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-   -   Ono Bipolar Transistor Replacement (http://www.diyaudio.com/forums/pass-labs/122821-ono-bipolar-transistor-replacement.html)

rsbay 10th May 2008 09:26 AM

Ono Bipolar Transistor Replacement
 
Hello,

what is the best replacement for

2SA991
2SC1844

in the Ono phono preamplifier?

Thanks for your help

Ralph

Nelson Pass 11th May 2008 05:59 PM

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.

chris86 13th August 2013 10:52 PM

@ Nelson
is it possible to replace the 2SA991 and the 2SC1844 with 2SA992 and 2SC1845? I think thats no problem or?

regards
Chris

h_a 19th August 2013 07:12 AM

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).

ticknpop 19th August 2013 03:23 PM

2sc1844 is available

B+D Enterprises - 2SC1844


2sa991

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

permaneder 21st August 2013 08:45 PM

Quote:

Originally Posted by h_a (Post 3600894)
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

chris86 21st August 2013 09:50 PM

Thanks, ive the focus on the 2SA970 for the 2SA991 and its available without problems.


Chris

permaneder 21st August 2013 09:57 PM

Quote:

Originally Posted by chris86 (Post 3604338)
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

chris86 21st August 2013 10:58 PM

Yes, thats clear... but thanks ;-)


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