2sk77b

[flocchini]

Very nice !!!!

 

[Zen Mod]

Bob , will reply to emails I owe you tomorrow , now I'm too sleepy 🙂

anyway , regarding your own development - if you did one channel , there is no reason that second can't work in same manner

there must be "just" some series of mishaps you had , so now you're simply unsure

methodical approach must result in working channel ..... and Papa's solution with that resistor as bias generator is not just elegant , it is also clever and effective - working in output node voltage stabilization , with mains fluctuations

what I drew with regs etc. is not better , it's just different ........ excercise of making amp which isn't exact copy of his

and , NB - he did all developing work .... I'm more or less just carbon-copying here .... difference is just Lilly-guild

 

[flocchini]

Thanks ZM
Totally appreciate Nelson's solution - having trouble with my implementation - its on me
I do like your boards !!!!

 

[Itsmee]

...pick one that shows a DC SOA line...

Good advice, the IXKN40N60C doesn't show one, so I tried to cook it, 4 hours at 36.5V 2.1A ~ 75W. I measured the source screw at 89°C! - not sure how accurate that is with an IR gun, the hottest part of the package was 76°C. My test bed heatsinks aren't that big, I need to bolt a couple together to push it further.
I have used some in a push pull amp for a few months without problems, +-24V rails at 2A bias.

 

[flocchini]

ZM

No worries re emails - just my brain rattling.

Best

Bob

 

[grimberg]

ZM,

I think you need to change the SMD bridge rectifier code on the diagrams, as DBDB101G does not exist.
I found On Semi DF02S and DF04S capable of 1A5 forward current and 200V and 400V PIV respectively. They are both in current production. I am guessing you will like one of them as suitable replacement.

 

[Zen Mod]

tnx Grimberg , good eye 🙂

though - you know that I treat BOMs as Dodos - always making my own and ordering what I really see on Vendor's site

rectifier in question is common breed , I'm using exactly same package in PSU for Iron Turtle relays , frankly not remembering data , but more than good enough for task

if I ever make a list of parts , it would be named as xxxV/xA/xxx package

 

[grimberg]

I am with you regarding the BOM as I like to select my own parts. The issue is the footprint you used on the PCB, which appears to be SDIP-4. The number of available devices in that package is limited, with Mouser showing only 6 active ones. There are many more through-hole devices available, in case you want to go old-school.

 

[Zen Mod]

nope

DFM , DIP-4, WOG ........ all of these you can squeeze in 4 holes 🙂

regarding your SITs - you need to test them in exact same conditions as in intended circuit - aroundish 30V of Uds and 3A Iq

for that you need gate voltage source too - say starting from -5V and going up

you can use 9V battery ...... or even Li-Ion 3V7 , with 10K pot across

heatsink it

entire setup funny drawn in SissySIT thread ........ somewhere

anyway , here it is , again

all that , presuming that you want to build amp shown in post #2 of this thread , also attached here

if you want to build what I proposed (most recently) , The World is your Oyster - just tell which and how many of N channel JFets you are having (speaking of input buffer parts) ?

 

[grimberg]

I want to build the version you are proposing, as it contains the input buffer. For that, I have a few 2SK170 from Mouser's last batch a few years ago. I also have some 2SK389-V acquired during member Tiroth's group buy in 2004.

 

[grimberg]

nope

I just realized that the cryptic "nope" at the beginning of your reply means you did not specify SDIP-4 but rather 4 through-holes and I misinterpreted the PCB preview you posted. Interesting, after so many years talking to you, now I am finally starting to understand you.

🙂

 

[Zen Mod]

🙂

you got it ....... 4 holes , and you can even solder those SMD ones (you mention) on them

been there , done that

pair of 2SK170BL per channel will do the job
2+2 even better

save those 389 for something demanding more Kosher parts ........

say that you have 4 pairs of 2SK170 ; JFets in pair being so-so close each to another (say 0.5mA) , while pairs being 1mA or so one from other

LTP is having two sides

one pair being A1 and A2 JFet , second pair being B1 and B2 JFet

combine A+B on one side of LTP ,leftover A+B to other side of LTP , trying to have close sum of mA on sides

hope I explained it well ......... trick used by Pa i n J2 - where he was using 2SJ109BL , two of them , but spreading JFets in one case between LTP sides , doing same with second 2SJ109BL ........ having same amount of mA Idss per LTP sides even when JFets aren't identical

Old Bull always having some tricks to teach young ones .....

anyway - same trick can be applied on two groups of JFets here , even if this isn't LTP

 

[grimberg]

🙂

hope I explained it well

You did. The only thing missing is the individual Idss of each member of a pair. Should we select each JFET wih Idss around 7.5 mA to 8.0 mA, or higher?

 

[grimberg]

Old Bull always having some tricks to teach young ones...

Robert Duvall playing Officer Bob Hodges made that very clear.

🙂

 

[Zen Mod]

You did. The only thing missing is the individual Idss of each member of a pair. Should we select each JFET wih Idss around 7.5 mA to 8.0 mA, or higher?

pretty much whatever you have

I chose sum current ( for 3pcs of 2SK2145BL paralleled in each section) of 20mA , arrangement I'm already using in Iron Pumpkins and SissySIT/B. M25, and that's way bellow Idss of each

so , sum current is what counts , and if you use them more , not a problem

make a list of JFets you have and I'll comment what I'll do , being in your boots

 

[Soundhappy]

Thanks AnthonyA and Zen Mod for 2SK77B datasheet sharing.
BTW others SIT's have interesting similar characteristics.
Mr. Michael Rothacher " example are legendary L'Amp 2SK180

 

[Soundhappy]

Good evening, gentlemen.
Where can we find real 2sk77b?
Thank you

Or maybe FAL Company get spare ? FAL Loudspeakers, S I T Amplifiers

 

[Zen Mod]

I see Cotton!

superwarm!

 

[petoluk]

SSAP4002M

A while ago, 5 of these SSAP4002M pucks were auctioned on Yahoo Japan; with my never-failing luck 😛, I only managed to score one of them, but I thought - it's just a 2SK77B with a house label, I'm bound to find another 2SK77B somewhere...

Well, to my utter astonishment, this turned out to be a P-channel SIT! 😱

(My curve tracer is out of order now, so I did just a quick test using the Atlas DCA75 Pro [not really useful for power devices, but better than a poke in the eye].)

 

[Zen Mod]

whoa!