Amplifier with 2N3055

[Tekko]

I was a bit bored and looked over at a disassambled regulated psu that has two 2N3055's in it and thought "i wanna build an amp with that!"

Heres the result after a few hours in simulation:
schematic with sim

 

[mnemneth]

First thing I noted is with your diff amp degeneration resistors R9, R16.

You have them shorted out, as your distortion text also indicates.

Sandy

 

[Tekko]

And now its playing:

http://i.imgur.com/LZPi0.jpg
http://i.imgur.com/SwGJg.jpg

This s the schematic on the board:
http://i.imgur.com/WAVUF.jpg

As im posting this, the amp is blasting music at pretty high volume.

 

[godfrey]

... two 2N3055's ...

So if you want stereo, it'll have to be single-ended class A.
Hehe - look Ma, only 30W dissipation for 2.5 watts output.

 

[Tekko]

If i want to make a stereo version of this, i'll just get more 2N3055's, their dirt cheap.

This heatsink is way undersized anyways, its already HOT!! And this amp runs only 100mA bias.

I have in a box at my old adress a large heatsink with 8 TO3 devices on them, actually 2 but the other one is clean.

 

[Tekko]

Update:

The two 2N3055's have been replaced with four 2N3716 on a much bigger heatsink.

However making that work was a chore, it took me half a day and loosing a transformer to find out that one of the 2N3716's had a short from c to b.

However once that transistor was disconnected and replaced, the amp sprung to life.

 

[nigelwright7557]

Update:

However making that work was a chore, it took me half a day and loosing a transformer to find out that one of the 2N3716's had a short from c to b.

Its worth fusing the secondaries to save the transformer if a short occurrs.

I have missed out the fuses myself before on a test rig,
Next thing I knew the transformer was bubbling due to a short !
Luckily i caught it just in time before the windings all melted together.

 

[Tekko]

In my case i dident notice it since the transformer was inside a plastic box down on the floor, when i heard the plastic bobbin bubbling and saw the smoke, it was already too late Secondary had already developed interturn shorts.

 

[Tekko]

Pics of prototype:

http://i.imgur.com/gDaaR.jpg
http://i.imgur.com/t8agH.jpg
http://i.imgur.com/aaC9X.jpg

Antithump delay:
http://i.imgur.com/gjs06.jpg

 

[Tekko]

Cleaned it up alittle:

http://i.imgur.com/3FFB1.jpg
http://i.imgur.com/rPFhY.jpg
http://i.imgur.com/XV264.jpg
http://i.imgur.com/yyEeC.jpg

Schematic:
http://i.imgur.com/UlYNn.jpg

It works and sounds really good.

 

[krachkiste]

Hi Tekko,

Is R3=680 in the LTC-schematic intentionally set to 680 Ohms?

 

[Tekko]

Yes and it also is on the actual board.