|
SET Asylum Single Ended Triodes (SETs), the ultimate tube lovers dream. |
|
|
|
SET Asylum Single Ended Triodes (SETs), the ultimate tube lovers dream. |
|
In Reply to: Thank you posted by Tre' on January 29, 2015 at 09:10:41:
Hi Tre:I didn't check your calculations or anything but I think
you got the picture.Just using a small signal model will make some crudballs
look like their ready for prom night...the tougher test.. and the more realistic... is the large
signal test.I found the following text on a Lundahl spec sheet...
to explain large signal vs small signal....FPL= large signal
FRL= small signalWe define Power Low Frequency Limit, FPL, as the frequency where wLP = RLOAD. (The reactive impedance of
the transformer equals the primary load impedance). At FPL, the output power is reduced to 50%.We define Response Low Frequency Limit, FRL as the frequency where a (small) output signal is reduced with
-1 dB due to finite primary inductance. FRL = w / p, if you solve w in
wLP = (RLOAD in parallell with RANODE).
In the FPL when the power is reduced by 3db the phase angle of the load impedance will be 45 degrees. Instead of your loadline being a straight line it's going to begin to look like a NFL football (i.e., ellipse). Your tube generated distortion is going to increase dramatically and that isn't even taking into account that the transformer borne distortion will also be going up at the same time.Plate curves assume a linear with frequency unchanging
pure resistance is loading the anode of the tube. If your instead loading the anode with a transformer... nothing could be further from
the truth. Now you must take into account the characteristics and functioning of the transformer... cause now we have reactive components in a complex relationship with "pure" resistances.Now the effective loadline can look more like a football or beachball.
And this elliptical loadline changes shape with frequency... so that your tube now has to drive an everchanging loadline....and it aint going to be pretty when having to do all that work.So instead of focusing on the "easier" small signal response... looking at and evaluating the large signal response (the decidely tougher test) will be much more predictive of how well your tube and circuit will perform.
MSL
Builder of MagneQuest & Peerless transformers since 1989
Edits: 01/29/15 01/29/15 01/29/15
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- RE: Thank you - mqracing 10:21:31 01/29/15 (0)
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2024, Audio Asylum, all rights reserved ]
