Yes, higher transconductance is why I chose the FQH44N10. It improves with higher Vds as well, which is how I have been running the later ACA builds as well as my F6. I think that is in part why my F6 sounds so good.
🙂😎 ok thank you for your feedback.
the ACAp_2 (IRFP140) is ready and will be burn in...the next few days i should have time to make a compare test. ACA vs ACA.
i am a bit in stress because my 28 years Accuphase P300V is after my failed renovation (changed all caps) again up and running. 🙂 i found a person with schematic and knowledge.. since 2 days it is at home. i burn in this amp too .....😀
chris
the ACAp_2 (IRFP140) is ready and will be burn in...the next few days i should have time to make a compare test. ACA vs ACA.
i am a bit in stress because my 28 years Accuphase P300V is after my failed renovation (changed all caps) again up and running. 🙂 i found a person with schematic and knowledge.. since 2 days it is at home. i burn in this amp too .....😀
chris
..last update..
Hi
I invest some more minutes🙄😀 to make a new list. i try to find similar power fets and if there are same types e.g. IRF150 from different vendors i put it in the list.
i marked some gfs values ...and correct some entries.
hopefully i do not dream about Ciss , gfs..😀
chris
Hi
I invest some more minutes🙄😀 to make a new list. i try to find similar power fets and if there are same types e.g. IRF150 from different vendors i put it in the list.
i marked some gfs values ...and correct some entries.
hopefully i do not dream about Ciss , gfs..😀
chris
Very useful! At the risk of being accused of “too anal”... if you have only so few parameters, i believe it would be better to reverse rows and columns... it allows for easier sorting by properly but also, easier to scroll than this horizontally-scaling table.
Those are designed specifically for RF applications. Not sure they would be a good match for audio, especially Class A.
But at least you now know the answer to the question "What device has the lowest Ciss for a reasonable transconductance and power capability?"
I'm looking for a helping hand to make sure of my understanding please.
I want to put together my ACA project but IRFP240 devices seem to be on long term backorder at the usual reliable suppliers, however, I do have a small stash of IRFP450 devices. I've studied the comparison spreadsheet posted by @chermann and I think the IRFP450s are suitable, giving a little more gain than the IRFP240s but at the price of a higher input capacitance resulting in more THD?
Does that sound corect or any other observations about using the IRFP450s?
I want to put together my ACA project but IRFP240 devices seem to be on long term backorder at the usual reliable suppliers, however, I do have a small stash of IRFP450 devices. I've studied the comparison spreadsheet posted by @chermann and I think the IRFP450s are suitable, giving a little more gain than the IRFP240s but at the price of a higher input capacitance resulting in more THD?
Does that sound corect or any other observations about using the IRFP450s?
yes...but we are talking about pico Farad = pF.
IRFP450 Ciss = 2600pF = 2,6nF..
IRFP240 Ciss 1300pF = 1,3nF
up to now i have no comparison in sound with different power FETS.
chris
IRFP450 Ciss = 2600pF = 2,6nF..
IRFP240 Ciss 1300pF = 1,3nF
up to now i have no comparison in sound with different power FETS.
chris
The IRFP450 will be functional, but perhaps not the best sounding option. Since it is designed for high voltage, its tradeoff is higher input and output capacitance and higher gate charge, all about twice those of the IRFP240, for about the same transconductance.
I would recommend trying the Fairchild FQA28N15, or its larger brother the FQH44N10. Both of these have been used successfully in amplifiers and sound very good. Their capacitance and gate charge figures of merit are comparable to the IRFP240, and their transconductance is considerably higher, especially so for the FQH44N10. And they are currently available at Mouser.
I would recommend trying the Fairchild FQA28N15, or its larger brother the FQH44N10. Both of these have been used successfully in amplifiers and sound very good. Their capacitance and gate charge figures of merit are comparable to the IRFP240, and their transconductance is considerably higher, especially so for the FQH44N10. And they are currently available at Mouser.
All of You Are Rockstars!
WOW, what a thread! Having built my only audio equipment more than 50 years ago (the three Dynaco kits), I'm a little rusty . . . Worse than that, my ignorance knows no bounds. Having now read this thread in its entirety, I realize I understand about 4% of what's posted here. Being a Virgo, I'm very good at following directions, which enabled me to build those Dynaco kits without any real knowledge of how/why things worked.
That being said, my impressions from perusing this entire thread is as follows:
1. Building the ACA is definitely worthwhile, and should be done!
2. Upgrading to premium parts is a worthwhile investment.
3. As 6L6 points out, the original V1.8 design works well enough on its own.
4. Going "full-in" on this upgrade gets me in way over my head -- upping voltages, etc.
5. I'm in awe of anyone who can look at a build, and immediately point out where the problems are!
So, I'll soldier on, build the basic ACA kit, and then dip my toes into deeper waters, once I have a working unit -- baby steps. I'm very grateful to be accepted into this amazing community, and the obvious genius of those who have contributed to this thread!
WOW, what a thread! Having built my only audio equipment more than 50 years ago (the three Dynaco kits), I'm a little rusty . . . Worse than that, my ignorance knows no bounds. Having now read this thread in its entirety, I realize I understand about 4% of what's posted here. Being a Virgo, I'm very good at following directions, which enabled me to build those Dynaco kits without any real knowledge of how/why things worked.
That being said, my impressions from perusing this entire thread is as follows:
1. Building the ACA is definitely worthwhile, and should be done!
2. Upgrading to premium parts is a worthwhile investment.
3. As 6L6 points out, the original V1.8 design works well enough on its own.
4. Going "full-in" on this upgrade gets me in way over my head -- upping voltages, etc.
5. I'm in awe of anyone who can look at a build, and immediately point out where the problems are!
So, I'll soldier on, build the basic ACA kit, and then dip my toes into deeper waters, once I have a working unit -- baby steps. I'm very grateful to be accepted into this amazing community, and the obvious genius of those who have contributed to this thread!
Last edited by a moderator:
Maybe I've been having a senior moment (again!) but suddenly I've found a couple of suppliers with IRFP240s on the shelf.
For those who have a good source for the IRFP240, check to see if they also have the IRFP140 in stock. In head-to-head competition, I prefer the sound of the IRFP140, running off a 28V rail, of course.
Hi.I have bought Sic mosfets UJ3C120040K3S from local distributor.Can they be used for audio? Any advantages over IRFP240?