250ti hissing

[FredEmmerich]

Don't know if this is the right section, but my 250ti's hiss when no source material is playing. I can switch beteen sources on my pre-amp and they all hiss, I thought it was just my CD player. My other speakers did not do this (L96, 4312, 4425). Could this be caused by ground loop problems?

thanks
Fred

[johnaec]

Ground loop problems will cause a hum, not a hiss. If you didn't hear it on your previous speakers, I'd venture to say their HF response isn't as good as the 250Ti's.

John

[FredEmmerich]

Hi John, thanks for the quick reply! Is the hiss something I can eliminate?

[JuniorJBL]

What kind of amp and pre are you using?

[FredEmmerich]

What kind of amp and pre are you using?

Amp is a McIntosh 2100 (105 watts) and a Mac C36 pre-amp. I just had the amp refurbished by the factory.

thanks
Fred

[JuniorJBL]

Are you hearing this same noise when the volume is all the way down. Or does it get louder as you turn it up?
Does it go away if you unplug the pre cables?

[FredEmmerich]

Are you hearing this same noise when the volume is all the way down. Or does it get louder as you turn it up?
Does it go away if you unplug the pre cables?

If I turn it all the way up the hiss goes up slightly. It does not go away at zero volume. If I unplug the amp from pre, it still hisses, same as at zero volume.

[JuniorJBL]

It would seem that the amp is a little noisy. You might try a noise filter on the power but that most likely will not cure your hiss. Maybe some of the amp gurus will chime in. If it is not very loud then I would not be concerned as Johnaec said you do have a bit better HF response than you did before. If you put one of the other speakers back on a channel and get closer to it you will most likely hear it as well.

[boputnam]

My other speakers did not do this (L96, 4312, 4425).When...? How long ago have you last checked the others?

There should not be that disparate of a HF response between these speakers - not anything that would affect a "hiss" (which is likely a relatively broad bandwith problem).

If you can, re-connect the 4312's and/or the 4425's and see if they too have this (possibly...) new hiss.

[duaneage]

If you JUST had it refurbished, maybe they left a screw loose somewhere. Check that the cabinet screws are tight, if a metal panel on the case is loose it will not shield the amp.
There could be a loose connection or missing screw on a PCB that grounds a board. Many times the circuit boards are grounded through a phillips head screw that goes to the chassis. Without a good ground an amplifier's pre stages will get noisy.

If the amp has a grounded 3 prong plug, try plugging it into a different outlet. The outlet may have a bad ground. Measure from the case of the amp to a ground connection on an outlet, should have almost 0V AC. If you see any voltage have the unit grounds checked again, especially if there is a lot of voltage (like 50 V)

Check the input cables. Replace with different ones or else disconnect them from the amp and see if the noise goes away.

I also have seen FET outputs that were noisy. I replaced a set on an amp years ago for someone to get rid of a persistant "air" in one channel.

It can be difficult to isolate these problems that is for sure

[FredEmmerich]

When...? How long ago have you last checked the others?

There should not be that disparate of a HF response between these speakers - not anything that would affect a "hiss" (which is likely a relatively broad bandwith problem).

If you can, re-connect the 4312's and/or the 4425's and see if they too have this (possibly...) new hiss.

Now that you mention it, I have not tried the speakers since I had the amp redone. I will hook up the old ones and see if that makes a difference.

I bought the ti's first, then the 4425's. I was surprised how close the 4425's sounded to the ti's. The ti's have much better bass, but I hope the HF hiss might be identifiable in the 4425's as well.

thanks
Fred

[boputnam]

... but I hope the HF hiss might be identifiable in the 4425's as well.I fully expect that is what you find. Let us know... :)

[CLASS A]

Don't know if this is the right section, but my 250ti's hiss when no source material is playing. I can switch beteen sources on my pre-amp and they all hiss, I thought it was just my CD player. My other speakers did not do this (L96, 4312, 4425). Could this be caused by ground loop problems? Hi, I own a pair of 250 Jubilees and the HF hiss as well with no signal, this is very normal. I have ground loops on my pre/power amps with everything running through a mains filter. I do have to put my ears to the tweeter to hear the hiss but it does not get any louder with volume gain or music playing.
Reat assure everything is fine.....
Cheers

[mike]

Mcintosh MC2100 amplifiers tend to have a little hiss at idle. They are otherwise good amplifiers.

Mike