Description
SV1 is the Power Scale solution for 99% of fixed-biased guitar, bass or synth amps
- Precision Power Scale for cathode-bias only
- Full product name: SV1-Zh
- up to 700V plate (Va)
- up to 700V screen (Vs)
- Power range: 100% down to zero
- Loudness range: unusably loud to unusably quiet
- PCB size: 2.6″ x 1.4″ 66.1 x 35.6 mm
- Built height: 1.3″ 33mm
- Controls included: Power Scale, Drive Compensation, Bias
- kit notes: 9-pages
SV1-Zh is part of our Precision Power Scale family using the Z-core main circuitry. SV1-Zh is very sophisticated yet fits into tight chassis spaces. Cord-wood construction allows this compact module size and requires careful assembly and soldering. For detailed assembly instructions see this thread in our forum:
https://theultimatetone.com/thread-324.html
Build time for this PCB is 2-hours. Installation time is extra.
Low-level resolution of the Power Scale sweep has been improved allowing you to precisely dial in the desired quiet level.
Screen voltage is typically just a few volts less than plate voltage, accommodated by the stock values in SV1-Zh. Changing one resistor allows Vs to be far less than Va, in amplifiers using a voltage-doubler supplier, or where a large resistance ties Vs to Va with a corresponding large voltage difference. SV1-Zh kit notes explain how to calculate this resistor value.
SV1-Zh maintains the shape of the output stage transfer function, which is key to maintaining the same tone from whisper to wail, but it is up to the player to set the panel controls correctly so the rest of the amp behaves as it should. A Drive Compensation pot is provided. Using DriveComp and Power Scale together maintains a given tone, while setting them differently provides four different operating modes for the amp. If the amp has a master volume that regulates ALL sounds of the amp, then the MV can perform the DriveComp function. Depending on the amplifier’s circuit, there is a single-knob solution as described in our forum: https://theultimatetone.com/thread-270.html
Most stock bias supplies are built almost as an after-thought despite the fact that the bias voltage is the most important voltage in the entire amplifier. SV1-Zh is best supported by RBX Raw Bias Auxiliary supply. See the SV1+RBX bundle page for a small discount. In some amps, RBX-LT can be used instead of RBX.
SV1-Zh uses small, non-critical pots, allowing easy placement of these components on a crowded front panel. Those supplied are 16mm and mount on individual PCBs to make wire connections easy. Kit notes include schematic, expanded board layout, and wiring instructions. Components use precise values and should be sorted prior to assembly. The connection points within the amplifier are common to all tube power amps and are shown schematically. For the pre-assembled kit, London Power has discounted our hourly rate by 20%. London Power is not responsible for any damage caused by misinterpretation of the kit notes
Available configurations:
SV1-COMP: Includes PCB, components, pots, kit notes; assembly required; installation required
SV1-BLT: PCB comes pre-assembled; includes kit notes; installation required
Note that the Built Kit will cover assembly of RBX or RBX-LT if either is on your order.
For more information about Power Scaling Kits, see also:
Who can install Power Scaling for you?
Licensed Power Scaling Builders and Installers
Questions bout the SV1 and RBX? Join the discussion of these products on The Ultimate Tone Forum!
