6L6, 6L6G, 6L6GA, 6L6GB, 6L6GC, and all other variants as well as , 5881, KT66.
A note with respect to the KT66. This tube is NOT AN EXACT 6L6 REPLACEMENT. Although it will work fine in most 6L6 circuits, the KT66 has a higher filament current of 1.27 amps and has a design maximum plate dissipation of 25 watts. The 6L6, 6L6G and 6L6GA have a maximum design plate dissipation of 19 watts while the 6L6GB and GC have a design maximum plate dissipation 30 watts. The 6L6 family of tubes have a filament current of only .9 amps. The higher filament current and the slightly lower plate dissipation specification for the KT66 is important, especially if you plan to use these tubes in a guitar amplifier. The extra filament current can prove fatal to power transformers in guitar amplifiers not specifically designed for the KT66. The KT66 tends to bias slightly different then the 6L6 as well. Unless you know exactly what you are doing, do NOT just plug in a pair of true KT66's in your amplifier if it calls for the 6L6. Another issue with the 6L6 tube family is that the older 6L6's (6L6, 6L6G, 6L6GA) are designed to handle lower plate voltages and maximum plate dissipate is only 19 watts. Although these tubes work fine in older amps with maximum plate voltages under 400 volts, and where biasing and operation has maximum plate dissipation limited to 19 watts, these tubes will NOT work in amps with plate voltages above 400 volts and or where the circuit will cause them to dissipate over 19 watts. In these applications (like Fender guitar amps made after around 1955) you need to use the 6L6GB, GC, or 5881 spec tubes. These can handle as much as 500 volts to the plate and will dissipate 30 watts. So, use KT66's ONLY in amplifiers designed to use this tube. 6L6, 6L6G, and 6L6GA tubes should only be used in amplifiers with plate voltages under 400 volts. Usually 20 watt amplifiers of pre 1955 vintage. The 6L6GB, 6L6GC, and 5881 will work in any amplifier that calls for a 6L6 type tube.
| Order No. | Tube type and description | Price each |
| 6L6G.005 | 6L6G US manufacturers clear glass | $35.00 |
| 6L6G.006 | 6L6G US manufacturers smoked glass | $35.00 |
| 6L6GA.011 | 6L6GA US brands | $30.00 |
| 6L6GAY.014 | 6L6GAY US brands | $30.00 |
| 6L6GC.022 | 6L6GC RCA black plate | $120.00 |
| 6L6GC.027 | 6L6GC US brands | $75.00 |
| 6L6GC.035 | 6L6GC / 5881WXT Sovtek full base | $10.00 |
| 6L6GC.036 | 6L6GC / 5881 Sovtek wafer base | $10.00 |
| 6L6GC.037 | 6L6GC Russian full base, thin bottle | $10.00 |
| 6L6GC.039 | 6L6GC Chinese | $10.00 |
| 6L6GB.050 | 6L6GB RCA black plate | $60.00 |
| 6L6GB.051 | 6L6GB US brands | $25.00 |
| 6L6WGB.060 | 6L6WGB/5881Tungsol | $60.00 |
| 6L6WGB.061 | 6L6WGB/5881 Tungsol Used tested good | $30.00 |
| 6L6WGB.062 | 6L6WGB/5881 RCA | $35.00 |
| 6L6WGB.063 | 6L6WGB/5881 Raytheon | $35.00 |
| 6L6WGB.064 | 6L6WGB/5881 Sylvania/Philips | $35.00 |
| 6L6WGB.065 | 6L6WGB/5881 GE | $35.00 |
| Order no. | Tube type and description | Price each |
| KT66.001 | KT66 GEC smoked glass | $300.00 |
| KT66.002 | KT66 GEC clear glass | $300.00 |
| KT66.003 | KT66 Shugang | $35.00 |