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04-25-2023, 12:06 AM
Hi Guys
The London Power Power Scaling kits come with two controls for the front panel: Power Scale and Drive Compensation. These two controls allow four ways to use the amp, one of which is Power Scaling where the tone is retained with loudness changes. The other modes are simply versatilities made possible.
Many players still want a 1-knob Power Scale solution, and there are situations where this is possible with the kits. Power Scale is a single-section pot where Drive Comp is supplied as a dual-pot and this is what you use for the single-knob solutions below.
If the amp has a master-volume preamp, such as the original "800" does, then the dual pot can replace the stock MV and the new Power Scale control. The Power Scaling goal is achieved as drive is in step with Power Scale and tone is maintained.
A Vox amp may come to mind here as those with an MV use a single-section pot. However, the MV is the cross-line type, the worst configuration possible, which would be greatly improved in function were it replaced by a 2-section pot wired in the more usual manner. This negates using the supplied DriveComp pot as a 1-knob Power Scale control. ***Edit: On later thought, a single-knob can work here. The MV section will just do what it always did and the Power Scale section will control output power ***
Amps that do not use a Schmitt splitter and instead have a gain stage followed by a concertina splitter are candidates for a 1-knob Power Scale solution. In this case, one section of the pot is placed between the gain stage and the concertina, with the other section used as the Power Scale control. It does not matter if feedback is wrapped around the PA.
If the MV is a post-PI type that is typically a dual-pot itself, then the above solution does not work. One would need a 3-section pot, which are available, but it is easier to find 4-sectiuon pots that are fairly common now for home theatre applications.
In fixed-biased amps, you still need bias controls per usual, mounted on the tube plane of the chassis and set ONLY at full power. These are not performance pots; rather, set and forget with each tube change or new PS installation.
The London Power Power Scaling kits come with two controls for the front panel: Power Scale and Drive Compensation. These two controls allow four ways to use the amp, one of which is Power Scaling where the tone is retained with loudness changes. The other modes are simply versatilities made possible.
Many players still want a 1-knob Power Scale solution, and there are situations where this is possible with the kits. Power Scale is a single-section pot where Drive Comp is supplied as a dual-pot and this is what you use for the single-knob solutions below.
If the amp has a master-volume preamp, such as the original "800" does, then the dual pot can replace the stock MV and the new Power Scale control. The Power Scaling goal is achieved as drive is in step with Power Scale and tone is maintained.
A Vox amp may come to mind here as those with an MV use a single-section pot. However, the MV is the cross-line type, the worst configuration possible, which would be greatly improved in function were it replaced by a 2-section pot wired in the more usual manner. This negates using the supplied DriveComp pot as a 1-knob Power Scale control. ***Edit: On later thought, a single-knob can work here. The MV section will just do what it always did and the Power Scale section will control output power ***
Amps that do not use a Schmitt splitter and instead have a gain stage followed by a concertina splitter are candidates for a 1-knob Power Scale solution. In this case, one section of the pot is placed between the gain stage and the concertina, with the other section used as the Power Scale control. It does not matter if feedback is wrapped around the PA.
If the MV is a post-PI type that is typically a dual-pot itself, then the above solution does not work. One would need a 3-section pot, which are available, but it is easier to find 4-sectiuon pots that are fairly common now for home theatre applications.
In fixed-biased amps, you still need bias controls per usual, mounted on the tube plane of the chassis and set ONLY at full power. These are not performance pots; rather, set and forget with each tube change or new PS installation.
