Servicing & Restoration

Like a well performing vehicle, every now and then it's good to get a checkup to ensure everything is running as it should be. 

Biasing is the term given to the adjustment of the output devices.  Many people believe that only valve amps are biased, this is a bit of a myth.  To understand biasing we need to understand that to make a full wave we need drivers for the plus part of the wave and the negative.  This can be the pair of valves you see in the back of your amp, that is why valve amps generally have pairs or quads as their output valves, there are other configurations however this is the most common layout and is known as a Class AB.  The purpose of the driver be a transistor or valve, is to convert the low current of the signal into a high current designed to drive speakers. 

Due to the losses and construction of a silicon transistor/ MOSFET means that it does not start to operate until it has a minimum of about 0.6V to turn it on.  As you can imagine that levels below this do not get amplified correctly and gives the wave a 'knee' curve and non-linear operation as can be seen on the below graph.


Heat can cause a big problem in amplifiers, power supplies and in fact all electronic devices.

Heat can be caused by and cause drift on tolerances, component behaviour and complete failure as well as sound difference on solid state amplifiers.

We now use thermal imaging to show us component temperatures speeding up amplifier repair and ensuring that we get right to the root cause of the issue! 

mosfet thermal imaging

Regularly checking of valve biasing can avoid an amp being continually overloaded and stressing the amp out.  This resistor had burned and blew as a result of the valves going short and damaging.  The remaining valve was very worn, with regular maintenance and servicing the valve should have been changed quite a while ago!

Raise a support ticket

Raising a support ticket with the workshop is the fastest means to get your equipment repaired. Its quick free and easy to do. You can view past repairs and raise new ones once you have an account.
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