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RE: Spice- I think I got it but.....

Posted by Tre' (P) on November 23, 2014 at 17:45:11

In Reply to: RE: Spice- I think I got it but..... posted by deafbykhorns on November 23, 2014 at 17:07:08:

To bypass the 300b cathode so that the -3db point is 2Hz so that 20Hz is flat and not phase shifted it would take a 185uf cap.

For 5Hz giving you 50Hz flat and phase shift free it takes 74uf.

With the 40uf cap you have in there, your sim, and the math shows, a -3db point of about 9Hz meaning there will be some measurable amplitude loss and phase shift all the way up to 90Hz, as shown.

Some people make a lot of different claims about this subject by that's just the way it is.

I didn't check the value for the input stage.


************

I assume the sim is taking into account the whole circuit, output transformer and all. It doesn't look particularly bad to me.

You're only down a fraction of a db at 20kHz.

From my way of looking at it,it's fine. I don't play bass with tubes
anyway.

Get some nice woofers and a SS amp and cross them at 100Hz and let the SS amp do what it does best and let the tubes do what tube do well.

I mean, what's the impedance of the output transformer? 10K?

With the 211 plate resistance of about 3.3k you end up with a damping factor of 3.

That's not going to control the speaker at bass frequencies anyway.

From the asterisks on down was just me thinking out loud, do whatever you want. :-)



Tre'


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"Still Working the Problem"

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