The Groove Tubes SAG-FHG Fender High Gain Kit kit includes 2 high gain preamp tubes and one matched 12AT7 phase inverter. All SAG kits are selected on a limited basis. The 2 selected high gain ECC83S tubes are optimized for the preamp stage of Fender amplifiers of all eras which use a 12AX7/7025 first gain stage.

Special Applications Group (SAG) provides further testing and grading for certain performance characteristics and these vacuum tubes are specially selected from premium Groove Tubes preamp tubes which have been tested to meet the GT standard.

This 3-tube set is optimized for Fender amps which use 12AX7 or 7025 tubes in V1 and V2. SAG-FHG includes two high gain preamp tubes to be used in the V1 and V2 positions, and one MPI (matched phase inverter) 12AT7 tube for the V6 position (in the case of blackface amps. The V1 and V2 tubes will increase the front end gain structure of the amplifier as much as 20% over typical stock tubes. The matched phase inverter tube will assure a balanced output section when used with matched power tubes (highly recommended) which will assure sustain across the entire range of your instrument.

The MPI (Matched Phase Inverter) is a SAG Selected 12AT7 as is standard Fender practice.

Each of the three kit tubes is marked as to it's specific rating. In the future if you wish to change your gain structure, it is a simple matter to request a higher or lower value as the actual characteristics of your amplifier's gain stage is now known.

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