Is Increasing the Power Supply Voltage in a Mosfet Amplifier an Easy Upgrade?

In summary, the speaker output stage of a 200 watt mosfet amplifier is being upgraded to handle a 1000 watt output by increasing the power supply from +-24v to +-36v. The existing circuit is a basic 100 watt mosfet amplifier but with a second channel. The user plans to hand assemble longer and taller heatsinks, mount components to the chassis, and add fans to handle the extra heat. The op amps will also be replaced with ones that can handle up to 30v. The large resistors on the n channel mosfets drain pin are likely current equalization resistors to balance the current among the devices. With the increased voltage, the resistors will have a voltage drop of 1
  • #1
Tesladude
168
1
I have an old mosfet amplifier which I plan to upgrade, I have never done this before but I am very experienced in electronics and have built many amplifiers before, just not mosfet amps. I am not 100% sure how the n and p channel mosfets are biased or set up but one upgrade I want to do with this amp is increase the power supply from +-24v to +-36v. So given that all components can handle this voltage and extra current which may come as an affect, will increasing the voltage screw up anything within the capacitor resistor and transistor setup circuit that comes before the mosfets themselves?(which I am not Familiar with). Or will it be an easy upgrade?
 
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  • #2
Why increase the voltage of the earlier stages? Only the output stage needs greater voltage to handle greater power. Duplicating the output stage and running the amps in a bridge configuration will double the effective output voltage without changing the supply voltage.

Your question has no answer without a circuit diagram of the existing amplifier.
 
  • #3
I know it may be a general question and i understand that to increase voltage i can simply bridge but my objective is to increase the power transformer to a 36v output, and add parralel/higher current mosfets to allow for 2ohm stability with an increased voltage output, thus turning a 200 watt amplifier into around a 1000 watt.

From what i can see, because i do not have an exact circuit diagram, it seems to be a pretty basic 100watt mosfet amplifier such as the ones you can find on circuitstoday.com. although there is a second channel which is why i say 200watts.So with minimal information let's ask, if i were to take a regular 100 watt mosfet amplifier circuit you can find online, useing a +-24v supply, if i know for a fact that all components can accept +-36v, then will making this increase cause the circuit (for whatever reason) to not work?
 
  • #4
I wouldn't do this. You will need extra heatsink, etc. Too much trouble, but this is just my opinion and of course you know what you paid for this advice. :) Also, plus and minus 36 volt supply rails won't get you to 1000 watts into 2 ohms unless you have a bridgeable 2 channel amp that you are doing this to.
 
  • #5
Just build a new 1kW booster amplifier, then drive it with the old one.
 
  • #6
Averagesupernova said:
I wouldn't do this. You will need extra heatsink, etc. Too much trouble, but this is just my opinion and of course you know what you paid for this advice. :) Also, plus and minus 36 volt supply rails won't get you to 1000 watts into 2 ohms unless you have a bridgeable 2 channel amp that you are doing this to.

Dont worry :) i got that covered!
I am hand assembling longer and taller heatsinks in order to overcome the extra heat, plus every component will be mounted to the chassy which has fins, and i am adding in 2 3cm fans, and in my experience even small fans like that can make a crazy difference. And yes it is a 2 channel bridgable amp but to keep things simple i have been talking about one channel.

So my question is about the circuitry, there are bipolar transistors and resistors which come before the power mosfets in order to "set them up for the audio"
Will increasing the voltage screw any of this up?
Or will it work juat fine but on a higher rail voltage
 

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  • #7
Ok i have discovered that the op amps are running off of a split supply composed of half transfomer output, so on a +-24 v system the preamp chips are getting +- 12 and they can only go to 18.
So i am switching out those with the lm883 which can get to 30v.
Also their coupling cap is only 16v so gotto bump that up too.

Question:
What are the large resistors places on the n channel mosfets drain pin for?
They are only like .1 to .3 ohm so what is their use?
 
  • #8
Tesladude said:
Ok i have discovered that the op amps are running off of a split supply composed of half transfomer output, so on a +-24 v system the preamp chips are getting +- 12 and they can only go to 18.
So i am switching out those with the lm883 which can get to 30v.
Also their coupling cap is only 16v so gotto bump that up too.

Question:
What are the large resistors places on the n channel mosfets drain pin for?
They are only like .1 to .3 ohm so what is their use?

Without seeing the exact circuit I can only guess but it's likely those are current equalization resistors. With several devices in parallel the device with the lowest ON resistance will carry the highest current so these resistors are selected to balance that current by making each leg close to equal without too much power dissipation (~1-2W) with a voltage drop of around 50 to 100mV on each leg at close to full power.
 
  • #9
Thats ingenious! I feel bad for not realizing myself lol.

So unning a 36v supply, by the time i start clipping it should be no more than maybe 32v, but let's jave headroom here...

36v into 2 ohms plus the .2 from the resistors is 16.36 amps, now divide that by two because i am adding in parralel mosfets to share the high current and we get 8.18amps at 36v.

8.18 times the .2ohms and we see a voltage drop of 1.62v and a heat disapation that 10watt resistors should hold up to Nicely.
Does that seem right?
How neccesary are these?
 

Related to Is Increasing the Power Supply Voltage in a Mosfet Amplifier an Easy Upgrade?

1. What is a Mosfet amplifier?

A Mosfet amplifier is a type of electronic amplifier that uses metal-oxide-semiconductor field-effect transistors (MOSFETs) as its main amplifying device. These transistors have low input impedance and high output impedance, making them suitable for amplifying high-frequency signals.

2. Why should I upgrade to a Mosfet amplifier?

Upgrading to a Mosfet amplifier can provide several benefits, such as improved sound quality, increased power output, and better reliability. Mosfet amplifiers also have a lower distortion and noise level compared to other types of amplifiers.

3. How does a Mosfet amplifier differ from other types of amplifiers?

Mosfet amplifiers differ from other types of amplifiers in terms of their operating principle. They use MOSFETs as their main amplifying device, which allows for a higher power output and better sound quality compared to other types of amplifiers, such as bipolar junction transistors (BJTs) or vacuum tubes.

4. Can I use a Mosfet amplifier for all types of audio equipment?

Yes, you can use a Mosfet amplifier for most types of audio equipment, including speakers, headphones, and subwoofers. However, it is important to check the specifications of your equipment to ensure that it is compatible with the power output and impedance of the amplifier.

5. How do I choose the right Mosfet amplifier for my needs?

When choosing a Mosfet amplifier, there are several factors to consider, such as power output, impedance, and compatibility with your audio equipment. It is also important to consider the brand and reputation of the manufacturer, as well as reading reviews and comparing prices to find the best option for your needs and budget.

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