The IFRP240's are hard to find right now. I need 8 of them for my Aleph J build. I have enough matched (Vgs) within 0.1 volt, but they're don't have the same lot code. Is there an issue using different lot codes together in the same channel?
I also have some 240's that have about 100 hours on them. Can these be mixed in with new devices? How about one channel new devices, one with used? The new and the used have different lot codes.
I also have some 240's that have about 100 hours on them. Can these be mixed in with new devices? How about one channel new devices, one with used? The new and the used have different lot codes.
matching is important
lot code isn't
same lot is sorta giving you more chance to get them matched ......
so, "matched" is goal
and - for J, you need 4 (matched) pairs
forget age and codes
lot code isn't
same lot is sorta giving you more chance to get them matched ......
so, "matched" is goal
and - for J, you need 4 (matched) pairs
forget age and codes
If you are paralleling them or otherwise obsessive then matching them for Vgs is sufficient, otherwise, have at it.
Sorry for the noob question, but which MOSFETs need to be matched to each other? My experience is with tubes and it's clearer to me what tubes/sections of tubes need to be matched.
IF you matched them, then that´s confirmed Reality you can trust.
Matching lot codes is an attempt to get similar parts, no actual confirmation, just hope statistics work for you.
In a nutshell: measuring beats guessing 1000:1
100 hours is nothing, in generals Semiconductors are incredibly stable, unless abused.
Matching lot codes is an attempt to get similar parts, no actual confirmation, just hope statistics work for you.
In a nutshell: measuring beats guessing 1000:1
100 hours is nothing, in generals Semiconductors are incredibly stable, unless abused.
@ Dr Greenthumb: You want to match the mosfets that are running in parallel so they share the same amount of current.
Referencing the schematics here:
https://www.diyaudio.com/archive/gallery/data/500/AJ_Sch.png
it means you want Q5 matched to Q6 and Q7 matched to Q8.
Referencing the schematics here:
https://www.diyaudio.com/archive/gallery/data/500/AJ_Sch.png
it means you want Q5 matched to Q6 and Q7 matched to Q8.
Matter of obsession really. Most of the devices in a matched quad are within 0.05 volts of each other. Since date code and age aren't issues for matching, the matched pairs I have on hand are within 0.03 of each other. Maybe I'm taking the measuring thing too far? For example, I've dialed the bias to 0.400, not 0.399, not 0.401...offset to 0.0 millivolts, +/- 5 millivolts.If you are paralleling them or otherwise obsessive then matching them for Vgs is sufficient, otherwise, have at it.
BTW, thank you for sharing your experience, knowledge, and designs! I've enjoyed building and listening to these amps. I have the Aleph put together (except when I toast the 240s), with the F6 on deck. I'm a tube guy at heart, but these caught my eye due to the lower part count. The lower cost for amplifying devices is a plus. A matched quad of Toshiba 2SJ74s for $50 is much easier on the budget than $250 for a matched pair of Telefunken 12AX7s. I just to say thank you and let you know you're very much appreciated.
