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 16th July 2004, 01:59 PM #1 fscarpa58   diyAudio Member   Join Date: Nov 2003 Location: Genova, Italy An Ultra -linear question Hi all, I have a serious problem with the concept of ultralinear characteristic curves. Suppose I have to find the static working point of an Ultralinear connected SE amplifier. I'll simly use the triode-connected plate curves since in static condition there is no difference between plate voltage and G2 voltage (a part from the different due to the DC loss in that part of the trafo). Well, but in dynamic conditions the voltage at g2 is a definite fraction (e.g. 40%) of that at the anode so the behaviour of the tube is very different and the triode curves become useless. However, I always read that the Ultralinear curves are traced by applying, in a slow variable way with two different generators, two different voltage to g2 and the anode respectively, being one 0.4 time the other. but this is very different from the real static case of trasformer loading where the static voltages, a part from the fall in the primary, are equal. So, it appear that the ultralinear curves refer to the dynamic case. Certainly, if one uses the UL curves to find tha static point, he will go in troubles and obtain wrong results. It seem , may be, that we need a different dynamic plot for every static work point. But it is impossible. I am very confused. Can somebody help me ? thak you in advance Federico Scarpa
 20th July 2004, 03:54 PM #2 fscarpa58   diyAudio Member   Join Date: Nov 2003 Location: Genova, Italy Hi, Also your opinions on the subject are welcome. Federico
316a
diyAudio Member

Join Date: Dec 2002
Location: West London
UL

Quote:
 Originally posted by fscarpa58 Hi, Also your opinions on the subject are welcome. Federico
Hello ,
I have also been pondering on the same subject as I'm about to press a quad of EL38 into UL service . The EL38 datasheet only shows pentode curves and this type does not seem to be used often for audio so I have been using comparisons of other similar valves such as the 807 and EL34 . On the Audiomatica website there are characteristic curves for pentode , UL and triode for the EL34 and 807 , may be worth a look

cheers

316a

 21st July 2004, 04:53 PM #4 fscarpa58   diyAudio Member   Join Date: Nov 2003 Location: Genova, Italy Hi 316a, thank you I know those curves but I really do not understand static versus dynamic description of UL connected tubes. It seems impossible to me to represent both static and dynamic UL behavior with the same curves. I'll continue to scan the web. bye Federico
 29th July 2004, 12:12 PM #5 fscarpa58   diyAudio Member   Join Date: Nov 2003 Location: Genova, Italy I don't find anything on the subject clearly explaining UL plate curves. any idea? Federico
 29th July 2004, 12:28 PM #6 SY   On Hiatus     Join Date: Oct 2002 Location: Chicagoland I guess I'm confused by the confusion! The static points need to be determined by static curves. Analysis of the dynamic operation requires dynamic curves. Remember, in the case of UL, the voltages are being applied via a transformer by definition. So they are different in that sense than pentodes or triodes, where there's really no difference between the AC and DC voltages. As a side note, EL38s work very, very well with a 6600 ohm p-p, 43% UL taps, and about 490V on the plate. I got 45 watts out of this configuration. __________________ "You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is."

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