DHA Hand built guitar, bass and keyboard amplifiers
and effects from Devon in the UK
Dave Hall Amplifiers www.davehallamps.co.uk
The VT1-MK3-Bass uses a single 12AX7 (ECC83) valve to generate classic pure valve
tones. There are two modes of operation, overdrive and clipping distortion which
also has 2 separate options of clipping. The VT1-MK3-Bass is a low to medium gain
effect and is intended to be used in front of a valve amplifier, but will also work
well with solid state amps. The foot switch provides a true by-pass and the LED indicates
if the effect is on or off and the cool blue back-light seen via the valve vents
indicates the power is on.
The controls are very simple, i/p pad, Level, Gain, Boost, Clip, Colour level, Colour
select switch and Boost by-pass. Level sets the output level of the effect to your
amplifier, there is a fair amount of gain generated by the valve and op-amp and this
will overdrive the input of your amplifier.
Gain sets the level into the second stage of the valve and hence the level of gain.
Use your volume control or on your guitar and/or the i/p pad to control the gain
on the first stage of the valve, you will find that the VT1-MK3-Bass responses very
well to this and you can control the break-up distortion like this.
The 3 position Clip switch is neat trick you won’t have seen before on this type
of effect. In the centre position (None) there is no clipping selected and the only
clipping heard at higher gains is the valve soft chipping. The Si position connects
two Silicon diodes across the signal path to produce a harder Fuzz type clipping.
The Ge position switches in 4 Germanium diodes, this is a much softer clipping, please
note because the Germanium diodes reverse voltage is much lower than Silicon the
volume will drop.
The Boost switch allows you to add extra clean output volume by switching in an op-amp.
The amount of volume is controlled by the Boost level control. This is a useful feature
when a low level of gain is required for a clean type setting but a higher than by-pass
output is still needed. The Boost switch is true by-pass so when it’s off the signal
path is pure valve.
The 3 position Colour select switch is used to select Colour 1, 2 or non which is
the centre position. When Colour 1 or is selected negative feedback is introduced
into the circuit the level of which is adjusted with the Colour pot. The Colour effect
is best heard at high gain which is an increase in distortion and compression.
So, just plug your guitar into the jack with the guitar drawing and your amplifier
into the jack with the amp drawing and you are off and running! The pedal is covered
for any parts and labour required to repair it should it go wrong within 12mths of
purchase. This does not cover misuse of the product but we will be happy to repair
this at cost as we will for any units which fail outside of the 12mths. The VT1-MK3-Bass
is fitted with 2.1mm external PSU adaptor for use with a 12v @ 1200mA external supply.
The inner of the connector is the positive, there is reverse polarity protection
so no harm will be done if you get it wrong.