The Signal Transfer Company

The Trimodal Power Amplifier: 2.0

Trimodal Power Amplifier
The Trimodal amplifier is a unique design that is instantly switchable between Class-A and Class-B. There are no compromises of any kind in either mode.

The Trimodal PCB has now been updated so that the latest MT-200 package output transistors can be used. The supply-rejection has been improved so that power supply reservoir capacitors of 10,000uF can be used if required, rather than the 20,000uF originally recommended. The noise performance has been improved, and there have been many other minor improvements.

  • Exceptionally low distortion into low impedance loads.
  • Unique design offers operation in three modes: A, AB and B as required- hence Trimodal Amplifier.
  • Very low distortion in all modes- barely measurable even with top-flight test equipment in Class-A mode.
  • Very low noise, due to innovative feedback design.

PCB 002: 27:50 each
Kit 002: 125:00 each

F E A T U R E S

Trimodal PCB

P C B

The Trimodal PCB is produced to the highest quality standards:
  • Double-sided plated-through-hole fibreglass PCB
  • Gold-plated pads
  • Fixing holes and output device positions provided for direct mounting to a heatsink.
  • Solder mask both sides and full screen print. Board size 138 by 130 mm.
  • Fully RoHS compliant.

S P E C I F I C A T I O N S

* The Trimodal PCB will actually operate correctly in Class-B mode from supply rails of +/-3V or lower, so initial testing can be done at low risk by slowly winding up a variable transformer. It will not of course meet its full specifications at this voltage.

Trimodal THD graph

This graph shows the amplifier THD when running from the minimum supply rails. Performance at higher supply rails is slightly improved.
Measurement system Audio Precision SYS-2702. Measurement bandwidth 80 kHz