Simple Circlotron with Lateral MOSFETs

[juma]

You can't expect a single, 200mW JFET to drive couple of Volts into 390R load...

If you want to use buffer and SE2BAL convertor from post #1 just change R19 and R21 to 3k3

 

[GuidoR]

You can't expect a single, 200mW JFET to drive couple of Volts into 390R load...

If you want to use buffer and SE2BAL convertor from post #1 just change R19 and R21 to 3k3

There's no free ticket...

many thanks


Guido

 

[vilfort]

Turning this into a hybrid

A differential amp/driver stage can easily be built using 3 triodes like say 6sn7. Keep the output stage with the SK135 source followers. Then add a Mullard-like front end albeit with 3 triodes. Grounded cathode first. Then directly coupled into a long tailed pair. Each of the plates connected to the signal caps on the MOSEFET gates. Simple and sounds great. True midrange magic. No feedback.😀

D.

 

[marktmeyer]

Vilfort, I have read as much as possible of your work, and was wondering what your present take is on the Hybrid Hafler mods. I am interested in doing a tube front end to either my DH500 or one of my DH200s. Have you ever done a pc board for the tube portion?

 

[drazen]

Hello everyone,
Finally I decided to make this Juma circlotron and I can say that this sounds really great. At first it was a little problem with the layout of the wiring and unstable DC offset and the current through the output MOSFET. Now everything is stable and is a great pleasure to hear the presentation of the sound of this amplifier.
I am very pleased and grateful to the constructor on the project.
PS. Cubie will wait a while to build.

 

[juma]

Hi Drazen,
congrats on your build, I'm glad you like it !

Talking about Cubie - I got a new circuit simmering, it'll be ready in a month or three... 🙂

 

[drazen]

Thank juma,

cirklotron after the trial period need housing, front, rear and top plate, which are now under construction.
Following the theme Cubie

 

[stein2]

I'd like to add a small contribution here. Built one of these but as a completely different beast with E88CC in gain stage instead (with a lot of help from Juma and Zen, to be noted) and later needed to figure out is there any difference in sound between the original and the hybrid version, so, built one more, this one, but as I didn't want SE on input, tried a bit different approach. It works fine (huge understatement) but I usually say "fine" when I can't find anything that would bother me. On the attached images the fulldiff sch. of the gain stage, one messy image of the amp and where it's used. This amp is the black one at bottom with the big VU meters...

 

[coolnose]

You can't expect a single, 200mW JFET to drive couple of Volts into 390R load...

If you want to use buffer and SE2BAL convertor from post #1 just change R19 and R21 to 3k3

Juma,

could I use your SE2BAL from the schematic using J271 (maybe in //) by "just" inverting the supply voltages ?

Thanks in advance for your comment.

Regards,

Max

 

[juma]

It should work with P-channel JFET (J271 with inverted polarity for buffer cell) but I'm not sure if it's worth the effort - lower gm, wildly varying Idss, different transfer curve....
You'll have to test and experiment a bit...

 

[coolnose]

It should work with P-channel JFET (J271 with inverted polarity for buffer cell) but I'm not sure if it's worth the effort - lower gm, wildly varying Idss, different transfer curve....
You'll have to test and experiment a bit...

Juma,

thanks a lot for your comment. It's not about having the pretention to make it "better" ... just having the J-fets and enough to match them...

Would you have a guestimation of what Idss to aim for ?

Thanks,

Max

 

[juma]

Idss is dictated by Pd_max but it's not crucial, non-linearities are too high, as well as Zout.
I would not do it with that part, but if you insist, go for it...