IRF511 Simple SRPP mosfet amplifier circuit

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noyan

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Joined 2004
#1
Hi,
I have designed and built the IRF511 Mosfet SRPP amplifier. It is so simple, contains a few components, easy to built, powerful and gives tube like sound. 🙂
IRF511 is very interesting mosfet. Input capacitance value is very low: (135pf only)
It is very fast: Turn-on delay time is 8ns, rise time is 25ns, turn-off delay time is 15ns, fall time is 12ns.

You must arrange the current with 100K stereo pot around 1.3-1.6 Amp.

An externally hosted image should be here but it was not working when we last tested it.
 
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#3
Hi Aksa,
Actually i have not measured it yet. But, i can say it's gain is quite much and was enough to drive my Tannoy Saturn S10 loudspeakers directly without preamplifier. About the local feedback, this is original SRPP design 🙂 SRPP design known with it's clean, open sound.
Noyan
 
#5
#8
noyan said:
In the spec page, max. dissipation of the IRF511 given as 43W. On my amp schematic each IRF511 takes 12V*1,5A=18W load. I am not sure that what if i push each of them till for example around 35W dissipation. Any comment? 😕
Click to expand...
Power MOSfets are cheap, simply buy a 250W part and you get peace of mind, provided your heatsink is big enough
Meanwhile, how can i calculate
Click to expand...
The theoretical peak current should be ~twice the quiescent current, that is 2A rms, thus 32W on 8 ohm ignoring the supply voltage and many other factors. With a real SRPP, you are lucky if you manage to arrive at 10W
or measure the real output of my ampifier? 😕
Click to expand...

Measure the rms output voltage on a load, then P=Vrms²/Zload
 
#9
Elvee said:
Power MOSfets are cheap, simply buy a 250W part and you get peace of mind, provided your heatsink is big enough

The theoretical peak current should be ~twice the quiescent current, that is 2A rms, thus 32W on 8 ohm ignoring the supply voltage and many other factors. With a real SRPP, you are lucky if you manage to arrive at 10W


Measure the rms output voltage on a load, then P=Vrms²/Zload
Click to expand...


Many thanks for your explanations 🙂
Why i am using IRF511, because it's input capacitance is very lower than the other mosfets. Also, it is looking faster to me. I thought that these parameters are important for better sound quality. Or, may be i am wrong??? 😕

Input capacitance: 135pf
Turn-on delay time is 8ns, rise time is 25ns, turn-off delay time is 15ns, fall time is 12ns.
 
#10
noyan said:
Why i am using IRF511, because it's input capacitance is very lower than the other mosfets. Also, it is looking faster to me. I thought that these parameters are important for better sound quality. Or, may be i am wrong??? 😕
Click to expand...
It is true that with this kind of circuit, the capacitance will be multiplied by Miller effect, and even a modest device like the the 511 will present a challenging load to the preamplifier. But that is the price to be paid for such a minimalist circuit.
The switching times are unimportant for linear applications, and the time constants of a big device are not very different from that of a smaller one
 
#14
I checked it and noticed that, it does not fit to my schematic. It contains two mosfets in one package but their source pins are common. So, I should use two devices (packages) for each channel. It will be too costly for me and unnecessarily very powerful as well.
 
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