Laney Pro Tube 50

lowell · 03-25-2009, 12:09 AM

I'm trying to fix this amp which has basically two problems. It makes this horrible tea kettle like feedback and has very little clean headroom. I believe I have narrowed it to the power amp, as I plugged the line out into another power amp and had neither of these problems. All the voltages check out and so does the bias. I tried swapping tubes as well. Someone said it could be positive feedback, but I disconnected the feedback loop and no change. Your insight is greatly appreciated.

lowell · 03-25-2009, 12:15 AM

Sorry I was writing quickly and forgot to mention that the distortion has somewhat of a phasing sound to it. Kind of a swirling.

gldtp99 · 03-29-2009, 01:14 AM

Since nobody else has replied i can offer this---- i have an AOR 50 and i've never gotten tones out of it that i really like----i 've done some de-gaining mods but it still isn't my (or anybody else's around here) cup of tea.
It sounds like you've done the basic troubleshooting to the power amp already.
i think that gutting the Laney AOR circuit and building a 2204 Marshall-type circuit on a turret board would be the best idea.
That's what i'm going to do to mine when i get time----no push-pull pots, no whacky switching, and tone response that i actually like.
If the problem with yours is in the Power Amp section, about the only thing you haven't checked is the OT---- swap another similar OT in for a test.....................gldtp99

03-25-2009, 12:09 AM	#1
lowell Senior Member Join Date: Jun 2007 Posts: 941	Laney Pro Tube 50 I'm trying to fix this amp which has basically two problems. It makes this horrible tea kettle like feedback and has very little clean headroom. I believe I have narrowed it to the power amp, as I plugged the line out into another power amp and had neither of these problems. All the voltages check out and so does the bias. I tried swapping tubes as well. Someone said it could be positive feedback, but I disconnected the feedback loop and no change. Your insight is greatly appreciated.

03-25-2009, 12:15 AM	#2
lowell Senior Member Join Date: Jun 2007 Posts: 941	also Sorry I was writing quickly and forgot to mention that the distortion has somewhat of a phasing sound to it. Kind of a swirling.

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03-29-2009, 01:14 AM	#3
gldtp99 Member Join Date: Sep 2008 Posts: 29	Since nobody else has replied i can offer this---- i have an AOR 50 and i've never gotten tones out of it that i really like----i 've done some de-gaining mods but it still isn't my (or anybody else's around here) cup of tea. It sounds like you've done the basic troubleshooting to the power amp already. i think that gutting the Laney AOR circuit and building a 2204 Marshall-type circuit on a turret board would be the best idea. That's what i'm going to do to mine when i get time----no push-pull pots, no whacky switching, and tone response that i actually like. If the problem with yours is in the Power Amp section, about the only thing you haven't checked is the OT---- swap another similar OT in for a test.....................gldtp99

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