do you have to bias guitar amp preamp tubes

But hey, can't do any harm making sure it's spot on.Guitarists will already be aware of the unmistakable effect the humble valve can have on their sound. When you adjust your bias, you are maintaining the amp at that operating point, but I am just saying a little drift away from it shouldn't be making a huge difference. However, having chosen the operating point, and designed a power supply to allow it, they could bias the valves to sit at that operating point using any method they want. Maybe even improved valve life if they move further away from the max.

I suspect this is what they have done - chosen a different operating point to the more normal one which would be optimised for power output, and sacrificed power for less distortion. I used to use a spreadsheet with valve models and graphs to play with operating points. Not familiar with the ARC design before now.Ī quick Google found a REF 75 amp - pair of KT120s? Choice of power supply, and bias point can result in less power, but maybe also less distortion. ARC (which I mention as example, not saying it's better than everyone else) choose manual, and they run their valves way below their power capacity, I was just pointing out that some high end amps choose one or the other approach. The very small amount the bias drifts, after initial settling in, should not effect the sound to any great degree.

The adjustments help you balance slightly unmatched valves, and let you set the bias for valves to account for the manufacturing differences between different makes, and even different designs and batches. class A, class AB, class B then small bias adjustments don't change the sound much in my experience. If you're not changing the bias so much that you alter the class of the amp, i.e. I find it makes more difference to the sound when you change the bias on preamp valves, but they aren't the ones that you typically adjust in a commercial amp, it's the outputs. I have built many valve amps (I know weird, but I love the technology) and experimented with bias points. OK, but I only question the need for pinpoint accuracy, and this gets back to the OPs question. ARC still use manual bias for example it's not like they're unaware of the (ancient) technology behind autobias. The reason for bias in the first place is for optimal performance. Autobiasing isn't as accurate as manually biased and.

Do you have to bias guitar amp preamp tubes