My amplifier - Rev .2

Autor

Beitrag

Savyasaachi
Inventar

#1 erstellt: 24. Aug 2006, 14:56

Hi all,

I have finally put my amp back together in one piece after much heartache.

I had actually given up on it completely and decided to chuck the thing.

However,

Arasu supported and motivated me to replace the blown parts and rebuild the amp...he said he would like to see me finish the damn thing and didn't want to see all that work and time to go waste.

Without his help and support this would not have been possible.

The amp is much better laid out than before and there are no hums or hiss noises.

There are also no heating issues.

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Parts that were made redundant
Transformer for the xover was removed and extra windings were made on the new tranny.
---------------------------------

The parts that were blown were...

Transformer-1 (350VA)(replaced with a similar rated one)
Bridge rectifiers-2( replaced with International Rectifier ones)
Capacitors..6X4700uF(replaced with 2x13000uF)
One LM4780 board(mids amp module)
replaced both the mid amp modules with LM4732 amps.
----------------------------------------

The entire amp was cleaned out..stirpped off all components laid bare and re built from scratch..

The position of the crossover too was changed to place it in the center so as to allow easy access to the trimmer pots.

The height of the Xover PCB spacer was increased..the board is now 50mm from the base plate of the amp.

Arasu also taught me to use proper type of wires..
Including color coding them so that it owuld be easy for anyone who opens it for maintainence

.

The layout could have been better..much better but for the fact that the mouting of the ICs did not facilitate a neater layout..
Ideally a single tranny with only one wire from the capacitors to the amp modules would have been desired(that was the idea actually)

Since i had already drilled holes for the ICs and redoing them involded too much work

we elected to try to make the best of it.

---------------------------------------

I had some oscillation problems with the previous amp when i played around with the gains on the xover...no such problem now

..
I have been able to properly adjust the gains for the mid and the highs..
Sadly i need to replace my woofers(some kids kicked them when in and they are beyond repair)

I guess that will happen only in November(Junia's

gettin them for me :D) ..i won't be here though

My other project too is nearing the end of the tunnel..
this too inspired by Arasu

...just some work on the case is left

...
more on this soonimages/smilies/insane.gif

Regards,
Sachi

Amplifer as it was before.

AMP Rev.1

Amplifier as it is now!

AMP Rev.2

[Beitrag von Savyasaachi am 24. Aug 2006, 15:05 bearbeitet]

ani
Stammgast

#2 erstellt: 24. Aug 2006, 15:15

Dear Sachi,

Congrats, do understand how you satisfied you feel after all the hours of strained neck and burned finger tips

From the pics I can see that you have almost made a gem from junk

Good work and keep it up.

Warm regards

Anil

BTW how does it sound wihtout the hum and unstability problems?

Amp_Nut
Inventar

#3 erstellt: 24. Aug 2006, 15:32

Great Job Savyasaachi, down to the wires ties used

SDhawan
Stammgast

#4 erstellt: 24. Aug 2006, 17:00

Dear Savyasaachi,

Congratulations !

Sanjay

Savyasaachi
Inventar

#5 erstellt: 24. Aug 2006, 17:59

Thanks Ani...and you bet!..
Building an amp is not as easy as i thought..and building one that can take punishment is presently beyond my capability..maybe need another ocuple of years before i can build something like that..

This amp has no portection circuit built in...and is the only major drawback.

It sounds very good(except the bass is not as good as a transistor or MOSFET based amp..not even close) especially since i can now vary the crossover gains for each driver without worrying abt stability/oscillation problems..

Tested it with a frequency generator to see how the crossover is workign....
Its very very good..crossing over exactly at 3400hZ...there is a point source from in between the tweeter and the midrange...exactly like how it is supposed to be...

Thanks ampnut,
it could have been better..much better is all i have learnt from building the amp a second time..i guess another 3-4 amps and i should gain enough experience to make a neat layout of the my amps

Thanks sanjay..

[Beitrag von Savyasaachi am 24. Aug 2006, 18:03 bearbeitet]

Savyasaachi
Inventar

#6 erstellt: 24. Aug 2006, 18:01

No more building chipamps for me...next only transistor based and MOSFET based amps..
am especially looking forward to building an N channel MOSFET amp for subwoofer duty..but this would take quite a long while..and a lot lot more reading..

ani
Stammgast

#7 erstellt: 24. Aug 2006, 18:10

Elektor had published a few Mosfet amps, the mini cresento was a good one, please dont forget that it was mid 80's design. They came out with a very simple, power darlignton bipolar transistor based sub woofer amp, think it was early 90's pls check it out may suit your purpose

Anil.

Savyasaachi
Inventar

#8 erstellt: 25. Aug 2006, 02:40

ani schrieb:

ahh the crescendo amps...yeah..they were very good amps..they still are..
designed in the 80s but still on eof the best
u have to understand that the topologies hardly change..even between companies..
its only the look and feel and that x factor that distinguishes between companies...
The crescendo would definitely work superbly for the mids..but the N channel MOsfet would excel in the lows.