Philips MyLiving Fremont LED light repair.Behringer XR18 repair (digital mixer repair).Please get in touch, the cost of valve amp bias is £37 and includes testing of all valves on a valve tester. My amp needs biasing and I don’t like maths! Biasing by ear or sight (or smell!!) could reduce valve life or damage your amp. I would recommend against these techniques and advocate either biasing to a value specified in manufacturers guidelines or to a value calculated to give sensible dissipation in the power tubes. I’ve heard of people turning the valves up till they ‘red plate’ and then just backing off a bit. Many people have their own ways of biasing an amp. I’ve got a fixed bias amp, but I put new valves in and turned the amp on. The voltages (often 300-700VDC) and currents involved can kill you easily. Valve amp bias must be done on a live amp – operating on a live valve amp is extremely dangerous if you don’t know what you’re doing. If your amp doesn’t have external bias pots then I would strongly recommend against doing your own biasing. The values change from amplifier to amplifier.
#Easiest way to bias guitar amp how to#
If you know how to use a multimeter you can place one across these pins and adjust the preset potentiometers to give the correct reading (given by manufacturer). some modern marshalls) provide a bias port on the back of the amp. You don’t need to bias if you buy Boogie valves for a Boogie amp. Boogie get a lot of stick for this on ‘the forums’, but I’d say their reasoning is sound. This is because during design they have permanently set the bias current for optimum performance with own brand tubes. Mesa boogie state that you should only use their tubes.If you change tubes in a cathode biased amp and the tubes red-plate, take the amp to a tech. This includes many designs using EL84s and 6V6s. Often smaller amps (<30W) are cathode biased. Cathode biased amps do not normally need biasing.Is valve amp bias always necessary for new valves? Red-plate – Not good! Valves glow a very bright pinky red all the way up the plates in the tube.
So the circuitry adjusts itself to match the valves.
This reduces headroom and increases power amp overdrive. ‘Hot’ biasing more power is dissipated (wasted) in the valve.‘Cold’ biasing – Higher fidelity, less distortion, longer tube life.Very ‘cold’ biasing can result in crossover distortion, which most find unpleasant.Biasing sets the amount of current running through a valve when there’s no signal. Here’s a simple guide to biasing for guitarists.