Tube DIY Asylum

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RE: 5R4GY and filter cap values

Posted by drlowmu on March 21, 2017 at 08:43:47:
A capacitor input filter ( first element after the rectifier tube ) is the worst possible design to have. The bigger the cap in uF value, the worst - off is the design.

The best practice is to always have a choke, of some kind, with adequate current rating, and lowest possible DCR and mass, as the first element the tube rectifier sees.

Chokes in tube amps, as for example, a 2A3 amp, need to all be 20 Ohms or less in DCR, and there is an advantage to getting down to ten Ohms or less. A double L/C section B+ filter is tops, as in L1/C1/L2/C2 to the Finals.

If employing high drop rectifiers, like a 5R4 or a whimpy 5Y3, you should avoid using larger uF C1 input cap values, its NG, design - wise, on a long-term reliability basis.

Jeff Medwin