Because their transconductance dIout/dVin is not constant unless Iout > 10 amperes, which is well outside the range of standard bias currents in audio gear, and well outside the range of standard heat dissipation capability of audio enclosures. It's laughably beyond the max possible current of the ACA power supply and howlingly beyond the max possible dissipation of the ACA heatsinks and chassis.
Here's the transconductance plot from the manufacturer's datasheet
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Here's the transconductance plot from the manufacturer's datasheet
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It's a known LDMOS transistor for Ham Radio Homebrew actually. If this part is known to handle high VSWR - i.e. mismatched antenna or feedline - that mean it translates into outstanding bass performance and subwoofer control?
thanks..but i just summarized the values from the datasheets that I got an overview because i am not an expert. for audio there is no need for high voltage parts, with the list you can see it clearly that mostly the lower voltage , e.g. 55V or 100Volt parts give the ideal values like IRFP240. the premium parts show us years ago that some changes can be done..irfp140 or the FQN044N...etc..
if you mean my matching list...yes i am happy with the matched parts...because the setup (= current + DC bias) is more easy and the temperature management is nearly the same for all 4 powerfets. for my small housing very important.
if you look at more powerful amps- meaning more voltage - the parts change e.g. Lufo or the Mufo...etc..--> this are other amps..
..and i am pretty sure that Nelson Pass did this searching long time ago
i am lucky that Tungsten and Mark give us advice's....do it..
chris
Last night I replaced Q1 on both of my v1.8 amps with IRFP044N. Its still early, but the sound is better overall than with the IRFP240. There is still a slight hint of distortion, but overall much improved. All frequencies seem to be more balanced and powerful than before. I can't help but wonder if I should have replaced Q2 as well. Since finding this thread, I have located and acquired a small quantity of IRFP040, IRFP044, IRFP044N, IRFP140, and IRFP140N. Any recommendations on which parts to use for the best performance using the 24V SMPS?
I am also building a pair of the tungsten audio premium versions to run with 28V linear supplies. Same question for those. I also ordered some FQH044N10 based on this thread. Some of these parts will end up in an Aleph J that I have boards for, but I want to finish maximizing the performance of the ACAs before moving onto to bigger things.
I am also building a pair of the tungsten audio premium versions to run with 28V linear supplies. Same question for those. I also ordered some FQH044N10 based on this thread. Some of these parts will end up in an Aleph J that I have boards for, but I want to finish maximizing the performance of the ACAs before moving onto to bigger things.
Hi Rocket,
From a post from the past that I offered:
To my hearing, the midrange is a bit richer with the IRFP044's in both the Q1 and Q2 positions. The IRFP 140 for Q2 and the IRFP440 in Q1 position has more of a leaner character, especially listening to piano and male voice. It is obviously a subjective call, but aren't they all to some extent.
I have retained the IRFP044's as my preference in both positions, and I have not had any temptation to return to the Cree C3M0065090D which was my favorite Cree that I tried. The Cree was more detailed I think, but the 044 won me over with it's lushness. I am using open baffle speakers, and their bass tends to be leaner, so that is why I ended up keeping the 044's.
Den
From a post from the past that I offered:
To my hearing, the midrange is a bit richer with the IRFP044's in both the Q1 and Q2 positions. The IRFP 140 for Q2 and the IRFP440 in Q1 position has more of a leaner character, especially listening to piano and male voice. It is obviously a subjective call, but aren't they all to some extent.
I have retained the IRFP044's as my preference in both positions, and I have not had any temptation to return to the Cree C3M0065090D which was my favorite Cree that I tried. The Cree was more detailed I think, but the 044 won me over with it's lushness. I am using open baffle speakers, and their bass tends to be leaner, so that is why I ended up keeping the 044's.
Den
hi Rocket..
up to know i have no listening comparison...but read post 677 and 679.from both experts you get following information:
less Ciss means better THD at about 3kHz
more transductance means = more Gain...not big as you might think..This will reduce the effect of any ripples in the speaker's impedance plot, usually around a crossover point(s)
but its a taste of your speakers and your personal like what is your better sound. ...we can update your ACA like our taste...like different chocolate --> dark or very dark chocolate...
my speakers are luxury but a closed box, in my small room it is the best for me. ..fast, exactly, open highs....i like themchris
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I can certainly try the 044s in both positions. I may have to order some new boards for that. I had to murder the IRFP240s to get them out of Q1. Thanks for the reply!
