Home |
Search |
Today's Posts |
#1
|
|||
|
|||
Tube amp makes noise on shutdown
There is no signal going to the amp and it's time to shutdown until
another day of listening arrives. Flip the power switch to off like I always do EXCEPT this time after about five seconds or so there is this brief sound out of the speakers. Sound lasts about two seconds and sounds like a sine wave sweep down in Hz and amplitude. BBBBBEEEEEoooooooppppp p p How bad is this? Can it be fixed? |
#2
|
|||
|
|||
Neil,
Is this a new occurrence for this amp, or a new amp to your system? It is quite possible that some amps will put out strange stuff as the power supplies come down, and most tube amps don't have protection relays to disconnect the speakers at power down. It would also be helpful if you mentioned what amp and preamp you are using. Lastly, it could be the preamp powering down in a less than graceful manner. (Try shutting off the power amp a couple of minutes BEFORE shutting off the preamp.) Regards, Tim Schwartz Bristol Electronics Neil Peters wrote: There is no signal going to the amp and it's time to shutdown until another day of listening arrives. Flip the power switch to off like I always do EXCEPT this time after about five seconds or so there is this brief sound out of the speakers. Sound lasts about two seconds and sounds like a sine wave sweep down in Hz and amplitude. BBBBBEEEEEoooooooppppp p p How bad is this? Can it be fixed? |
#3
|
|||
|
|||
Some amplifiers can make some noise as the power collapses. This may be due
to something with the inverse feedback circuits, or something starting to oscillate as the power collapses. If all is working properly, this should not be something to worry about. Tube amps generally don't have protection relays, as like in the solid state amps. This means that with the tube amp on the power down, the speakers are still connected. -- Jerry G. ====== "Neil Peters" wrote in message ... There is no signal going to the amp and it's time to shutdown until another day of listening arrives. Flip the power switch to off like I always do EXCEPT this time after about five seconds or so there is this brief sound out of the speakers. Sound lasts about two seconds and sounds like a sine wave sweep down in Hz and amplitude. BBBBBEEEEEoooooooppppp p p How bad is this? Can it be fixed? |
#4
|
|||
|
|||
Hi,
If this amp has always done this, I would not worry. Some amps employ both current and voltage feedback to enhance the damping factor and linear frequency response. This is normal in some amps as the different stages loose power upon shutdown. But, if the amp has never done this before, it could be foretelling a problem that is starting to rear it's ugly head. A lot of modern amps use all kinds of solid state regulators and such in their power supplies and some of these can cause some strange oscillations as the amp initially powers on and when it is powered off. Bill B. Neil Peters wrote: There is no signal going to the amp and it's time to shutdown until another day of listening arrives. Flip the power switch to off like I always do EXCEPT this time after about five seconds or so there is this brief sound out of the speakers. Sound lasts about two seconds and sounds like a sine wave sweep down in Hz and amplitude. BBBBBEEEEEoooooooppppp p p How bad is this? Can it be fixed? |
#5
|
|||
|
|||
Neil Peters wrote:
There is no signal going to the amp and it's time to shutdown until another day of listening arrives. Flip the power switch to off like I always do EXCEPT this time after about five seconds or so there is this brief sound out of the speakers. Sound lasts about two seconds and sounds like a sine wave sweep down in Hz and amplitude. BBBBBEEEEEoooooooppppp p p How bad is this? Can it be fixed? Thanks guys! |
#6
|
|||
|
|||
It sounds like an instability in a feedback circuit. But, I have
actually seen a bad tube cause this. The only way to really find out for sure is to do some tests on the amplifier. It is probably nothing too big. My only concern would be if the amp is producing a high frequency oscillation you can not hear when it is on, and that oscillation only becomes apparent when the amp is turned off and the voltage dropping is allowing the oscillating problem to drop enough in frequency so it becomes audible. It would not be a bad idea to have the amp checked out with a signal generator and scope. If you can not find anyone locally to work on it, I service tube audio here in north Florida. People send me amps no one else can fix from all over the world. You can check me out at: http://home.alltel.net/wbittle1 Ozzy 2005 wrote: Neil Peters wrote: There is no signal going to the amp and it's time to shutdown until another day of listening arrives. Flip the power switch to off like I always do EXCEPT this time after about five seconds or so there is this brief sound out of the speakers. Sound lasts about two seconds and sounds like a sine wave sweep down in Hz and amplitude. BBBBBEEEEEoooooooppppp p p How bad is this? Can it be fixed? Thanks guys! |
Reply |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
on topic: we need a rec.audio.pro.ot newsgroup! | Pro Audio | |||
DNC Schedule of Events | Pro Audio |