Ask entire community (enthralling title)

[BeardyWan]

Hi All,

I am playing with a 2sk180 in common drain with 193V choke load.
The input sgnal is stepped by an autoformer (per M2). This is a PC 10k/150 - so 8.2:1 voltage gain. Input signal is 1V rms and output impedance is about 5ohms. Voltage rails are gnd and -48V.

I have a 2sk170/2sj74 pair for an input buffer and in order to retain high frequency response it appears I have to use a second buffer after the voltage amplification stage and prior to the big SIT.

I am trying to keep this as simple as possible, so is there a way of getting rid of the second buffer (maybe driving the autoformer with more current??), and if so can any one suggest a solution?

thanks
Beardy

 

[Zen Mod]

8.2:1 ........... or 1:8.2?

 

[BeardyWan]

I'm running it as a step up, so 1:8.2
😱)

 

[Zen Mod]

so , Rout of buffer (approx 20R) is multiplied with 8.2^2

20 x 67.24 ~ 1350R

too much

you can try to implement sole 2SK170 , in ACA style , as buffer after xformer , doing two jobs - buffering da thing and biasing it

connect xformer as autoformer , so lone cap in chain can be in between xformer and following buffer

 

[BeardyWan]

Thanks ZM!
OK. So no easy way of getting away from second buffer.

If you will indulge me I have a further newbie thoughts:
1. If I use an LSJ689 for second buffer (single pJfet buffer and ccs), then I get some modest "distortion cancellation' as my output SIT is n channel. Any issue with this?

thanks again,
Beardy

 

[Zen Mod]

just go for it

it'll sing , no doubt

and you can always try something else and judge with your own ears/brain

 

[BeardyWan]

Many thanks for your help.