Hey, folks, need some help.
Just for hoots I swapped the donut OT in my amp for a Heyboer that I got to audition. Sounds about the same to me, except now the thing motorboats like there's suddenly a tremolo circuit in the amp! Yuck. Any ideas on why this change (that's the only change I made) would suddenly cause that?
Cures for motorboating?
Moderators: pompeiisneaks, Colossal
Cures for motorboating?
Rich Gordon
www.myspace.com/bigboyamplifiers
"The takers get the honey, the givers get the blues." --Robin Trower
www.myspace.com/bigboyamplifiers
"The takers get the honey, the givers get the blues." --Robin Trower
Re: Cures for motorboating?
Often, motorboating is caused by leaky filter caps, but your amp worked fine until you swapped the OT. I would play with the lead routing, as the source of the oscillation could be some internal feedback between leads or even a ground loop. Make certain you reinstalled all the grounds after the swap.
Re: Cures for motorboating?
OK, it's time for....stupid amp builder confessions!
So the amp was going "wo wo wo wo wo wo" on low notes as if there were a slow tremolo operating.
So this morning I reflowed the six joints and redressed the leads. I did find that the 4 ohm connection wasn't solid.
Um, here's the stupid part: It turned out to be an odd resonance in the guitar due to an out-of-tune low E string!
Next time I'll tune up first.
No extra charge, here's the sonic comparison between the Heyboer OT and the Trafomatic toroid I had made. Both have 4K primaries and 4/8 ohm secondaries. Heyboer rated at 40 watts, the donut at 50.
The donut is brighter and passes more upper mids than the Heyboer, but the Heyboer is a wee bit louder. Both have really nice detail, but the note separation is just a wee tiny bit better thru the donut, maybe because of its brightness. When the amp is really cranked, the Heyboer makes more of its own contribution to the distortion than does the donut. I'm not sure which one I like better yet, but they're both nice.
So the amp was going "wo wo wo wo wo wo" on low notes as if there were a slow tremolo operating.
So this morning I reflowed the six joints and redressed the leads. I did find that the 4 ohm connection wasn't solid.
Um, here's the stupid part: It turned out to be an odd resonance in the guitar due to an out-of-tune low E string!
Next time I'll tune up first.
No extra charge, here's the sonic comparison between the Heyboer OT and the Trafomatic toroid I had made. Both have 4K primaries and 4/8 ohm secondaries. Heyboer rated at 40 watts, the donut at 50.
The donut is brighter and passes more upper mids than the Heyboer, but the Heyboer is a wee bit louder. Both have really nice detail, but the note separation is just a wee tiny bit better thru the donut, maybe because of its brightness. When the amp is really cranked, the Heyboer makes more of its own contribution to the distortion than does the donut. I'm not sure which one I like better yet, but they're both nice.
Rich Gordon
www.myspace.com/bigboyamplifiers
"The takers get the honey, the givers get the blues." --Robin Trower
www.myspace.com/bigboyamplifiers
"The takers get the honey, the givers get the blues." --Robin Trower
Re: Cures for motorboating?
I have a similar story. I was getting a warbling sound on notes up around the 12th fret. Someone suggested I lower the pickups - bingo!
