High Beta & FT BJT for audio

[diyiggy]

Hello,

May you advise me on high beta, high FT, NPN/PNP TO92 or smd please .

MPSA 018 and BC560 with beta around 500 measured for real seems interresting,

Anything better for audio ?

thanks

 

[lineup]

I use
KSC1845 npn
KSA992 pnp
but
BC550C and BC560C are also good

 

[diyiggy]

Hi Lineup,

many thanks for your input.

I readed in Art of Electronics iirc the MPSA 18 was advertd 1800 beta but in the book on real measurement it was nearer average 500.

Which is close for the complement to the BC560 I surmise.

 

[Bensen]

2sc2713-BL/ 2sa1163-BL is what I use when power dissipation allows to use SMD.

 

[Mark Tillotson]

I readed in Art of Electronics iirc the MPSA 18 was advertd 1800 beta but in the book on real measurement it was nearer average 500.

It's gain increases significantly with collector current, but its low-noise performance is best at low current, so both figures may be valid for different regimes.

 

[diyiggy]

2sc2713-BL/ 2sa1163-BL is what I use when power dissipation allows to use SMD.

I have some ! 🙂 never checked the Beta, I have no handy device to do that, it is a little borring with a dvm when smd. I suspect the L highest Hfe are more close to 500. I'm looking for a little more >= 700.

For the double Toshiba NLA you use in your ad1862 I found some Tosh close equivalent (but surely not as good) :


HN1A01F / HN1C01F


For thhe single I also found a smt equivalent of the MPSA18's Hfe not sourcable anymore in Europe :


MMBT6429LT1G, often measured 900 Hfe but smd. Dunno for the low noise though. MPSA often measured 700 for the ancient one and not new fab ones that are close to 500 like the BC550.

Some told about Zetex 790 and 689 as well with maybe better low noise figure in close TO92 like package.

I imagine smd and beta close to 900.

Also hard to find PNP equivalent to those.

I am not sure if I should focus on TO92 or sot-23 for I/V with input current as low as +/- 1 mA that needs big boost if playing with discrete typology else than Jfet input.

I wonder how people refurbish ancient amps and pre with all those disseapered Toshibas.
Arre there some BJT we should source before they are gone ?

I have trigered already the KSc1845 and KSA 992.

 

[diyiggy]

It's gain increases significantly with collector current, but its low-noise performance is best at low current, so both figures may be valid for different regimes.

and if the load has low impedance as well ? (which term is not clear to me as I don't know if it is the input of the said transistor or what is seen after...but that is another stroy)

 

[Mark Johnson]

Here's what I measured in August 2023. MPSA18 on LockyZ curve tracer --> export to ASCII --> import into Excel --> plot on semilog axes. You can find the post (here).

Honestly, the ancient ones were onto something when they used the PN4250A wherever possible. Nelson Pass, Deane Jensen, James Bongiorno, et al. They violated one of your requirements in post#1 and they had good reasons.

Today the only source of brand new, freshly manufactured PN4250A's and MPSA18's, seems to be Central Semiconductor. They distribute thru Mouser and DigiKey.

edit- I've attached a datasheet of a new device NOT available to the ancient ones. Take a look and if you purchase, specify part number suffix W .

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[diyiggy]

Hi, Thanks,

Here at Mouser in CE, MPSA18 are not sourcable. I was told the On semi (around 500 Hfe average) has way lower Hfe than the older Fairchild (around 700 average).

PN4250A from Central Semi-conductor are in stock though : enough Hfe (>=700) and low noise enough ?( marked 250 from 800 mas at 1 mA)

For information, have KSC1845 better noise figure in the Hfe<500 BJTs, please ?

I extend the thread : what should be nowadays the two or three NPN/PNP TO90 needed to fix older amp/pre, please ?

 

[Mark Johnson]

Sanyo's were better but they've been discontinued. These, you can buy today for $0.24 (qty=100 pricing)

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