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Re: Interstages with very high inductance

Posted by mqracing (M) on April 3, 2007 at 12:04:12

In Reply to: Re: Interstages with very high inductance posted by SomeJoe on April 2, 2007 at 20:42:26:

Joris:

Hi. I wanted to add or mention another strategy that I think works better with tubes having high or relatively high r sub p's....

I think in these cases one of the best coupling methods is to LC couple to the next stage. If your going to try to use a conventional 2 winding IT--- you'll already have the L and the C in the signal path--- but perhaps not so much optimized.

So--- why not use a grid choke where you can get several kilos of L's and the high impedances produced by that L. Yeah... you'll need to use a blocking cap in series... but remember that the series fed IT will also likely have an even larger cap in the signal path (the last C in your power supply feed).... and if you are going to use a parafeed IT (an improvement over the series fed IT) you will still have the cap in the signal path... but even the parafeed IT will not be able to produce as efficiently the L that the grid choke delivers.

then for loading your anodes... you can resistively load them or use plate choke load the anodes. I am assuming that if it's an LTP--- that you would want to use a CCS in the tail... to make it very long and tie it down...

LC coupling gives you the speed, dynamics and punch of having some iron in your diet. With none of the relative drawbacks of a bifilar wound transformer and without the sub-optimalities of trying to design a conventional 2 winding IT that is capable of delivering the same magnitude and quality of load imepedance to the anode of your driving tube as well as the grid choke can.

msl

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