If you simply want to improve the sound of your Supersonic 60 Head while maintaining the amps root character and functionality, this kit will do it. It uses five standard ECC83S's to replace the 12AX7's along with a balanced ECC81 for the phase inverter. More warmth and a sweeter sound! 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.
All you need to adjust the bias on a these amps is a multimeter and you can use the test points #49 and #50 to measure the bias in Millivolts. You can also use a bias probe and digital multimeter to do the job or the Eurotubes "Pro One". All of these are are available in the "Related Products" tab. We typically bias the JJ 6L6GC's in these amps to between 36 to as high as 44mA or 33 to 40mA for 5881's. If you use the test points you can use the HotRod Deluxe bias video for reference. The procedure is the same but the test point locations are different, see the image below.