John Curl amp

[Ipanema]

Mike,

You might consider changing the driver stage to Fet to get closer to JC design philosophy. 😀

 

[MikeBettinger]

You can hand match 2sk170 and 2sj74 parts. This will work just as well, but you have to buy more than a minimum to get good matches.

Hi John,

I don't want to appear out of it here, but can you suggest a source? I have no problem buying a bunch and putting in the effort to sort them, but if I deal with MCM or whoever they rarely have more than a handful and no idea whether their a bl or gr, etc. I'd have no problem going to Toshiba but I doubt I'd meet their minimum order on a few hundred FET's.

Thanks, Mike.

 

[sklimek]

Hi,

tech-diy, he matches as well. Mostly 'BL'

http://tech-diy.com/smallsignal.htm

 

[john curl]

Mike, what part of the USA do you live?

 

[Upupa Epops]

Guys, do you have some experiences with mosfets on input position ? With really modern types like zvn/zvp 3306 or 3310 ( or similar ), not with old irf 110 ?

 

[PMA]

Guys, do you have some experiences with mosfets on input position ? With really modern types like zvn/zvp 3306 or 3310 ( or similar ), not with old irf 110 ?

He means input stage with these mosfets, instead of jfets.

 

[roender]

Guys, do you have some experiences with mosfets on input position ? With really modern types like zvn/zvp 3306 or 3310 ( or similar ), not with old irf 110 ?

If you want linear transconductance characteristics you need at least 300mA through them ... Way to much for an input stage

 

[Upupa Epops]

Is it your practical experience with them ?

 

[roender]

I never try it for an input stage, sorry

 

[Upupa Epops]

I had try it with very surprising results... 😎

 

[roender]

What was the bias current through them?

 

[Upupa Epops]

Cca 5 mA for differential pair...

 

[PMA]

Pavel (upupa),

I have library models of these parts. But I am expecting John will draw the bow here .. 😀 😀

 

[MikeW]

location

I am in Massachusetts. Almost in New Hampshire.

 

[PMA]

Hereby JC3 with Zetex mosfets 😀

Biasing them is a bit unpractical.

 

[PMA]

.... nice limitation :

 

[Upupa Epops]

And OLG ?

 

[PMA]

OLG, CLG:

(OLG is 4dB higher than with JFETs)

 

[PMA]

.... BUT mosfet input stage itself (not the whole amp) has higher distortion than the jfet one.

 

[john curl]

You can buy what you need at: The Company Store or Erno Borbely. The prices are reasonable for out of production parts.