The Odyssey Circuit

Found in all F-Series Amplifiers

The Odyssey circuit is an evolutionary tube ciruit technology, new to the world of audio amplifiers.

Consisting of two gain stages, it simplifies the signal path and reduces phase inversion along the way. This new concept reduces distortion and lowers the negative feedback (NFB) to 4.5dB – making a stable environment for your favorite music.

The results are stunning with smooth detailed highs, a full weighty midrange, an open, wide and deep soundstage of three dimensional imagery and bass that will compete with any solid state amp. An overall well balance of sound and performance.

This circuit is used in all Black Ice Audio F-Series amplifiers. They come in various sizes with different output tubes, power supplies, and chassis configurations.

I have built over 100 tube amplifiers over my long career and have analyzed the strengths and weaknesses of all the designs out there. The goal for Odyssey was to design a circuit without the limitations of previous circuits.

One of the most important things is to reduce the amount of stages that are in the negative feedback loop around the amplifier. Most push pull power amps use three or four stages. Each stage and the output transformer causes some phase shift at high audio frequencies.

It is very difficult to make these amps unconditionally stable with negative feedback and no matter how you do it the sound is compromised. Negative feedback is needed to keep the distortion below 1% at full power, some amps use 20 to 30 DB feedback.

The Odyssey circuit is a symmetrical push pull design configuration with very low negative feedback. It has only two stages, an input and output stage. The input stage uses a 12AX7 dual triode in the SSRP configuration, it has high gain, low distortion, and low output impedance so the output tubes can be driven directly with no buffers. 

There are two negative feedback loops, one negative, and one positive. They are adjusted for only 4.5DB negative feedback which causes no audible side effects whatsoever and no tricky networks are needed to keep the amp stable, square waves are perfect.

To keep the distortion below 1% at full power with only 4.5 DB negative feedback the input stage bias is adjusted to cancel distortion in the output stage.

Dimension Pro

Found in Foz SSX Sound Stage Expander and F360 Preamp

The Dimension Pro is a breakthrough ‘dimensional shaping’ circuit – transforming your music into a custom experience by giving you the ability to adjust the size of the soundstage in your room.

This circuit is an electronic fix for out of place speakers and hard to control rooms. The speakers and the room will disappear with a turn of the dimension pro knob. Allowing the listener the ability to focus or widen the soundstage.

The results are increased three dimensional images and an expansive soundstage that has the ability to expand beyond the walls of the room.

It has built in Hi and Low frequency equalization, dimension control, signal direction display, optional ambiance surround outputs with back channel level control, 5 inputs, and a record loop in and out. It is connected between program sources and the power amplifier.

The input stage uses a 6SN7 dual triode tube with no negative feedback which has become an audiophile favorite. The High EQ control provides plus and minus 11dB and the Bass EQ provides plus and minus 15dB boost or cut both EQs with a bypass switch.

When the dimension control is in the center position it is bypassed, clockwise increases the stage width and depth, counterclockwise reduces stage width and depth which will make the center dialogue track sound louder and more focused for watching movies.

The high voltage B+ power supply has soft (slow) turn on and low output impedance with no ac ripple to cause ac hum. The PC layouts are a work of art with short direct audio paths, signal grounds, and power supply feeds. High quality best sounding components are used throughout.

The sound stage is wide and deep without the optional surrounds and even larger with them connected. The sound is very musical, smooth, warm, sweet, and detailed. The controls allow the user to tailor the sound to his or her liking.

This is a vacuum tube sound processor with bass boost, dimension control, directional display, and three inputs. It has unity gain and can be connected between a signal source and amplifier/ preamplifier or record loop.

The dimension control adjusts the soundstage depth and width. In the center position, it is in bypass causing no effect, turning the control clockwise increases the stage width and depth, turning counterclockwise will narrow the stage and decrease the depth. This will make the center dialogue track sound louder and more focused for watching movies.

