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**Enzo** · 07-25-2008, 07:57 AM

You need to consider the applications. My personal favorite high power general use TO3 transistors are the MJ15024 and MJ15025. They can be used as outputs in oh so many places.

I do repair work, so I am putting parts in existing circuits. If you plan only to be building your own, then you don't need as large a selection as I do. For example your small BC550 and similar. I would have those in stock as well as some American numbers in the 2Nxxxx series and the MPSxxxx series, and also some Asian numbers like 2SC945, 2SA1015, 2SC1815. Many of them are equivalent, but the leads are in different order. Fortunately the larger transistors all seem to agree on lead order. On the other hand there is absolutely nothing wrong with mixing 2N4401, BC550, and 2SC1815 all in the same circuit in different spots.

I think you will find that transistor choice is remarkably non-critical. I am more inclined to look at noise figure than any curves. This is especially so in power amps, where the whole thing is so heavily fed back that it almost doesn't matter what transistor you use as long as th volts and amps are enough. it is the whole circuit that is linear moreso than each part in it.

**Robert M. Martinelli** · 07-25-2008, 09:29 AM

Noise is your enemy!

Hi Akis,
Enzo is right ( as usual ), low noise is the most important thing to look for, personally I have used several low noise transistor over the years, starting with the good ol' 2N929 and 2N930 in the '70s (Geez, I was only ten then....), then 2N2484 and 2N5210. recently I have built a phono RIAA preamp using japanese 2SC1815 transistors and they behaved exceptionally well, allowing me to import my old LPs into my PC with astonishing results - you' ll find also european BC109C performs well - if you need low noise FETs then the best sounding choice ( and a low noise one ) is the BC264C.
If in need of low noise opamps, the best compromise between price and quality are the NE5534 and OP27 ( single, 741 pin compatible ) and the NE5532 ( double, 4558 pin compatible ) there are also other high-end opamps like the AD745 but these are best suited when a low impedance source is used ( mics ) - I usually design and build guitar / bass preamplifiers so i stick with NE5534/5532.

Don' t make the mistake that transistors are the sole responsible for optimal performance - always use premium-grade components ( caps and resistors ) - I always use precision metal oxide resistors, their noise figure is much better than carbon resistors.

Hope this helps

Best regards

Bob

**Enzo** · 07-25-2008, 09:53 AM

I have to admit i don't know much about the BC series of small transistors. I stock some types but only because they are used in products I service. I never think of them when I want a transistor for something I am making or for using as a sub. Nothing wrong with them of course, but between the asian series and the American series, I have all my bases covered. So I never learned all their characteristics.

Other low noisers I stock:
2N4124/4125 (NPN/PNP)
2N5088/5086
2N5210
MPS8097
MPSA18

**Robert M. Martinelli** · 07-25-2008, 01:03 PM

Oops... I forgot.....

I forgot to mention the 2N4104, which has a (slightly) better noise figure than the 2N5210....

Enzo, I think it' s normal that the BC series is not so widespread / used in the US, being an european series, basically the BC109 is very similar to the 2N2484, but with a higher Ic (which is not an issue in small signal circuits design ), the NF is still very good ( well, when it was first introduced it was outstanding, we' re talking about the mid-to-late sixties....).

The 2N5210 is a good choice, and, as I already said, I found the Japanese 2SC1815 extremely quiet; I don' t use much the Motorolas (MPS and the like) because their availability here is not so good, in fact, when I had to repair some Dunlop Wah I replaced them with BC109s, of course all of us have to work with what you have handy, without having to wait weeks for a spare BJT...

Well, I think we gave our mate a good list to choose from....

Best regards

Bob

**Steve Conner** · 07-25-2008, 04:55 PM

here's a list of my favourites for audio/linear use:

small signal:
low voltage:
2N3904
2N3905

medium voltage:
2N5401
2N5551

high voltage:
MPSA42
MPSA92

(I keep three kinds because high-voltage transistors always have worse beta than low-voltage parts)

driver: high voltage (don't know any good medium/low voltage parts)
MJE340
MJE350

output: high quality (can also be used as driver in really big amp)
MJL3281
MJL1302

output: metal TO3 package, more beta droop than above but really tough
MJ15024
MJ15025

I made my first hi-fi amp entirely out of these parts, except for the MPSA42/92 (it only had 50V rails) and the power devices (I used MOSFETs, didn't know any better at the time)

One advantage of these four output devices is that there are ready-made SOAR protection circuits for them in the Douglas Self book.

BTW, it's cool that Enzo has a choice of transistors to cover all the bases, but what about the emitters and collectors?

**rocket** · 07-25-2008, 08:17 PM

Are the BC109 better than the more modern BC549/BC550?

Which would be SMD substitutes?

what are the eqivalent PNP typs for BC109?

**Enzo** · 07-26-2008, 12:08 AM

Steve, once I cover all the bases, I have enough types to consider myself a collector.

**Robert M. Martinelli** · 07-26-2008, 06:12 AM

BC109 vs. BC549/550 ? No match!

