ARC LS25 mkII adjustment

Actually preamp tubes, in many cases, should be adjusted. However, biasing preamp tubes is not a simple task and it requires changing resisters. I believe the differences we hear when rolling tubes can often be how the tube is affected by the current bias setting. This is why it is always better to replace preamp tubes with tubes selected by the manufacturer.

Jazzgene, Did you change the adjustment?

I think John probably knows better than to change those adjustments.

If it was my preamp and I suspected adjustments have been changed I would ship it to Audio Research, so I know it is working properly.

I think a lot of audiophiles try equipment that isn't working properly or not broken in and decide they don't like it. These hybrid preamps take a few days of warm up to start sounding their best.