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
At 24USD and 40USD each, I'm out on those until the price comes down at least 10X.
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?
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!
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