First watt F2j with SJDP120R085

[kinku]

Thanks Michael. Apologize for showing off my ignorance and poor reading skills.
Will changing the second MOSFET IRFP9240 with a newer sicFet recommended?

 

[Zen Mod]

no need for that

upper mosfet is "just" decent CCS

 

[Michael Rothacher]

Aside from the lowish Pd, the Wolfspeed C2M0280120D looks like a nice part.

Approximately a 4:1 safety margin in the F2.

I seem to recall trying these in an AMP CAMP a year or so ago and the distortion was roughly cut in half. I could be mis-remembering

Thanks Michael. Apologize for showing off my ignorance and poor reading skills.

No need to apologize, this is the happy fun crew There's plenty of confusion about power JFETs in their various forms.

But if you misbehave we throw you out the little round window on the side of the boat.

 

[Michael Rothacher]

BTW: If you're looking for a pair of SJEPs to make an F2J, tell the hoarders to loose their treasure!

 

[Dennis Hui]

Mike, thanks for the reminder on the Cree part. Will add to mouser order for next time.

Kinku, have you tried contacting Dr Mazolla (semisouthfan) if he still has SJEP available?

 

[cwtim01]

Zenmode it is hard to source those SJEP jfets. Do you know any other drop in replacements ?

If you do have a nicely matched quad of SJDP120R085, I do have this quad of SJEP120R125 where we could swap. Measurement was provided by Dr. Mazolla (Semisouthfan).

I'm not interested in swapping with unmatched R085 though. PM me if interested.

 

[kinku]

Mike, thanks for the reminder on the Cree part. Will add to mouser order for next time.

Kinku, have you tried contacting Dr Mazolla (semisouthfan) if he still has SJEP available?

Dr.Mazzolla is not visiting DIY audio since September 2016. Does anyone know his email?

 

[Dennis Hui]

Dr.Mazzolla is not visiting DIY audio since September 2016. Does anyone know his email?

I guess you can try sending him a PM (look under Contact Info):

diyAudio - View Profile: Semisouthfan

 

[kinku]

Michael are you suggesting no need to desperately try for SJEP as the quality of audio( distortions) may be the same with Cree mosfets?

 

[Nelson Pass]

For an amplifier like this, the absolute distortion measurement is not the
only criterion. Each of these parts will have a slightly different sound, and
part of the entertainment is experiencing these differences.

 

[Michael Rothacher]

We cross-posted.

What he said.

 

[kinku]

no need for that

upper mosfet is "just" decent CCS

For using C2M0280120D I need to change R3 /R6 or both for biasing correctly I guess?
Thanks Papa. Decided first trial with Cree !

 

[Michael Rothacher]

I think you could start with the F2J values. You might want to put the zener back in. You could probably take R6 up a bit if all goes well and you want to try that.

 

[kinku]

What are the voltage ratings for the caps ?
FIRST WATT F2J

Is C5 a metal film resistor?

 

[Zen Mod]

PSU being 24Vdc nominal (more likely 22V5 , originating from 18Vac secondary) , all caps min. 25Vdc

C5 best if solid cap

 

[kinku]

Thanks Zen mod. More questions as I am collecting parts. What should be the Value of L1?
What should be the power supply rated minimum?
How can I calculate heat sink requirement for passively cooled design?

 

[Dennis Hui]

L1: http://www.diyaudio.com/forums/pass-labs/91168-diy-f2-clone-2.html#post1068548

PS: Standard first watt: 300VA 2x18VAC transformer.

Heatsink: F2 manual states total dissipation as 150W. You can use FW standard
chassis or store chassis

https://diyaudiostore.com/collections/chassis/products/deluxe-ultimate-amplifier-chassis

as guides.

 

[Michael Rothacher]

 

[Dennis Hui]

I have to say ZM has never looked better.

I really need a work shop and a picture of Papa to go with it.

 

[Zen Mod]

Thanks Zen mod. More questions as I am collecting parts. What should be the Value of L1?
What should be the power supply rated minimum?
How can I calculate heat sink requirement for passively cooled design?

Papa is routinely using 300VA xformer for stereo amp
just take al ook at any one-polar FW PSU

L1 is drawn as separate but somewhere in text is explained as internal inductivity of locally connected series wirewound resistor