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Info on the new Bias Tremolo feature in the Amp Block?


Power User
Hi All,

Disclaimer - I have never used a real bias tremolo, that i am aware of.

Just been playing around with the new bias trem feature and some amps sound really amazing ("peli cachu sanctaidd" - Welsh for you know what!) with it and some sound, well .. just erm "balls"?

I am guessing that this is just due to the circuits of that amps and the way the Tremelo circuits interacts. therefore some amps will sound inherently better than others.

Are there any general guidelines as to what amps will sound better or worse?

I assumed vintage fender types would be best suited, but that does not seem the complete answer in the limited testing i have done....although the amount of gain seems to have an impact ... the cleaner the better.

Clean on the Princeton or 59 Bassman sounds amazing...but when you get to on the edge of break up you get this odd unpleasing distorting ghost like notes.

is it just that Bias Trem sounds better on clean amps, or should I be looking at specific amp types?

Thanks in Advance

just noticed this .....Firmware 10 release notes: "Based on a Swart Atomic Space Tone. As with the actual amp the bias tremolo is particularly effective"
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Fractal Audio Systems
See the release notes. If the power tubes are being overdriven the bias tremolo can add lots of crossover distortion.


Power User
From Release Notes:-

Added Bias Tremolo to Amp block. This is a true bias tremolo and works by varying the bias of the virtual power tubes. The tremolo action is therefore different than other types of tremolo and the amount of tremolo varies with a multitude of variables, most importantly the tremolo is “self-ducking” and decreases at higher signal amplitudes. Note particularly that bias tremolo is a somewhat crude tremolo circuit and it’s interaction with the power amp depends on many things including damping, bias, etc. On some amps high values of bias trem depth can result in excessive crossover distortion. On other amps the amount of tremolo can vary greatly between loud and soft playing. All this, however, is part of the allure of bias tremolo as it results in a particularly “organic” sound. Control of the bias tremolo is afforded by the Trem Freq and Trem Depth parameters. A modifier can be attached to Trem Depth to facilitate engaging and disengaging the tremolo via footswitch or for other applications.
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