View Full Version : Help with sounds and symptoms


wharf rat
11-05-2011, 09:41 AM
New to tubes and repairing. I have a Fisher X101B integrated amp and when I play phono I occasionally get a very high pitch sound. I don't know the difference between hum, buzz, shrill, microphonic, etc.

Would someone explain the differences in these sounds and what they mean. Thank you.

jaymanaa
11-05-2011, 10:03 AM
A high pitch sound could be an oscillation, is it in both channels or just one?

Radioboy
11-05-2011, 11:21 AM
Well, when I think of high-pitched noise...it's really more like a Squeal. Tough to descirbe, but I imagine you'll know it when you hear it. (It's cause by a mutliple of things...)

Microphonic usually means that the tube itself is picking up and amplifiying ambient sounds. In extreme causes, in a console for instance, you can knock on the wood console, and that knock would be picked up and amplified through the speaker. Or you could tap the tube with a pencil (Or chopstick) and the knock would echo through the speaker.

Shril is a nebulous term...I've hear it used in reference to audio quality. Light, tinny, lacking bass, fatiguing to the ears. An Analogy: Listenng to a piccolo playing high notes for an hour, versus a tuba pumping out an oompah bassline.

Buzz/Hum can sometimes be used interchangably.

I think of Hum as an electically generated intereference. (Like 60 cycle). It's usually constant, sometimes dependant on volume control.

Buzz, I think, referes to momentariy rattles. Somtimes caused by the speakers, bad tubes, loose wood on a cab, etc. For examble, you might only expereince buzz on low notes. (Ever sit at a stoplight next to a bass-mobile with a rattling trunk?)

Anyway...those are just my opinions, feel free to disagree....

wharf rat
11-05-2011, 09:48 PM
my sound is in both channels.

dsndblm
11-05-2011, 10:12 PM
Have the 12AX7's in the phono stage been tested? Kinda sounds like a bad tube.

Is your X 101 B recapped? The 101 B uses the 7591 cathode current to power the phono and preamp tube filaments. The 7591 cathode, phono and preamp circuit has a 100uf electrolytic that might be bad.

Can you post some pictures of the amp? I can supply a schematic if needed.

Clean&Tight
11-05-2011, 11:13 PM
New to tubes and repairing. I have a Fisher X101B integrated amp and when I play phono I occasionally get a very high pitch sound. I don't know the difference between hum, buzz, shrill, microphonic, etc.

Would someone explain the differences in these sounds and what they mean. Thank you.

Is there a joke I'm too stupid to get with "towel" instead of "town" in your signature line?

Thomas