As you might expect, one or two of his patented technologies feature in the Signature headphone amp. While branded as a tube (valve) amp, the Signature is actually a hybrid design that combines both valve and solid state electronics. This, along with its unique and patented circuit topologies, aims to elevate the headphone listening experience on a number of levels.
The circuit incorporates a pair of 12AX7 dual-triode valves in a low distortion series regulated push-pull configuration in the input/driver stage. High speed, high current video buffers are then used to drive the headphones directly. The video buffers provide a pure audio path with low output impedance, low distortion and a wide signal bandwidth, allowing the natural smooth sound of the valves to pass straight through to the outputs.
A patented bass boost equalizer circuit improves low-frequency bass impact without adding bass boom or muddiness. There are three positions on the bass control: minimum, maximum and off, enabling a tailored sound depending on choice of headphones, music and personal audio preferences.
Another unique feature is a surround sound function, designed to add spaciousness to stereo headphone sound. A patented ‘Panorama Control’ circuit applies an out-ofphase cross-blend to create a sense of depth and space; it moves the dimensional soundstage outside of your head, creating a more natural result. Again, this feature can be set to minimum, maximum and off positions to enable a listener-defined experience.
In the Signature’s elegant circuit, the valve amplifiers, buffers, bass EQ and surround sound processing are all configured in a single stage. Negative feedback is applied around this stage in a single loop. Output offset is controlled with DC servos, allowing the video buffers to directly drive the headphones with no output capacitors in the signal path. There is only one coupling capacitor per channel in the signal path and it is enclosed within the feedback loop, hence capacitor colourations are eliminated.
Distortion and noise are below the threshold of hearing while the bandwidth is very wide, at around ten times the threshold of human hearing (2 Hz to 200 kHz at -3 dB). The power supply uses separate oversize storage capacitors on each amplification path of each channel to provide a rock solid supply voltage without voltage regulators to affect the signal. The circuit is configured so that audio signals from one channel cannot couple to the other, preserving soundstage width and depth. This power supply provides the benefits of dual mono and batteries in a simple AC powered circuit.
A 35-second muting circuit eliminates turn on/off transients. Two stereo inputs and a stereo tape output are provided, with front panel selector switches for added usability. Industrial design by Fred Hulen incorporates the classic hallmarks of the Fosgate Signature range: a slim, simple yet elegant aesthetic. Complementary anodized aluminium finishes on the faceplate, transformer covers and valve socket flanges are offset by the black painted top and gorgeous real wood side panels.
Pricing
£1,500
Technical specifications
Frequency response 2 Hz to 200 kHz at -3 dB
Voltage gain 15 dB
Signal to noise ratio 95 dB
Headphone impedance drive range 30 – 500 Ohms
Maximum output voltage 26 volts into 500 Ohm load
Maximum power output 1,000 mW RMS 30 Ohm load
Distortion 0.1% @ 250 mW 1 kHz 30 Ohm load
Maximum bass boost 6 dB @ 30 Hz
Dimensions 7″ (w) x 11″ (d) x 5.5″ (h)
Weight 5 lbs
Warranty 2 years
