Two Notes VB-101 - Manual (Page 13)

Part 2
Warning regarding the proper use of a
loadbox with a tube amplifier
1 What is a loadbox ?
When normally using a tube amplifier, it is recommended to always connect its power output to
a speaker cabinet prior to powering it up. The speaker cabinet (4, 8 or 16 Ohms) must always be
connected to the corresponding Speaker Output of your amplifier. Not doing so can lead to partial
or complete destruction of the output stage of the tube amplifier.
Most tube-amplifier makers protect their products with fuses or other protection systems, but some
amplifiers still remain insufficiently or not at all protected. It is impossible to predict the behavior of
all the amplifiers on the market in cases when they are used without a load (a speaker cabinet or a
loadbox).
The electronic term that describes the speaker cabinet with respect to the amplifier is the "load":
the cabinet is said to "load" the amplifier. The term loadbox will fit any product embedding such a
load. The main parameter of the loadbox is its impedance, expressed in Ohms. An 8-Ohm loadbox
will need to be plugged into the 8-Ohm Speaker Out of the amplifier. As the power that is sent to
the load is changed into heat, please do follow the cooling recommendation of the loadbox — or
otherwise overheating may cause some damage, both to the loadbox and to the amp.
The TORPEDO VB-101 is a loadbox. This term indicates that the TORPEDO VB-101 is a load that can
electrically replace the speaker cabinet while dissipating (transforming into heat) the power that
comes out of the amplifier.
The embedded load in the TORPEDO VB-101 is a resistive one: it is a network of resistors that
matches 8 Ohms. This type of system is widely used in the industry to silently test amplifiers.
Always connect the Speaker Out of your tube amplifier to a proper load
(speaker cabinet or loadbox). The TORPEDO VB-101, once it is powered
up, constitutes such a load. Please note that you must always power
up the TORPEDO VB-101 before your amplifier.
Two Notes Audio Engineering Torpedo VB-101 13