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Old 13th January 2020, 04:45 AM   #201
TungstenAudio is offline TungstenAudio  United States
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So far the most powerful Mosfets I’ve used in my ACAs are the IRFP140. Run with 28V, a single stereo amp had better sound than my two original ACAs run as parallel mono blocks. I also bought sets of IRFP150 and even IRFP044N. I think the more powerful devices can definitely make a difference, and will work best with higher supply voltage. I did have really good results using FQH44N10 Mosfets in my F6. They have better performance numbers than the IRFP150.
The changes I’ve made to R3 and R4 are important to allow higher bias current. I would suggest 0.56 Ohms for higher power. It’s also best to use a dropping resistor of 499 Ohms above the input JFet with the higher supply voltage.
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Old 13th January 2020, 05:14 AM   #202
lifefordota is offline lifefordota
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By changing higher value MOSFET can provide higher watt per channel? Is it possible to use the existing meanwell power supply to modify the MOSFET?
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Old 13th January 2020, 05:18 AM   #203
TungstenAudio is offline TungstenAudio  United States
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I would recommend building a higher voltage linear supply to get higher power per channel. I suppose you could also find a 27V or higher SMPS brick if you wanted to try that instead. Part of the power limitation of the regular ACA is the supply voltage. The circuit can make good use of a better PSU if you are willing to build your own.
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Old 13th January 2020, 05:31 AM   #204
Metropolis is offline Metropolis  United States
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Thanks TungstenAudio. Did you have to change Q2 as well, or can that remain the IRFP240?
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Old 13th January 2020, 05:38 AM   #205
TungstenAudio is offline TungstenAudio  United States
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The two Mosfets don’t have to be identical, but I would recommend at least an IRFP140 for Q2. I think an interesting combination to try would be an FQH44N10 for Q1 and an IRFP150 for Q2. Power at 28V or 30V.
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Old 13th January 2020, 05:54 AM   #206
Metropolis is offline Metropolis  United States
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Thanks! Dumb question of the day: what are you using from the data sheet of the MOSFETS to determine which device to use?
In the summary they have Vds, Qg, Rds, etc. I’m not even sure which parameters to consider ��
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Old 14th January 2020, 06:34 AM   #207
RafaPolit is offline RafaPolit  Ecuador
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Quote:
Originally Posted by TungstenAudio View Post
The two Mosfets don’t have to be identical, but I would recommend at least an IRFP140 for Q2. I think an interesting combination to try would be an FQH44N10 for Q1 and an IRFP150 for Q2. Power at 28V or 30V.
Can you elaborate on the "don't have to be identical" comment. Is it a "it really doesn't matter" or is it a "you could get away with it" type of comment?

Because you could get away with a car with four different sizes of wheels, but it wouldn't drive smooth or be durable. If you use different finishings for your seats, on the other hand, it really wouldn't matter.

So which is this scenario? Thanks.
Rafa.
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Old 14th January 2020, 11:30 AM   #208
TungstenAudio is offline TungstenAudio  United States
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Just as the Zen V4 is capable of using different types of Mosfets in the different positions, so is the ACA. Done with some thought about the different roles of each device, this may even have some benefits to the sound of the amp. The upper device is simply an interactive current source, while the lower device is the controller.
This is DIY; try it and see if you like it.
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Old 14th January 2020, 08:17 PM   #209
zhud is offline zhud  United States
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I have been using 28 volts with the original modified ACA from this thread and noticed it sounded much better than it did when it was at 20. My meanwell won’t supply more than 28 with the voltage adjustment cranked to its limits, I often wonder if it would stay in the operating region at 30-32 volts.
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