Operation Manual

Setting the Parameters

GRID

The grid is one of the poles of the tube. In the

triode tube used on this model, there are 3 poles,

the cathode, the plate and the grid. The elec-

trons are attracted towards the plate if the heated

cathode is loaded with voltage. By changing the

voltage on the grid, the voltage flowing to the

plate greatly changes.

NONLINEAR DISTORTION

An amplifier without distortion amplifies input in

proportion (=linear) with output, as shown in

the figure below.

If the bias voltage is changed, input and output

are not in proportion with each other, as shown

in the figure on the left. The distortion caused

by this is called non-linear distortion.

CLIPPING DISTORTION

If the drive is at the maximum, the end of the

waveform is cut (off), as shown in the figure

below. This is called clipping distortion.

Bias voltage and Nonlinear Distortion

To make the vacuum tube function as an audio amplifier, a minus voltage called bias voltage is

added to the input terminal (called grid) as well as the audio signal.

Although, the bias voltage is generally fixed so that the distortion of the output wave-form of

the tube is at the minimum, the bias voltage can be changed when the tube amplifier is overdriven

on this model.

By this parameter, you can adjust the characteristic of distortion to your taste.

The change the bias voltage gives to the sound distortion may not be very noticeble, depend-

ing on the drive amount or the drawbar registration. The best way to check it precisely is as

follows:

1. Set the Drawbar registration at “00 8000 000” (either manual).

2. Locate the TUBE AMP - OD page.

3. Set the Drive near 40. (Make sure it is not the maximum value.)

4. Move the cursor to BIAS.

5. Play the chord on the manual as shown.

Change the value of BIAS, pressing the keys. The degree of distortion is slight near “0”, but

the distortion increases, if you change the value towards “+” or “-”. Such a distorting sound is

called “nonlinear distortion”.

NOTE: On the original B-3, distortion occasionally would occur naturally as the instrument would

age. On this organ, you can create natural-sounding distortion intentionally.