do you know what difference between positive and negative bias in a tube power amp ?

[tony ky ma]

maybe not everybody knows about bias in a tube power amp . bias is a in-put voltage to tube for control the current through the tube and this current is driving the speaker to sound. almost 99% of audio tube is in negative bias (-v), like 300B in -74v bias will have 60ma of 350v supply to a 2.5K transformer can delivery 8W of 8 ohm speaker in single end amp, for more power 845 in 1000v 100ma can have 20 watts SE also in negative bias. but this type needs protection for bias failure, once when bias turn to 0 will melt down the tube. Mr. shisido in Japan found some transmitting tubes have no more jobs in transmitting and try to convert to use in audio because price were very in bargain with supper quality, like tubes in picture, if put it in negative bias will needs very high voltage supply (over 1500v) also don't sound good too, so he found out positive bias for those tubes like 826 in +26v will has 100ma in 250v supply same 8 watts out put, also on the top sound quality much better than in negative bias use , sound worm thick with more 3D body image, 809 with same 8 watts, 812A 808 will have 12 watts, 838-30 watts, 805-45w, 810-50w, 833-100w, all in SE amp. these tubes are very tough because they built for commercial and military , no protection needs for failure bias, 0 bias means less current, the only thing is need a power or semi power tube to drive the positive bias because of low impedance. not too many bland name with positive bias amp in the market, only WAVAC in production, they got the right from Mr. Shisido but in very high price or you can build your own . I started tube with EL34, 6550 and later changed to 300B, but now all my 4 amps for my 4 ways system all in this type
tony ma

 

[FrantzM]

Those who like tube amps have a positive bias, those who don't....

 

[tony ky ma]

It is hard to say tube amp is the best, it depend on personal favor, but one can check with his own system to see the amplification is right or not, first, will not feel sound come from the speakers unless face close to the speakers. next turn volume control up and down and see the sound stage is moving or not beside the loudness changing, turn up, sound stage feel get close to you, and turn down, feel go far from you, not only the loudness change. if it can't be like that ,means need improvement in amplification
tony ma