My Aleph3/5-BA-2-Semisouth-J2 Clone Monster

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chip_mk

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Zen Mod said:
gate current - pretty much predictable - counting on Jfet input/transfer capacitances ; small bjt is already small ..... why choking him also with smaller voltage :devily:
Click to expand...

Actually I was talking about DC current. Looking into datasheet it seems the gate absorbs probably couple of mA with no AC signal present. Generg can check this by measuring voltage drop across gate resistor R52. What is more peculiar, it seems input impedance of the SS device is negative at low Vgs which could affect stability.
 
generg

generg

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:D:D:D Thanks to all that contributed to my growing knowledge .......:D:D:D

so many suggestions I have to buy a second soldering iron.....:):)


the next days I will try some ideas and btw: does anybody know why the aleph ccs makes distortion lower but only at smaller levels of signal...?
 
Zen Mod

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Zen Mod

Zen Mod

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NB that arrangement of source/drain resistors in post #85 is different in another important/tricky/interesting way - with usual Aleph arrangement of output sense resistors, loudspeaker's back EMF is included in modulation of Aleph CCS

at least as I see it

which way you'll prefer ..... dunno
 
generg

generg

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The results are embarrassing,

With the J-fet inputstage the SemiS sound better than the IRF in the signalpath and the aleph current sound mix with the IRF is not so pleasant to my ears, so better no aleph feedback.

But with the original IRF9610 input stage and the IRF output stage it's another world of sound, more earthbound, more dynamic, sharper, a little bit more dirty in sound.

Of course not the resolution, the airiness of the J-FETs ..... It seems difficult to get both.

Is it possible the j-fet input stage I used has no good point to work, because I loose 17V over the 1k resistor leading to the SK170, from the positiv 24V ?

I did not hear Babel two crowns for over a week, because I have only one set of power supply, but for the sure it was the best sound I heard up to now.
But only 13 W at 4 ohm is not much and wanted to see what the alephs can do.
And I do not want to stop to make experiments. I think I need another set of heatsinks and so on that I can hear with the best set I have and at the same time experiment with another set.
 
Zen Mod

Zen Mod

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generg said:
.....
Is it possible the j-fet input stage I used has no good point to work, because I loose 17V over the 1k resistor leading to the SK170, from the positiv 24V ?

......
Click to expand...

that's irrelevant

that 1K resistor is just saving your CCS from excessive dissipation ;

there is no embarrassing result ... when one is learning from results

try Babelfish Two Crowns with 2 pairs in output
 
Nelson Pass

Nelson Pass

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generg said:
My main question is the Aleph CCS still working after all modifications?, Should I readjust it? In which direction to keep the high power with 4 Ohm.

Are at high power levels both, the SemiR100 and the IRF working together, so I get a sound mix?
Click to expand...

You want to adjust it for best measurement and/or best
sound. Ideally the Aleph IRF240's will not contribute
much to the sound on their own, but of course no situation
is ideal. I can tell you that they measure a little
differently than other FETs in the same spot.

:cool:
 
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