Ono Bipolar Transistor Replacement

[rsbay]

Hello,

what is the best replacement for

2SA991
2SC1844

in the Ono phono preamplifier?

Thanks for your help

Ralph

 

[Nelson Pass]

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]

@ 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]

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]

2sc1844 is available

B+D Enterprises - 2SC1844


2sa991

http://www.ebay.com.au/itm/2SA991-Transistor-x-1-pieces-/161024086110

 

[permaneder]

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]

Thanks, i´ve the focus on the 2SA970 for the 2SA991 and it´s available without problems.


Chris

 

[permaneder]

Thanks, i´ve the focus on the 2SA970 for the 2SA991 and it´s available without problems.


Chris

Note: 2SA... and 2SB... are PNP and 2SC... and 2SD... are NPN

 

[chris86]

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