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FS-100 PF and GM70 and 845 amp DIYers

Posted by Tanker (A) on June 16, 2018 at 08:06:16

I have both FS-100 PF and FS-100 choke from Mike still sitting in the shelf. It's been 10 yrs since I have not touch the soldering iron. I think it's time for me to start my hobby journey again.

1. What are your recommending on operating point for GM70 or 845 and a single stage driver tube for SE? I already have preamp so gain is not a problem. I might interest in driving it into A2 also if A1 does not have enough juice to drive my Merlin speaker. But for now I think pure class A would be fine to drive it.
2. For power supply transformer currently I have 1400 VRMS @300mA. I plan to use full wave bridge rectifier. The plan is using 5R4WGB or 866A with choke input filter. Choke will be installed on the low/return side of the supply for sure. I know I need 3 separate filament tranny for the fullwave bridge. Any recommendation on other rectifier and Damper diode tubes besides 5R4 and 866A? Any problem you see in using 5R4? Any advice on designing such high voltage power supply would greatly appreciated.
3. I have long thought about the capacitors for power supply as well as output cap for the parafeed. 2000 V plus is not easy to find. So the plan is to use 1000V-1100 Volt cap rating connected in series. For output coupling I am able to find 6uF @2000V oil cap. I wanted to use quality cap but not really sure if they rated this high of the voltage. Any brand of output coupling cap do you recommend?
4. The plan is to have two separate mono blocks for left & right. In addition power supply will be separate from the main driver and output tube components. Therefore, the system will have 4 blocks. The reason is that I wanted to build and use this as a universal power supply (including negative bias voltage) for modification later to drive other configuration.
5. Thanks in advance for all the inputs and recommendation. Also understood Mike does not warranty on using his gears on such a high voltage.

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