COLIN WONFOR: What is bias from a technical aspect?

Colin Wonfor

Dear Colin, What is bias from a technical aspect? I was talking to a repairman who fixes a brand of high end equipment I like and own. I commented that the higher end models sounded much better even through crappy speakers than the lower end models (both of which I own) and he replied it was probably due, in part, to the higher end system's "better biasing". What does that refer to? (in "technical laymen's" terms) I've heard correctly "biased" phono preamps and the difference is night and day. Is this something similar, but system wide? Thanks!

Bias is normally how and where in the output devices are sitting in their conductive mode i.e. A/B, A (pp) and B. This bias setting is often in Semiconductor amps – just the amount of current in static mode the devices are set. This will often show up in poor kit as a tizz or even poor top-end distorted just like poor crossover distortion ( when one device turns off and the other turns on) and it is not comfortable to listen to.

Now from your Technician perspective what often show up in good kit on crap speakers is caused by damping factors. This is where the amp has control on the speaker motor or voice coil thus no floppy cones + better distortion results. The higher the damping factor = the more control. Now sometimes designers get the damping factor right but now the have a poor slew rate so it still sounds bad.

The TQ Iridium a SECA designs has no cross over distortion and the TOCA's is the same. The iridium damping factor was well over 1000 which is huge + a slew rate of >500V/uS. Most amps are only 20V/uS. So you get high speed current and control. deep Bass and a sweet top end. Very hard to do in a SECA design. Ask anybody. Meanwhile, that’s why I am now bald.

Thank you for the question.