Hi All! I’m in the final stages of an Aleph J build and have a question about the mosfets I purchased (a very long time ago) from Jim’s Audio on eBay. I have attached some photos of the eBay ad text and of the actual mosfets for your consideration. Are these mosfets well enough matched for my build, or should I buy a new set from the DIY Audio store? I’m mostly a tube guy, and I don’t understand how the Jim’s Audio ones I have compare to the DIY Audio store’s sets. I have also attached a photo of the DIY Audio store’s description of their mosfets for your consideration. Any guidance and advice would be much appreciated.
Jim’s Audio description
Jim’s Audio mosfets
From the DIY Audio Store
My Aleph J
Jim’s Audio description
Jim’s Audio mosfets
From the DIY Audio Store
My Aleph J
Thanks! I wish I had purchased more of them. It was actually a single heatsink from a solar energy application that I cut in half. Is there any benefit at all from having a closer match? Does the DIY Audio store mosfets being matched to .1V mean that the numbers on them would be something like 4.1-4.1-4.2-4.2? I’m confused. Are the ones I have better matched?
Yes, yours seem a bit better matched than the 0V1 guarantee of the store, yours being within 0V03. But remember, Papa himself matches for the store too, and finds 0V1 more than good enough as most other components in the circuits are not matched and provide greater controbutions to distortion etc than the mosfets as long as within 0V1. On that note, using a torque wrench for tightening the MOSFETs to the sink in itself is a measure leading to more even current sharing. Go figure.
Better matching in paralallel applications means better current sharing, prolonging device life and also providing a bit lower distortion. For the J, two and two are in parallell. It is very nice to have all 8 matched, but this is not nescessary.
Follow 6L6’s advice and you’ll sleep well.
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If you want more that are well matched, order in increments of 25 so you get entire manufacturer tubes. This increases the likelihood that transistors come from the same die lot and you’ll get lots of close matches.