Ask MetaFilter questions tagged with stereo and noise

Lite Rock, Less Talk? I'd like neither, please.

strangecargo — Thu, 15 Jan 2009 00:59:16 -0800

(Electronics|Stereo)filter: What is causing this infuriating noise in my preamp and how do I fix it? Links to sound files and long list of symptoms in extended. I have this preamp and ever since moving to my current apartment in San Francisco, it generates a really loud noise that sounds like a combination of 60 Hz hum and FM radio broadcasts. The noise is loudest when the volume knob is turned all the way down, but it doesn't go away when you turn the volume up. And this is what it sounds like when you go from zero gain to full gain and back. The noises don't sound that loud when played back on a computer, but that level of noise is pretty dang loud when sent to the input of a power amp.

The maybe pertinent facts (numbered because there are a lot of them):

1. I recorded the linked sound files by plugging in the output of the preamp into the line in of a MacBook Pro. No mixing or diddling with the file other than that.

2. You can clearly hear the station identifier for KOIT in the first sound file I linked. This is an FM station. What the heck? I was under the impression that FM was way too complicated for equipment to randomly pick up unless it was designed specifically to, you know, receive FM radio.

3. Changing the vacuum tubes inside the preamp doesn't change the nature of the noise.

4. I have other audio equipment (both solid-state and tubed) that doesn't make this sort of noise.

5. The noise is generated independent of what I have connected as an input or output (or if there's anything connected at all).

6. I can't seem to reproduce this noise outside of my apartment (friends' places, hifi shops, etc). Whenever I try, the preamp is noiseless and dead silent.

7. Physically moving the preamp around my apartment doesn't seem to change the noise either.

8. I live in an old apartment without grounding in most of the electrical sockets, but the noise doesn't change if I plug the preamp into a grounded outlet. I've checked that the grounded outlets in my apartment are indeed grounded with one of these devices.

9. I live sort of near Sutro Tower (but who in SF doesn't?). Wikipedia tells me that KOIT broadcasts from Sutro Tower. I also live right next to the N Judah MUNI line. Sometimes my lights dim when it goes by. I suspect the power is probably kind of dirty.

10. Using a different power cable doesn't do anything.

11. For what it's worth, here's a look at the circuitry inside the preamp.

I've been investigating this problem on and off for the last year or so and I still haven't figured out what's causing the problem. Do any electrical engineer types have an suggestions for further testing or solutions to this problem? I have a digital multimeter and oscilloscope at my disposal for the collection of further data.

I'm quite attached to this preamp (more so when it isn't making this noise), so please don't tell me to replace it.

Noisy Neighbours Require Political Manouvre

Popular Ethics — Thu, 23 Nov 2006 20:13:14 -0800

Apartment Etiquette - Dealing with a stereo hound next door. I just moved into a new apartment building I quickly found out that my neighbour likes to invite his friends over regularly to show off his base-pounding stereo. Sigh. So this afternoon, when he was on a "trial run" before his friends showed up, I walked over, introduced myself, and politely asked him to turn it down. He did, but they're back to their regular habit this evening (even turning it up to full, then quickly down, as if I might not notice).

OK, so I haven't been in an apartment building in years. I haven't built the thick skin yet. I wonder though how I can go about enforcing my request without a) whining impotently or b) escalating the conflict.

Thoughts?

Get this Mother^$(ing Thump out of my Mother$(#ing car!

toxic — Tue, 29 Aug 2006 20:49:00 -0800

Very strange electrical noise getting into radio on newly imported 1997 JDM Toyota Tercel hatchback. Radio replacement is imminent, but there's So I bought this car, without checking to see if the radio worked, because I'd planned to replace the radio anyway (Japan's FM spectrum is 70-90 MHz, New Zealand's is the more normal 88-108, so even if it were working, the original Japanese radio would only get 2-3 stations).

A couple of days after I bought the car, I turned on the radio for the first time, and was greeted by very strange noises.

The noise is a repeating "Thump Thump Thump", that comes out of both speakers when the stereo is turned on. It doesn't matter what the volume knob is set to, it doesn't matter where the fader/balance knobs are set, it comes out of both speakers at the same volume (fairly loud, but not eardrum-shattering)

I'm hoping that this is just a bad amplifier in the stock unit, and that the replacement radio that I've got ordered will take care of this, but I'm concerned that it may be indicative of some other kind of electrical problem in the car.

I'm wondering if anyone else has heard similar noises from their Toyota, or has any further insight on this. Anyone?

How can I make my stereo quieter?

bcwinters — Mon, 15 Nov 2004 08:29:08 -0800

How can I make my stereo quieter? [MI] I have a Harman Kardon receiver (sort of an ordinary home model with a bunch of regular RCA inputs and two sets of speaker-wire outputs) and a pair of Fisher speakers that date from the 70s that my dad gave me. I have a bunch of regular devices running into a switcher box that then feeds into the stereo -- the TiVo, the PS2 & GameCube, my Mac, etc.

The problem is that even the line-level inputs like the TiVo are WAY too loud since I moved to an apartment with a smallish living room. I can't even turn the volume halfway between zero and one without feeling like I'm going to wake the dead, especially in the evening. The speakers sound great and warm and I don't really want to replace them. I am not an audiophile although I do care about halfway decent, natural sound.

I bought some highly-rated bookshelf speakers a while ago, thinking they would have a lower overall output, and they sounded so tinny compared to the floor speakers I was used to that I had to return them. Today I searched on Google for something to reduce or limit the volume and all I could find were sort of audiophile-ish devices that cost $200 or more.

Can anyone recommend some kind of not-that-expensive device I can stick between the stereo and the speakers (or between the switcher box and the stereo, or whatever) that will reduce the overall volume so I can have more control over the sound? Thanks!

Ask MetaFilter questions tagged with stereo and noise

Lite Rock, Less Talk? I'd like neither, please.

Noisy Neighbours Require Political Manouvre

Get this Mother^$(*ing Thump out of my Mother$*(#ing car!

How can I make my stereo quieter?

Get this Mother^$(ing Thump out of my Mother$(#ing car!