Babelfish F8

[Zen Mod]

There was/is Scryer ........ but - as Everyone and His Cousin is making Not Exactly Clone Of But DIY Version ....... here is mine

Just enough difference to original one, that I can call it Babelfish, but also iteration enabling every Greedy Boy to make it, needing "just" pair of moderately matched 2SJ74 (any suffix) or readily available LSJ74 instead

OS devices for Desperate Poor Greedy Boy are IRFP150, while "just" a pair of Semisouth SJEP120Rxxx will bring you to Ultimate Sonic Bliss, Nirvana, There is No Go Further yadayadaetc.

Here, funny pics

Dual rails, regular FW Format rails, Iq settable in range of ~ 1A25-1A8, with Zen Amount Pot (Copyright my Bruder @generg )

Mu resistors arrangement blatantly and shamelessly taken from ....... you know


Edit on 12.02.2025.

• Babelfish F8b, proven and tested, post #144 https://www.diyaudio.com/community/threads/babelfish-f8.419127/post-7903434
• Babelfish F8m, proven and tested, post #181 https://www.diyaudio.com/community/threads/babelfish-f8.419127/post-7906167

 

[Zen Mod]

Now, pics showing proto phase, as proof that I didn't just dream of ........ though, never underestimate capabilities of dreaming

Not once I had problems solved while dreaming

Curse of Living a Dream

 

[Zen Mod]

I'll be back pronto, don't interrupt

 

[Zen Mod]

Desperate Poor Greedy Boy iteration, all IRFP150

Iq 1A8, regular FW (nominal) 24Vdc rails, 4R Load

 

[Zen Mod]

Desperate Poor Greedy Boy iteration, all IRFP150

Iq 1A8, regular FW (nominal) 24Vdc rails, 8R Load

 

[Zen Mod]

Not So Desperate but Rich Greedy Boy iteration, SJEP120R085 down, IRFP150 up

Iq 1A8, regular FW (nominal) 24Vdc rails, 4R Load

 

[Zen Mod]

Not So Desperate but Rich Greedy Boy iteration, SJEP120R085 down, IRFP150 up

Iq 1A8, regular FW (nominal) 24Vdc rails, 8R Load

 

[Zen Mod]

Lazy ZM, forgot to measure Rout/DF ..... but - who cares; see at FW site and slide down (no output cap)

gain is ~ 1V34pp to 8Vpp, meaning ~0V5rms for 1W@8R .......... call it 15.5db

some notes I made:




Jun 2024 schm; my setting Iq 1A8 all cases

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
2SJ74BL Idss 6.5mA

IRFP

drain resistor 680R + 500R trimpot; 680R fixed increased with 330R fixed (fast, instead of changing trimpot for 1K)

Ugs 3V54
U(680+330)=2V65 so I= 2.62mA
Utrimpot=0V91 so 339R

Cold state:
On thump +0V2 non audible
initial offset 200mV
Off thump +1V5 non audible

Hot state:
On thump -0V1 non audible
offset 0
Off thump +1V5 non audible


Semisouth

drain resistor 330R

Ugs 1V43
U(330)=0V83 so I= 2.52mA
Utrimpot=0V6 so 238R

Cold state:
On thump -0V2 non audible
initial offset 120mV
Off thump +0V9 non audible

Hot state:
On thump -1V2 slight thump/buzz
offset 0
Off thump +1V non audible



XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
2SJ74BL Idss 8.1mA

IRFP

drain resistor 680R + 500R trimpot

Ugs 3V5
U(680)=2V37 so I= 3.48mA
Utrimpot=1V13 so 324R

Cold state:
On thump +0V2 non audible
initial offset 200mV
Off thump +2V1 non audible

Hot state:
On thump +2V non audible
offset 0
Off thump -0V17 non audible


Semisouth

drain resistor 330R

Ugs 1V43
U(330)=1V162 so I= 3.52mA
Utrimpot=0V269 so 76R

Cold state:
On thump +1V5 non audible
initial offset 120mV
Off thump +0V9 non audible

Hot state:
On thump -1V2 slight thump/buzz
offset 0
Off thump +1V1 non audible



XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
2SJ74BL Idss 10.88mA

IRFP

drain resistor 680R + 500R trimpot

Ugs 3V5
U(680)=2V58 so I= 3.79mA
Utrimpot=0V97 so 255R

Cold state:
On thump +0V15 non audible
initial offset 100mV
Off thump +1V6 non audible

Hot state:
On thump -0V2 non audible
offset 0
Off thump +1V6 non audible


Semisouth

drain resistor 330R

Ugs 1V43
U(330)=1V21 so I= 3.66mA
Utrimpot=0V22 so 60R

Cold state:
On thump -2V1 slight thump/buzz
initial offset 100mV
Off thump +1V1 non audible

Hot state:
On thump -2V2 slight thump/buzz
offset 0
Off thump +1V1 non audible

 

[Zen Mod]

As seen from schm, care taken that OLG stays the same, whatever 2SJ74 Idss used........... and [fixed+trimpot] in JFet drain dimensioned to cover all JFet Idss/output part combinations

Now - I have stash of 2SJ74BL enough to cover 30-40 stereo kits

Schm is yours, go for it

Same as with B. A1 - I'll have full kits (pcbs with all parts, including IRFP outputs) as soon I'm able to organize my impossibletoorganize Mighty MySelf

It'll last as long my stash of BLs I have, will save small amount of 2SJ74V for my own Scrooge purposes

Development of this one was a case of Humbling Mighty ZM; my first intention was to include follower stage in between input JFet drain and output gate, to enable possibility od Schaded arrangement for output part on negative rail ........ but resulting in just too big sum of specific TempCo-s ........ amp really not knowing is it going, or simply going back

Not healthy situation for any speaker on market

You can see details on pics shown, few parts positions not existing on final pcbs

So, that's it - this one tricky to Babelfish, being so simple and not really much to add, without adding more drawbacks than pluses

 

[Demonkleaner]

Wow ZM, you are on a roll! And I'm still working on heatsinks

 

[Zen Mod]

How it sounds - Spooky

Worthy being new F in Papa's stable, even if declared as "just" evolution of Aleph J

IAIMH can say how it sounds, same as one of Yank Fabulous Four (you know who you are) but I forgot who made it .......... and in what exact iteration ........ I had few of them (iterations), shown one being final

 

[Zen Mod]

you are on a roll!

just roll of posting

these really being properly cooled of ........... and I have more of same temperature

 

[chromenuts]

Glad I still have my hoard of Semisouth…I’ll take 2!

 

[Norgaard]

"GULP"

I'll take two also
😆

 

[flocchini]

I know, I know I said no more amps 😊 but I do have 4 matched R085s that Mike M sent me. This I think is more interesting than a F7 which has a placeholder on my list. Just my thoughts

 

[Zen Mod]

Bubba's thoughts, Command to ZM

Assembled pair of pcbs going to Ca next week

In Davis, everything is Glowing in the Dark

 

[nicoch58]

Me like the most less complicate ZM disign
a kit for me !

 

[flocchini]

Thank you kind sir. I hope your trust in me is warranted 😊

 

[Zen Mod]

Warranted, certainly

 

[jims]

Two for me. Unfortunately i have no semisouths. I could steal them from my J2.