I'm building my second M2x, this one is for me to play with (first M2x build resides at my folks place).
I'm curious if anyone has tried the Fairchild FETS FQA12P20 / FQA19N20. If so any comparison to the IRFP240 / IRFP9240. I was gifted a set of the Fairchilds from a very generous fellow DIYer for just such a build.
I see @Bones13 mentioned using "Fairchild" FETS, but wasn't sure which type and my thread search so far hasn't turned up anything.
I'm curious if anyone has tried the Fairchild FETS FQA12P20 / FQA19N20. If so any comparison to the IRFP240 / IRFP9240. I was gifted a set of the Fairchilds from a very generous fellow DIYer for just such a build.
I see @Bones13 mentioned using "Fairchild" FETS, but wasn't sure which type and my thread search so far hasn't turned up anything.
Haven’t used the Fairchilds in M2x, (but have in F5T, BA-3, and Aleph J) generally speaking, they are fantastic sounding devices and I’d look forward to hearing them in M2x.
🙂
🙂
Thanks Jim, I think I'll give them a try!
Anyone have thoughts on if I should be changing any resistor values to accommodate the Fairchilds (FQA12P20/FQA19N20)?
I'm still too much of a noob to feel confident I won't make a dumb mistake that other more experieneced builders might consider an obvious oversight.
Anyone have thoughts on if I should be changing any resistor values to accommodate the Fairchilds (FQA12P20/FQA19N20)?
I'm still too much of a noob to feel confident I won't make a dumb mistake that other more experieneced builders might consider an obvious oversight.
Nah.
The optocoupler bias won’t care one bit who made the output devices.
The optocoupler bias won’t care one bit who made the output devices.
There really any difference between the farichilds and the IRFs? I almost used FQA12P20/FQA16N25C for the M2X but keep saving them for some future use I have yet to identify 🤔
I bought the Fairchilds many years ago for an F5 turbo I eventually realized made way more power than I needed 🙂
What makes the Fairchilds sound more neutral?
What makes the Fairchilds sound more neutral?
Don't have any equipment to measure, but I will do a wild guess based on how I picked the jfets and mosfets. Keep in mind, my boards were for the original F5 without P3. I did:
- Matched 2SK170 and 2SJ74 with Patrick's degeneration trick.
- Matched the mosfets at the intended biased point, in other words, tried to get matched NNPP as close as I could.
- Do the above for each channel and tried matched the 2 channels as close as I could.
Their designs are similar. Each is a composite amplifier, employing a pair of ICs within a single NFB loop. JFET inputs are used in both designs. Both have high output current (200mA and 100mA) and both feature a high slew rate output. (4200V/usec and 1700V/usec) .
I built both, but I don't remember liking one more than the other. The are a great design, I think you, may worry more about quality of all parts working together than just the one part. The only way you will really know is to build them both. Everyone's perceptions are different.