GlassWare Audio Design
Thanks for Supporting the Tube CAD JournalNew Balancer PCB and Kit
New Revision-2 ACF 12Vac Tube Stereo Buffer
Product Description
Introducing the new revision of the ACF 12Vac PCB and part kits, which now incorporates a better high-voltage power supply. The key advantage of the Aikido 12Vac is that it can be operated from a lowly wallwart power supply, yet develops a fairly high-voltage B+ for the triodes and power the heaters with clean DC voltage.
The ACF12Vac board holds two unity-gain tube-based buffers that provide low distortion, low output impedance, and stellar PSRR (power supply rejection ratio), all without the use of a negative feedback loop. It is both simple and effective.
The ACF (Aikido Cathode Follower) circuit delivers roughly a gain slightly less unity. It can be used with either 12AU7 or 12BH7 or ECC99 tubes or with 6.3volt tubes, such as the 6QA8, 6CG7, 6FQ7, or 6DJ8. The heater power supply is regulated. The raw B+ comes in at about 160Vdc and is usually about 130Vdc after the cascading RC filters.
Why would you need a unity-gain tube buffer? Although theoretically the purest path to follow, passive line stages often disappoint, proving inadequate and incapable of adequately driving high-capacitance cables or low-input impedances. In addition, many solid-state audio devices just sound too cold and brittle on their own. Adding a tube-based buffer can help humanize the sound, perhaps due to harmonic enrichment.
The PCB can be also configured as a White cathode follower.
The power supply is internal to the 12Vac ACF PCB and receives its power from an external transformer, usually a 12Vac wallwart. The 12Vac voltage runs through an elaborate voltage-multiplier circuit that develops both a high-voltage B+ and a regulated DC heater voltage. The voltage-multiplier creates a raw DC voltage of about 160Vdc from a 12Vac wallwart.
IMPORTANT: If a power jack is used to receive the AC voltage from the wallwart's power plug, it must be fully insulated, as the incoming AC voltage is NOT referenced to ground. In other words, the plug's outer barrel must not be grounded. The easy solution is to use an insulated power jack.
The ACF 12Vac stereo PCB is extra thick, 0.094 inches (inserting and pulling tubes from their sockets won't bend or break this board), double-sided, with plated-through heavy 2oz copper traces and a part placement silkscreen on both sides, and the PCB is lovingly and expensively made. The boards are 7.2 by 4 inches, with four mounting holes, which helps to prevent excessive PCB bending while inserting and pulling tubes from their sockets.
The part kits include all the parts needed to populate the PCB (including the coupling capacitors and hex standoffs and heatsink), except for the vacuum tubes. The parts are all high-quality and name brand, such as On-Semi, Nichicon, Vishay.
Includes 16-page user guide with schematics and instructions.
The ACF12Vac board holds two unity-gain tube-based buffers that provide low distortion, low output impedance, and stellar PSRR (power supply rejection ratio), all without the use of a negative feedback loop. It is both simple and effective.
The ACF (Aikido Cathode Follower) circuit delivers roughly a gain slightly less unity. It can be used with either 12AU7 or 12BH7 or ECC99 tubes or with 6.3volt tubes, such as the 6QA8, 6CG7, 6FQ7, or 6DJ8. The heater power supply is regulated. The raw B+ comes in at about 160Vdc and is usually about 130Vdc after the cascading RC filters.
Why would you need a unity-gain tube buffer? Although theoretically the purest path to follow, passive line stages often disappoint, proving inadequate and incapable of adequately driving high-capacitance cables or low-input impedances. In addition, many solid-state audio devices just sound too cold and brittle on their own. Adding a tube-based buffer can help humanize the sound, perhaps due to harmonic enrichment.
The PCB can be also configured as a White cathode follower.
The power supply is internal to the 12Vac ACF PCB and receives its power from an external transformer, usually a 12Vac wallwart. The 12Vac voltage runs through an elaborate voltage-multiplier circuit that develops both a high-voltage B+ and a regulated DC heater voltage. The voltage-multiplier creates a raw DC voltage of about 160Vdc from a 12Vac wallwart.
IMPORTANT: If a power jack is used to receive the AC voltage from the wallwart's power plug, it must be fully insulated, as the incoming AC voltage is NOT referenced to ground. In other words, the plug's outer barrel must not be grounded. The easy solution is to use an insulated power jack.
The ACF 12Vac stereo PCB is extra thick, 0.094 inches (inserting and pulling tubes from their sockets won't bend or break this board), double-sided, with plated-through heavy 2oz copper traces and a part placement silkscreen on both sides, and the PCB is lovingly and expensively made. The boards are 7.2 by 4 inches, with four mounting holes, which helps to prevent excessive PCB bending while inserting and pulling tubes from their sockets.
The part kits include all the parts needed to populate the PCB (including the coupling capacitors and hex standoffs and heatsink), except for the vacuum tubes. The parts are all high-quality and name brand, such as On-Semi, Nichicon, Vishay.
Includes 16-page user guide with schematics and instructions.
