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Wejp 13th October 2004 07:36 PM

My new hifi amplifier (pictures)
 
2 Attachment(s)
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. :)

Nuuk 13th October 2004 09:37 PM

Nice work and well documented! ;)

wigginjs 14th October 2004 01:34 AM

Wow, lots of work. Looks very professional. Congratulations, I admire your work.

troystg 14th October 2004 04:25 AM

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

Upupa Epops 14th October 2004 08:37 AM

Nice profesional work ? Are you joking ? Only big effort ;) , guys.

Wejp 14th October 2004 09:31 AM

Thanks for your nice replies guys. :)

Quote:

Originally posted by rabstg
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

digi01 14th October 2004 10:20 AM

Wejp,wonderful design!
I like your works from my heart.

:up::up::up:

digi

Upupa Epops 14th October 2004 10:26 AM

To digi 01 : So you must have in your heart rather mess :xeye: :cool: .

digi01 14th October 2004 10:32 AM

:D

Yes,it is full of circuit and hook wires,even in my dream :xeye:
anyhow,I like diyaudio;)

Upupa Epops 14th October 2004 10:40 AM

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


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