Good Transistors? (BJT)

Morrist · 24th January 2002, 02:57 PM

I'm planning to design and build a preamp and a power amp, both single ended, both using BJTs.

I know that my power amp will have a two stage configuration; first stage a voltage amp and second a current amp. I'm not sure whether the preamp will have one or two stages.

My question is: What transistors would suit such applications and are there significant differences in sonic characteristics from transistor to transistor? Naturally, I would like to try some of the better ones.

Any help would be greatly appreciated.

Morrist

hugobross · 24th January 2002, 03:52 PM

the mj15003/15004 pair of motorola is very popular among the DIYers for use in the current amplifier of the output stage.

Best regards,

Hugobross

Morrist · 24th January 2002, 07:41 PM

Thanks a lot, that's exactly what I was looking for in the current stage.
Any ideas for the other stages?

hugobross · 24th January 2002, 07:47 PM

not especially, but just have a look what kind of transistors are used in other (good) designs. Rod Elliot's pages are a good reference for this.

http://sound.westhost.com/index.html

Best regards,

HB.

paulb · 24th January 2002, 07:51 PM

Watch out for fakes. See
counterfeit mj15003's (pics)

mlloyd1 · 25th January 2002, 12:04 AM

Borbely's web site is another good place to look for ideas about driver and small signal bipolar transistors, JFETs and power MOSFETs:

Borbely Audio link

Michael

Morrist · 25th January 2002, 01:14 PM

The 2N3906 seems to be used quite a bit for preamps, has anyone had any experience with these?

sonnya · 25th January 2002, 01:52 PM

I have used the 2N3906 a lot. The DC currentgain is more flat than ~ BC560C.

Okay the noise level is 2 dB higher and the gain is the half of the BC560C but the smallsignal currentgain is nearly flat over 1mA.

Try it, but be carefull to use it as a replacement for BC560C. "Cobo" (Twice the BC560C) and "Cibo" is higher.

Sonny

R. McAnally · 26th January 2002, 01:59 AM

I use MJ21193/4 or MJL21193/4 output devices in almost all of my amplifiers. They handle enormous amounts of current and are highly reliable, as I have never had one go bad yet -- they have even survived a couple short circuit situations (oops!). If you are concerned about the best linearity (i.e. lowest distortion) I would check out the 2SC3281/2SA1302 pairs. Doug Self published a paper showing their exceptional distortion performance with varying impedances, compared to many other popular choices -- they are the basis of his "load invariant" low distortion amplifier design!

Happy amp building!

AKSA · 26th January 2002, 02:53 AM

Good BJT transistors.......

I second Randy's suggestion. The 2SC3281/2SA1302 are the most linear devices I know, and beat the ubiquitous mosfet hands down; they have nominally flat beta from 100mA to 7A! They are 12A 150W devices with ft of 30MHz and minimum beta of 60. Typically I measure around 100, so they are very easy to drive. Vceo max is listed as 200V, and in practice with sensible rail voltages (less than 50V) it is very difficult to kill them by exceeding SOAR ratings. More Vcc requires protection, of course.

A couple of years ago Toshiba announced they would be superseded; the new numbers are 2SC5200/2SA1943 and the older versions are proving very hard to obtain now. The replacements are identical except for Vceo which is now 230V.

I use these in the AKSA; they are superlative devices and I cannot recommend them highly enough. They are not cheap, but they are the best.

Cheers,

Hugh

www.printedelectronics.com

24th January 2002, 02:57 PM	#1
Morrist diyAudio Member Join Date: Jan 2002 Location: Labrador City	Good Transistors? (BJT) I'm planning to design and build a preamp and a power amp, both single ended, both using BJTs. I know that my power amp will have a two stage configuration; first stage a voltage amp and second a current amp. I'm not sure whether the preamp will have one or two stages. My question is: What transistors would suit such applications and are there significant differences in sonic characteristics from transistor to transistor? Naturally, I would like to try some of the better ones. Any help would be greatly appreciated. Morrist

