It started life as an ab165. Someone let it get really crappy on the inside. Chassis was rusted and all the guts were just gross. I gutted and rebuilt to aa165 with vintage wire, etc...kept the trannies, swapped the pots, kept the blue caps, removed the death cap, all new carbon comp resistors.
Anyway, it sounds great...but th we re is this really wierd noise as its warming up. Starts humming then goes away on its own. Take a listen.
1966 aa165 bassman
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1966 aa165 bassman
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It's all about the tone!
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Reeltarded
- Posts: 10189
- Joined: Sat Feb 14, 2009 4:38 am
- Location: GA USA
Re: 1966 aa165 bassman
Ok that is so effing cool!! Use it as an effect.
At the end of the sweep start playing Children of the Sun!!
Anda one! Anda two!!
Sorry. Not helpful. I am more A&R than management.
At the end of the sweep start playing Children of the Sun!!
Anda one! Anda two!!
Sorry. Not helpful. I am more A&R than management.
Signatures have a 255 character limit that I could abuse, but I am not Cecil B. DeMille.
Re: 1966 aa165 bassman
I know...it sounds really cool. And once it goes away it stays gone. It happens about a minute after the standby gets flipped and it is there even with the volume turned down. It does go away when the PI tube is pulled. The PI is a new JJ, and I have tried an old also...makes no difference. I have swapped out the preamp tubes...same thing.
It's all about the tone!
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JazzGuitarGimp
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- Location: Northern CA
Re: 1966 aa165 bassman
I'm wondering if it's a parasitic oscillation. Sounds to me like there's more than just 60Hz or 120Hz going on there.
Lou Rossi Designs
Printed Circuit Design & Layout,
and Schematic Capture
Printed Circuit Design & Layout,
and Schematic Capture
Re: 1966 aa165 bassman
If you have the 1R cathode resistors to set bias, try monitoring the output tube current as it's warming up. If it's parasitic, it may just be going frequency-inaudible; if so, the current would stay high, maybe even rise after you stop hearing It.JazzGuitarGimp wrote:I'm wondering if it's a parasitic oscillation. Sounds to me like there's more than just 60Hz or 120Hz going on there.
But the transition from noise to no noise seems abrupt, almost like a cap finally charging.
If it won't do it with no PI tube installed and volume pots make no difference, it's either in the PI or a tone recovery stage. Try pulling the channel preamp tubes, one then the other to see if it's in a channel or in the PI.