![]() The PS-11 high-voltage power supply kit is available, which includes all the parts and nylon standoffs and optional zeners, at the GlassWare-Yahoo store.Īlternative Transformer-Coupled Output Stagesįasten your mental seatbelts, as things are not nearly as simple as you might imagine. ![]() ![]() ![]() The PCB is quite compact, in spite of the big capacitance it holds. Resistors R5 & R6 and capacitors C5 & C6 serve as high-frequency snubber circuit that converts HF hash and RFI into heat. To use a center-tapped secondary, as most tube power amplifier power supplies do, we leave the following parts off the PCB. The schematic shows the full-wave bridge setup, where a secondary without a center-tap is used. Here is the complete schematic for the PS-11. (Most existing tube power amplifiers cannot support DC voltages for all the heaters, as their power transformer heater winding voltage is too low and its current rating too weak to suffer the rectification losses.) The PS-11 does hold, however, a two-resistor voltage divider and capacitor shunted circuit to reference DC voltage to the AC heater winding, which helps prevent hum. No heater power supply is provided, as the 6.3Vac winding is used to power the heaters in most tube-based power amplifiers. A quick rule of thumb might be that the zener should draw about half the current as the driver stage. The zener current limits should never be approached, save at turn-on, when no tubes are conducting yet. By using four zener break voltages, we can select the shunt regulated driver-stage voltage in 25-volt increments. These last two voltage outputs also use RC filtering that hold 47♟/500V capacitors, bypassed by 2.2♟/630V capacitors polypropylene capacitors. The input-stage output cascades from the driver stage, so it can benefits from the regulation. The driver stage offers the option shunt regulation of the voltage with a string of zeners. On the other hand, we could leave resistor R9 off the PCB and attaches the leads from an external choke instead. The RC resistor can be shunted by an optional 12V zener, which would function much like a swinging choke, as at idle the RC filter scrubs away ripple, but at full output the zener engages thus, the output tubes do not see their B+ voltage collapse, as the zener's engaging stops the voltage from dropping any further across the RC resistor. Here is the simplified and truncated schematic of the circuit after the rectifiers. Each 470F/250V capacitor is shunted by a 110k/3W bleeder resistor that also ensures equal voltage division between capacitors. The output stage consists of two 470F/250V capacitors (C7 & C8) in series, making for a total of 235♟ of capacitance and a 500V rating, which then travels through a an RC filter (R9, C11, C12) that holds the same two 470♟ capacitors in series both sides are bypassed by 2.2♟/630V capacitors polypropylene capacitors. The PS-11 makes building a tube power amplifier much easier, as it provides three output voltages taps: one for the output tubes, one for the driver stage, and one for the input stage. Well, the workaround is not to use metal standoffs, replacing them with nylon standoffs, which I fortunately have. How had I failed to list them at the store? Well, after finding my assembled test build of the PS-11 PCB, I discovered my previous reasoning for withholding the release: the rectifier circuit pads at the bottom of the PCB were too close to the mounting hole.Įverything was great, until a metal 1/4 inch standoff was attached to the PCB. Had I sold out and never made more PCBs? I found the files for the user guide and, then, I found the PCBs, which were made nine years ago. He could not find it at the GlassWare-Yahoo store-nor could I. He planned on running 6.3Vac on all the heaters and required a high-voltage power supply capable of withstanding a B+ voltage of 440Vdc. A customer asked which GlassWare power supply would be best suited for his rebuild of an old tube power amplifier he owned. This is something of an embarrassing story.
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