Author: Stewart - Page 22 - Valve Tube Guitar Amps

Steps to follow when changing your valves in your amp

Amplifier valves get hot and there are very high voltages present, so make sure the amp is switched off and and the valves are cold. Hot amp valves can give you a bad burn ! The output valves , the rectifier, and ECC99’s all get especially hot ! My most recent burn was off the little output valve in the picture above, the EL84 output pentode The first basic question is how often to replace […]

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“Why don’t valves ( tubes) have One Year warranty ?”

I offer 120 day warrant on valves ( tubes) . Why is this so great and why dont valves have a one year warranty like everything else?

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Why Change the rectifier valve in your amp

Rectifier Valve ? Many of the vintage amplifiers such as the Vox AC30 , Fender Twin Reverb use a rectifier valve. Other amps use modern silicon diodes. The rectifier valve ( or diode) is a key part of your amplifier’s power supply. Its job is to “convert” or rectify the AC voltage coming from the transformer into the high DC voltage needed by your valves in your amplifier. The output valves need the highest voltage

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Useful Table on Bias current for output valves

I thought this looked like a really useful table on bias current for output valves. The top of the page allows the super techie types to do an exact calculation based on measured voltages in your actual amp and the configuration of the circuit. The featured picture is actually all the tools ( apart from the right screwdriver). It is simply a multi-meter and a special adapter. You plug the adapter into the output

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Electrolytic Capacitors

Electrolytic Capacitors You find electrolytic capacitors in the power supply and decoupling of valves in Hifi and guitar amps. They are like a battery because they have a positive and negative terminal. In you amp power supply they can have values of 22 up to 200 or more uF ( uF= micro-farads). Electrolytic capacitors store energy, and often they are working at voltages of 500 volts DC ! When you switch off your amp , they

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Small Capacitors in Guitar Amps

Small Capacitors in Guitar Amps Your amp is filled with small capacitors as in the picture below. They come in many different colours so this is jut a sample In simple terms, is in the filter circuits ( tone shaping) or to pass the audio ( AC) signal to the next stage of the amp while blocking the DC voltages. Values are typically in the range 0.001 to 0.47 uF. In valve amps there are

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Wirewound Resistors In Your Amp

Wirewound Resistors In Your Amp Wire-wound resistors in your amp are used when a lot of power needs to be dissipated in your amp and usually these are around the output valves for bias resistors. As the name suggests the resistors are made from restitive wire that is wrapped around a piece of material to make a resistor. They are used especially in amps with an output of 40 watts or more. There is a

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