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wleediy 8th October 2004 06:10 PM

BC 408 and other transistors, how they sound....
hi all,

I have posted this is AA tweaker forum with no advise, so I guess this is a more appropriate place to get the advise.

I have just replaced an input NPN transistor in my Mac 1700 line stage. I used transistor sockets and tried BC 409 first.
Initially with transistor of same hfe, around 500. No osc and sounded a hair better. Then I tried hfe 150 BC409. Very slightly better again. My theory is that lower hfe may reduce TIM.
After that I tried BC 408 of around 130 hfe. Now the sound is significantly better. The slight dryness of this late 60s amp is gone.
I am trying to change some of the PNP transistor. I have bought BC 556C, BC557B,BC558C, BC559B,ZTX 300, and ZTX 500 without really knowing what they are for other then general purpose transistors and way cheap in comparison to tubes.
Any advise which are good for low noise, which are for higher current, and which are good for high voltage line stage output stage ( more then 50 Volts in Mac)?

tks and best rgds

William Lee

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