FAB Modules

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Decibels and Voltages. dB, dBu… How do I convert from Volts to dB?

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Applications, FAB Modules, Tips
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Okay, how do we find out what’s the maximum output capability of your FAB module system? To answer this question, we first need to segue and talk about decibels.

Wikipedia says: The decibel (dB) is a logarithmic unit that indicates the ratio of a physical quantity (usually power or intensity) relative to a specified or implied reference level.

Basically, it’s saying that decibel is nothing but a RATIO between 2 numbers. Example: Instead of saying the 2nd number is 2X the value of the 1st number, we say it’s 6dB larger, or 6dB more.  A decibel allows us to compare 2 numbers logarithmically, comparing 2 numbers whose ratio are either very, very small or very, very large.

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FAB2110 – Loading your Input Transformer, Square Wave Testing

For testing audio, square waves are typically used because they can reveal a lot about the system’s response with just a quick visual analysis. What’s so special about square waves? Why not use a typical “Sine Wave” or “Triangular Wave” for testing instead?

The reason is (if you remember your calculus class), the “ideal” Square Waves are composed of an infinite summation of sine waves of different frequencies. It has a single sine wave fundamental frequency, and all it’s odd harmonics. The amplitude of each odd harmonic is 1/n.   Represented by this equation: (credits: Wikipedia)

squaresum

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FAB2120 – Carnhill Input Transformer Module

This is similar to our FAB2110 Input Transformer Module… but instead of using a CAN type transformer, we’re using a Carnhill/UK Input Transformer, (model VTB-9045) typically used in Neve preamps.

The VTB-9045 Carnhill Transformer is a Low Level Audio Signal Transformer, with a turns ratio of 1+1:2+2.  DC Coil resistance is 24+24:130+130 ohms.

To mount the Carnhill transformer horizontally on this FAB board, a separate Carnhill PCB Adapter is also required.  Both boards will be provided when you purchase this FAB board.

CarnhillPCBAdapter

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FAB3346 – Balanced Line Driver (Unbalanced to Differential) Module

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FAB3000 Output Modules
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FAB3346 is an unbalanced to balanced line driver module using a THAT1646 PDIP8 chip.

The THAT 1646 is a new generation of monolithic audio differential line driver offering improved performance over conventional cross-coupled  designs. Based on a high-performance, fully differential opamp and laser-trimmed thin-film resistors, the THAT 1646 exhibits low noise and distortion, high slew rate, and wide output swing. The THAT1646 is stable when driving difficult loads, and have short-circuit protected outputs.

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FAB6012 – Rotary-Switch/Switch Module

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FAB6000 User Input Modules
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The FAB6012 is a double-wide module that incorporates (4) LED-lighted Push-Button switches, a (12) resistor network, and a 12-step Grayhill 71-series Rotary Switch.

The (4) Push-Button switches are wired to automatically lit-up when you depress the switch. In addition, there are (4) output Logic control headers, each corresponding to it’s own switch control.  You’d wire these terminals to the Logic-controlled relays on your FAB Modules (for example: Phantom power, Polarity Reverse, Pad, etc…)

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