Apex AX6 used drivers 2SA1837 pnp & 2SC4793 (pnp) These are Vceo 230
TGM8 used BD139 and BC140 for drivers, which are Vceo of 80
I used TIP41C npn and TIP42C pnp for my Apex 6 prototype. These are Vceo of 100.
The toughest of predrivers used in Peavey PA amps is MJE15032 and MJE15033 with Vceo of 250.
There are long threads devoted to specifying the fastest VAS (621) and driver transistors. They are talking about pushing from 70 mhs Ft to gigahz.
The 2SA1837 2SC4397 for sale from digikey don't even have a datasheet available from the company that produced them. The datasheet digikey downloads is a Toshiba one, but that is not who makes the part they sell. The fairchild alternative BD139/140 for sale here (farnell) don't have Ft specs. So the 3 mhz Ft TIP41c TIP42c strike me as having really nice safe operating area (SOA) with 100 Vceo. I do have some MJE15032-33 for the Peavey PA amp predrivers, and they are ON semi and real from farnell. But were are $1.37 each with Ft of 30 mhz.
In UK you might be able to get real toshiba or sanyo transistors. I can't buy toshiba/sanyo here in the USA without entering the e-bay/counterfeit supply sources. I don't know why this blinding speed is required for music which tops out at 20 khz. or my best speakers which top out at 14.5 khz. I supppose I should buy and read John Curl's book.
Last edited:
I've ended up using TIP41C and TIP42C. I had to joggle the legs to swap the position of the collector and base, but it was easy to do. New trim pots fitted and everything working perfectly. I've set the bias and soak-tested it, and it's sounding great.
Job done!
Job done!
- Status
- Not open for further replies.