The Raptor
EMMELINE By Ray Samuels Audio

Stealth Pre-Amp/Headphone Amp

The Stealth is designed with the highest quality audiophile grade components and the shortest possible paths for the audio signal to pass through. The capacitors utilized are the purest polypropylene by Hovland (Musicap) as they are well known to be very musical and warm. The film resistors are Halco H2 1watt which are highly respected in the audiophile community for the quality of sound they produce. As a volume control, the Stealth design accommodates the DACT stereo attenuator for its transparency and accurate tracking. All components are hand selected and matched between left and right channels and soldered with their values facing up and toward the same side. The tube sockets are ceramic with gold contacts for the highest conductivity they can offer in relationship to the tubes pins.

The Stealth is built on a solid PC board with the highest quality of a military grade FR4 material with a dual sided two oz. pure oxygen free copper. The components are soldered with military specification solders, and cleaned from all residue and contamination to a perfect shine. The stealth design has no wires as they tend to color the signals with their impedances and resistance. The signal lanes are separated from the power lanes by patches of solid copper grounds. The Stealth has four inputs and two outputs, all designed around a rotary switch on a special I-O PC board thereby completely eliminating the use of wires and making the signal paths short and pure. A large advantage of this design is that you will find no wires routed all over the amp to the rotary switch, eliminating any chance of cross-talk between the channels.

The Stealth is capable of driving two or four monoblocks for bi-amping a speaker system. The function rotary switch takes you through the sequence of turning the filament (heater) on first then sending a signal to the power supply to turn the DC Voltage on, during these operations, the audio signal is completely muted, then last, the audio signal is passed through the tubes.

The Stealth, when used as a pre-amp, runs in a pure class-A single ended with only the one Hovland Cap in the signal path. When designing the amp, many ideas came to mind as to what choice of tubes to be used. Knowing that new old stock tubes (NOS) tubes were getting scarce, and their prices where hitting the roof, the decision was made to design the circuit around the new stock tubes, which are available and for a low price. For drive tubes, the choice was made to use a 6SN7 from Electro Harmonix, while the input tube would be a choice of a smaller nine pin tube which is readily available opening up many more tubes to select from. This design decision permits the circuit to operate many low, medium, and high gain tubes that are available today from current manufacturers. NOS tubes are also available and will provide the user with even more choices. You can use 12-AU7, 12-AT7, 12-AX7, and many more.

The Stealth will enable you to adjust your gain (volume) to your liking depending on the strength of your input signal. This will eliminate the need for a gain switch especially when an attenuator is being used. Thus the flexibility and strength of this amp will make you appreciate the variety and number of tubes that it can accommodate to tailor the sound to your liking. The Stealth’s chassis is a custom built black anodized aluminum, silk screened with silver lettering. It shields all electronics components from RF signals noise through DC ground of the power supply.

In other very high end audio components, you will find that many manufacturers house their power supply in a dedicated external chassis away from amplifier’s chassis to eliminate hum caused by the noise of AC current and the noisy transformers. The Stealth is no exception, as the power supply is housed in a very elegant black anodized aluminum chassis, and connected to the amp through a 5.5 foot shielded detachable umbilical cord. The transformer is a toroidal type known to be very efficient and run cool while operating without any noise or magnetic field that can cause all kinds of interferences. The AC is rectified through a full wave bridge rectifier, then stored in two separate filters while smoothened by a polypropylene capacitors. The raw rectified DC voltage is passed to a high voltage regulator capable of providing 700 ma of current. This is a state of art regulator chip is designed to work with very high voltages to provide the precise regulation needed. The regulated voltage is then stored and smoothed by another stage of filtering.

The filament voltage is provided by a high quality switching power supply that delivers 2.5 amps of current to drive any hungry tube filament with no problem. There are no upgrades offered or required with this preamp/headphone amplifier, as all parts used are of the highest audiophile quality.