What are you trying to do with an amplifier like this and 3.5mm jack sockets? You are certain of shorts when the jack is plugged in and at these currents, the components will burn.
If you are trying to make a speaker driving amplifier use fixed connections or a Neutrix Speakon, which won’t short
I did something like this, so basically, I put two holes for speaker connector which looks like this. Is this a possible solution? And I can use speakon for input ?
The first rule of connectors is don’t surprise people. Speakon is intended to be a speaker connector, so don’t use it for anything else.
RCAs are sensible for the inputs.
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And to follow on from @davidsrsb - what devices are you planning to plug into this. If you already know what you are planning to interface this with, your choice of connectors becomes much simpler - there is often a degree of standardisation here; XLR or ¼" jacks for microphones, RCA for line inputs, speakeron or binding posts for speaker outputs etc. Don’t make it hard for your final user to have to find a converter cable to adapt their device to your amplifier. Unless you deliberately don’t want anybody else to be able to connect anything to this you are best off using conventional type connectors where they are expected.
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Thank you, I will change that.
How can I deal with ± 15V supply. I know that I need barrel jack, but 15V supply is not that common, so is it a better option to change it to 12/24V ? Would that have a big impact on my circuit?
That is a question about circuit design, not PC layout. It is not a trivial question - electrolytic capacitors are often the most failure-prone devices in an electronic circuit, so it is common to use capacitors with much higher ratings than what the circuit seems to require.
What voltage do you expect across the capacitor? An electrolytic capacitor’s operating lifetime decreases significantly as the voltage across the capacitor gets close to the rated voltage. Using a capacitor rated for 16 volts in a location where it routinely sees 15 volts is not recommended. I can’t point to a credible reference, but I recall 50% or even 100% as suggested design margins. That is, your capacitor rated for 16 volts shouldn’t be used in a circuit location where it regularly sees more than about 10.7 volts; or perhaps no higher than 8 volts.
Unless I missed it in an earlier post, you haven’t told us what you expect of this circuit. Questions about power dissipation in output transistors are actually questions about thermal design, and this Forum isn’t really a place for a tutorial about thermal analysis. The “36 watts” value you quoted is for operating with an infinite heatsink that keeps the transistors at nominal room temperature. In more familiar terms, think of a heatsink fabricated from a 10-pound (5kg) slab of copper, with liquid nitrogen running through it.
Your thermal analysis will start with the power dissipated by these transistors when they are idling with no signal applied. In turn, this is a function of the supply rail voltage and the zero-signal collector bias current. For a push-pull output stage operated in Class AB with 15 volt rails, this is typically a watt or two. If the stage is operated in Class A, the zero-signal power dissipation could be a few dozen watts.
Dale
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Hello,
Thank you for the reply.
When I started this project, I didn’t have a lot in mind, I just thought I could make an amplifier which is as simple as possible to give me reasonable gain on the output. Now, since I am learning more I see that I need to pay attention a lot more to my elements and their datasheet. For example, output resistors dissipation, capacitor voltages, transistors power dissipation etc.
Since I see that +/- 15 V is rare to find in amplifiers, I’ve decided to change it to +/- 24 V, and by doing that I get a lot more power on the output. but I know I have to change a couple of things because of that. Now the average output power is ~26 W, but I have ~2.5 A going through output resistors.
I have done some more calculations, so my output RMS current is ~1.8 A. Average power of output transistors is ~ 6 W. Voltage across my 1000uF cap is ~ 12 V, so I will use 1000uF 25VDC cap. I think it all looks fine now, I just want to ask is ~75 mV DC on the output a problem?
I have made noise simulation for my amplifier which looks like this, and I can’t quite get a grip of it. Is it considered high noise, and what happens after 1 MHz ?
Your simulation assumes a resistance load. Real loads have capacitance and will turn your circuit into an oscillator. The standard solution to this is the so called “zobel network” of a 10R in series with 100nF to ground and a 1uH inductor in parallel with 10R put in series with the load
This link has an example
http://aioengineerthis.blogspot.com/2015/02/50-watt-audio-amplifier.html
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