3. Back Panel Controls
AC Power
Always use a grounded AC cord, and make sure that a proper ground connection is
supplied to the amp. Never attempt to lift or defeat the ground connection to the amp.
Fuse
A standard 2A slo-blo fuse should be used. The fuse holder is integrated into the AC
input.
Power Switch
When powering up the amp, it is recommended that you allow the tubes to warm up for
about 1 minute before playing.
Speaker Jack
The speaker jack is located on the back of the chassis, and is labeled “EXT SPEAKER”.
This is because whether using it for the internal speaker, or to power an external
speaker cabinet, this is the jack to be used. It is a standard ¼” mono jack. The output
impedance of the amplifier is 8 Ohms. If you wish to use the Gremlin with an extension
cabinet, it’s best to use an 8-ohm cabinet. You can connect it with a standard ¼” mono
speaker cable by pulling out the plug from the internal speaker, and plugging the cable
into the speaker jack. But you MUST do so with the amplifier OFF.
Attenuation Control
The Gremlin contains a built-in Ironman II precision attenuator. The attenuator allows
you to reduce the volume level of the amplifier while allowing its output tube to operate
at full output power, for natural power tube overdrive and distortion. This attenuator
uses transformer coupling and a precision tuned reactive load to best preserve the
natural tone and feel of the amp, even at very low volume. This is the same general
approach used in the highly regarded Ironman II standalone attenuators.
There are many different approaches that can be used to generate overdriven and
distorted tones as a low volume. For example, master volume circuits, or a power
reduction scheme such as London Power Scaling have both been used successfully on
various amp models of other brands. However, for the more vintage sounding tones
that the Gremlin is designed to achieve, a good quality attenuator such as the built-in
Ironman II is the best way to preserve tone and feel at very low volume, because it
allows the output stage to operate the same way at any level of attenuation.
The attenuation control determines the amount of power sent to the speaker, but does
not affect the operation of the output stage of the amplifier itself. The attenuator
absorbs and dissipates any excess power generated by the output tubes that is not sent
to the speaker.
The attenuator is internally connected between the amplifier output and the speaker
jack – the same way an external attenuator would be connected. However, the input of
the attenuator is not accessible, so you cannot use the built-in Ironman attenuator to
attenuate the output of some other amplifier.
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