BD138/139 vs.Toshiba's 2SC2238 / 2SA968

Archived from groups: rec.audio.tech (More info?)

Friedrich,

Probably not much of a difference for a headphone amp. The Toshiba
transistors are in a TO-220 case, so a bit more built in heat sink.
They are 1.5 Amp rated, instead of 1 A, and they are higher voltage, but
that's not likely to be an issue here.

The higher F(t) can sometimes be a problem in older products, causing
unwanted oscillations that have to be compensated for. I've had this
problem on old (early) transistor amps that used 2N3055 which have an
F(t) of 4MHz. While new 2N3055's still have the same spec, many have a
much higher F(t) which can cause oscillations.

Regards,
Tim Schwartz
Bristol Electronics


Friedrich Stockhammer wrote:
>
> Hi,
> output transistors for headphone or line amps - BD138/139 vs.
> Toshiba's 2SC2238 / 2SA968.
> Toshiba's 2SC2238 / 2SA968 have a higher ft - about 100 MHz
> --
> Greetings
> Friedrich Stockhammer
> http://www.stockhammer.at/

Archived from groups: rec.audio.tech (More info?)

On Sat, 17 Sep 2005 12:05:26 GMT, Tim Schwartz
<toschwartz@worldnet.att.net> wrote:

> Probably not much of a difference for a headphone amp. The Toshiba
>transistors are in a TO-220 case, so a bit more built in heat sink.
>They are 1.5 Amp rated, instead of 1 A, and they are higher voltage, but
>that's not likely to be an issue here.
>
> The higher F(t) can sometimes be a problem in older products, causing
>unwanted oscillations that have to be compensated for. I've had this
>problem on old (early) transistor amps that used 2N3055 which have an
>F(t) of 4MHz. While new 2N3055's still have the same spec, many have a
>much higher F(t) which can cause oscillations.

I want to use them in a project with LM6171 - please see at
http://www6.head-fi.org/forums/sho [...] ge=1&pp=20
--
Greetings
Friedrich Stockhammer
http://www.stockhammer.at/