The back panel.

Input of the power cable (AC240V)
Connect your Hehku only on grounded power sockets. If the power socket isn’t grounded, you risk electrical disturbances on the amplifier and getting an electric shock.

In case of disturbances, the fuse will shut down the main current of your Hehku. The fuse doesn’t have to be changed after this becuse it’s automatic, so only pressing the button on it sorts it out. However, if this happens often, that indicates that there is something wrong with the amplifier and you need to get in contact with the manufacturer for further instructions and maintenance.

Chart for the tubes
You may switch the tubes by yourself by carefully following the placement-instructions on the chart for the tubes. The tubes can only be replaced with other tubes with the same exact type designation. Using any other kind of tubes leads to breaking the amplifier and termination of the guarantee. Always consult a professional f you’re even a slight bit hesitant about the tubes or any other instruction.

Foot switch
The foot switches should be connected on the back panel. It can only be done while the power of the amplifier is turned off or it risks short circuit, which will damage your Hehku in worst case-scenario. Using any other cord than a 6mm stereo plug cord for the foot switches also poses this risk.

Two of the first connections are 4 ohm. If you connect two 8 ohm speakers into the amplifier simultaneously, they form a 4 ohm collateral impedance together and therefore you need to use 4 ohm connections. The main-connection on these amplifiers is 16 ohm and therefore only 16 ohm connections should be used.

Technically, other kinds of connections can be used for example, when looking for a different kind of power amp distortion to the sound. In this case however, it has to be taken into consideration that it lowers the life expectancy of the power amp tubes (2xEL84).

Always use cord that is exclusively manufactured to be used on amplifiers. A standard guitar-cord is to be used under no circumstances since the amplifiers hold high voltage which damages these thinner cords and hence poses a threat to both the amplifier and the person using it. Never switch your tube amplifier on before you make sure that it is connected properly. If your Hehku is used without the speakers, the expensive terminal adapter may get damaged which automatically leads to termination of your Hehku’s guarantee.

It is possible to connect the EF86 to be used as either triode or pentode. The sound differs and the volume is louder when used as pentode. This switch is often done with a triode/pentode pull-switch. Before you pull or press this switch, the gain-function must be set to zero. This prevents the amplifier from making a snapping sound and therefore preserves both the amplifier and your ears. The back panel may also have a triode/pentode-switch. This affects the power amp tubes functionality and halves the power, but also influences the sound. When using this switch, make sure the stand by-switch is set to zero to prevent that same snapping sound described earlier.

Some of the Hehkus utilize the ultralinear-functionality of the terminal adapters when halving the power. This is done by a switch on the back panel. When using this controller, the stand by-switch should be set to zero.

Foot pedal
Several Hehkus come with a foot pedal, which is used to control spring reverb and switching between channels among other functionalities. If your pedal has two switches, the amplifier comes with a stereo plug cord, which you need to connect to the foot switch-contact on the back panel. Never use standard guitar cord for this purpose for it can cause short circuit and in the worst case-scenario blow-out of the fuse. Make sure that both ends of the cord have stereo plugs with metalled or plastic-plated bodies, because the plugin poses 9v tension which can cause small snap on your lips if it hits the mic stand, for instance. If you lose the cord of your foot pedal or some dumbass steals it, we will be happy to make you a new one that fits your Hehku perfectly.