RE: How can the interstage drive either 300Bs or 2A3s without any modifications? - Acoustic-Dimension - ANK AudioKits Forum

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RE: How can the interstage drive either 300Bs or 2A3s without any modifications?

Acoustic-Dimension

In Reply to: How can the interstage drive either 300Bs or 2A3s without any modifications? posted by Frihed89 on April 30, 2010 at 16:11:46:

They don’t use the ‘same’ power supply. There are different voltage taps on the powertransformer. This way the 300B is supplied with a higher B+ then the 2A3.

The voltage on the interstage transformer and driver tube is lower then the high tension on the 2A3 output tube, so with a different voltage dropping resistor ( 300B versus 2A3) in the power supply, it is made sure that the tension on the driver tube is correct.

With a driver tube and interstage that is designed to drive a 300b tube (to be able to provide the needed voltage swing), driving a 2A3 tube is no problem as the 2A3 requires less voltage swing.

P.S. a 300B (in it’s normal A1 operation point) does not need a driving current. That’s the difference between tubes and transistors, tubes require no current, only voltage.
But the 300b requires a very large voltage swing. Not many drivers can supply this (without distortion). When you change the anode load from a resistor to an interstage, the interstage will give you about 40% more voltage swing at the same distortion, or for the same voltage swing about 40% less distotion, and the the distortion also has a much nicer distibution of the harmonics.

An interstage does not care which tube it has to drive, the only important thing is making sure that you select the right driver tube. The driver tube must be able to supply the needed voltage swing and (very important) have the right internal resistance. It can’t be too low or too high. A driver tube with a to low or to high internal resistance will turn the interstage into a ‘tone controle’

Best regards, Peter

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Follow Ups Full Thread

Topic - How can the interstage drive either 300Bs or 2A3s without any modifications? - Frihed89 16:11:46 04/30/10 (7)

RE: How can the interstage drive either 300Bs or 2A3s without any modifications? - Acoustic-Dimension 03:17:17 05/16/10 (0)

RE: How can the interstage drive either 300Bs or 2A3s without any modifications? - GTCharlie 01:34:05 05/01/10 (5)

Yes, but...the advertising doesn't exactly say that. Nt - Frihed89 23:26:31 05/02/10 (4)

Si would like to know truthfully how the interstage kits for the parallel 2A3 and 300B differ - Frihed89 23:27:47 05/02/10 (3)

RE: Si would like to know truthfully how the interstage kits for the parallel 2A3 and 300B differ - GTCharlie 03:13:29 05/04/10 (2)

RE: Si would like to know truthfully how the interstage kits for the parallel 2A3 and 300B differ - RC Daniel 20:56:14 01/02/11 (1)

Thanks - Frihed89 08:41:32 02/18/11 (0)

Follow Ups

RE: How can the interstage drive either 300Bs or 2A3s without any modifications? - Acoustic-Dimension 03:17:17 05/16/10 (0)

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