Learn about Power Scaling from Its Inventors
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The newest term in Power Scaling is “Super Versatile” (SV).
Our SV-range of Power Scaling kits represents a breakthrough in performance and value, combining the sophistication of our former “Super Flexible” kits with the cost-performance of the “Super Budget” kits – so SV also means “Super Value”.
The majority of guitar and bass amplifiers (>99%) have nearly identical plate (Va) and screen (Vs) voltages that are separately filtered and most operate at <550Vdc – with the bulk of these below 500V. These amps can be described as having “dual-node” output stages as far as their power supplies are concerned, and they require two paths of high-voltage control to Power Scale them. Most of these amps will be fixed biased, but the high-voltage description here also covers most cathode biased amps.
There are dual-node supplies generated by voltage doublers, with Va being twice as high as Vs. These can be described as “disparate-node” supplies. Lower-wattage amps (50-120W) like the MusicMan RD-series, Sound City and most Univox amps have Vs of 250-350V and Va of 500-700V. Larger amps like Ampeg’s SVT and V-9 (300W), and Fender’s PS-series (300-450W) have Vs of 350-450V and Va just under 800V. The highest-power amps tend not to be Power Scaled as the users of such amps have no interest in playing quietly.
To accommodate this range of amp voltages, particularly the screen, SV boards provide an easy means for matching the stock ratio of Va and Vs by a simple resistor change. The kit notes explain what is required. let us know the amp model you are installing the kit into, and we can provide a custom resistor value.
SV1 is the Power Scale solution for fixed-biased amps. In most cases, the amp will also require RBX Raw Bias Auxiliary Supply as the stock bias supply may not support SV1.
SV2 is the Power Scale solution for cathode-biased amps. These will also require VCK Voltage Clamp Kit to maintain preamp voltages and tone.
The voltage limits for SV1 and SV2 are:
Vs 4V to (Va-4V)
There are tiny amps and simple amps that use the same supply node for both plate and screen. This group includes ultralinear-wired, triode-wired, and true-triode amps. These supplies are “single-node” and require a single, high-voltage regulator path. These amps may be fixed biased or cathode biased. SV84 is the choice for most of these amps, which tend to be <450V. For the rare single-node fixed-biased output stage, add TBS Tracking Bias Supply and RBX Raw Bias Auxiliary Supply to SV84.
The voltage limit for SV84 is 450V.
SV1 and SV2 have recently been made about one-third smaller than their original form, allowing them to be fitted into any amp that needs them.
All of these supply arrangements and their families of amplifiers can be Power Scaled using London Power’s “Super Value Super Versatile” SV Power Scale kits.
SV1 Power Scaling Kit
All kits require proper heat-sinking, usually accomplished by mounting the pass elements to the chassis. High-bias amps and high-power amps will require extra heat sinking and/or fan cooling. All kits use a Drive Compensation control to assist in keeping tone exactly where the player needs it, which also allows four operating modes of the amp. The SV Power Scaling kits all use printed circuit boards – with small boards for the pots to make wire connections easy – and all pots are 16mm. For more information, our book TUT4 provides a complete tutorial on Power Scaling methods, while TUT6 expands on the discussion of DC Power Scaling.
Note that the SB-1, SB-2 and SB-84 PCBs are still available for licensed users of these products.
Like all of our other kits, London Power’s Power Scaling kits use high-quality, reliable components, including precision metal-film resistors, metal-oxide power resistors, long-life electrolytics, ceramic and plastic caps, all on a high-quality printed circuit board. Pots are 16mm non-critical types of standard values. Semiconductors are used well within their limits but proper heat sinking is required, as explained in the kit notes. Mounting hardware is included.
For more information about Power Scaling Kits, see the links below and visit our forum theultimatetone.com
Who can install Power Scaling for you?
Licensed Power Scaling Builders and Installers