Tube Biasing - Decware TORIIJR Owner's Manual

T O R I I J R O W N E R S M A N U A L
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OUTPUT TUBE DESIGN CHOICE
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The TORII JR comes from a long line of TORII amps, which all have been designed
around EL34 output tubes. Although the big brother to this amp, the TORII MK4 can
use your choice of a variety of different output tubes, including KT66, KT77, 6L6
without adjustments, it is important to understand that the TORII JR, can not.
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Due to the fixed bias design of this amplifier it must be adjusted for each specific quad
of output tubes you put it in it.
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We chose the EL34 as the default tube in the TORII JR., because we feel due to the
ultra-linear output design the EL34 sounds best in this amp. EL34's are the only tube
that can take advantage of the the Hazen Grid Mod which has been implemented in
this amplifier!
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TUBE BIASING

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The TORII JR has an adjustable fixed bias set to 40mA with the EL34 output tubes it
shipped with. Using anything else may increase the milliamps (mA) beyond this very
critical point so different quads and types output tubes MUST NOT BE USED without
re-adjusting the bias. Please see the section at the end of this manual titled "HOW TO
BIAS FOR DIFFERENT TUBES"
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HAZEN GRID MOD
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Supporting our choice of EL34 output tubes, is what we call the Hazen Grid Mod, aka
Christmas Comes Early Mod, where we couple the suppressor grid and cathode through a film
capacitor increasing clarity by reducing stray electron bounce. This pushes the sonics of this
popular tube up the fidelity later even higher. Other popular tubes like KT66, 6L6, KT77, KT88
etc., have the cathode and suppressor grid internally connected with a piece of wire and can
therefor not benefit from the Hazen Grid Mod.
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Decware High Fidelity Engineering Co., East Peoria IL, USA www.decware.com