hiss with no inputs

hi,

loving my new bose system.

with no inputs whatsoever, with all trims completely off, at about 1/2 master volume I start getting a high mid-range, low high-end hiss.

quite pronounced at 3/4 full master volumne.

is this right? is it potentially a power line issue?

michael
Original Post
Hi Michael,

I read your post and wandered off to the other room and fired up my System.

I *can* hear a hiss with
- no inputs
- trims off
- Channel Levels on Remote at 0
- Master Volume 1/2 to 3/4 to 12+

It is not very loud. With
- the Master Volume at 1/2 way,
- in a room about 35' x 40'

Within 4 feet I am aware of the hiss

Standing 8 feet away it blends into background noise (although that room is pretty quiet).

Looking at this another way.
- In a live music situation I probably wouldn't notice it.
- If the System is in a playing situation, I doubt you would hear it in the audience.
- If I was playing, or playing background music with the trims set normally and the Levels and Master at 12 1/2 way - at 8 feet away, I wouldn't notice.

That last three conditions describe how I run my System most of the time. The hiss is so far in the background I just don't notice. That's why I had to go and actually listen for it. Tried it with two different Systems - pretty much the same results for both.

Now, I can hear it and am aware of it if I'm within 4 feet and I listen for it. But I would also not be standing with my ears that close to the L1 with all the settings up that high if I was actually playing. Well in tight quarters maybe half-way, but certainly no higher.

If it seems louder to you than what I've tried to describe, can you talk more about the setting in which you are hearing it?
Hi ST,

Thanks for such a generous reply (with personal testing on multiple units no less...wow!)

Since writing, I've seen that there are are some other posts about similar experiences.

I'm not sure what to tell you more about the settings...no plugs, all trims and levels completely off, one base unit, all EQs at "0" (12 noon), turn unit off and back on with this set-up.

Yes, I am within 4 feet and there is very little ambient noise when I hear it. Yes, I think in a performing situation, or when something is playing, no one would notice.

I guess for such an expensive piece of equipment, I was somehow dreaming it would sit in complete silence without any inputs or trims on! (and was a bit worried something was wrong with MY unit).

So, with your help, I think the unit is probably fine, and I will carry on.

I've got a bunch of new stuff I'm integrating right now(new mac powerbook, MOTU traveler, Logic Pro, a DigiTech looper, etc. etc.) and have this deep fear on one side that I've spent too much money too fast and should have bought a cheaper traditional PA at this point, and this big thrill on the other that says "Oh, this sound is incredibly off the charts...I think I need to get one more of these for when I want to run out stereo and/or have a bit more umph for other people to play through it with me."

thanks again,

michael coombs
quote:
Originally posted by Michael C.:
I've got a bunch of new stuff I'm integrating right now(new mac powerbook, MOTU traveler, Logic Pro, a DigiTech looper, etc. etc.) and have this deep fear on one side that I've spent too much money too fast and should have bought a cheaper traditional PA at this point, and this big thrill on the other that says "Oh, this sound is incredibly off the charts...


Hi Michael -

My experience is that you won't regret getting a PAS instead of a cheaper traditional system. No 3-way system can come close to the PAS for clear sound delivery in small, medium, and even large rooms, and hearing what the audience hears creates a much better show for all.

quote:
...I think I need to get one more of these for when I want to run out stereo and/or have a bit more umph for other people to play through it with me."


Like many others who are using the PAS I agree with you - I'm up to three systems now...and it just gets better!
quote:
Originally posted by Michael C.: ...with no inputs whatsoever, with all trims completely off, at about 1/2 master volume I start getting a high mid-range, low high-end hiss.

quite pronounced at 3/4 full master volumne...


I'm not where I can try this yet, but ... might this be an artifact of open connections?

Try connecting a good (well-shielded, sturdy) cable (preferably XLR) to an input device (e.g.: laptop, iPod, keyboard), but don't play anything. Does the hiss increase or decrease?

If it decreases, then the System is apparently picking up some free-air signals someplace - that may be an issue of design for Hilmer (or others) to address. I know some audio components use input connectors which "short" the input when nothing is plugged in just to try eliminating most of those "nothing is connected but I get a hiss/hum" issues.

(If the 'hiss' increases, it is hard to draw any conclusions, because there are so many possible sources of introduced, rather than intrinsic, 'hiss'.)
Someone mentioned that keeping your excess cord lengths wrapped in a circle could create an FM antenae which would cause problems.
Personally with all my cords I wrap them in circles and keep them each in place with a velcro strap.
XLR's, Mic Cords, The Cord connected to my light controller, power cords....everything is kept in a circle for managability. They stay that way and wrap up nicely at the end of the night. Thank You Velcro!!!!
I too though have a hum and would like more input on solutions.
Wrapping cords in a different way is major to me
but not a problem if it solves the hum.

Note: Brand New Mixer---Numark 1200 DM
Later
Gary
Hi Gary,

I think of hum and hiss as two different animals. When looking to solve a hum problem, try to identify the culprit by starting with the simplest possible signal path and then add pieces until the hum is present. I've found that hum is most often caused by either a ground loop, or by running cables too close to a transformer, like the ones used in those wall wart power supplies. Whatever the cause, hum can usually be eliminated. Let us know if you need more help with troubleshooting...
I don’t know what I’m trying to say here but I sleep in my lazyboy, because I have a bad back. So I have a radio alarm clock on one side of my chair and a portable phone on the other. And even with the radio off if I get to close with phone it starts to pick it up and hum/hiss. Almost kind of like both of them. It just goes to show you, it can be just about anything.
I have it too with two PAS’s; and I don’t remember having it with just one… but I am to laze to go looking for it. It’s just not that bad.
Oh that reminds me – The ultimate laziness is when you go down and buy a lazyboy and when you get it home you never have the energy to put the back on the seat.
quote:
Originally posted by Gary in Midland TX:
Someone mentioned that keeping your excess cord lengths wrapped in a circle could create an FM antenae which would cause problems....


Gary,

Maybe you're referring to one of my postings (http://bose.infopop.cc/eve/forums/a/tpc/f/397605594...161081762#8161081762). Basically, if you put a coil of wire carrying significant 60 Hz power on top of a coil of unbalanced instrument input cable, you will have inductive coupling of the 60-Hz signal into your input line. If you have hum, and you've tie-wrapped the power cables along side your input cables, the first thing to do is to try separating them. You will have coupling if the wires lie parallel to eachother, but having them in coils increases the inductance.

--Rick
Thank y'all for the responses.
I'll do my best to seperate everything as explained but it's slow here until end of January.

I'll try to do a dry run with cords every which a way to see what happems but since I live in 2nd floor apt. it's tough to set that up.

I also noticed the tinitus(sic) (ringing of the ears) is more pronounced since I got the PAS. It's now constant and louder than before.

In theory it should be less. Shouldn't it?

I'm preparing for a Bridal Fair on Sunday and we'll get an idea of whether the Bose name makes an affect to clients inclined to choose a DJ on brand names and presentation.

Later,
Gary

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