clintrubber
Well-known member
This is about a Rickenbacker TR120B bass combo (early '80s), for which I've yet to find the schematic.
Many 'close'/related schematics around, but not the exact schematic (in case anyone.... thanks!)
Interestingly, this bass-combo seems to have a 15" speaker with an additional winding.
Some quotes of long ago from the company-boss Mr Hall:
"I seem to remember that the TR120B had two upgrades from the TR35B: a dual speaker coil and a piezo tweeter. The extra coil was connected to the power amp to provide damping feedback, while the Motorola piezo was able to be switched on and off."
"It's been a long time since I've looked at one of these so my memory is a bit fuzzy. However, as I recall, this was the model that has an additional winding on the voice coil core which is connected to the power amp. It serves to sense where the cone is and adjusts the damping factor of the amp dynamically. If you have the cabinet open, see if there isn't an extra set of lugs on that speaker."
Since these rickresource.com-quotes are from long ago, I'd figure it'd be better to post here @groupdiy.
While this additional coil won't be wired in total mysterious ways, it's funny exactly this amp-schematic is not 'around' or discussed. So I'm curious if anybody has it or knows more?
(BTW #1: This position-sensing makes one think of the old Philips Motional Feedback system for hi-fi speakers, although there another kind of sensor was used.)
(BTW#2: As it seems, the Rickenbacker RB120 is the follow up type of the TR120B, but this schematic (see: RB120 powerstage ) is conventional w.r.t. powerstage & speaker-connection.
And possibly due to the higher power, it neither uses the 'usual' lift-up low-value resistor in series with the speaker to provide some current feedback, as is often done in low to medium instrument power amps for some added 'beef' in the sound.)
Thanks!
Many 'close'/related schematics around, but not the exact schematic (in case anyone.... thanks!)
Interestingly, this bass-combo seems to have a 15" speaker with an additional winding.
Some quotes of long ago from the company-boss Mr Hall:
"I seem to remember that the TR120B had two upgrades from the TR35B: a dual speaker coil and a piezo tweeter. The extra coil was connected to the power amp to provide damping feedback, while the Motorola piezo was able to be switched on and off."
"It's been a long time since I've looked at one of these so my memory is a bit fuzzy. However, as I recall, this was the model that has an additional winding on the voice coil core which is connected to the power amp. It serves to sense where the cone is and adjusts the damping factor of the amp dynamically. If you have the cabinet open, see if there isn't an extra set of lugs on that speaker."
Since these rickresource.com-quotes are from long ago, I'd figure it'd be better to post here @groupdiy.
While this additional coil won't be wired in total mysterious ways, it's funny exactly this amp-schematic is not 'around' or discussed. So I'm curious if anybody has it or knows more?
(BTW #1: This position-sensing makes one think of the old Philips Motional Feedback system for hi-fi speakers, although there another kind of sensor was used.)
(BTW#2: As it seems, the Rickenbacker RB120 is the follow up type of the TR120B, but this schematic (see: RB120 powerstage ) is conventional w.r.t. powerstage & speaker-connection.
And possibly due to the higher power, it neither uses the 'usual' lift-up low-value resistor in series with the speaker to provide some current feedback, as is often done in low to medium instrument power amps for some added 'beef' in the sound.)
Thanks!
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