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Hey Guys/Gals,

I'm sourcing parts for my build and need to know minimum voltage rating acceptable for the tone control caps in the 6-way switch for the EF86. I have some 200V russian K40s in very small values but not sure if that is enough, I'd rather use a much higher then close to limit. Thanks for the help!

The anode voltage at the EF86 is only 90 to 120 volts so your capacitors would work. However, it's a good idea to have the caps rated for at least double the expected voltage.

Thank you very much for the response I have been slightly obsessing over this the last 24hrs. debating whether I should seek-out and purchase 400v variants. My issue with that is right now all the tone caps will be K40y-9s PIO, if I go to 400v then I am 98% sure that I would have to use something else for the two smallest values. Nearly every component I spec'd is over spec'd to a degree. I bought an Elma rotary switch spec'd at 2A @ 42VDC instead of the Lorlin which is 1A @ 24VDC, have PEC 2w pots on the way and a Edcor cxpp 25w-4k primary for the OT. I am making a 2 channel Matchless clone with one channel being a Spitfire and the other based on the Nighthawk. A volume and tone for each and a master volume and it will have tube reverb. This all started because I had a Hammond 270FX that was very lonely and wanted friends to play with.

I'm ok with using the 200v caps with that type of difference in rating, at worst I think I am looking a it being like 65-67.5% of the caps rated value, that's in line or better then the cushion afford by most designs of the filter caps in the power supply. I am using 4.7M resistors instead of the 5.1M because they were availible in a resistor I wanted to use. Could someone tell me what if any difference there is going with the 4.7M for the tone control as opposed to the 5.1M? Thanks for all the help. This will be my first build.

The contour switch has a pretty subtle effect on tone from one setting to another, so using 4.7M resistors instead of 5.1M shouldn't make much of a difference. The only way to know for sure is to try both values and see if you can hear any difference.

agree with mitch m

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Stephen
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