For sale is a collection of 5-12AX7 pre amp tubes. Each one has a different character and drive. Various manufacturers are Groove Tubes, Ruby, JJ, etc. I sold my Shuttle 6.0 and no longer need these. For those of you that have the micro heads and want to experiment with tone, this would be a great, inexpensive way to go. All 5 for $25.00 shipped conus. PayPal is fine.