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Old 10th May 2008, 08:26 AM   #1
rsbay is offline rsbay  Germany
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Default Ono Bipolar Transistor Replacement

Hello,

what is the best replacement for

2SA991
2SC1844

in the Ono phono preamplifier?

Thanks for your help

Ralph
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Old 11th May 2008, 04:59 PM   #2
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These are listed as low noise and high gain, with a 60V rating.

In point of fact, the critical ones are the NPN cascoding on the MC stage
and the current source for the diff pair, where they will see about
30V.

I don't know of a direct replacement, but looking at my parts supply,
I would try the MPSA18 or MPS6571 for these two parts and use
a high quality 60V device elsewhere.
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Old 13th August 2013, 09:52 PM   #3
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@ Nelson
is it possible to replace the 2SA991 and the 2SC1844 with 2SA992 and 2SC1845? I think thats no problem or?

regards
Chris
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Old 19th August 2013, 06:12 AM   #4
h_a is offline h_a  Europe
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You can use any bjt with suitable voltage rating in these positions, however, noise performance may suffer.

Looking at the datasheet of the 2SC1845, it will work as it has a 120VCE rating, but it will have a bit higher noise level (look at the noise plots).
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Old 19th August 2013, 02:23 PM   #5
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2sc1844 is available

B+D Enterprises - 2SC1844


2sa991

http://www.ebay.com.au/itm/2SA991-Tr...-/161024086110

Last edited by ticknpop; 19th August 2013 at 02:27 PM.
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Old 21st August 2013, 07:45 PM   #6
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Quote:
Originally Posted by h_a View Post
You can use any bjt with suitable voltage rating in these positions, however, noise performance may suffer.

Looking at the datasheet of the 2SC1845, it will work as it has a 120VCE rating, but it will have a bit higher noise level (look at the noise plots).
Try 2SA872(A)E and 2SC1775(A)E
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Old 21st August 2013, 08:50 PM   #7
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Thanks, ive the focus on the 2SA970 for the 2SA991 and its available without problems.


Chris
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Old 21st August 2013, 08:57 PM   #8
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Quote:
Originally Posted by chris86 View Post
Thanks, ive the focus on the 2SA970 for the 2SA991 and its available without problems.


Chris
Note: 2SA... and 2SB... are PNP and 2SC... and 2SD... are NPN
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Old 21st August 2013, 09:58 PM   #9
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Yes, thats clear... but thanks ;-)
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