Tube KT90 Single Ended Amplifier
I’ll try to use KT90 KT90 tube origialy of EI, EI, but a long time ago and set very difficult, an AE of avian EH KT90.now get. Valve origin PL509 sweep tubes for color TV and a high plate.JJ PL509 new type. But without top-modified thin plate.so new valve on the PL509.
EH KT90 plate size is exactly the same size China.very Slim EL156 skiny.I will try a KT90 KT90 use now.some said that even KT88.but tube plate is slightly larger and has the power, KT88 disspation 50W. I am now and wait while KT90.
Important: KT90 is not a replacement for the KT88 and 6550th some exsample said triode connection and B + is 300V
Bias is approximately 40V with very different usage 2.5kohm KT88.few amplifier and anode current are 300V ~ 80mA to approx.
KT88 is compatible to 3.5 K ohms and 80 mA at 390 V amplifier is difficult to use. the tension plate, I 405 V voltage, even when the use value KT88/6550.no bias.slightly need to drowning that KT88.81mA with 390 ohm cathode 10W.voltages 32V.sound is very clear and low CEDA is very clear that the KT88, but envy and high tones, as KT88SE power.mid few. See circuit diagram.
Then two components are replaced.now I + B is 93mA and the cathode 394V.29V voltage.a little softer than before.sound of 80mA, then and now better than metal before.few days later, replaced tube driver from 6U8 to 6AN8.
Load impedance transformer 2.5K ohm.this time using audio-OPT-20S Toei.Power Tango Transformer MX205.
The tube drivers will be replaced by Russian Mil Spec 6AN8A 6F1P NOS. This tubes 6AN8A is good, but the tubes are expensive and very difficult to get a good time.
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