LuDEF

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#121
yup, we both know that (and probably most of Greedy Boyz) ........ and those are exact reasons why it's done

though, I'm not overly excited with capacitances, when sorta decent enough source follower is what LU's gate sees

in present version, autoformer is main clogging device in freq. domain, but I like what it does in broader picture

frankly, I'm almost sure that I'm not going to like more any of upcoming amps with active FE, instead
 
#122
lhquam said:
I am trying to understand the "triode" character of the cascoded LU JFET. Vds is held constant via the cascoding, so any triode behavior that the JFET might have had is made to disappear. Below is a simulation, showing the LU1014 JFET with and without cascoding. The curves in the lower plots show drain current vs. Vds for 3 difference values of Vgs. The uppermost plot shows Vds across the cascoded JFET.

What am I missing about the triode behavior of the LuDEF?
Click to expand...

If you are in the low voltage high current quadrant, the curves are less concave-up and the gate probably is drawing significant current. At very high current, the device is more like a BJT.

The attached curve is Vgs from -1.2v to -0.4v.
 

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#123
Zen Mod said:
...
in present version, autoformer is main clogging device in freq. domain, but I like what it does in broader picture

frankly, I'm almost sure that I'm not going to like more any of upcoming amps with active FE, instead
Click to expand...

It is hard to get enough voltage gain out of an autotransformer with a source-follower output stage, particularly when driving much gate capacitance.
 
#124
woofertester said:
If you are in the low voltage high current quadrant, the curves are less concave-up and the gate probably is drawing significant current. At very high current, the device is more like a BJT.

The attached curve is Vgs from -1.2v to -0.4v.
Click to expand...

That low voltage region is below the voltage needed to bias the cascode FET and would occur in operation with 25V rails only when the output voltage approached the V+ rail voltage.
 
#126
Yeah, in that low voltage region, it's a mini-SIT.
Curves traced with Vds set to 2.5V before turning on the gate. Y is measured across 1ohm so current is low
Then Vgs (V) at -0.8, -0.9, -1.0, -1.1, -1.2, -1.3
Yep gotta cascode to keep it in the magical triode region.

Hmm... wonder if there is a way to trace the cascode module?
 

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#131
My Amps of high desire for 2021 (because I did not participate the VFET lottery, leaving it for others)

1. LUDef
2. SissySit R3
3. 2SK182 variations of DIY Sony VFET

Thanks of ZM, Mr. Pass and the DiyAudio Team it looks like 2021 is going to be a very good year for us greedy builders 😀
 
#132
I also did not participate as I'm already blessed with the diy Sony Vfet... Next to that I have some of the usual suspects in a drawer too, but these latter don't seem to be a guarantee for success at the standard FW voltage and power levels and I don't really want an electric stove for daily use....
Looking for a SE (H2) type of amp in at least the same league as my PP (H3) Vfet. This one seems to fit, or maybe the babelfish J2 with the 2 SJEP's that are on their way. Difficult decision!! Oh yes, and the amp needs to have a "Zen Amount Pot" 😀
 
#133
all roads are leading to Rome

whichever, build for fun and because you can and because it makes you feel better, while listening the music all the time, on whatever is handy

though, I confess - i have enormous fun producing new concoctions, while not being burdened with choice between them ...... so I'm in super position :clown:
 
#139
steve jones said:
Apologies if already covered, what is the gain and power output of the LuDEF?
Click to expand...

gain is autoformer arrangement, so almost 4V/V, meaning 12db

for power - read text on graph's bottom, first posts


Berny said:
MZM, which of your 'SE' power amp creations is making you the proudest, something like: "look ma, with no hands and no feet!!!"?
Click to expand...

ZM being, in best case, Greenhorn trumpet player attending glorious Jazz Standards, and trying to not make a mess of them ....
In other words - even with all the fun, I can't say that any of amps I "made" can be declared as my creations ...........
though, it just came to me - Iron Pumpkin is mine enough, so I can call it my creation ...... damn proud and damn cocky about 🙂


flocchini said:
Rome = Nirvana?????
Click to expand...

yup, even Nirvana is 'Talian invention :rofl:


marconi118 said:
Any comment if the lu1014 triode cell sounds bettere in LUDEF or in Single ended Amp. Like the pass Sony Vfet Amp?
Click to expand...

can't make parallels as that .... you can make comparisons between apples and oranges only if using them with speakers which both apples and oranges can feed properly
ok, not so hard condition, for me easy, and then I can't say which is better, when properly made - there are obvious differences but, when something is good enough, you can't simply say it is worse or better than something else, also being good enough

choose by color of case ..... or anything else , not involving ratio :clown:
 
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