I offer two matched pairs of GK-71 tubes, measured in triode connection and selected from rather big quantity.
Measurements have been done at 20V heater voltage from lab power supply, + of heater supply (common point) was connected with plate and grid1 supplies. Grid1 (control grid) bias is -30V referenced to common point, Grid2 (screening grid) is connected to Plate via 120R, Grid3 (suppressor grid) is connected to common point. Plate currents were measured at 290 and 300V plate voltages referenced to common point.
The first pair is a real dream of audiophiles, Foton 1964 year, NOS, NIB, military tests passed.
Foton Tube I 135,3mA 144,2mA Rp=1k12
Foton Tube II 135,6mA 144,5mA Rp=1k12
I ask 150USD for this pair.
The next pair is Uliyanovsk production, 1977 and 1979 years, NOS.
Uliyanovsk Tube I 123,1mA 131,4mA Rp=1k20
Uliyanovsk Tube II 121,8mA 130,0mA Rp=1k22
I ask 70USD for this pair.
It should be noted, that GK-71 in triode connection seems quite close in parameters to GM-70, but actually it is better than GM-70. Think about typical 1k8...2k2 Rp of GM-70, or 2k5...2k8 of 813 tube. SE output trafo is much more economic with GK-71.
And, since Grid-3 has a separate pin, one is free to perform experiments, for instance by connecting Grid-3 to Common point via film capacitor and observing variations in sound.
Shipment of one pair is 10USD worldwide by registered air mail with tracking possibility.
Measurements have been done at 20V heater voltage from lab power supply, + of heater supply (common point) was connected with plate and grid1 supplies. Grid1 (control grid) bias is -30V referenced to common point, Grid2 (screening grid) is connected to Plate via 120R, Grid3 (suppressor grid) is connected to common point. Plate currents were measured at 290 and 300V plate voltages referenced to common point.
The first pair is a real dream of audiophiles, Foton 1964 year, NOS, NIB, military tests passed.
Foton Tube I 135,3mA 144,2mA Rp=1k12
Foton Tube II 135,6mA 144,5mA Rp=1k12
I ask 150USD for this pair.
The next pair is Uliyanovsk production, 1977 and 1979 years, NOS.
Uliyanovsk Tube I 123,1mA 131,4mA Rp=1k20
Uliyanovsk Tube II 121,8mA 130,0mA Rp=1k22
I ask 70USD for this pair.
It should be noted, that GK-71 in triode connection seems quite close in parameters to GM-70, but actually it is better than GM-70. Think about typical 1k8...2k2 Rp of GM-70, or 2k5...2k8 of 813 tube. SE output trafo is much more economic with GK-71.
And, since Grid-3 has a separate pin, one is free to perform experiments, for instance by connecting Grid-3 to Common point via film capacitor and observing variations in sound.
Shipment of one pair is 10USD worldwide by registered air mail with tracking possibility.
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Offer another tested GK-71 tubes, 25USD per 1pcs NOS, 15USD per 1pcs used. Shipment woldwide 10USD per pair, 15USD per quad (tracking is available).
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