Originally posted by rocket View Post

Are the BC109 better than the more modern BC549/BC550?

Which would be SMD substitutes?

what are the eqivalent PNP typs for BC109?

Simply there' s no match, the BC109 is the clear winner....

The BC109(A,B,C) ( the BC109 is built in three "ranks" of gain, C being the highest ) has a much better noise figure than the BC549/550, 1,5 dB typ. versus 4db typ. - the BC109 has been introduced with low noise input stages in mind, the 549/550 is just one of the countless "general purpose" BJTs with a good, but not outstanding, noise figure. Only the Japanese 2SC1815 does better than the 109, with a typ. NF of 1 db, and better still should be the newer 2SC1815(L) which, according to the manufacturer ( Toshiba ) sports an impressive 0,2 db NF in the audio spectrum ( up to 16 Khz ).

I have also used 2N3904/05 but their noise figure is around 5 db so I use them only in "general purpose" applications, relying on the BC109 and the 2SC1815 for low-noise apps ( e.g. small preamps to be installed inside guitars/basses, FXs etc. )

The complementary types for the BC109 and the 2SC1815 are the BC179 and the 2SA1015 respectively.

I can' t help you in finding SMD equivalents, because I don' t use SMDs in my designs, partly because it' s a hassle to get good results on a homebrew basis, partly because I don' t like to have more stray capacitance to deal with on my PCBs, so my circuits are probably "bulkier" but the performance is not compromised by the search of extreme miniaturization, which I don' t need.

Enzo & Steve, I consider you "emitters" because each one of your posts radiates wisdom, so you both are "wisdom emitters"!

Hope this helps

Best regards

Bob

**Enzo** · 07-26-2008, 11:08 AM

We'd beta stop talking about ourselves, there's nothing to gain.

**Steve Conner** · 07-26-2008, 12:58 PM

If these transistor puns get any worse I'm going to breakdown

About SMT equivalents: The guys at the semiconductor companies know that a component part number is a brand just like Strat or Big Mac. (I tried to open a 555 franchise next to the 7-11, but they wouldn't let me.) So they brought out SMT versions of many of the popular transistors, with the same base part number, to make it easier for you to spend your money with them. Some examples:

2N3904 -> MMBT3904
MPSA42 -> MMBTA42
2N7000 -> 2N7002 (odd one out?)

I don't know of any SMT equivalent of the BC108 or 2SC1815. I think their heyday was in the 1980s, and nobody makes the BC108 any more at least. The 2N4401/4403 are low-noise transistors that also come in SMT, though.

Transistor technology just keeps improving. I found an old Sansui stereo amp from the late 70s in a dumpster. It was still in the original box, unused and working. I had a listen to it and put it straight back in the dumpster

**AkisTzortzis** · 07-27-2008, 09:40 AM

Thanks guys.

I remember the NE5532 as well as the TL071 and the TL081 and the LM831 as being low noise op-amps.

The BC109 and the BC550/BC560 have same noise figure 4db (max) on Philips datasheets.

I read that there are a lot of fakes around, lots of people complaining about component failures and discovering fakes! That means I cannot possibly buy anything from ebay or any other internet site!!

Which also means I am limited to what RS have because I trust them as a reputable shop.

As I live in the UK they mostly do not have anything 2N and 2SC except the very very common types.

Therefore, I have made a short list of what I can buy with confidence, and it looks like this (for power transistors) - the strange figures in some places are prices in UK pounds (for less than batches of 25)

****************************************
low power:

0.06 0.075
BC550C (NPN) BC560C (PNP) - 45V, 100mA, 500mW, hFE=420-800, 1.2db (fairchild/philips)

.23 not available
2SC1815 (NPN) - 2SA1015 (PNP) - 50V, 150mA, 400mW, hFE=up to 700 for "GR" , 1.0db

.63 .50
2SC2547 (NPN) 2SA1085 (PNP) - 120V, 100mA, 400mW, hFE=200-800, 0.5db?! (no datasheet available)

BC817-40 (NPN) BC807-40 (PNP) - 45V, 500mA, 250mW, hFE=250-600 (very linear up to 30mA, ok-ish to 60mA), no noise figure

.124 .166
BC337-40 (NPN) BC327-40 (PNP) - 45V, 500mA, 625mW, hFE=250-600 : >450 up to 15mA, >400 up to 80mA, 375 up to 100mA, falls sharp to 150 at 500mA, no noise figure

.864 .808
BC142 (NPN) BC143 (PNP) - 60V, 1A, 750mW, hFE=60-90 up to 500mA (not linear)

BC639 (NPN) BC640 (PNP) - 80V, 1A, 830mW, hFE=140 up to 20mA, 130 up to 100mA, falls to 50 at 1A

***************************************
***************************************
***************************************
***************************************

high power

0.36 0.374
TIP31C (NPN) TIP32C (PNP) - 100V, 3A, 40W, hFE=10-50

MJE15034 NPN, MJE15035 PNP - 350V, 4A, 50W, TO-220, hfe>=100 Ic<1A - falls to 15 <4A
Complementary silicon plastic power transistors are designed for
use as high?frequency drivers in audio amplifiers.

