low noise replacement for BC547, BC557, BD135, BD136

k.junold · 19th April 2001, 10:16 PM

Hi!
Does anybody have an idea of low noise and/or more fast
replacement transistors for the above types?
please mail to: konstantin.junold@web.de
Thanks!

blmn · 19th April 2001, 11:12 PM

k.junold,

I don´t have Douglas Self´s book with me now, but, you can find at Douglas Self´s site (www.dself.demon.co.uk) articles about power amps using japanese series of low power transistores with low noise and high Ft. (2SA970 etc.)

regards

peranders · 12th February 2004, 01:31 PM

What are your application? Transistors don't have to have low noise. It depends where they are. Normally only the input transistors are important. BC546, 547 548 549 550 556 557 558 559 560 etc are normal and OK in most situations. BD135 136 137 138 139 140 don't have to have low noise in most situations.

The speed is also OK 100-300 Mhz for the BC types and aorund 100 MHz for the BD types.

Pedja · 13th February 2004, 02:42 PM

Hi P-A, nice, quick answer.

peranders · 13th February 2004, 02:47 PM

Very low noise transistors have drawbacks (not so fast, higher capacitances, not so high Hfe in some cases) so that means (as allways) that you must choose transistor type with taste. Each transistor must be chosen considering what it should do.

Pjotr · 13th February 2004, 03:13 PM

Besides that Per, ultra low noise only makes sense in low signal apps AND low source resistance. I.e. MM pre amps and even then … The BC446 – BC 560 small signal transistors can be considered low noise for nearly all audio apps.

Cheers

Pedja · 13th February 2004, 03:46 PM

…and besides all that, the question was asked 3 years ago.

peranders · 13th February 2004, 04:10 PM

Quote:

Originally posted by Pedja
…and besides all that, the question was asked 3 years ago.

Hm, but why was the thread so high up....?

Pedja · 13th February 2004, 05:24 PM

No idea. It was high before you have answered?

As about the thread topic, since the question was what is lower noise replacement for BC547, the answer can be BC549/550 (549/550 are lower noise than 546/547/548).

Pedja

pjacobi · 13th February 2004, 05:32 PM

Anyway, just imagine the pure guy asking the original question:

Sitting in front of the PC, soldering iron switched on, desperately pressing 'refresh'.

And no answer for three years.

And to be not 100% off topic: 3 BC547 would have lower noise than one BC547, but you must have well matched devices to get fair current shating without further measures.

Regards,
Peter Jacobi

12th February 2004, 01:31 PM	#3
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	What are your application? Transistors don't have to have low noise. It depends where they are. Normally only the input transistors are important. BC546, 547 548 549 550 556 557 558 559 560 etc are normal and OK in most situations. BD135 136 137 138 139 140 don't have to have low noise in most situations. The speed is also OK 100-300 Mhz for the BC types and aorund 100 MHz for the BD types. __________________ /Per-Anders (my first name) or P-A as my friends call me

13th February 2004, 02:47 PM	#5
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	Very low noise transistors have drawbacks (not so fast, higher capacitances, not so high Hfe in some cases) so that means (as allways) that you must choose transistor type with taste. Each transistor must be chosen considering what it should do. __________________ /Per-Anders (my first name) or P-A as my friends call me

13th February 2004, 05:32 PM	#10
pjacobi diyAudio Member Join Date: Jan 2004 Location: Hamburg	Anyway, just imagine the pure guy asking the original question: Sitting in front of the PC, soldering iron switched on, desperately pressing 'refresh'. And no answer for three years. And to be not 100% off topic: 3 BC547 would have lower noise than one BC547, but you must have well matched devices to get fair current shating without further measures. Regards, Peter Jacobi __________________ -- YMMV

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19th April 2001, 10:16 PM	#1
k.junold diyAudio Member Join Date: Apr 2001	Hi! Does anybody have an idea of low noise and/or more fast replacement transistors for the above types? please mail to: konstantin.junold@web.de Thanks!

19th April 2001, 11:12 PM	#2
blmn diyAudio Member Join Date: Feb 2001 Location: .	k.junold, I don´t have Douglas Self´s book with me now, but, you can find at Douglas Self´s site (www.dself.demon.co.uk) articles about power amps using japanese series of low power transistores with low noise and high Ft. (2SA970 etc.) regards

13th February 2004, 02:42 PM	#4
Pedja diyAudio Member Join Date: Jun 2002 Location: Serbia	Hi P-A, nice, quick answer.

13th February 2004, 03:13 PM	#6
Pjotr diyAudio Member Join Date: Nov 2002 Location: Netherlands	Besides that Per, ultra low noise only makes sense in low signal apps AND low source resistance. I.e. MM pre amps and even then … The BC446 – BC 560 small signal transistors can be considered low noise for nearly all audio apps. Cheers

13th February 2004, 03:46 PM	#7
Pedja diyAudio Member Join Date: Jun 2002 Location: Serbia	…and besides all that, the question was asked 3 years ago.

13th February 2004, 05:24 PM	#9
Pedja diyAudio Member Join Date: Jun 2002 Location: Serbia	No idea. It was high before you have answered? As about the thread topic, since the question was what is lower noise replacement for BC547, the answer can be BC549/550 (549/550 are lower noise than 546/547/548). Pedja

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