Want all the gain you can get? This is the High Gain Option Retube Kit for the early X60B amps that came with 6L6's. The preamp section uses three handpicked High Gain ECC83S's with one balanced for the phase inverter in V3. The default power tubes are a matched pair of the JJ 6L6GC’s but you can configure this kit to use the JJ 5881’s by clicking on the "Customize" button!
Most of these amps are fixed bias but over the years many have been modded to be adjustable bias. If your amp is adjustable bias then all you need to check and adjust the bias is a Multimeter if you use the Carvin method. For more accuracy you can also use a bias probe and a Multimeter, or our all-in-one Eurotubes "Pro One" bias probe that reads both the plate current and the plate voltage simultaneously. These are available under the "Related Products" tab.
You can use our Carvin bias video for reference which we did on a V3. If you're going to use the Carvin standby switch method then between 70 to 80mA is correct. The video below explains the difference between bias probe types.