Today I noticed an amplifier with a large number of 100V capacitors installed directly on the power amplifier boards. I wonder what kind of protection they use?
Hegel H30 Power Amplifier Review - YouTube
Hegel H30 Power Amplifier Review - YouTube
I tend to agree with H713's post #40 about too much caps...
And I mentioned in a previous post here about the Mcintosh products, particularly the MC2300 utility amp, commonly used for outdoor bands needing the power and reliability to endure the heavy use at concerts and other venues.
There is a "beyond a certain point" AKA "Diminishing Returns" that some people don't understand.
But I think that the OP cakyol may have been listening to people on the subject of those car amps that use monsterous values of capacitance and heavy gauge wiring to pump their annoying bass out to passing homes and contests for "who's got the loudest".
Of course, all that is silly stuff, and has nothing to do with good design practices of audio equipment.
Some of the finest audio amplifiers as mentioned only need maybe 30-50kuF in their supplies.
And I mentioned in a previous post here about the Mcintosh products, particularly the MC2300 utility amp, commonly used for outdoor bands needing the power and reliability to endure the heavy use at concerts and other venues.
There is a "beyond a certain point" AKA "Diminishing Returns" that some people don't understand.
But I think that the OP cakyol may have been listening to people on the subject of those car amps that use monsterous values of capacitance and heavy gauge wiring to pump their annoying bass out to passing homes and contests for "who's got the loudest".
Of course, all that is silly stuff, and has nothing to do with good design practices of audio equipment.
Some of the finest audio amplifiers as mentioned only need maybe 30-50kuF in their supplies.
I'm not impressed.
Just another "monster" amp with a matching pricetag - marketing hype at its finest.
It looks artisanal. But I love the idea of placing capacitors on the amplifier board. The only thing I don't know yet is how to protect such an amplifier from an accident and what protection should be chosen. SMD capacitors would look nice, but apparently they would cost a lot more.
In general, I like the SMT technology, it looks nice, compact with a minimum of parasitic inductances and capacitances.
https://www.lcaudio.dk/images/Millennium/xp7.jpg
In general, I like the SMT technology, it looks nice, compact with a minimum of parasitic inductances and capacitances.
https://www.lcaudio.dk/images/Millennium/xp7.jpg
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I'm not sure 50W resistor will live long. 10R with 115 VAC means about 1300 W dissipated acros a resistor case. I think it is rather a job for 5x or 10x large 0.47R ...1.0R NTC-resistors (20-25 mm ones). They are designed to withstand transients and will lower their resistance if accidentally became hot.
For example, MF72-0.7D25.
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Solid tantalum capacitors have excellent characteristics: high specific capacitance, small dimensions. The ESR value of such capacitors remains unchanged with increasing frequency or even decreases, and the impedance value at frequencies of 100 kHz and above reaches a minimum value. In addition, they are highly reliable and compatible with all common installation technologies.
https://doc.platan.ru/pdf/datasheets/vishay/m34.pdf
https://doc.platan.ru/pdf/datasheets/vishay/m34.pdf
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I have been grappling with this. As you correctly indicated, the resistor will get very hot for about 3-4 seconds. I do not know how many on/off cycles it may last.
I am still not sure about a thermistor either. I have never seen one explode
Tell me your experiences.Hi Gunfu, I am not quite sure what you mean by your wire lengths...
In any case, the saving grace is, since BOTH a thermistor and a resistor will be shorted out with a reliable relay after about 3-4 seconds, the heating will not be an issue for long.
The problem comes if the relay does not engage. In this situation, it SEEMS like a thermistor MAY last out longer without destruction, but I am not sure.
And the reason I am extending the delay time to 3-4 seconds (only 1 or so second is actually needed till the magnetic field is established on the toroid), is that I want to limit the current ALSO on the secondary while the large caps are being charged, thus also limiting the current on the secondary to the capacitors, until they charge to a reasonable threshold.
In any case, the saving grace is, since BOTH a thermistor and a resistor will be shorted out with a reliable relay after about 3-4 seconds, the heating will not be an issue for long.
The problem comes if the relay does not engage. In this situation, it SEEMS like a thermistor MAY last out longer without destruction, but I am not sure.
And the reason I am extending the delay time to 3-4 seconds (only 1 or so second is actually needed till the magnetic field is established on the toroid), is that I want to limit the current ALSO on the secondary while the large caps are being charged, thus also limiting the current on the secondary to the capacitors, until they charge to a reasonable threshold.
Yes, I was not intending to cut them anyway. In fact, since the thermistor temperatures may be very hi, I was even going to mechanically bend and secure the connections with screws since solder alone will not be enough and may melt. In the event the solder melts, the contact will still be very secure.
My experience tells me to use parts in their clear stated ranges. If manufacturer state something in a datasheet - I will use it. So I digged into 50W Hitano AH series resistor datashee and found this:
Maximum Working Voltage determined by E=√P*R, Maximum Overload Voltage equals to 2.5 x E.
For our case Max.WV E=√50×10 = 70 V (DC I believe).Then max. OV equals to 2.5 x 70 = 177 VDC or 125 VAC. It seems your guess to use 50W 10R wired resistor is ok (with 115 VAC mains).
It depends of cause how often an amp will be turned on and off. Possibly there is a need to use two 50W rated resistors in series or something like this to be sure it will live long.
But I still prefer NTC (because of their temperature-dependent resistance) - they seem to me much safe.
Maximum Working Voltage determined by E=√P*R, Maximum Overload Voltage equals to 2.5 x E.
For our case Max.WV E=√50×10 = 70 V (DC I believe).Then max. OV equals to 2.5 x 70 = 177 VDC or 125 VAC. It seems your guess to use 50W 10R wired resistor is ok (with 115 VAC mains).
It depends of cause how often an amp will be turned on and off. Possibly there is a need to use two 50W rated resistors in series or something like this to be sure it will live long.
But I still prefer NTC (because of their temperature-dependent resistance) - they seem to me much safe.
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People do it all the time with oversized caps. I can see no tangible benefit to go from 100mF to 500 mF in a 500W amp, and I can see a big downside.
I think most people who build with such ridiculous amounts of capacitance have never seen what that kind of cap bank can do. I've seen what happens when a capacitor bank of that size dumps all its energy at once in a fault condition. You don't even want to be anywhere near it.
I don't know what configuration this is in, but 500 mF at 95 V stores about 2.26 kJ of energy. I don't want to be within 10 feet of that when it goes off, and I would definitely want hearing protection and a lexan shield.
Protection circuits for this kind of thing are a lot more complicated than what is found in a traditional amplifier. It's also pretty dangerous to be working on it live, since if anything goes off... it's going to quite literally explode in your face. We've all seen amps "blow up" and shoot pieces of transistor case across the room. This would be taking it to a new level, a level more commonly seen when physics experiments suffer a fault.
i design and build all of the traffos used in my amp projects, who are you to say i am wrong....? when you yourself said it can be small...
the biggest traffo used in typical audio power amp i did was 2500volt amperes, i designed it to have low magnetizing current by running low flux densities...
look at the flux densities versus mmf curves of silicon steels....
those are outside the design parameters, a 60hz traffo when used in a 50hz will run higher magnetizing currents, whereas a 50hz traffo will run lower magnetizing currents when run in 60hz source...
why will you run it at 1hz?, it is the height of folly, it does not take a genius to figure that one out..
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