Babelfish XJ , or JX …….. or whatever (Aleph X servo for Greedy Boyz)

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#141
oh yes , just go with them , even if I slightly prefer J271 to J270 , at least by data (Yfs, Idss etc.)

frankly , I couldn't hear difference in Babelfish J - J271 vs. 2SJ74BL

though , we all know that I spent substantial time with elephants , and I didn't made side by side comparison

but , pleasure is certainly guaranteed when you successfully cheat all odds :clown:

one thing more - I remember realizing that J309 and J310 are the same thing , just different Idss range...... so I chose 309 as more convenient for my needs (310 being sky high with max Idss)

same applies for J270 and J271 , and I chose J271 (J270 being sissy low with min Idss)

so , if you buy J270 , buy , dunno, at least 50pcs , test them at 9-12V for Idss and for Aleph J use these with Idss of at least 7-8-9mA
 
#142
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#144
Hi Zen Mod,

I sent you am email but forget about it. The most important info I would need was for the electrolytic capacitors for the I/S. Minimum voltage and best use type?

C1 35V? low ESR, High ripple, audio grade, general purpose?
C3 35V? low ESR, High ripple, audio grade, general purpose?
C4 is 7pF OK?, Silver Mica preferably?
C5 35V? low ESR, High ripple, audio grade, general purpose?
C6 low ESR, High ripple, audio grade, general purpose?
C7 35V? low ESR, High ripple, audio grade, general purpose?
C8 35V? low ESR, High ripple, audio grade, general purpose?
C9 is 7pF OK?, Silver Mica preferably?
C11 35V? low ESR, High ripple, audio grade, general purpose?
C12 low ESR, High ripple, audio grade, general purpose?

I'm pretty sure all resistors are 1/4W min rated, otherwise stated?

Q4 and Q10 ideal Idss (Can't remember if they've been substituted by J271 in my set)

Those Shinkoh resistor values are not easy to find, I'll try and find a good source.
- Looks like the schematics calls for parallel resistors (ex : R8, R9), correct?
- So if this is the case, you have one Shinkoh on top and a regular resistor on the bottom of the PCB?
- That second resistor in parallel has to be 2W or 1/4W is ok?

ZD1 and ZD2 are 7.5V Zeners?



Thanks for everything! 🙂

Do
 
#145
be patient with me 🙂

struggling to tie zillion ends , some of it left even before I did leave for a week

now when I'm back , I'm trying to sort all that ....... e-mails not being easiest

lemme see...... - resistors in parallel - it's either Shinkoh or plain MF , not two of them in parallel

take a good look at my blog , FE pics and you'll see it

precisely , use either :

- R11 or R12
- R13 or R14
- R15 or R16
- R17 or R20
- R46 or R47
- R21 or R22
- R25 or R27
- R37 or R38
- R43 or R44

my personal impression is that Shinkoh or whatever are not worthy of hassle




C1- even 16V is enough , same for C11 , good quality ..... you choose your fave poison ; Elna , dunno which series but 125C , so certainly pro quality - that's my choice

C3,C8 - same as above , but 35V for better sleep

C4,C9 - good quality , anything from 4p7 to 10pF will do ...... either Mica or - as I'm using those tiny NPO smd , making my own legs on them :rofl:

C5- 16V is enough , no mumbo jumbo needed - generic brand name quality

C6 - same as previous for type , but as written on schm - use 35V and upwards ...... 50V ideal

C7 -higher than rail voltage , generic brand name quality

C12 , data written on sch, generic brand name quality

all resistors are regular MF , which are in fact 600mW

except , obviously, all source resistors in OS , which are 3W MOX

also , it's clever to use 1W or 2W small MOX for R10,R4,R51,R60

Q4 and Q10 , ideal Idss above 6mA , because they're biased to some 5mA ; use either J271 or 2SK170BL , no difference to my old fart's ears



ZD1 and ZD2 , yeah , 7V5 - whatever you have - anything up from 500mW will do the job
 
#149
Hi Zen,

Since I'm placing orders for all parts, I was wondering which resistor type would be ideal for best noise figure on the O/S for Source resistors.

Pricing is not an issue at all so here's the two I'm thinking of :

Vishay CPF31R5000FKE14 metal film 3W 1% 100ppm
CPF31R5000FKE14 Vishay / Dale | Mouser Canada

or

Panasonic ERX-3SJ1R5 metal film 3W 5% 300ppm
ERX-3SJ1R5 Panasonic | Mouser Canada

or

TE Connectivity MOX 3W 5% 350ppm
ROX3SJ1R5 TE Connectivity / Neohm | Mouser Canada


I kinda prefer the Vishay for the best specs, the other ones are 5% and 300+ppm...


For the 40x 180R (20 per O/S PCB), can I use 178R or 182R instead of 180R? Will it affect the sound signature? me think not but just want to ask the master for best advice.

What do you think?

Thanks
Do
 
#153
Thanks for the info Vitalie!

The only issue I’m seeing is the extreme high price and shipping is 27$usd. The shipping should cost no more than 10$usd for something that small and light as this.

The diyaudio store sells matched sets of 8 Lsj74 for 65$usd but I don’t know if set A or B is best... I would need Idss closer to the highest A or lower in the B and there’s no garantit of what I’ll get.

I’ll see if there are other options.

Thanks
Do
 
#159
pinnochio - as input JFets are biased in LTP with CCS in tail , only important thing is that you have JFets with Idss greater than Iq in circuit

programmed current in LTP is around 10mA , so each JFet conducting half , 5mA

now you have a choice - either Toshibas you have , or J271 from Mighty Moi

🙂
 
#160
Hi Zen,

I’m very far from being at your skill level, so if you tell me those Toshiba are good, I’ll use them. On the other hand if you tell me that optimally I should wait for the J271, then I’ll definitely follow your advice.

All I know from those Jfets is that they are genuine, bought them many years ago from Fetaudio. They’re a full match quad of NNNNPPPP and matching is 0.2mA, Idss is 11mA. Unfortunately, I have no clue at what voltage they were matched, it remains a mystery to me...

So I’m aiming for the best results, thus I’ll wait to know what the Mighty Zen tells me I should go for.

Cheers!
Do
 
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