Hello John,

Regarding your question, the 6V6 Valves we use in the DSL15 are Shugang, we cannot recommend any Groove Tube valves as we do not use this brand. All valves must be replaced with the same type ie they need to be 6V6.

Groove Tubes are simply rebranded tubes from various manufacturers.  The nice thing about them though is that when you buy a set,  they are matched to each other and to a perceived gain level.  Note that many manufacturers do this.  Groove Tubes have been doing this for many years.  Note that Fender owns Groove Tubes, and they're stock to any Fender amp.

Shugang tubes are good quality tubes.  If you need a source to purchase tubes, go to Tubedoctor.com.   There you will find different recommendations.  I'm a big fan of Electro Harmonix tubes, which Marshall used for many years.