The PWB-S7P (unassembled) and ASM-S7P (assembled) is a complete power supply and Wide Bandwidth / Low Z regulation system specifically designed to support the Dynaco Stereo 70 power amplifier. It includes HV rectification to support the entire amplifier and three regulators (Plate HV supply, Screen Grid HV supply, and Bias Supply) to maintain a consistent and near infinite current supply for the Output Stage(s).
Also included is a Complete Bias Supply - rectification, filtering, zener diode regulation, and adjustment potentiometers. The adjustment potentiometers and test points are conveniently placed to appear at the front of the amplifier to simplify setting the bias.
Our Plate and Screen Grid regulators are our proprietary Hi-Speed Low-Z designs that are the result of extensive development and refinement. They are "Audibly Inert" allowing the audio circuitry to "speak" with its own clear voice. Typical "cookbook" HV regulators have an uneven impedance curve (adding the same signature voice) and ring terribly upon high frequency transients (resulting in harshness). Our regulators have been optimized not only for Low Impedance (Z) but maintain that impedance consistently from DC to 1MHz. More importantly, the circuitry is damped optimally so that there is absolutely no ringing under any circumstances. The result is a completely inert power supply that neither adds nor subtracts from the amplifier circuit but delivers instantaneously the current required. For a more detailed discussion of how power supplies significantly impact your amplifier, refer to our "Audibility of Power Supplies" white paper.
With stable regulation, after you turn on your amplifier, the operation of the output stage bias quickly reaches and maintains the desired operating point and will continue over the full lifetime of the tubes. The benefit is "set & forget" biasing (90 days) and significantly extended tube life (since bias currents do not drift unknowingly upward). In addition, your amplifier will sound the same, day to day, over the full lifetime of the output tubes.
Installation is very easy - the PWB / ASM -S7P module is designed to physically "Drop In" to the bottom of the ST-70 chassis (on 1" standoffs) using existing holes - no drilling cutting or hanging appendages. All the connections from the power transformer, "Quad" filter capacitor, and other power supply connections terminate on the module - its easier that the building the original ST-70.
Our Stereo-70 Power Supply / Regulator Module is available in as either a blank board, kit (blank board with all components), or fully assembled and tested board. For those purchasing the blank board, we have available the Stereo-70 Power Supply / Regulator Semi-Pac that contains all of the semiconductors specified for the the PWB-S7P. Both Standard and Premium Semi-Pacs are available (premium grade operational amplifiers are supplied with the premium version)
Blank Board, Stereo 70 Pwr / Reg : P/N PWB-S7P = $81
Semi-Pac, Stereo 70 Pwr / Reg : P/N SEMI-S7P = $62
Premium Semi-Pac, Stereo 70 Pwr / Reg : P/N PSEMI-S7P = $83
Full Kit (Board & All Components): P/N KIT-S7P = $288
Assembled Board, Stereo 70 Pwr / Reg : P/N ASM-S7P = $350