SemiSouth boiler room

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Of course it varies with bias and a little bit from device to device, but at VDS = 11.7 V and ID = 1.38 A and VGS = 1.575V, I have data for one SJEP120R100 where rds = 91 Ohm and gm = 10.8 S so mu = rds*gm = 983.

How the drek (thanks zen) can a power JFET with these specs get anywhere close to the operation of a real 6L6 Tube?

Are there characteristic curves of this modified R085 device you'd be willing to share?

I can guess there might be some serious source degeneration and/or VGS attenuation going on in there...
 
How the drek (thanks zen) can a power JFET with these specs get anywhere close to the operation of a real 6L6 Tube?

Are there characteristic curves of this modified R085 device you'd be willing to share?

I can guess there might be some serious source degeneration and/or VGS attenuation going on in there...

In the solid-state tube, we are not modifying the SJDP120R085 JFET so much as we are using it in an application. We use a 6L6 data sheet to determine the characteristic curves. 😉
 
Surprised that one would want to emulate a 6l6.
My '64 Fender Bassman uses those tubes (AA864).
Works fine, has done since I bought it used, in early 70s.
Amazes me that someone would go to large efforts to replicate such
I mean it is good.. but it Ain't That good.
Most of it's popularity with Guitar people lies in it's Vintage (drifted resistors 😉 sound.
 
Trying to read between the lines, Papa told us he was testing these awhile
ago and we haven't heard an encouraging review so I'm assuming not worth it?

I did test these, and I liked the UJN1208's particularly, and so far they appear
to be the best depletion mode power JFET I have, by a small margin.

Here are some curves operated Common Source into 8 ohms, with Vds at 32V,
and 2.3A bias.

The distortion vs amplitude shows three bias settings, with +2nd harmonic,
-2nd harmonic, and suppressed 2nd (the lowest).

The distortion vs frequency is seen with low impedance vs high impedance
sources as are gain/frequency response.

😎
 

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In the solid-state tube, we are not modifying the SJDP120R085 JFET so much as we are using it in an application. We use a 6L6 data sheet to determine the characteristic curves. 😉

Hello Dr. Mazzola.

Does your note above suggest the current designs with R085 continue to use the Bender's original power output transformer? Do you foresee a change to a different power output transformer which can manage a much higher current at reasonable Vds with R085?
 
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