The directional display shows the dominant sound energy in the four cardinal directions, center front, center back, left, and right. The bass boost control increases the level of the low frequencies. The signal path uses a 9 pin 12AU7 dual triode tube to give it a detailed warm smooth analogue sound. (The 12AU7 is a close cousin to the octal 6SN7 used in the F360).

The circuit board layout is very clean with short direct signal paths, grounding without ground loops, and excellent power supply. Parts are high quality and selected for the best sound and long-term reliability. The sound is very musical and will improve the performance of any tube or solid-state audio system and the controls allow the user to tailor the sound to his or her liking.

It is part of US patent 5,883,832.

F360 Space Matrix Circuit

Only found in the F360 Preamp

The 360 Space Matrix Circuit is the original circuit that started the surround sound movement.

The circuit was designed to increase the three dimensional depth for a two channel stereo system. The addition of the rear channels use ambience to bolster the front channels to create more spatial depth and better three dimensional images of the sound stage.

The results are a more life-like presentation and an experience of turning your room into the venue.

Crosstalk Reduction Circuit

Found in F159 Phono Stage Preamp and Foz XTR Crosstalk Reduction

The cross reduction circuit is the most important tool to add to your turntable setup.

A well calibrated crosstalk reduction circuit can eliminate the ‘what is playing in the right channel is also playing in the left and vice versa’ effect that comes from the cartridge. The improvement is up to 49dB of channel separation resulting in better pin point three-dimensional images in the soundstage, clearer and more defined highs and tight control detailed bass.

The circuit also has a bonus feature which saves hours by adjusting the cartridge’s azimuth electronically. Correcting azimuth is aligning the stylus so that it rests perpendicular in the grooves of your favorite vinyl. When azimuth is off, one channel is in-phase and the other channel is out of phase and the result is out of place images on an unbalanced soundstage.

A calibrated crosstalk reduction circuit can compensate up to 7 degrees of axial tilt which reverts the out of phase channel back to in-phase resulting in positioning the images back to their rightful place on the soundstage.

The F159 has an XTR (crosstalk reduction) circuit built in with a DB meter with calibration controls. There is a gain switch on the back panel to select 40 DB or 60 DB gain for using normal or low output cartridges. Cartridge loading controls are provided for loading MC cartridges, the rotary control covers the range from 10 ohms to 1,000 ohms.

The circuit is very unique with only two stages and no negative feedback loops. A low noise field effect transistor is used along with a low noise 6922 (6DJ8) dual triode tube in the input stage, the unit is dead quiet using low output cartridges.

A 6922 (6DJ8) is used in the output stage with pure class A MOSFET output buffers for low output impedance and low distortion. The RIAA phono EQ is a passive circuit positioned between stage one and two. The gain switch is also located between stage one and two. The high voltage B+ power supply has soft (slow) turn on with low output impedance.

The circuit boards are beautiful with short audio paths, grounding, and power supply feeds. This unit is very musical and will let you hear just how good vinyl can sound. We do not think there is a better sounding unit out there at any price.

Wonder how we came up with the F159 model number? Believe it or not Jim Fosgate has built 159 phono preamps to date, this is number “159”.

This is a signal processor for improving the sound of a phono system by increasing channel separation. It has unity gain and connects between the line level phono preamp output and the preamp/amplifier input, or tape monitor loop.

It increases channel separation using cancellation techniques. It will correct for cartridge axial tilt errors which is especially useful with arms that have no axial tilt adjustment. It has a DB level meter that is used to adjust the controls for nulling channel crosstalk from left to right and right to left.

A test record purchased separately is used to supply test signals to calibrate the left and right controls. Phono cartridges are delicate precision transducers, they are rarely in perfect balance and or symmetry. Most cartridges sound better with correction, including many very expensive ones. Some cartridges we have measured had less than 20 DB channel separation without correction and around 40 DB with correction.

The sound stage can sound wider, and cleaner with better imaging. The signal path uses only one stage and sounds very musical with a natural uncolored sound. The audio paths are very short and direct, with massive power supply, and excellent grounding. Components have been selected for best sound and long-term reliability.