I use the Herbies Audio Labs Hal-o dampers on the 6922 tubes in my ARC LS-15. They did make a difference. They cleared up the soundstage a little and separated things a little better, but don't expect night and day difference with 6922 tubes that are low noise and low microphony, such as carefully selected and properly matched set of EH6922 tubes for example. WHats good about Herbies, is they come off easily and the never stick to the tubes due to heat.
http://herbiesaudiolab.home.att.net/
http://herbiesaudiolab.home.att.net/