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SAC amplifier

•  Push–pull Class AB
•  Rise time < 2 µs
•  Damping factor 3000
•  Output with field effect transistors
•  Power RMS 120-220 Watt / 8 Ohm
•  2x 42 - 2x 63 VDC
•  100 x 50 mm, ~ 30 mm high
•  Components with board mono
•  kit to solder yourself 38€buy

heat sink required, e.g. from 75x160x40mm (6506G)
Mounting phalanx (photo) between heat sink and board recommended.
- DXF file for machine production of the phalanx
- GIF file with the dimensions of the phalanx


The amplifier circuit principle of the SAC isolated and placed on the smallest possible board. The module can be operated using the power supply unit without further adaptation to transformers with 2x 30 - 45 VAC AC voltage. Depending on the voltage, outputs of 120-220 watts at 8 ohms can be achieved. The current supply capability is so high that the amplifier can also be operated in bridges - the minimum impedance is then 4 ohms, the pulse power up to 480 watts. With an extremely low internal resistance and no relays, the sophisticated circuit controls the loudspeakers with an excellent damping factor of 3000.
Review 6moons: SAC Il Piccolo



Example with outsourced transformers

Supply amplifier

•  longlife Vishay BC capacitors
•  4 x 10.000 µF / 63 Volt
•  newest design with 41mm height
•  4 x Philips MKT foil capacitors
•  inline bridge rectifier or single diodes
•  up to 8 amps of current / 480 Watt
•  100 x 100 mm, high 55 mm
•  Components with board
•  kit to solder yourself58€buy

Supply SAC AMP

There is the option of connecting an amplifier module on three sides. A connection of two amplifier modules is very good in symmetrical operation, because such a power supply is used very evenly in phase opposition. It does not matter whether the signal is fed symmetrically using XLR or asynchronously using Cinch and the two amplifier modules are self-symmetrizing using a bridge circuit. Of course, use in a stereo application with only one power supply is also possible. When used as a mono block, the transformer, power supply and amplifier can also be connected in a row in a way that is easy to connect and short of cables.


For a suitable transformer, some things should be considered, such as efficiency / power loss. As the voltage increases, the amperage should also increase. The smaller the ampere indication on the transformer, the higher the open circuit voltage of the transformer deviates upwards. The dielectric strength of the capacitors in the power supply should be taken into account - at 10,000µF/63Volt the AC voltage of the transformer should be max. 42 Volt (~ VAC * 1.4 = VDC). So for lower VA power rather orient at the lower end of the possible voltages. A conventional transformer with sheet metal laminations can store more magnetic energy than a toroid, but should possibly be shielded laterally with sheet metal. The advantage of a toroid is only the smaller lateral radiation and thus a renouncement of a structural shielding. For the operation of both stereo channels, transformers with 2x37VAC and 4.45 Ampere in traditional design have proven themselves well (330 VA). As potted toroidal cores also e.g. 2x36VAC with 3.5A were used originally. The manufacturer of the original transformers was Kramer in 32289 Rödinghausen Germany, the first one mentioned was a modification for SAC - a standard 500VA which was unwound to 330VA, this significantly reduced the mechanical hum. Otherwise, this manufacturer seems to me to be very good value for money: ring core transformers

Electrical connection

The mains voltage connection in front of the transformer is not shown here, since this is only permitted by trained persons. Danger to life when working on mains voltage. Transformers are not offered.

Amplifier SAC AMP

additional heat sinks required


If the amplifier is to be connected in a row with the transformer in front as shown, the power supply board must be rotated - the components are fitted on the other side of the power supply board. The power supply board is printed on both sides and can be equipped on both sides, which gives further connection options such as result in the angled direct screw connection of the amplifier to the power supply.

SAC Amplifier


One SAC amplifier for each stereo channel on a common power supply and transformer.

SAC Amplifier

symmetrical, XLR balanced

Two SAC amplifiers for one stereo channel on a common power supply and transformer.

SAC Amplifier

active subwoofer