Picked up a used Vox AC15c1 for a great price. The amp still had the stock Chinese tubes, and they were on the way out. Ordered a JJ tube kit for my Vox from Tubedepot, but none of the 12ax7 were marked as the balanced tube. If I plug in a unbalanced 12ax7 for the phase inverter, could that cause issues with the amp? Thanks for any info.