mlloyd@cbnewse.att.com (michael.lloyd) (11/08/90)
Greetings: I want to share some information on semiconductors for audio projects that DIYers may have some interest in. 1. One source for 2SK146GR JFETs: Dalbani Corporation in California; voice telephone: 1-800-325-2264; fax: 213-727-6032, 213-888-6032. This device is a dual n channel JFET. It features high gain and very low noise. This dual part is two matched single devices (2SK147GR) squeezed into a metal can (i.e.not monolithic duals). Erno Borbely uses this part and its complement device, the 2SJ73GR, in several of his preamp designs featured in "The Audio Amateur" magazine (unfortunately, I haven't found a source for the 2SJ73GR in this country; has anyone else?). They show up in various manufacturers products as well (eg. Halfler XL-280, Accoustat TNT 200 and TNT 120). I think Dalbani charges about $2.69 each for quantities of 5 or more for the 2SK146GR. By the way, the Idss range for this "GR" suffix is 5 to 10mA. I think other companies sell the 2SK146 part, but Dalbani was the ONLY company I contacted where when I asked what suffix was available, they went and looked at a part to answer my question, instead of telling me "that information is not in the computer" or "our parts are stocked in a warehouse and we can't give you their number so you can call and ask them". 2. Motorola has released two sets of transistors that could be of interest to DIYers. The first is a pair of driver transistors: 2SC3298B and 2SA1306B. These are insulated (i.e. no external metal tab connected to the collector) in plastic. Quick specs. are: Vceo 200V, Ic max 1.5A, Pd 20W, fT 100MHz, hFE range: 70-240. The other set are output devices: 2SC3281 and 2SA1302. These are in the large plastic single screw mountable package (only one hole drilled in the heat sink, as opposed to four {plus alignment!} for the TO-3 metal can. Quick specs. are: Vceo 200V, Ic max 15A, Pd 150W, fT 30MHz. Call Motorola's literature center to get detailed data sheets if you're interested. The driver pair would seem to be useful also in preamp line driver and headphone power amp circuits, although the 200V breakdown voltage may seem to be a bit overkill. So what are you DIYers doing out there? Michael Lloyd