HELP!!! HRD piercing squeal.....

throstur · December 7th, 2003, 03:52 PM

I have a vey annoying problem with my HRD. When I turn up the Master volume and Drive to 6 or more, on the Drive / More Drive setting, I get a piercing squeal, even if the guitar is disconnected. Anybody experienced a problem like that?

Dacious · December 7th, 2003, 06:42 PM

You almost certainly have a preamp tube in the first two postions that is microphonic. The drive stage on these cascasdes the preamp tube gain stages. Any tendency to feedback will cause this.

throstur · December 7th, 2003, 07:02 PM

Quote:

Originally Posted by Dacious

You almost certainly have a preamp tube in the first two postions that is microphonic. The drive stage on these cascasdes the preamp tube gain stages. Any tendency to feedback will cause this.

Do you think this tube is blown or defect in some way then? :o Forgive me, My English is not very good when it comes to technical terms. But I think I have got the hang of it now. What you mean is that one or more of the lamps in the preamp channel GETS michrophonic and starts to pick up surrounding noise. Thanks a lot!!!!!!!

Dacious · December 8th, 2003, 06:37 PM

Get yourself a 12AX7. I can't remember if those amps have two or three preamp tubes. Look at the back. The little tubes on the right are the two channel preamps and the phase inverter. The phase inverter is the one closest to the middle, to the power tubes.

Swap your spare into the two channel slots in turn and try turning up again. You should find swapping one of them out will stop the squealing. I would suspect the outermost tube.

Combo chassis are the worst for squealing preamp tubes, because the speakers shake the whole cab. What is happening is something in the internals is not welded quite right and is resonating. The amplifier is boosting that signal, and it is then feeding back on itself. Reasonably common in high gain designs.

December 7th, 2003, 03:52 PM	#1 (permalink)
throstur TDPRI Member Join Date: Oct 2003 Location: Iceland Posts: 59	HELP!!! HRD piercing squeal..... I have a vey annoying problem with my HRD. When I turn up the Master volume and Drive to 6 or more, on the Drive / More Drive setting, I get a piercing squeal, even if the guitar is disconnected. Anybody experienced a problem like that? __________________ Throstur Vidisson "Rebel without a clue"

December 7th, 2003, 06:42 PM	#2 (permalink)
Dacious Friend of Leo's Join Date: Mar 2003 Location: Godzone Posts: 2,612 35 Photos	You almost certainly have a preamp tube in the first two postions that is microphonic. The drive stage on these cascasdes the preamp tube gain stages. Any tendency to feedback will cause this. __________________ My other Telecaster is a Thinline The Tele Bible, Ch 1, v 10 Love thy Telecaster, covet not thy neighbour's Strat!

December 8th, 2003, 06:37 PM	#4 (permalink)
Dacious Friend of Leo's Join Date: Mar 2003 Location: Godzone Posts: 2,612 35 Photos	Get yourself a 12AX7. I can't remember if those amps have two or three preamp tubes. Look at the back. The little tubes on the right are the two channel preamps and the phase inverter. The phase inverter is the one closest to the middle, to the power tubes. Swap your spare into the two channel slots in turn and try turning up again. You should find swapping one of them out will stop the squealing. I would suspect the outermost tube. Combo chassis are the worst for squealing preamp tubes, because the speakers shake the whole cab. What is happening is something in the internals is not welded quite right and is resonating. The amplifier is boosting that signal, and it is then feeding back on itself. Reasonably common in high gain designs. __________________ My other Telecaster is a Thinline The Tele Bible, Ch 1, v 10 Love thy Telecaster, covet not thy neighbour's Strat!