Vox VBM1 owner manual Brian May Special Signal Path Flowchart

Brian May Special Signal Path Flowchart

9V BATTERY SIMULATOR

TREBLE GAIN

T

SBOOSTER

	9V BATTERY SIMULATOR		T	HEADPHONE
			R	AND
			S	RECORDING
	OUTPUT		SPEAKER SYSTEM	OUTPUT
		TONE
BOOSTER ONLY	TRANSFORMER		EMULATION
	SIMULATION
OUTPUT JACK
T
R			VOLUME
S	PREAMP			T
	& DRIVER STAGE PUSH-PULL OUTPUT STAGE			S

	10 Watt	EXTERNAL
	POWER AMP
		LOUDSPEAKER
GAIN SWITCH
		OUTPUT

With reference to the above flowchart:

i)The TREBLE BOOSTER stage is a direct copy of Brian’s homemade Treble Booster pedal. The only things different are:

a)Our circuit is connected to the gain switching circuit to reduce the pedal booster gain in the LOW Gain switch position. This is required to clean up the operation of the pedal circuit

b)The output is fed through the GAIN control. The original pedal does not have this. With the GAIN control turned up full (i.e. on “10”) and the GAIN switch on HIGH, this is equivalent to the original pedal. The GAIN control allows for different sounds to be produced.

ii)The BOOSTER OUTPUT jack allows the Booster to be fed into another amp (AC30 Normal channel for instance) for Brian’s on-stage sound. Use of this jack makes the rest of the Brian May Special inoperative. This has been done for the reason that, due to circuit constraints, the output from the booster pedal section is different depending on whether or not it is plugged into the “Deacy” circuit, or into another amp that has a much higher input impedance.

iii)PREAMP & DRIVER STAGE.

This follows the original as much as possible, but:

a)Silicon PNP transistors are used in place of the original obsolete Germanium types, but they have been chosen for similar operation, and also have extra circuitry to help them “believe” they are Germa- nium.

b)The inter-stage driver transformer has been replaced by an electronic transformer simulation. This was required to try and emulate the performance of the original obsolete transformer.

c)The addition of the gain switching circuit.

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