Ilya-V Posted March 16, 2020 Share Posted March 16, 2020 Hi, first post. I would like to know what Bias and Bias X controls do in terms of component emulation, beyond the general 'feel' descriptions I can already find. I will elaborate the questions further; BIAS: My question is whether this control changes the cathode resistance and changes the negative voltage on the grid of the power tube? If so, what range does this control have in terms of effective bias idle wattage? ie; If the emulated tube wattage is 30W (6L6 for that matter),, does changing BIAS between 0 to 10 changes the idle current from 0W to 30W at idle (full class B to full Class A)? So BIAS value of 6-7 where most emulated class AB amps are set will result in 60%-70% of Tube wattage at idle, like real tube amps biased at? BIAS X: (Excursion I assume?) If that indeed excursion, my question is what component does this control emulate exactly? Does this change the voltage swing of the phase inverter, maybe the coupling capacitors size, or grid resistors size? https://www.ampbooks.com/mobile/amplifier-calculators/bias-excursion/ SAG Does this emulate the HV++, HV+ voltage drop with a resistors in series with the power supply when a large current is drawn? In a tube amp the secondary winding of the power transformer has significant resistance, so when the amp draws current, all the anode voltages of the amp drop or 'sag'. I've bought a Helix recently and these controls imo are very important part of the power amp emulation. I would appreciate the Helix much more if I actually knew what these controls do in terms of component emulation. I've also built and modded a few tube amps, hence the technical questions. Thank you. 1 Quote Link to comment Share on other sites More sharing options...
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