Fosgate Signature: An Incredible Dual-Tube Headphone Amplifier
Following up the enormous success of the Fosgate Signature Phono Preamp, Jim Fosgate turns his considerable talent towards headphone amplification. The Signature Headphone Amplifier is the culmination of almost two decades of research and listening. Combining a tube input stage with a wideband solid-state output, the Fosgate Signature Headphone Amp drives a broad range of headphones, delivering the rich full-bodied sound which is the hallmark of Fosgate designs.
"A new high in high-end headphone amplifier design."
– Steve Guttenberg, CNet.com
Mirroring the aesthetic of his Signature Phono Stage, Fosgate’s Signature Headphone Amp is gloriously simple yet elegant. A slim profile, with a broad shouldered faceplate, lightened slightly by the soft silver of the anodized aluminum. Complementary finishes on the transformer covers and tube socket flanges are offset by the black painted top and gorgeous wood side panels, identical to those used on the Signature Phono Stage.
"It is indeed a reference quality amplifier. Dynamics are just out of this world! Resolution and harmonic integrity is unsurpassed."
– John Chen, Director of Sales, Grado Labs
Similar configuration to the award-winning Fosgate Signature Phono Preamp; a pure signal path with low output impedance, low distortion and very wide signal bandwidth. The Signature Headphone Amp uses a pair of 12AX7 vacuum tubes in a low distortion SRPP configuration, paired to high speed, high current wide-bandwidth video buffers are used to drive the headphones directly. These video buffers are not OpAmps and have no voltage gain; they provide an optimal high impedance load to the tubes and a low output impedance on the output allowing the Signature Headphone Amp to drive most headphones to surprisingly high levels without audible distortion or coloration.
"The Fosgate Signature is a good example of how you can create a headphone listening experience that will rival ultra-expensive speaker-based stereos in many ways. Definitely recommended for owners of high end, efficient headphones, the Fosgate Signature made great music for me!"
– Skylab, Inner Fidelity
Power Supply Design
The power supply is similar to the one used in the Fosgate Signature Phono Preamp, using 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 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.
More Technical Info:
The Signature Headphone Amp’s elegant circuit has the tube amplifiers, buffers, bass EQ, and surround processing 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, thus capacitor colorations are eliminated. Distortion and noise are below the threshold of hearing. The bandwidth is very wide allowing audio signals to pass through without colorations. Bandwidth is an amazing “ten times” the threshold of human hearing, 2Hz to 200kHz at -3dB.