Embedded Files
I revisited the Bassman (actually the Bassman Redux) after installing the Amp-Aid Tremolo and Reverb systems. They are really a great addition.
I revisited the Bassman (actually the Bassman Redux) after installing the Amp-Aid Tremolo and Reverb systems. They are really a great addition.
I'm now using the amp more in group sessions so I decided to tackle the problem of too-much bass that is just part of the Bassman design. I often turn the bass control all the way down, but sometimes it's still too boomy and the bass strings have to be avoided.
I'm now using the amp more in group sessions so I decided to tackle the problem of too-much bass that is just part of the Bassman design. I often turn the bass control all the way down, but sometimes it's still too boomy and the bass strings have to be avoided.
There are a number of ways to overcome this, but I opted to modify the tone stack with a switch that changes the "slope" resistor. This gives 3 settings for normal (stock), "less", and "even less" bass.
There are a number of ways to overcome this, but I opted to modify the tone stack with a switch that changes the "slope" resistor. This gives 3 settings for normal (stock), "less", and "even less" bass.
The impact on the amp tone is to lower the bass response and to move the scoop in the response curve lower. Both are effective in reducing boominess.
The impact on the amp tone is to lower the bass response and to move the scoop in the response curve lower. Both are effective in reducing boominess.
The change is simple once you find a spot on the panel to mount a 3-position mini-toggle. It's a SPDT-center-off mini-toggle. I placed it next to the treble control. The slope resistor is the 56K resistor at the input of the tone stack in the schematic section shown below.
The change is simple once you find a spot on the panel to mount a 3-position mini-toggle. It's a SPDT-center-off mini-toggle. I placed it next to the treble control. The slope resistor is the 56K resistor at the input of the tone stack in the schematic section shown below.
Find and remove the 56K resistor, it's located near V2 on the eyelet board. Use a 2-conductor shielded cable (or 2 single-conductor shielded cables) to extend the connection points where the slope resistor was, to the new switch, as shown in the diagram below. Solder three resistors to the switch with short leads. Then solder the cable connections across the center resistor, as shown.
Find and remove the 56K resistor, it's located near V2 on the eyelet board. Use a 2-conductor shielded cable (or 2 single-conductor shielded cables) to extend the connection points where the slope resistor was, to the new switch, as shown in the diagram below. Solder three resistors to the switch with short leads. Then solder the cable connections across the center resistor, as shown.
The cable ground(s) are connected to a ground point on one end of the cable. Any ground and either end is fine. The signal amplitude in the cable is large so the shield minimizes "broadcasting" or coupling into other chassis wiring and causing problems.
The cable ground(s) are connected to a ground point on one end of the cable. Any ground and either end is fine. The signal amplitude in the cable is large so the shield minimizes "broadcasting" or coupling into other chassis wiring and causing problems.
That's it. You now have three tone stack options. In the center-off switch position, the slope resistor becomes 120K - which completely removes all traces of boominess from the amp. In one "on" position, the slope resistor becomes 120K in parallel with 300K, or about 86K. This is a nice middle setting with reduced bass. The other "on" position makes the slope resistor 120K in parallel with 120K, or about 60K, which is close enough to the initial 56K value.
That's it. You now have three tone stack options. In the center-off switch position, the slope resistor becomes 120K - which completely removes all traces of boominess from the amp. In one "on" position, the slope resistor becomes 120K in parallel with 300K, or about 86K. This is a nice middle setting with reduced bass. The other "on" position makes the slope resistor 120K in parallel with 120K, or about 60K, which is close enough to the initial 56K value.
There is no popping or other side effect, so it's a worthwhile mod that adds more tone color options and has no down-side.
There is no popping or other side effect, so it's a worthwhile mod that adds more tone color options and has no down-side.
Page updated
Google Sites
Report abuse