Audio - linear transistors

[AkisTzortzis]

You can buy these from RS, prices in pounds, I have not looked in the specs, but they look suspiciously similar :0

5.76 4.79
(RS: 2SC3281 NPN - 2SA1302 PNP)

[Steve Conner]

No, the 2SC/2SA and MJL... parts are in plastic TO-247 packages that don't fit my heatsinks. The MJW... are the TO-3 ones, and I heard they were discontinued.

[Robert M. Martinelli]

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?

As I told I built a preamp with BJT socket, but I used a Yokogawa signal analyzer with FFT analysis and even a built-in plotter and all kind of gizmos ( I was running a calibration lab then and I had a lot of nice equipment to play with... ) - a meter measuring RMS is not enough because noise covers the whole spectrum and so your measurements would depend on the meter' s bandwidth....

Using a preamp with a very high gain and a socket to quickly snap in BJTs under test is a good idea though.....connecting it to a headphone amp ( LM386 ) and shorting the input to GND could be a good way to sort them "by ear" - after all we' re trying to spot hisses in the audible range....so if your hearing is good you' ll most likely be able to tell the difference - not a very scientific approach, but a reasonably workable one....

Best regards

Bob

[Enzo]

MJW1302/3281?

Mouser has both types in stock for $3.22 each. They may be an old type, but they are selling them in RoHS versions, so if they are discontinued, it must have been recent. They are from ON Semi. Looks like 174 in stock now with 250 more in 9 weeks.

[AkisTzortzis]

MJW1302/3281?

Mouser has both types in stock for $3.22 each. They may be an old type, but they are selling them in RoHS versions, so if they are discontinued, it must have been recent. They are from ON Semi. Looks like 174 in stock now with 250 more in 9 weeks.

I wouldn't mind betting they cost 3.22 POUNDS in the UK.