100W RMS solid state amp

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Mosfet circuit burned out after 2V overload...
http://www.ebay.fr/itm/EBB-150-Mosfet-Power-Amplifier-Module-125W-RMS-Audio-Disco-PA-/121457218844

>>1186640
>There's a bunch of "vintage" store to make every kind of tube amp, where my 70s semi-conductor electronics are?!?!?
I'm not sure exactly sure if I'm understanding what you are asking, but you shouldn't buy vintage transistors, since there are a lot of knock offs floating around the web. People find cheap transistors and remove all the markings on them and replace them with product codes and makes of desirable brands. It seems weird, but it is done to rip off audiophiles who "need" that exact vintage transistor.

Your best bet is to use google and find a modern equivalent of the transistor that you are looking for from a reliable source like mouser or digikey or whatever is the equivalent from where you are from, since there are knock offs of more expensive modern transistors as well.

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>>1186659
Maybe I've been a little vague on this point. I heard about these crooks methods to get the "new old stock" germanium transistor to put in your fuzz pedal...
I'm not planing on making a transistor amp with vintage part. Just like the tube amps I made (pic related) I want to follow a vintage schematic/PCB, with brand new components. I was hoping to find equivalent semi-conductor part quite easily, but it's not the case. Just like I don't find a "reference" schematic for a simple 100W amp.
For instance for a tube amp, I may go for a bassman-like circuit.

>>1186696
>"reference" schematic for a simple 100W amp
the 'hitachi lateral mosfet' is what you're looking for
as seen in MF100, MXF200, DNA200 etc.

the circuit has a reputation for going completely bugfuck nuts with RF oscillation, consider yourself warned.

>>1186640
It's all in Spanish, but the tutorials are very good
http://construyasuvideorockola.com/proyectos.php

>>1186640
patient's in v-tach, let's cardiovert!

>>1186919
pretty nice website!

>>1186720
thanks!

The biggest problem with simple solid state power amps is biasing and heat dissipation. Good bias control increases circuit complexity. I would not feel good about putting an amp in the wild that didn't have good protection either. For example, what happens if you short the speaker terminals on a peavey bass 400? They may last but they are not "protected," and I can almost guarantee that no vintage guitar amp has proper heatsinking.

On that mosfet amp board - is there a trimpot? The bias may have been off. That failure looks pretty catastropic.

An option that I think you should seriously consider is to use class D power amps to replace the older ones. Find one with low distortion. The industry moved to them long ago and SS guitar amps usually run clean power stages anyway. If you are concerned about "compression" at high volume, jut hang a limiter in front of the power amp so that you never, ever clip the power amp.

>>1186640
That picture is showing crossover distortion on a class ab amplifier. You nead to bias the transistors so each one switches on to handle the right part of the sine wave. Right now they are switching on too late and are not held open by enough current.

>>1187582
sunn beta power amp circuit uses 4 power transistors, plus one to drive each side (total=6)
Datasheet for these TO3 beast is claiming a 115W dissipation max (each!).
2N3055 / MJ2955
The amp is claimed to be 100W on 4Ω (that's one kind of sweat security coefficient, doesn't it? :D ). Sure that's not a protection against shorts on speaker, but if that issue should become a problem, it must be the result of misuse. Troubleshot: don't let children play with adult stuff!
To go by your side, circuit has a system to catch up on biasing while temperature rise (forgot the name of that tweak)

>>1187958
indeed, picture is showing crossover distortion from a sunn beta lead amp. There's only one trim on the circuit, which I biased, without solving the problem.
I don't want to spent hours to conclude that a power transistor needs to be changed, hence the whole power semi-conductors has to be changed... Are you reading through me guys?

I searched for class D stuff, but what I found didn't suit the power supply of my existing amps.

>>1187958
It also shows other distortion. Maybe something in the feedback path has failed?

>>1188768
>Datasheet for these TO3 beast is claiming a 115W dissipation max (each!).
SOA limitations are normally bigger problem with BJT amps. And that "115W" is rather hypothetical, as it requires an infinite heatsink.

>>1188782
>SOA limitations are normally bigger problem with BJT amps
Probably not here with 2N3055, though.

>>1188782
>>1188786
sorry but what does SOA means?