• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

KT120: When does it starts to sing ?

I have exchanged my EL34 with the KT120 for testing purposes. Both run at [email protected] For the EL34, a good operating Point as 350*0,55=19,25 Watt. For the KT120 I guess not optimal.

Ths question is if playing with the bias (easy) or the voltage (difficult), will Change the Sound in what way.

Currently the KT120 has a very good Body, a very good depth, but at the same time it Sound like a liitle curtain or minimal fog is between you and the musicians. While the EL34 is mor like you can touch them. The EL34 is nevertheless a Little less good organizes interms of who stands where, both left-right and front-back.

Does anyone have made the comparison and can share your experience ?

Best Regards
 
What transformer are you using Raa?? If the outputs are 5kRaa or higher, give the Russian 6P3S and 6P3S-E a try, better suited to 350V, but back off the bias. The 6P3S-E wafer base sound great and are low cost. The down side is that they cannot drive low impedance transformers, they run out of steam. For 4.3kRaa iron I use 6550 or Kt88's, I would recommend the Kt120's for 1.9Kraa applications with decent B+ 400 to 450V and run the heaters at 6.3V or a little hotter do not exceed the 6.9 limit. . A major design concern is over the input miller capacitance, the grid 1 capacitance difference between the EL34 and Kt120 are about double, 15pf to 29pf... The KT120s have to be driven to overcome that. The best substitute for EL34's that I like are the Svetlana 6550=C= tubes, best clarity and sound stage, better sound with less feedback needed.