Matched input transistor set for Adcom Amplifiers
17 in stock (can be backordered)
Two pairs of matched Fairchild KSC1845, for input section of Adcom GFA-535, GFA-545, GFA-555, and many others. Matching is performed at 1mA collector current. Includes copper foil tape and heat-shrink tube for thermal bonding.
Contact me if you need transistors matched for a different collector current, for a different amplifier. Labor charges apply for special matches.
These transistors should be thermally bonded, so that their gain vs. temperature will track together. Copper foil tape and heat-shrink is included for this purpose. Apply epoxy between the transistors, wrap them in copper foil, and then shrink-wrap. (Don’t use thermal paste as this can creep and ooze and attract dust.)
This is the jig I use to find the matching pairs of transistors. Read all about it here on this thread at DIYaudio.com.
I match the devices to within 1% on the jig, with the fan keeping their temperatures even, and then confirm that result with the transistors thermally bonded in still air.
Assuming the rest of the amplifier is running well, with the inputs shorted, you should see less than 20mV on the outputs of a GFA-5×5 MKI, with the input shorted, and less than 5mV on a MKII. (MKII has a DC servo, so the DC offset you see at the output is not an indicator of good matching.)
|Dimensions||2 × 2 × 1 in|