My new hifi amplifier (pictures)

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Hello everyone,

i've just finished my new hifi amplifier. It is build around two TDA7294 and it has six line inputs, two line outputs and an additional headphone amplifier.
I've made lots of pictures while building it. You'll find them on my homepage. :)
 

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Hi Wejp-

Very ambitious project. Came out very nice.

1. I love the heatsink! Man I wish all heatsinks were connected on the ends like that so they didn't sing on their own. :)

2. May I ask for some information on your input selector circuit? I would like to build something similar.

Thank you in advance,

Troy
 
Thanks for your nice replies guys. :)

rabstg said:
Hi Wejp-

Very ambitious project. Came out very nice.

1. I love the heatsink! Man I wish all heatsinks were connected on the ends like that so they didn't sing on their own. :)

2. May I ask for some information on your input selector circuit? I would like to build something similar.

Thank you in advance,

Troy

Sure you may ask. :)
The input selector consists of two parts: The Controller board with a PIC16F84A micro controller that reads a matrix keyboard with eight buttons. I connected the keys as a matrix to save some i/o ports on the controller. The controller has an integrated eeprom where I store the selected input, so when the amp ist shut down and then later powered on again it remembers the input which was selected last.
Again to save i/o ports, the controller outputs the selected channel as a 3bit binary number and an additional 4028 decodes it to a decimal.

The other part is the board with the relais for input switching and the preamp.
The relais are switched through small transistors.
The main preamp has a gain of 4 and uses a NE5532A opamp. The gain is required to compensate for the volume loss at the balance potentiometer (which normally is in middle position so voltage drops by 50%) and to increase the line level to the level required by the TDA7294's.
For the two line outputs, that can be used as a record output for Minidisc or tape, I also used NE5532A, but these opamps work with a gain of one.

If I forgot something you wanted to know, just ask. :)

/Johannes
 
Upupa Epops said:
Yes, my too :cool: - but to show pics of prototype and wait for compliments is for me too " strong cofee " ;) .

So you think only those who have profesionally manufactured PCB's and cases may post their pictures? :xeye:
I just wanted to build one nice sounding amplifier and not many and that's what I have done. And it really sounds nice. :)
You don't have to like it. Others do. And that's okay.
 
Hi All-

What Upupa is referring to is called "constructive criticism" and it has its place.

The project as a whole is excellent.

The wiring could be cleaned up to make the project look better and possibly assist with stray or spurious noise.

P2P wiring is absolutely fine for DIY. Why do you think component leads are so long? To solder to a PCB?

Louis W. Erath (AKA "the wire burner") has built some of the ugliest, worst laid out components I have ever seen. But rarely is there an Engineer with more vision and talent than his.


Hey wejp-

The thought process behind the project is the most important task.

However the execution is a close second.

With minimal effort you could clean up the wiring and then it would go from a "birds nest" as Upupa put it, to an adequate installation that will simply be overlooked. It takes ALOT of effort to create art with wiring.

That is my constructive criticism to hopefully make you better.

My compliments still remain on the scope of the project, the logic of the project, and the drive for completion.

As a last note, would you have the schematic of the input selector section available for posting?


Thanks again,

Troy

PS, this is a forum.. EVERYTHING should be taken with a grain of salt.
 
Some people just want to build an amp and listen to it. If they have little experience and the end result doesn't look "prefessional" on the inside but the sound coming out of it is enjoyable for the listener, then they accomplished what they intended to do right? Not everyone wants to build amps after amps like alot of us do.

Either way, nice beginning with that amp, alot of us built worse circuits and wouldn't post them ;).
 
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