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RE: OPT for 2A3/300B design

Posted by drlowmu (M) on July 11, 2011 at 10:18:35

In Reply to: OPT for 2A3/300B design posted by masterofdisaster on July 10, 2011 at 19:37:15:

Hi,

You state this :

"I'm using some highly modified Khorns with constant impedance crossovers. My flavor would to have be an extended bottom end."

here is how I would do this :

K Horns are about 105 dB, you will operate at about 1/4 to 3/4 of a watt most of the time, so you do NOT need to use or consider the worse-sounding 300B tube.

You can easily use a 2A3, or even a Type 45 on your load. My vote would be to build a JJ-2A3 40 amp with 250 VDC P-K and about 42 to 43 mA. current.

"My flavor would to have be an extended bottom end."

To get that GREAT low end, (and great voltage stability, self regulation), you want to have low DCR iron in the power supply / B+ filters. Do a Pasternak Flywheel L1 using a Triad C-56U with 20 uF C1, and use the new 27 Ohm DCR Edcor 2 HY Ls as L2, with 50 uF as C2, feeding each 2A3 tube.

This will "ROCK your socks off" on the low end.

It would help to have a low DCR power trannie also, about 20 Ohms DCR (or less, I use 9 Ohms) across half the HV secondary (center tapped ground to one end of the HV winding).

Then you are on your way to "fly with the eagles". Use two 5U4s to rectify the B+.

Load the 2A3 hard, use 2.5K to 3.0 K for the output trannie, not 5K !!! No "polite" amps please, we want the K Horns to sound realistic. Lets boggie some cats !!

Jeff Medwin

Edits: 07/11/11

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