Page 61 - Triwatt Custom Lead Amp Builder's Guide

 Add grid stopping resistors to help tame oscillation. If you have oscillation with your amp,
you can sometimes help it by installing grid stopping resistors. The grid stoppers can also
subtly roll off high end as well.
 Add high frequency roll off caps in parallel with the plate resistor. This is sometimes used
to "mellow" out a stage (reduces highs).
 Adjust the grid leak resistor. Reduce the value to attenuate the signal into the stage to
control the gain.
 Use a shielded cable from your input jack to the first gain stage. This can reduce RF, buzz
and general reduce noise.
 Replace all plate resistors (and resistors of 100k or above) with metal film types. This can
help reduce hiss..

Running EL34 Tubes in the TRIWATT

THIS MODIFICATION IS EXPERIMENTAL & AND DONE AT YOUR OWN RISK.

The EL34 can work in a TRIWATT but you have to make a couple of changes. This will definitely
have similar headroom to a 4 holer and a bit more volume than the standard TRIWATT.

The variable bias switch works by putting a second resistor in parallel with the 180K (6V6) .
Default is 180K in parallel with 620K = 140K (for KT66 setting). You may not have enough
adjustment in the bias pot to get EL34 in range. So you can try a 1M resistor in place of the 620K
KT66 resistor. In parallel with the 180K 6V6 resistor = 152K.

Plug the EL34 in and put the switch to the KT66 setting which is a higher voltage by about 15V-
18V or so than the 6V6

Carefully set bias of the KT66 setting to get around 33 mA/mV max. on the power tubes, at 450v.
You may still have to play with the bias resistor to get into range.

When you use them, set the output impedance to 4 ohms and plug into an 8 ohm cabinet.

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TrinityAmps TRIWATT Builders Guide Ver. 2.31.docx
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