Just wanted to drop in and share some experience. I recently was able to get my hands on a ts 5998 at a reasonable price, and paired with the Mullard ECC82, the crack boasts a wonderful signature for my t1s - the highs are pulled back into equilibrium, the bass is much more present, but still tight, and the mids balance detail and warmth wonderfully. These tubes really allowed me to hone in on the sound I wanted for my t1s, and I would highly recommend some rolling to anyone interested in tweaking their amp/phones synergy. Just my 2 cents!