Still another mj15003 ampli

[xcicc]

Hi, I want build this simple amplifier but I want change/use only 20v because I don't need too much power.
Any suggestions are welcome
Thanks

 

[Mooly]

It should be OK on -/+20 volts although R3 will need to be lowered to maintain sufficient zener current. 3k9 would seem suitable.

 

[xcicc]

Thanks, how can calculate how much power on 8 hom load @ 20v?

 

[Mooly]

Realistically its probably good for around 16 watts rms into 8 ohms. That assumes it can swing to say -/+ 16 to 17 volts or so. 16 volts peak is 11.3 volts rms which is 15.9 watts rms (8 ohms). You might get a fraction more, or a fraction less.

 

[xcicc]

Thanks thanks a lot

 

[Mooly]

Your welcome.

 

[xcicc]

work in progress.....

 

[xcicc]

any ideas or suggestions are always welcome
thanks

 

[vzaichenko]

Hi, the layout looks good, but all the high-current traces, like rails, connections to the collectors/emitters of the output transistors and their emitter resistors, output terminals and the ground - must be as wide and thick as possible.

 

[xcicc]

I just finished the new version

 

[vzaichenko]

R18, R19 are 5W - should be much bigger. Also, connections around them - to emitters as well as to the inductor at the output - should be wider. That's where the highest currents will go through.

 

[xcicc]

no in the original project R18,R19 are 2W 0.5 hom but I want use only 20V rail less power less dissipation I hope...

 

[vzaichenko]

OK, for +/-20V rails 2W is enough.

Simple calculation of the worst case (square wave at full amplitude):
Maximum amplitude = 18V (roughly), at 8 ohm load the current is 18/8 = 2.25A
2.25A * 2.25A * 0.5ohm = 2.53W and you have it half of the time 2.53/2 = 1.265W

 

[xcicc]

Yes thanks thanks a lot

 

[xcicc]

I thought about changing the transistors in the package TO5 type BC140 and BC160 2N1711 or any other suggestion for the transistors? only TO5 package
thanks

 

[jaycee]

To be honest, for just +/- 20V rails you could go even simpler.

TO-5 is quite obsolete so i dont see why you'd want to use them. I'd consider using flatpak mount devices like TIP2955/TIP3055 or TIP35/TIP36. For the rest, small signal transistors like BC546/BC556 or 2N5401/2N5551 will do perfectly well.

 

[xcicc]

It is ok, but the project is certainly not of recent conception.
I can consider the transistor BC546 / BC556 or 2N5401 / 2N5551 but the final I will use the pair MJ15003 MJ15004

 

[jaycee]

Fair enough.. they are just a bit over-the-top for a small amplifier, but they will work

 

[xcicc]

well hopefully it will be paid at least the job

 

[lisoformio]

Will this amplifier be available for listenings?
What about power supply? Regulated?