I noticed on the updated Germino website that Greg's very popular, highly regarded Classic 45 models no longer ship with new production KT-66's (but NOS GEC KT66's are available at a $400 upcharge). I did a double take!! I mean, why make a JTM45 without KT-66's, right? I wondered if it was a misprint so I got in touch with Greg. Not a misprint. Here is the skinny..... "I know it seems a sacrilege to offer a JTM-45 replica like the Classic 45 and not ship the amp with KT-66's. The fact is that current production KT-66 from both China and Russia are prone to production problems. When I buy tubes from a company such as Groove Tubes I (and you the customer) are paying for a duet or quartet of tubes that supposedly has been put through rigorous testing. I have had about a 60% to 70% rejection rate on the GT KT-66HP. When pushed into hard clipping the tubes will drift and are no longer matched or give proper performance. Other OEM's have had the same problem. Honestly and frankly I don't have the time being a one man shop to go thru 3 sets of output tubes when bench testing an amplifier to find one pair that holds bias steady and that offers good sonics. I like the GT KT-66HP soundwise better than the Chinese KT-66. The Chinese KT-66 is sold under several names, Sino, Harma, Valve Art, Groove Tubes KT-66C and all of these are made in the Shuguang factory. Again, some production batches are OK and others not very good sounding. These tubes seem to lack midrange richness, plenty of highs and lows, very hollow in the middle. With the fantastic short bottle 6L6WGC available from TAD and the great new Tung-Sol 5881 is was a logical decision to go over to this tube type. In addition these tube types work well with both the upwards impedance match of 6.6K (running a 16 ohm load and amp hardwired at 16 ohms) and at a downwards impedance match of 3.3K (running an 8 ohm load and amp hardwired at 16 ohms). I will be glad to accommodate an order using current production KT-66's as long as you realize you may be getting a tube set that does not deliver 100% in the sonics dept. NOS GEC KT-66's while pricey at $350 to $400 a pair offer supreme tone and longevity far beyond what any current production tube set could offer. These are usually good for about 8000+ hours. I hope this clarifies the reason for using the new TAD 6L6WGC. I think that if you do a search for this tube on www.thegearpage.net or the new Tung Sol 5881 you will find only rave reviews about both. Keep in mind that the very first JTM-45's were shipped with 5881's prior to the switch over to KT-66's." We are in the Golden Age of amp building, but apparently at the end of the welfare line of vacuum tube production.