Aleph J variant with N-channel JFETs?

[woofertester]

Is there an already baked schematic of an Aleph J with N-channel JFETs on the input?


I have bought some 2SK170 parts on speculation and they appear to be genuine with some good matches. So far, no luck fining genuine 2SJ74 on spec that are genuine and are resonably priced.



I am matching for Idss and gain around the 5mA bias point.

 

[Zen Mod]

Idss matched will suffice

already done ............ search for inverted aleph

 

[Zen Mod]

http://www.diyaudio.com/forums/pass-labs/243204-inverted-aleph.html?highlight=inverted+aleph

http://www.diyaudio.com/forums/pass...p-2sk715-vp2106.html?highlight=inverted+aleph

 

[Zen Mod]

btw. MMBFJ271 is cheap

of course , you need some setup for matching ...... an you still can solder these with decent solder station ....

 

[woofertester]

btw. MMBFJ271 is cheap

of course , you need some setup for matching ...... an you still can solder these with decent solder station ....

Thank you for the inverted links. I will save those designs.



Is the MMBFJ271 as low noise as the 2SJ74?


I bought a SOT23 socket and this might be a good part to start using that socket with.

 

[woofertester]

....additional question. Is there a complement to the MMBFJ271? I am searching but have not found one.

 

[Zen Mod]

for line level duty , which is the case here , I don't care for noise difference between Toshiba JFets and J271

no direct complement , though I have bunch of J309 with bunch of J271

one day I'll maybe make something of them , together

 

[woofertester]

for line level duty , which is the case here , I don't care for noise difference between Toshiba JFets and J271

no direct complement , though I have bunch of J309 with bunch of J271

one day I'll maybe make something of them , together

Thanks. I will order some of the SOT23 version of the J271 and see how they measure and how they work in circuit. You are correct that the SOT version is much less cost than the TO92 version. More important, they are actually in production and available.



The SOT23 version datasheet is very quiet about noise. The TO92 datasheet says that noise is maybe 10X of the Toshiba part. As of today, I do not have a way to measure the noise. That is on the list to acquire or build.

 

[mkc]

Sorry, for reviving this old thread.

@Nelson: Any experience with FQA9P25 instead of IRFP9240 in an Aleph output stage?

Perhaps even with J113 as n-channel input stage instead of 2SK170.

Mogens

 

[Dennis Hui]

You might find this thread interesting:

UDNeSS, or You don't need Semisouth's

This is a J2-like topology using j113 for the input stage.

 

[Zen Mod]

making Aleph J from Babelfish ᄅſ....or FW J2 on Steroids .... or Not your Father's J2! is trivial

 

[mkc]

Hi Dennis,

Thanks. I did see Patricks amplifier and I'm sure it's a great amplifer.

However, I was just toying with the idea of an mirrored Aleph and not using the IRFP9240 since the Harris parts is not available.

Mogens

 

[mkc]

Hi Zen,

Yes, I'm sure you are right. Also, a nice amplifier.

Btw. Living in the northern part of Denmark enabled me as child to see a lot of swedish tv for children. It was the best. Pippi and also Emil.

Mogens

 

[Dennis Hui]

I was mostly pointing that out for the j113 front-end. With some minor mods
one should be able to graft that onto an Aleph output stage with P-channel
mosfets. (I think the Fairchild part you mentioned should work fine.)

 

[Zen Mod]

I told ya it's easypeasy

 

[grimberg]

You have a natural talent for making complicated designs. 🙂

BTW, there is something weird going on with Q2's emitter and Q3's base. 😕

 

[Zen Mod]

You have a natural talent for making complicated designs. 🙂

BTW, there is something weird going on with Q2's emitter and Q3's base. 😕

yup, deleted resistors

 

[EUVL]

The J113s we have measured have much lower transconductance than in the LT Spice model.
You will need 3x J113 in parallel to match the Yfs of a 2SK170.
But you will then have a Vgs of something between -1 and .1.5V.

Not that it is an issue in the Aleph J.


P.