26th January 2002, 02:53 AM	#10
AKSA diyAudio Member Join Date: Sep 2001 Location: Melbourne, Australia	Good BJT transistors... Good BJT transistors....... I second Randy's suggestion. The 2SC3281/2SA1302 are the most linear devices I know, and beat the ubiquitous mosfet hands down; they have nominally flat beta from 100mA to 7A! They are 12A 150W devices with ft of 30MHz and minimum beta of 60. Typically I measure around 100, so they are very easy to drive. Vceo max is listed as 200V, and in practice with sensible rail voltages (less than 50V) it is very difficult to kill them by exceeding SOAR ratings. More Vcc requires protection, of course. A couple of years ago Toshiba announced they would be superseded; the new numbers are 2SC5200/2SA1943 and the older versions are proving very hard to obtain now. The replacements are identical except for Vceo which is now 230V. I use these in the AKSA; they are superlative devices and I cannot recommend them highly enough. They are not cheap, but they are the best. Cheers, Hugh www.printedelectronics.com

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
What transistors do you recommend for a good LTP input?	EWorkshop1708	Solid State	14	3rd September 2011 12:37 PM
NOS Transistors and Tubes Always A Good Thing?	DreadPirate	Solid State	1	1st October 2007 09:47 PM
Transistors - good replacement?	Stuey	Parts	7	25th March 2007 11:27 AM
can't find good complementary transistors	keantoken	Parts	28	12th September 2006 11:22 PM
Good Power Transistors for sale	dmfraser	Swap Meet	1	9th February 2005 03:17 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

24th January 2002, 03:52 PM	#2
hugobross diyAudio Member Join Date: Jun 2001 Location: Flanders, Belgium	the mj15003/15004 pair of motorola is very popular among the DIYers for use in the current amplifier of the output stage. Best regards, Hugobross

24th January 2002, 07:41 PM	#3
Morrist diyAudio Member Join Date: Jan 2002 Location: Labrador City	Thanks a lot, that's exactly what I was looking for in the current stage. Any ideas for the other stages?

24th January 2002, 07:47 PM	#4
hugobross diyAudio Member Join Date: Jun 2001 Location: Flanders, Belgium	not especially, but just have a look what kind of transistors are used in other (good) designs. Rod Elliot's pages are a good reference for this. http://sound.westhost.com/index.html Best regards, HB.

24th January 2002, 07:51 PM	#5
paulb diyAudio Member Join Date: Jun 2001 Location: Calgary	Watch out for fakes. See counterfeit mj15003's (pics)

25th January 2002, 12:04 AM	#6
mlloyd1 diyAudio Member Join Date: Feb 2001 Location: illinois	Borbely's web site is another good place to look for ideas about driver and small signal bipolar transistors, JFETs and power MOSFETs: Borbely Audio link Michael

25th January 2002, 01:14 PM	#7
Morrist diyAudio Member Join Date: Jan 2002 Location: Labrador City	The 2N3906 seems to be used quite a bit for preamps, has anyone had any experience with these?

25th January 2002, 01:52 PM	#8
sonnya diyAudio Member Join Date: Oct 2001 Location: Denmark	I have used the 2N3906 a lot. The DC currentgain is more flat than ~ BC560C. Okay the noise level is 2 dB higher and the gain is the half of the BC560C but the smallsignal currentgain is nearly flat over 1mA. Try it, but be carefull to use it as a replacement for BC560C. "Cobo" (Twice the BC560C) and "Cibo" is higher. Sonny

26th January 2002, 01:59 AM	#9
R. McAnally diyAudio Member Join Date: Jan 2002 Location: California	I use MJ21193/4 or MJL21193/4 output devices in almost all of my amplifiers. They handle enormous amounts of current and are highly reliable, as I have never had one go bad yet -- they have even survived a couple short circuit situations (oops!). If you are concerned about the best linearity (i.e. lowest distortion) I would check out the 2SC3281/2SA1302 pairs. Doug Self published a paper showing their exceptional distortion performance with varying impedances, compared to many other popular choices -- they are the basis of his "load invariant" low distortion amplifier design! Happy amp building!

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)