Question on brands & quality of transistors

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sumotan

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Joined 2013
#1
Hi guys
Im pretty new to SS stuff some am learning & trying to understand
as much as I can. Got some question pls.

1. transistors for example 2n5401 is there a difference in quality or
SQ between brands ?

2. SQ wise does the germanium type sounds better then silicon version ?

3. When matching pairs what figures are looking for, closest to data specs
or ?

4. As a input differential pair, is matching a must for optimum SQ. Myself
I think so cause I see different dc offset between 2 modules & even if
it doesn't affect much, that difference already bugs me. lol

Many thank Guys
 
#2
A transistor has a specific specification shown on the manufacturers data sheet. In essence a transistor of the same type number will behave at least as good as the data sheet.
Germanium transistors were obsolete in the 60's and have a useable guaranteed life of 25 years.
When matching, use the data sheet and Hfe readings.
A matched differential pair means what is states, matched. Hfe and other measurements the same in other words.
 
#3
I found 2n5401 from ON semi had amazing gain and low noise. Way better than the datasheet. They have quit making the TO92 ones, they couldn't get their price. They bought fairchild, we'll see what happens. On semi TO3 transistors are the best in the world for BJ output transistors, TO220 drivers are quite good.
I've found ST & fairchild silicon transistors to be quite reliable. If you don't overstress them. Fairchild has some excellent offerings in the MOSFET range. No lateral mosfets though, the darlings of many circuits here. Fairchild mosfets are more use for disconnect circuits for speaker and output transistor protection.
Germanium anything has temperature sensitive leakage & gain, so the operating point moves around, so bad that most 1958-64 circuits were unstable hot. I wouldn't mess with it, even though you can again buy it.
 
#4
Agree and add:
1) transistors from "known" brands are all good (Fairchild/ST/ON/Toshiba/etc.) ; "mystery" brands may be good or not.
2) as noted above, Germanium is obsolete and was never good, not even in the old days.
It was used just because there was nothing else available and, at the time, was a novelty.
3 &4 : you may Protoboard a design and try different transistors in it until you get (near) perfect matching.
Mind you, just holding a transistor in your hand wil change its Vbe appreciably, until it cools down again, which can take a few minutes.
 
#6
What you got was the generic answer.

However there are some differences.
Take the popular BD139/140 from Onsemi you get one version.
From Fairchild you can get them graded for hfe the -10 is lower than the -16.
Fairchild also has a Y version of the 2n5401 which is the high beta group.
I seem to remember seeing SOA differences across brands in some cases.
There is talk of the NLA Phillips BD139/140 being much faster than what you
can get today - I'm not sure if is it true.

I wonder if parts without a noise spec are roughly the same.
Are their quasi saturation and early voltages the same?
 
#10
They sound the same because their electrical parameters are the same.
Change a parameter a little bit (by swapping in a different device) and a good amplifier will still sound the same. It the sign of good quality design that production tolerances do not change performance.

Make a big change in one, or many parameters, can change the electrical performance and that may result in an audible change. Our ears are not very good as measuring instruments. But ears/brains are quite good as comparison devices.
 
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