F-4/BA-3 Transistor Kit
Included in this kit are the semiconductors needed to complete an F-4 amplifier or BA-3 output stage, with the exception of the input JFETs. MOSFETs were matched in accordance with standard operating conditions. This is enough transistors for 2 channels (one stereo amplifier).
The IRFP9140/IRFP240 MOSFETs were matched at the rail voltage and current that the BA-3 and F4 articles suggest, specifically, 22v and .4A, and then grouped by VGS to within .1V.
- The current batch of kits includes Harris IRFP9140 instead of the International Rectifier version. These have better distortion characteristics and are a sonic upgrade, but it should be noted they are rated for 100V.
- Any numbers on the MOSFETs are ID numbers only, and are not related to their measurements nor their matching
F4 is a great sounding amp and a fairly straightforward build. Only issue I had was a slight mismatch in the Mosfets that showed up measuring bias across the 0.47 ohm resistors. No idea how common that is but fixing it required swapping two mosfets. If you have the ability to match test the mosfets before installing I suggest you do that otherwise you may have to desolder and reinstall them to get a better match. Also, strongly recommend using a 7-8K resistor for R9 instead of the 10K that is specified in the BOM. I wasn't able to bias one side high enough with that 10K resistor.
Excellent kit! My F4 works great! Thank you!
Excellent kit, service and delivery . Now working perfect in F4 .
Having the mosfets matched in advance is a times saver and worked out well repairing a F4 channel.
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Great service! Parts arrived very quickly with everything accounted for. About to start my F4 build! Thanks DIYAudio Store!
Great to have matched mosfets.
Hello , I received the DAS 10469 with the delivery time indicated by your site. I didn't install the transistors yet but every thing seems in order. Concerning the DAS107 07. I still didn't received anything
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