...measurements
i try different frequencies, e.g. 4HZ and try to get the fg = 110k Hz
i use 1Vrms input to look at the output.
finally i get with 1900mVrms in about 11,6Watt into 4R.
i try different frequencies, e.g. 4HZ and try to get the fg = 110k Hz
i use 1Vrms input to look at the output.
finally i get with 1900mVrms in about 11,6Watt into 4R.
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smps filter
I tried the different amps an before i made a sound explanation i want to clarify about the first filter with my setup and the updated version:
please use the bigger coil then 40µH...its definitive better. i used 100µH not at the pic.
Cin -L-Cout filter
on the pic you can see that at the input i used after the Cin 220nF KEMET -grey -3 parallel resistors which i had in my "waste" box. 3//12R = 4R
then i use a 100µH coil (not at this pic)
at Cout i use
36pF black
820µ/50V ruby
+ new - 22µF/400V ruby
chris
I tried the different amps an before i made a sound explanation i want to clarify about the first filter with my setup and the updated version:
please use the bigger coil then 40µH...its definitive better. i used 100µH not at the pic.
Cin -L-Cout filter
on the pic you can see that at the input i used after the Cin 220nF KEMET -grey -3 parallel resistors which i had in my "waste" box. 3//12R = 4R
then i use a 100µH coil (not at this pic)
at Cout i use
36pF black
820µ/50V ruby
+ new - 22µF/400V ruby
chris
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sound impression..
My first impression about 2 "identical" ACA premium amps is following:
all components are exaclty the same exept the IRFP 240 vs 140. + i add at my input cap and parallel to the big output cap a Wima 4,7µF/63
the IRFP140
is more relaxed and more clearer. the the top end feels ultra clear at my 4R NADA speakers but its not hurting. the control at complex titles feels with the IRFP140 better.
the IRFP240 feels more softer and maybe for long term listening more relaxed. but this will be comment by me after some days.
with both amps running 200Watt heat is really a heater in my cellar
chris
My first impression about 2 "identical" ACA premium amps is following:
all components are exaclty the same exept the IRFP 240 vs 140. + i add at my input cap and parallel to the big output cap a Wima 4,7µF/63
the IRFP140
is more relaxed and more clearer. the the top end feels ultra clear at my 4R NADA speakers but its not hurting. the control at complex titles feels with the IRFP140 better.
the IRFP240 feels more softer and maybe for long term listening more relaxed. but this will be comment by me after some days.
with both amps running 200Watt heat is really a heater in my cellar
chris
Hi Chris,
Thanks for your report!
It is always exciting to listen to the effect of new combinations of components.
I will make a listing of my current changes to the default ACA. I also liked the the sound of the 140 Mosfet over the 240, though the 240 never sounded bad to me.
Duty calls me to chores, ie mowing the yard, but will gather up my changes soon for your consideration.
One thing that I did find improving, and Jordi did also, another experimenter with the ACA, was raising R14 to 2K from the default 1K value.
I had put a potentiometer in place of the resistor to dial in different values, and both Jordi and I could not hear any benefit from going beyond 2K. When I measured the capacitance of the pots 2K setting, it was also adding .33uf, of capacitance from the potentiometer, so my final was to parallel a .33uf cap with the 2K metal film resistor. On my speakers, some open baffle DIY, the capacitance added some fullness to the sound.
On to the yard.......................
Den
Thanks for your report!
It is always exciting to listen to the effect of new combinations of components.
I will make a listing of my current changes to the default ACA. I also liked the the sound of the 140 Mosfet over the 240, though the 240 never sounded bad to me.
Duty calls me to chores, ie mowing the yard, but will gather up my changes soon for your consideration.
One thing that I did find improving, and Jordi did also, another experimenter with the ACA, was raising R14 to 2K from the default 1K value.
I had put a potentiometer in place of the resistor to dial in different values, and both Jordi and I could not hear any benefit from going beyond 2K. When I measured the capacitance of the pots 2K setting, it was also adding .33uf, of capacitance from the potentiometer, so my final was to parallel a .33uf cap with the 2K metal film resistor. On my speakers, some open baffle DIY, the capacitance added some fullness to the sound.
On to the yard.......................
Den
Hi
here are some impression about my 2nd ACAp.
about the golden sticker : i got this from my brother in 1990 if i start with audio. it was a motivation but i did nearly nothing.
now audio DIY its like a drug
chris
Chris,
Cool label on your amp! Better get some more made up