do you have to bias guitar amp preamp tubes

Like a stomp-box, diode-clipping lends a killer sound at a lower volume. Plus, many amps don't begin to distort until turned up too loud for many venues. That isn't all bad! Clipping the loudest parts is also a form of 'limiting' - you loose some dynamics, but accentuate the lower-volume sounds. So it's peaks are simply 'chopped off.' But it also results in more attenuation, as some of the signal is lost. And even then, the whole signal isn't dissipated, only the portion of the signal above that forward voltage. If a diode is connected between the signal path and the ground, the signal won't be channeled (shunted) to ground until it exceeds the forward voltage. But they don't operate 'perfectly.' All diodes have a 'forward voltage' - they won't conduct until that voltage is reached. Wow-at first glance, a diode connecting the the signal path to the ground looks like a short circuit! How can this work? In theory, diodes conduct current in only one direction. Video clip shows the three switch-selected settings: 1) clean 2) medium clipping 3) max clipping: Of course, diode-clipping can be used (and is) for solid state amps, too. And since our new sound is contained within a tube amp, it will help to soften the effect.

Plus we can utilize asymmetrical clipping to emphasize the 'correct' harmonics. 'Peak clipping' more closely approximates tubes than 'crossover clipping,' which is common to transistor design. Tubes clip with a softer 'shoulder' and have a more pleasant, warm sound.of course, it's a matter of taste, after all.īut a carefully designed diode-clipper circuit can mimic those tube characteristics.

The danger of converting a tube sound into a harsh 'solid state' sound exists. In fact, some big-name amp manufacturers (Marshall and Fender, for instance) have used diode clipping for a more ballsy sound (especially at low volumes.) In fact, it's made a bit of a resurgence in boutique amps. Preamp clipping can be simulated by installing a diode-clipping circuit.

'Real' tube overdrive isn't possible without major changes (adding additional preamp stages, etc.), but here's another option: Here's a relatively simple way to add some 'bite' to your old guitar amplifier.Īmplifier overdrive and distortion is usually achieved by signal clipping-pushing the gain until the signal peaks are chopped off.

Do you have to bias guitar amp preamp tubes