B1 Buffer Preamp

[Vix]

Actually, it's just two switched inputs. They both go through the
volume control and buffer.

That was too easy!! 😀 :Rofl:

What next? "It's just a single-ended 2SK170 BL, with another 2SK170 BL as a current sink, with a single PSU, CRC" ?

To Jacco and Zen Mod: Or is it GR? Whatever that means...

 

[jupiterjune]

GR last posted here 5/25. Anyone heard from him?

JJ

 

[Zayan]

Someone guesses this suppose to be the input circuit from F4.




Zayan

 

[juma]

yes, it looks very similar to F4 input buffer 🙂

 

[Nelson Pass]

It is not the same. This buffer is single-ended.

 

[stefanobilliani]

current sourced ?

 

[Nelson Pass]

Of course.

 

[Babowana]

Source follower,
a bit adding the 2nd harmonics?

 

[syncmaster]

Common Gate 😀

 

[juma]

It is not the same. This buffer is single-ended.

Like this ?

 

[Vix]

Or, can it be something like "Buffer for Blues", but, instead of the resistor (R 19) it uses a Jfet current source?

 

[jupiterjune]

Like this ?

No Erno, not like that.

 

[Krzysztof]

transistors

Hi Nelson,
Did you used in B1 buffor pre following transistors : 2SK170 and 2SJ74 ?

 

[Nelson Pass]

Re: transistors

Hi Nelson,
Did you used in B1 buffor pre following transistors : 2SK170 and 2SJ74 ?

I refer you to posts 45, 46, and 47

The devices are either 2SK170 or 2SK370

 

[mlloyd1]

for folks that want to read about design of the jfet single ended buffer, i wanted to share again this article from dennis feucht.

i first saw this circuit in the early 70's (yes, i am an old phart 🙂 ) in some old (even back then) national semiconductor datasheets showing test circuits for some of their parts.

i don't have access to an audio precision (maybe mr. pass can share some data at some point), but you can get pretty good performance from this circuit using some cheaper, easier-to-get jfets like the 2N5484, etc. so, save your 2SKxxx for your phono preamps.
😀

enjoy!
mlloyd1

 

[Nelson Pass]

for folks that want to read about design of the jfet single ended buffer, i wanted to share again this article from dennis feucht.

i first saw this circuit in the early 70's (yes, i am an old phart 🙂 ) in some old (even back then) national semiconductor datasheets showing test circuits for some of their parts.

i don't have access to an audio precision (maybe mr. pass can share some data at some point), but you can get pretty good performance from this circuit using some cheaper, easier-to-get jfets like the 2N5484, etc. so, save your 2SKxxx for your phono preamps.

An oldie but a goodie. I dropped the Source resistors on mine.

I don't have 2N5484 distortion curves, but the 2SK170 is pretty
spectacular, and the LSK170 is available and cheap enough.

😎

 

[Vix]

...but the 2SK170 is pretty spectacular...
😎

😎 🙂

 

[mlloyd1]

agreed!

also, oddly enough, the 2SK369 is still around and relatively cheap as well.

... but the 2SK170 is pretty spectacular 😎

mlloyd1
(who is hiding his 2SK146 and 2SJ73 stash from the wife for fear that she will sell them on ebay! 😱 🙂 )

 

[arupg]

Love the knobs on the Front panel - a reminder from the Theshold days.....

 

[mlloyd1]

nelson:

anything you can share at this point on the differences in the distortion spectra for these buffers built with or without source resistors?

the answer "be patient and wait for my article" is a valid response.

🙂

mlloyd1