Starting new kt120 UL project.

[catalin gramada]

Hello. Get new toys thinking to start a new project. 4xKT 120 in UL mode . 650 V / 2300k load. Power supply plan:

[nickb]

A UF5408 does not have a high enough reverse blocking voltage for this. Worst case 470VRMS = 658V peak and the diode will have to block twice that = 1316V. You need to you two in series in each leg of the bridge and use say 1M parallel resistors to equalise the reverse voltage across them. That's total of 8 diodes and 8 resistors.

[catalin gramada]

A UF5408 does not have a high enough reverse blocking voltage for this. Worst case 470VRMS = 658V peak and the diode will have to block twice that = 1316V. You need to you two in series in each leg of the bridge and use say 1M parallel resistors to equalise the reverse voltage across them. That's total of 8 diodes and 8 resistors.

Thanks Nick

[Leo_Gnardo]

Hello. Get new toys thinking to start a new project. 4xKT 120 in UL mode . 650 V / 2300k load. Power supply plan:

Looking forward to see how this develops. I have been intrigued with KT120 since they came out but never bought any to try. Amp should have plenty of kick I expect.

[catalin gramada]

Hello.
May I use 1900k OT for a kt88 quartet in UL mode, supplied at 600V, please? Thanks

[Helmholtz]

May I use 1900k OT for a kt88 quartet in UL mode, supplied at 600V?

KT88 datasheet recommends Zaa = 7k for a pair at Va = Vs = 560V with UL (40% taps).
That results in Zaa = 3.5k for a quartet.
Generally it is advisable to increase Zaa with higher Va.

I think you could use your OT if you double speaker impedance.

[pdf64]

Dunno how accurate this online loadline tool is https://www.vtadiy.com/loadline-calc...or/#calculator