How do you know the VAS or driver transistors are fast without buying & testing?
People are always speifying BD139-140 (tgm8) or 2SA1837 2SC4793 (apex AX6).
I'm in the USA. newark has BD139-149 but they are from fairchild. The datasheet guarentees no Ft or output capacitance. Neither does the Phillips datasheet I downloaded. If they just put new paint on a TIP41 how would I know? Aside from the package. I'm already using TIP41C, they are about $.26 instead of $37 for BD139-140 but TIP41C Ft is 3 mhz which is not 30 or 70. TIP41 has more SOA current. Which is important when I do stupid stuff like yesterday leaving apex6 prototype on the lightbulb for 30 minutes when I thought I had plugged in the soldering iron.
Digikey has 2SA1837 2SC4793 for $.85 but they are from digital technology, not toshiba. When you download the datasheet from digikey, you get the toshiba datasheet, not the digital technology one. 70 mhz Ft sounds good but trying to buy real toshiba stuff puts you into the e-bay/counterfeit market.
Peavey designed the PV-1.3k with 2sa968 2sc 2230 which are 100 mhz Ft and c0b of 30 pf, but they did a service bulletin to change to MJE15032/33 at 30 mhz Ft because maybe they could get real ones from on semi instead of imitations specified with a silk screen and paint?
People are always speifying BD139-140 (tgm8) or 2SA1837 2SC4793 (apex AX6).
I'm in the USA. newark has BD139-149 but they are from fairchild. The datasheet guarentees no Ft or output capacitance. Neither does the Phillips datasheet I downloaded. If they just put new paint on a TIP41 how would I know? Aside from the package. I'm already using TIP41C, they are about $.26 instead of $37 for BD139-140 but TIP41C Ft is 3 mhz which is not 30 or 70. TIP41 has more SOA current. Which is important when I do stupid stuff like yesterday leaving apex6 prototype on the lightbulb for 30 minutes when I thought I had plugged in the soldering iron.
Digikey has 2SA1837 2SC4793 for $.85 but they are from digital technology, not toshiba. When you download the datasheet from digikey, you get the toshiba datasheet, not the digital technology one. 70 mhz Ft sounds good but trying to buy real toshiba stuff puts you into the e-bay/counterfeit market.
Peavey designed the PV-1.3k with 2sa968 2sc 2230 which are 100 mhz Ft and c0b of 30 pf, but they did a service bulletin to change to MJE15032/33 at 30 mhz Ft because maybe they could get real ones from on semi instead of imitations specified with a silk screen and paint?