T-7581A-TUNG-MP - Matched Pair version | Body Height | 3.688 in. |
Capacitance, grid to plate | 0.6 pF |
Capacitance, input | 10 pF |
Capacitance, output | 6.5 pF |
Grid 1 Voltage | -14 V |
Grid Circuit Resistance (Rg), Cathode Bias | 0.5 MΩ |
Grid Circuit Resistance (Rg), Fixed Bias | 0.1 MΩ |
Heater Current | 900 mA |
Heater Voltage | 6.3 V |
Heater to cathode voltage (Uk/f) | 200 V |
Item Diameter | 1.562 in. |
Item Height | 4.25 in. |
Plate Current, pentode (Ia) | 210 mA |
Plate Current, triode (Ia) | 72 mA |
Plate Dissipation (Wa) | 30 W |
Plate Resistance (Ra) | 22.5 KΩ |
Plate Voltage, pentode (Ua) | ≤ 500 V, 70 V typical |
Plate Voltage, triode (Ua) | ≤ 450 V, 250 V typical |
Screen Current, pentode | 25 mA |
Screen Current, triode | 5 mA |
Screen Dissipation | 5 W |
Screen Voltage, pentode | ≤ 450 V, 300 V typical |
Transconductance (S) | 6,000 μmhos |
T-7581A-TUNG-MQ - Matched Quad version | Body Height | 3.688 in. |
Capacitance, grid to plate | 0.6 pF |
Capacitance, input | 10 pF |
Capacitance, output | 6.5 pF |
Grid 1 Voltage | -14 V |
Grid Circuit Resistance (Rg), Cathode Bias | 0.5 MΩ |
Grid Circuit Resistance (Rg), Fixed Bias | 0.1 MΩ |
Heater Current | 900 mA |
Heater Voltage | 6.3 V |
Heater to cathode voltage (Uk/f) | 200 V |
Item Diameter | 1.562 in. |
Item Height | 4.25 in. |
Plate Current, pentode (Ia) | 210 mA |
Plate Current, triode (Ia) | 72 mA |
Plate Dissipation (Wa) | 30 W |
Plate Resistance (Ra) | 22.5 KΩ |
Plate Voltage, pentode (Ua) | ≤ 500 V, 70 V typical |
Plate Voltage, triode (Ua) | ≤ 450 V, 250 V typical |
Screen Current, pentode | 25 mA |
Screen Current, triode | 5 mA |
Screen Dissipation | 5 W |
Screen Voltage, pentode | ≤ 450 V, 300 V typical |
Transconductance (S) | 6,000 μmhos |
T-7581A-TUNG - Single version | Body Height | 3.688 in. |
Capacitance, grid to plate | 0.6 pF |
Capacitance, input | 10 pF |
Capacitance, output | 6.5 pF |
Grid 1 Voltage | -14 V |
Grid Circuit Resistance (Rg), Cathode Bias | 0.5 MΩ |
Grid Circuit Resistance (Rg), Fixed Bias | 0.1 MΩ |
Heater Current | 900 mA |
Heater Voltage | 6.3 V |
Heater to cathode voltage (Uk/f) | 200 V |
Item Diameter | 1.562 in. |
Item Height | 4.25 in. |
Plate Current, pentode (Ia) | 210 mA |
Plate Current, triode (Ia) | 72 mA |
Plate Dissipation (Wa) | 30 W |
Plate Resistance (Ra) | 22.5 KΩ |
Plate Voltage, pentode (Ua) | ≤ 500 V, 70 V typical |
Plate Voltage, triode (Ua) | ≤ 450 V, 250 V typical |
Screen Current, pentode | 25 mA |
Screen Current, triode | 5 mA |
Screen Dissipation | 5 W |
Screen Voltage, pentode | ≤ 450 V, 300 V typical |
Transconductance (S) | 6,000 μmhos |
Product Reviews
I had a 1950's Fisher AZ-80 monoblock hifi amp that originally used EL37's, which of course are no longer available. Wanted to use KT-66's but most of them are too fat a bottle to fit under the tube cage. Also, the cathode bias circuit was running the KT-66's at 28 watts plate dissipation (on a 25W tube) which could not easily be rectified without mods. These 7581A's fit nicely in the chassis under the tube cage, and are rated at 35W dissipation. They biased at 28 watts idle so no issues there, and sounded great.
Not sure why you leave a tube review when you should be reviewing the post office for damaging your shipment...
I'll leave a tube review. These are wonderful tubes. I've used a pair in an Ampeg B15 bass amp clone and also rotate a quad of them in a Dynaco ST70 HiFi amp. In the bass amp, they offer exceptional bass tone with clean articulate highs and solid mids. They will break up when pushed hard, but do offer a bit more clean headroom then their 6L6GC cousins. I would say they are a 6L6GC that can take a bit more heat. In the HiFi amp they offer a different flavored tone structure then the EL34 / KT77 the amp is built around. In that amp the mids are very slightly pulled back (compared to an EL34, you'd never noticed if you hadn't listen to the amp with EL34). The bottom is tight and much harder hitting than an EL34. Highs are clean not harsh. I use these for hard rock, they hold up very well in that "wall of sound" type of music, but don't suffer with lighter stuff. I could be happy leaving them installed all the time to be honest. Add to that, they have a great blue glow when the lights are down. I have a few vintage 6L6GCs that do it too, but I've not had many new issue tube glow. Purely visual, but in an open chassis like the Dynaco, it's very cool...