The HotBox is a power attenuator which absorbs a large proportion of the output power from your amplifier and converts it into heat instead of volume. This allows you to enjoy the real tone of power valves saturating into overload, but without the hearing damage.

Power levels

Your HotBox is rated for 130 watts. This rating is the loudest amplifier you should use with your HotBox. As long as your amplifier is well serviced then you can turn it up to 11 and drive it as hard as you like, for as long as you like: The HotBox is built exactly for this purpose. You can also always use a lower powered amplifier without issue.

Connecting your HotBox

To use your HotBox simply connect it in-line with the speaker output of your amplifier. Your amp or head goes to the Amp In socket on the box and your speaker or speaker cab connects to the Speaker Out sockets.

In the case of combos this is usually the built in lead. You may use either or both of the speaker out jacks on the HotBox at the same time. They are wired in parallel thus connecting two 16 ohm cabs will give the same impedance as connecting one 8 ohm cab.

Getting great tone

The aim of any attenuator is to let you drive your tube amplifier into ‘saturation’. This is a level unique to tube amps where they compress in a really pleasant way to sound ‘rich’ and feel ‘sensitive’ when you play.

If you run your amp too quietly it will simply sound clean and linear, if you run it too loud it will clip in a harsh and unpleasant way.

When you are in the ‘sweet spot’ all your channels and pedals, from clean to extreme, will be harmonically enhanced by your saturated amp.

In order to find the sweet spot of your amplifier we recommend you set your amp to clean and the HotBox to -4dB. Now slowly turn up the master volume on the amp, whilst increasing the attenuation to -8dB or more, until you get a clean sound that sounds great to your ears, at a real-world volume that also suit you.

Reactive Modes

The HB130 offers four modes that change the ‘feel’ of your amp and attenuator interacting.

  • Resistive This mode is bright and the reactance of your transformer is coupled to a resistive only load creating a very tight, rock’n’metal sound.
  • Blue This mode is slightly warm and lightly reactive. It gives a firm nuance and feel, ideal for precise players which retains a lot of pick attack clarity.
  • Green This mode is moderate and versatile. It has a midrange-focused feel and balanced reactance comparable to the most popular speakers.
  • Cream This mode is extremely reactive and warm, similar to a speaker with an over-wound voice-coil and is ideal for groovy, bluesy, doomy players.

The reactive modes change the ‘feel’ far more than the tone. They’re not like a dramatic EQ and can it can be quite difficult to choose which you prefer by ear alone. Instead we recommend you simply play your favourite riffs and licks, turn the control and trust your instincts.


Bypass can be safely operated in any mode at any time, however we strongly advise that you do not play loudly whilst switching, or switch very rapidly otherwise there is a risk that energy stored in your transformer will be reflected back into your amp and eventually damage it.



Does the impedance (16 ohm, 8 ohm, 4 ohm) really matter?

You must always match the amp (or head) impedance to the HotBox otherwise you will stress your tubes and transformer. However, you can mismatch your speakers by up-to half or double (but only when not in bypass mode) because the HotBox acts as a partial buffer.

I measured my speaker impedance and it’s 7.3 ohm / 13.5 ohm etc.

Speaker impedance is only a very rough measurement. So 7.3 means ‘8 ohms’ and both 13.5 or 17.1 are ‘16 ohms’ (or 15 ohms on vintage amps).

Will the HotBox change the sound of my amp

All attenuators have a tonal response, just like all speakers do. You can use our reactance dial to tune that ‘feel’ and you also might prefer to use a lower powered speaker, perhaps 5 to 10 watts, to compensate for your speaker not working as hard as usual.

I accidentally connected the leads the wrong way around.

This will not damage your amplifier. However, anything above a few watts will quickly damage the HotBox, particularly the sensitive Fine control.

The Fine control sticks, wont turn, smells burned, or doesn’t work

At some point, someone has connected the speaker leads the wrong way around and melted the control. We know no-one would do this on purpose, accidents happen, so please just message us or send us an email and we’ll help you get it fixed quickly and cheaply.

Can I use the HotBox to direct record?

We sell a number of killer add-on units to enable direct recording, please check our website. We don’t offer a built-in line out because we’d have to make it cheap’n’nasty to keep the price down and that sort-of compromise is just not our style.

Can I use the HotBox as a dummy load, without any speaker?

Yes. Switch to Fine mode and you may safely disconnect all speakers.

Will the HotBox get hot?

It depends on your amp, your playing style and the air temperature. If the HotBox gets super hot your amp valves or bias may be faulty and we strongly recommend you get your amp tested by a skilled technician because it may be outputting too much power.

Will the HotBox hurt my amplifier?

Absolutely not. Your amplifier can not tell the difference between a HotBox and a speaker. However, because you will be running your amplifier at a very high level, possibly in continuous overload conditions you should expect your power valves to wear out at a faster rate, just as if you were playing regular stadium gigs and you should service it accordingly.

Conditions and guarantee

All Audiostorm pedals are and designed and hand built by Sean Mandrake. As such, every pedal will vary slightly and cosmetic imperfections are to be expected and are considered normal.

Every pedal is built from carefully selected parts. If your HotBox malfunctionsAudiostorm will repair or replace it (whichever we deem more practical) for at least twelve months from the purchase date. Beyond this, as part of our lifetime warranty, we will attempt to repair any HotBox for cost only.

This guarantee excludes damage caused from unreasonable abuse. This includes but is not limited to: liquid damage, high impact physical damage, cosmetic damage and failure to follow the guidelines in this manual. The use of this unit and commitment to a guarantee also requires that the end-user agrees that they certify any equipment this HotBox is connected to as is in good condition, thoroughly serviced, safe, operates within the specified power levels, and is appropriate for use.

The user also accepts that the HotBox may get hot and takes full responsibility for ensuring the safety, typically by placing it out of reach, of anyone who may accidentally touch it without realising.

Note: This User's Manual is adapted from the official manual created by Audiostorm in PDF format, without modification of the content. We just rewrite the PDF, into responsive mobile friendly pages.So, you can read this document anytime and anywhere.

Similar Manuals

you're currently offline