questions about your FCUPS

[f1802llk]

Dear Brian,

I am thinking about getting one of your FCUPS for my PP KT-88 integrated amp which is similar to your Ella. With four KT-88 tubes biased at 50ma, and add in driver, input, and bias supply, I'd need about 260ma total from the PS, I guess. Do you think it is feasible for my amp using just one FCUPS module by adding some extra caps? Your mentioned that there are points for adding 20uf caps right after the rectifier and 20uf after the electronic choke to increase the current, would it be ok if I add 33uf after the rectifier, and will this give me even more current?

Finally, if I use it in virtual battery mode, can I add some RC sections to provide B+ for driver and input stages? Or do I have to use it in virtual choke mode in order to do this?

Thank you,

Frank

[f1802llk]

Dear Brian,

I have one more question: with the maximum input of 380AC using diode rectifier, what will the B+ voltage be coming out of the power supply module?

Thanks,

Frank

[brian]

Hi Frank
The main limitation on the current draw is caused by the ripple in the 1st stage. So if we increase the current draw of the FCUPS then we need to also knock down the ripple or things will start to overheat. At 350 V and 250 milliamps the peak to peak ripple is about 75 volts in the 1st stage. If we place an additional 40 uF (or total of about 60 uF) we knock it down to about 25 V peak to peak which will create far less heat. 75 V will likely lead to MOSFET thermal clamping, but 25 V is no problem. so if we follow the capacitance vs. voltage scale as written in the instruction manual then one FCUPS module should be good for 250 milliamps from a 350 V/0.5A winding. voltage output would be between 422 440 V. On the B+.
Yes no problem adding CR after the FCUPS to supply the driver stage.
So as to whether it would work in your amplifier, if you could tweak your voltages back just a little it should be OK.
Regards
Brian

[f1802llk]

Dear Brian,

Thank you for the reply. Would it work if I put your FCUPS after the conventional CL, something like: AC in -> rectifier -> filter (C) -> choke (L) -> FCUPS, with about 520V after L and going into your FCUPS? If this works, then I don't need to redesign my amp with lower B+ in order to use your UPS, and presumably, I don't need to add extra capacitors to your UPS.

Thank you,

Frank

[brian]

Sure, the less ripple going in, the less stress on the filter components.
And you still get the power and punch of the FCUPS.
Brian