" to TRS 1/4" or TRS to XLR?

Always use Balanced cables in Pro Audio.

[Loopagator]

Yes, 1/4" to XLR from 002 to speakers.

Cheers.

[OddsAre]

1/4" TS or 1/4" TRS? sorry to ask again, but too many music stores sell XLR to 1/4 TS unbalanced cables to people who think they are buying a balanced cable.

TRS:

http://media.zzounds.com/media/feed/large/MONMSLST.jpg


TS:

http://cachepe.zzounds.com/media/quality,85/brand,zzounds/fit,400by400/nys224-1c8f9251befb8ad7ea8e2463a26d263c.jpg

[Loopagator]

Thanks. They're definitely balanced, TRS, two ring connectors to the 002, then XLR to back of the speakers.

[OddsAre]

huh, sounds suspect for sure. So you are saying that when the speakers are unplugged from the Digi 002 the hiss and buzz go away? Or even if you keep the speakers plugged in but disconnect the firewire cable? Have you tried a different Firewire cable? Or plugging the Digi 002 into a plug on a different circuit?

Have you tried plugging other sources into the speakers such as an external CD player?

[Loopagator]

I just spoke to a guy from Yamaha who gave me the following explanations:

1. The hiss is normal for these speakers. Something about the amount of circuitry pre-volume. The hiss is a constant feature, regardless of volume or power (have tried them in every room in the house).

2. The buzz is a typical/classic earth loop. The way to eliminate it is to sever the earth connection in the output connector (lead that goes to the 002). This apparently breaks the loop but maintains the audio/balanced cable integrity.

I mentioned this to my gear guru and he said it's an easily done modification. I would do it myself, but the hosa cable is moulded plastic.

The buzzing stops if I turn off the LCD, or if I remove the firewire cable from either the computer or 002. The firewire cable is the quickest way/weakest link for the current to complete its loop. Not sure if I'm really explaining any of this well. Joseph spent A LOT of time talking about it in great detail. Kudos to Yamaha Tech support in Australia.

Thanks for your interest. Perhaps you have other thoughts.

[albee1952]

Not sure if this will help but it may get you thinking in a new direction. Is everything plugged into the same power outlet? If not, then you may have a ground loop. You can try cutting the wire to pin 1 on the XLR's going into the speakers(or get some XLR barrels wired to lift pin 1). Also, if the speakers have a -10/+4 switch, use the +4 position(lower input gain=lower hiss).

[randyT]

If you open the shield on the TRS only do it on one end (monitor speaker end) and leave the other end connected so you still get the shielding effect. You could also use an isolation transformer. http://www.ebtechaudio.com/he-2des.html.

[Loopagator]

Everything is plugged in to the same two-socket wall plug: two six plug power boards are full!

The Yamaha guy recommended that the jack end to the 002 output should be the one to modify. He didn't mention the XLR end to the speaker input. Either way, isn't at least one end maintaining the shielding integrity?

Thanks for your response.