2SJ109 and 2SJ74 in GR version???

[carlomar]

Hi,
I m planing to build my first NP project, Aleph J.

I have some 2SJ109 GR and 2SJ74 GR.
I cant find BL version.

I know GR have less Idss.


My question is, can i use GR version in single or in paralel, at front end of Aleph J?

 

[Blues]

Carlo, check this thread...scroll down for the P-P only matched 2SJ74BLs.

http://www.diyaudio.com/forums/pass-labs/160380-pass-diyers-7.html

 

[cviller]

You could try to parallel the GR's and get sufficient bias, but you also increase transconductance - probably not a problem though.
If this is your first NP project, you might what to start with something where you don't need to tweak as much, but if you are used to adjusting circuits, you should be able to make it work.
What is the idss of the parts you have?

 

[carlomar]

Carlo, check this thread...scroll down for the P-P only matched 2SJ74BLs.

http://www.diyaudio.com/forums/pass-labs/160380-pass-diyers-7.html

Tanks

 

[carlomar]

...If this is your first NP project, ...
...What is the idss of the parts you have?

For a first NP project do you recomend me other project?(Aleph30,F4, F5,??)
My speakers are not high efficiency.

Idss of my GRs are 2,5 - 6,5mA
I think the corrent in front end is about 8,5mA???

 

[bobodioulasso]

F5 is simpler and you can adjust the bias to fit your heatsinks size. It works well even leaving class A, which is not the case for an aleph which has to stay into class A.
F5 does not need transistor matching...

 

[cviller]

1. For a first NP project do you recomend me other project?(Aleph30,F4, F5,??)
My speakers are not high efficiency.

2. Idss of my GRs are 2,5 - 6,5mA
I think the corrent in front end is about 8,5mA???

1. I would recommend a project where you do not need to diverge from the original schematics, so the alephj is just as good as many of the other projects.

2. The idss is a bit low for most power amps - a phono stage or a preamp would better utilize your grs. For BA-1/2 it might actually work since it has an additional stage before driving the output devices.

Alternatively you could save your GR parts for a GR project and get some BLs for the amp you would like to build the most.

 

[carlomar]

Thanks,

I think i go for F5.

 

[carlomar]

What is the (volt) input for full power in F5?
Can i use it whith a passive pré for 2Volts CD output?

Tanks

 

[EUVL]

F5 has a gain of 6. So 2V RMS output (standard for CD) will give you 34V peak to peak at full volume. The standard F5 should do 40V peak to peak without clipping.

Patrick

 

[Nelson Pass]

Idss of my GRs are 2,5 - 6,5mA

I would go with the 6.5 mA, and you should be fine.

😎

 

[masag1]

@carlomar

I have some 74BL at home, and need GR's . Can we change our j-fets?

Regards

Sam

 

[carlomar]

Tanks


masag1,

I send PM

 

[carlomar]

I would go with the 6.5 mA, and you should be fine.

😎

So, if i go to Aleph J, to use my 2sj109GR, i have to reduce a litle The corrent in front end to not excess 6,5mA?

Or can i use the original Schematic?

Thanks🙂

 

[Zen Mod]

use ones with biggest Idss , and do not change schematic

 

[Nelson Pass]

I run parts at Idss, and they don't distort much at all.

 

[carlomar]

@carlomar

I have some 74BL at home, and need GR's . Can we change our j-fets?

Regards

Sam

Thanks Sam for change our J-fets.

Now i have same 74BL 🙂