1.10 0.88
MJE15028 (NPN) MJE15029 (PNP) - 120V, 8A, 50W, TO-220, hfe>140 Ic<1A - >100 Ic<2A - 3A=75 6A=40
These devices are designed for use as high?frequency drivers in
audio amplifiers.

1.20 1.35
MJE15030 (NPN) MJE15031 (PNP) - 150V, 8A, 50W, TO-220, hfe>140 Ic<1A - >100 Ic<2A - 3A=75 6A=40
These devices are designed for use as high?frequency drivers in
audio amplifiers.

MJE15032 (NPN) MJE15033 (PNP) - 250V, 8A, 50W, TO-220, hfe>100 Ic<2A - 10A=15
These devices are designed for use as high?frequency drivers in
audio amplifiers.

0.81 0.81
BD909/911 NPN - BD910/912 PNP - 100V, 15A, 90W, TO-220, hfe>100 Ic<1A - falls to 15 at 8A

1.70 each
MJL3281A (NPN) MJL1302A (PNP) - 260V, 15A, 200W, TO-264, hFE>100 Ic<4A >70 Ic<10A !!!
High?End Consumer Audio Products
?Home Amplifiers
?Home Receivers
* Professional Audio Amplifiers
?Theater and Stadium Sound Systems
?Public Address Systems (PAs)

5.76 4.79
(RS: 2SC3281 NPN - 2SA1302 PNP)
MJW3281A (NPN) MJW1302A (PNP) - 230V, 15A, 200W, TO-247, hfe>100 Ic<4A, >90 Ic<7A, >80 Ic<10A !!!
The MJW3281A and MJW1302A are PowerBase power
transistors for high power audio, disk head positioners and other linear
applications.
Features
* Designed for 100 W Audio Frequency
* Gain Complementary:
Gain Linearity from 100 mA to 7 A
hFE = 45 (Min) @ IC = 8 A
* Low Harmonic Distortion
* High Safe Operation Area ? 1 A/100 V @ 1 Second
* High fT ? 30 MHz Typical

MJW21193 (PNP) MJW21194 (NPN) - 250V, 16A, 200W, TO-247, hfe>60 <4A,
The MJW21193 and MJW21194 utilize Perforated
technology and are specifically designed for high power
disk head positioners and linear applications.

MJ15024 (NPN) MJ15025 (PNP) - 250V, >80hFE Ic<2A, >40 for 5A,>15 10A, 16A, TO-3, 250W
The MJ15022 and MJ15024 are PowerBase power transistors
designed for high power audio, disk head positioners and other linear
applications.

**Robert M. Martinelli** · 07-28-2008, 09:24 AM

Originally posted by AkisTzortzis View Post

Thanks guys.

I remember the NE5532 as well as the TL071 and the TL081 and the LM831 as being low noise op-amps.

The BC109 and the BC550/BC560 have same noise figure 4db (max) on Philips datasheets.

Hi Akis,
If you read the post in which I talked ' bout 5532/5534s, you' ll find I have mentioned they are opamps indeed, I started the paragraph with "If in need of a low noise opamp......" - TL071-081s are only Jfet input drop-in replacements for 741s, but their NF don' t even come close to the one of the 5534s....

The NF you' re referring for BC109s is the max., but I can assure you that the typ. NF of a "good" ( not fake ) BC109 is about 1,5-2 db; in fact, I have built a small preamp with sockets to test BJTs dynamically and a good 109 has always outrun 550s; as I told you the only BJT with a better NF is the 2SC1815 / 2SC1815L, so, even if they' re not readily available in your area I encourage you to find some on the internet and give 'em a try, you won' t be disappointed ( with the exception of fake ones

).

Enjoy!

Bob

**AkisTzortzis** · 07-28-2008, 10:05 AM

How do you test the noise figure in theory? I have not looked much into it other than take the figure offered in the datasheets and choose the smallest possible numbers :-)

How about a pre-amp with 25x amplification, with the input shorted and an RMS meter at the output? And then simply replace the first stages' transistors and see which AC RMS reads less? Or perhaps feed an input signal and see which set of transistors produce .. hmm what?

**Steve Conner** · 07-28-2008, 10:45 AM

One way of testing noise is to build a microphone preamp and try different transistors in it with the gain turned up full.

Out of interest, does anyone know a source for the MJW1302/3281? They're the TO-3 versions of those super-beta power transistors. I want to build an amp with them, but all I have is heatsinks drilled for TO-3s.

The fake thing mostly applies to popular audio power transistors, I think. You get people buying up a crate of old 2N3055, rubbing the ink off and stamping "MJ15024" on there, before unloading them on Ebay. This has caused quite a few PA amp repairs to explode on the launch pad

So you should buy power trannies from a respectable outlet like RS, Farnell or CPC, and test some samples to make sure they meet spec before buying 32 for your Daddy Of Son Of Zen amp

http://sound.westhost.com/counterfeit.htm

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