2SJ109 and 2SJ74 in GR version??? - diyAudio
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Old 12th February 2010, 10:12 PM   #1
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Default 2SJ109 and 2SJ74 in GR version???

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?
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Old 12th February 2010, 11:42 PM   #2
Blues is offline Blues  United States
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Carlo, check this thread...scroll down for the P-P only matched 2SJ74BLs.

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Old 13th February 2010, 05:34 AM   #3
cviller is offline cviller  Denmark
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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?
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Old 13th February 2010, 07:43 AM   #4
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Quote:
Originally Posted by Blues View Post
Carlo, check this thread...scroll down for the P-P only matched 2SJ74BLs.

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Tanks
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Old 13th February 2010, 07:53 AM   #5
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Quote:
Originally Posted by cviller View Post
...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???
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Old 13th February 2010, 10:48 AM   #6
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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...
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Old 13th February 2010, 02:23 PM   #7
cviller is offline cviller  Denmark
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Quote:
Originally Posted by carlomar View Post
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.
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Old 13th February 2010, 11:55 PM   #8
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Thanks,

I think i go for F5.
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Old 24th February 2010, 11:36 PM   #9
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What is the (volt) input for full power in F5?
Can i use it whith a passive pr for 2Volts CD output?

Tanks

Last edited by carlomar; 24th February 2010 at 11:38 PM.
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Old 25th February 2010, 03:55 AM   #10
EUVL is offline EUVL  Europe
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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
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