ok, thanks for the advice, I'll be sure to wipe everything down tonight. |
Skf3636, the deoxit gold is good stuff, but should be used sparingly, particularly in tube gear! If I were you, I would pull all the tubes out, and carefully wipe down the sockets and bases of the tubes to remove excess chemical. Too many times, I have seen contact cleaners cause problems later on, as the chemistry can break down and become conductive in the presence of heat and high voltages. If that happens, you will first notice it as a loss of high frequencies. |
Update - I took Jea48's advice to clean the tube sockets and pins. After a little more research, I bought some deoxit gold at the local guitar center, sprayed it on every tube in the system, and unplugged and replugged every tube a few times. I then had to leave for a while, and when I returned I turned on the amps and there was absolutely no noise with the volume on or off. And the music sounded crystal clear. I think the cleaning worked, and for anyone landing on this thread in the future, I highly recommend using deoxit gold for periodic maintenance of a tube amp. Thanks again for all of the responses. |
Sometimes AC power switches can develop issues that will cause crackling. This is caused by bad contacts in the switch. Tapping on the switch can sometimes excite the behavior.
If you get a pinging sound by tapping on the switch, it is because vibration is transmitted from the switch to the tubes through the chassis. |
Both channels are affected.
Skf3636, Both channels?...... Have a feeling it is something in the power supply. Could be a loose connection. Maybe a cold solder joint. |
Thanks for the responses. I'll try the quick method of cleaning the tubes/sockets. Both channels are affected. I'll also get the tubes checked at a local shop if I can't get it working properly. |
Skf3636,
Both channels or only in one?
Could be a dirty and or corroded tube socket/s or tube pins.
Quick method of cleaning is to unplug and reinsert tube/s in socket several time to clean the pins and socket contacts.... |
No one's necessarily leading him astray. I certainly agree with what you say about pinging sounds being heard routinely when one taps on preamp tubes, but crackling or ripping noises that come and go is fairly symptomatic of a problem with an amp's output tube(s). On the other hand, a troubled or overly stressed preamp tube usually sounds almost like one very gently clearing his throat or a high pitched eeeee sound. At least this has been my experience on a number of occasions. |
He said specifically he tapped on the preamp tubes and got a pinging sound. He also then says he gets that sound by tapping on the on-off switch of the pre-amp. Let's not lead this guy astray by not dealing with the actual problem he is describing |
Incidentally, chances are all your amps' tubes are not bad. I've experienced loud crackling through a speaker several times before with just one of my six output tubes per monoblock being bad. |
I agree with Marakanetz on both points, especially the loud crackling, which typically indicates a problem with amp output tubes. |
I don't think it's preamp. I think it's amplifiers. Tapping tubes isn't a good idea at all. |
Another question. Does your preamp have the switch on the back for low and high gain? If on high switch to low gain and see if this helps solve your problem. |
I don't think the preamp which he is talking about has adjustable tube biasing. A lot of preamps will ping if you tap on the tubes and does not mean that they are bad. Does the pinging get worse as you turn up the volumn? |
Did you check bias?
Tubes that are out of bias deeply might not be good anymore and certaly can pick up microphonies.
If the amp is new and tubes are deeply out of bias or you shouldn't bias these amps at all(have manuals?), you should contact the manufacturer or dealer.
At this point I would assume that one or more tubes per each channel went bad and would not continue to use them.
You should perform bias procedures with dummy resistor connected instead of speakers until you get them all biased properly. |
The pinging you here is microphonics caused by high gain in the preamp. You might try tube dampers on your preamp tubes |
