Well said. Interesting thing watching a person out of their comfort zone. Thanks for the help. I may need it again.
This concerned a question I had about using 2SK2013/2SJ313 in F4. Would anybody care to explain the reason for this being a bad idea. I don't doubt it, just don't understand why. I know on the F4 thread, there was discussion of how the mismatch of the 240/9240 fets had a part in the sound of the amp. I believe it was a factor in the 2nd vs 3rd harmonic nature of the amp. What is the devil in this detail?
well - calculate needed number of them to have same current capacity as originals , then calculate what's capacitance as seen from driving end ; then decide .
maybe that wasn't so bad idea as I implied , but I prefer using some other - more robust - laterals for said job .
Zhou have them all
edit: - I'm not tricky for not saying numbers , but too lazy to remember ( even if I have them in my shop) and too lazy to see what outputs are used in EUVL's SUSY F5 ; I'm thinkin' on those
maybe that wasn't so bad idea as I implied , but I prefer using some other - more robust - laterals for said job .
Zhou have them all
edit: - I'm not tricky for not saying numbers , but too lazy to remember ( even if I have them in my shop) and too lazy to see what outputs are used in EUVL's SUSY F5 ; I'm thinkin' on those
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So you are worried about Miller effect and paralleling of outputs. They have about 1/7 the Ciss and 1/10 the Yfs of their counterpart, but more linear as Juma has said.
Zen, can I ask another question regarding capacitance please? I see in the datasheet is a graph that shows capacitance vs temperature, does this add to the miller capacitance? I saw the increase was quite alot for running 50C.
they'll be at >50C anyway
regarding capacitances - I mention that as general - you must calculate on that always ;
in this case I'm primary not feeling right using plastic cased devices for task , if we have more rugged ones
regarding capacitances - I mention that as general - you must calculate on that always ;
in this case I'm primary not feeling right using plastic cased devices for task , if we have more rugged ones
I didn't see that in the datasheet. Where is it. I saw temperature plotted vs I and Vds
In a 25-30W SUSY version of BA-2, they seem doable. I am going to build the standard F4 and F5. Then compare to J4 and J5(J for Juma!) should be easy switch with minimal changes. ZM, have you tried them in your Pumpkin? Have less gain, so i guess this would hurt V swing.
Generg tried them in 
; it's best to ask him ( he'll respond , as always )
I'm , as always , lazy bastard , when that type of tweaks is in question
; it's best to ask him ( he'll respond , as always )I'm , as always , lazy bastard , when that type of tweaks is in question
My F4 is up and running: finally!
Thanks so much for this: after having parts sitting around for a long time I finally did the metalwork and got my F4 going using these extremely clear and helpful guidelines.
I'll post pictures as soon as I can: in the meantime it's sounding fabulous with my Pi Seven speakers. I'm using an Audio Research LS-3 preamp to drive the F4, but my plan is to build a BOZ.
And thanks of course to Nelson: we met briefly at the Burning Amp and you were kind enough to provide me with some transistors and a heatsink, among other bits.
The bass control and ability to separate instruments is the most striking first impression: Head Hunters is electrifying, and Charles Mingus' bass is astonishingly lifelike. Oh, and it's absolutely completely quiet: I've never had an amp so quiet.
It's replacing a Music Reference RM-9, which is no slouch, and has done great service over more than 15 years.
Tim
Thanks so much for this: after having parts sitting around for a long time I finally did the metalwork and got my F4 going using these extremely clear and helpful guidelines.
I'll post pictures as soon as I can: in the meantime it's sounding fabulous with my Pi Seven speakers. I'm using an Audio Research LS-3 preamp to drive the F4, but my plan is to build a BOZ.
And thanks of course to Nelson: we met briefly at the Burning Amp and you were kind enough to provide me with some transistors and a heatsink, among other bits.
The bass control and ability to separate instruments is the most striking first impression: Head Hunters is electrifying, and Charles Mingus' bass is astonishingly lifelike. Oh, and it's absolutely completely quiet: I've never had an amp so quiet.
It's replacing a Music Reference RM-9, which is no slouch, and has done great service over more than 15 years.
Tim
My F4 pictures...
😀
😀
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
That looks like the picture you see in the dictionary if you look up
craftsmanship.
I like the rake of the channel boards.
😎
If you look up barnacle, you will see my picture
craftsmanship.
I like the rake of the channel boards.
😎
If you look up barnacle, you will see my picture
You are too kind. I"m not much good at metalwork, so I used a standard door lintel extrusion (a bit thin, but cheap) damped with that stick on stuff you get for car panels, and a bit of plywood with redwood strips for the front and back.
I angled the power boards because I thought it would spread the heat across more of the fins.
I'm happy to bring it up...I don't think I can bring my speakers, though unless someone wants to help me with a truck...
An externally hosted image should be here but it was not working when we last tested it.
I am wondering if I can use +-40V supply for F4.. Using LT1084s to regulate it @ +-23V for J-FET stage, but unregulated +-40V for power mosfets?