Switchable Hi-Z input impedance, how ?

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#362
yeah, I get my silly ideas

well, like you said, maybe I better stick to the jboz, maybe with j310

my idea with j310 with BS170 ?
I might get burned forever for this
it would be like a bastard all N channel version of BA3 frontend

you have permission to shoot me now😀
 
#363
No need to shoot ... yet 😉
BA3 is complementary, symmetrical, push-pull circuit. It' cannot be done with N ch. devices only. Same sex transistors allow for quasi-complementary, circlotron or single-ended arrangements, and neither of those can qualify for BA3
 
#364
OK, its already complicated enough

with the j310 being a tougher one, maybe a symmetric output buffer would be a better idea ?

but Im in doubt about all the resistors around the att pots
 

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#365
1. What do you mean when you say: "with the j310 being a tougher one" ?

2. First you want all N ch. devices (and the buffer is a great place to do it) but now you want complementary pair, push-pull buffer ? It makes sense only if you want to drive the next stage which has 1k-3k of Zin...
 
#369
tinitus said:
shoot, forgot I think you said j310 cannot replace a sk170, directly

any ideas ?
Click to expand...
Not directly - they belong to different construction groups.
If you want complementary buffer with J310 first you have to find a P ch. complement for it.
And if you want a single ended buffer with J310 (like B1) you'll have to put up with Zout of few hundreds Ohms or to use coupling cap.
 
#372
juma said:
And if you want a single ended buffer with J310 (like B1) you'll have to put up with Zout of few hundreds Ohms or to use coupling cap.
Click to expand...

ah, I see what mean
if no cap, there would need to be resistors to adjust the dc, and thus higher zout

could a j310 output buffer look something like in this ?
 

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#374
tinitus said:
...
could a j310 output buffer look something like in this ?
Click to expand...
Yes it could, but since you have a lot of BC547 you can use them as CCS (see attached sch.). If you plan to use SMD J310 don't go over +/-12V PS voltage and to lower the Pd you can change R4 from 68R to 100R. Expect Zout in range of 100 to 150R (R6 included).
 

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#375
hey, thats the one, I like it, simple and very cool looking buffer
thanks juma

any alternatives to the j310 ?
(and not to forget, I still have 2sk170)

and btw, also have some 2sj313/2sk2013
but again, different stuff, I know

oh, and it appears all my BC547B, are...B types, Motorola(736ZF)
 
#376
tinitus said:
... any alternatives to the j310 ?
(and not to forget, I still have 2sk170)...
Click to expand...
BF245C can be used - it's cheap and abundant, but with it you can expect a bit higher Zout (200 - 250R).
You better save k170 for hi-fi projects but if you insist to use them this way, set the current through BC547 CCS to about 80-90% of Idss (by means of R4 - higher resistance => less current)


tinitus said:
...oh, and it appears all my BC547B, are...B types, Motorola(736ZF)
Click to expand...
It doesn't change anything important here...
 
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