Please help me building audio grade power supply

[subro99]

Hi Gurus,

Have come to you once again..............

This time trying to build a power amp with LM49810 chip poised to deliver 200 watts each channel.

Bought the kits and made the heat sinks.

Just one issue - i have a 40-0-40 7.5 Amp traffo where as the circuit required +60 Volts, -60 Volts and +45 Volts & -45 Volts.

My friend FM Saheb has advised me to by another 30-0-30 Traffo.

Isn't there any other way? I don't want 2 traffos in same cabinet as i suspect too much emf .......

Can a simple volltage devider formula won't work?

Should i post the circuit diagram?

Later on, i shall be expecting your comments to improve the stock kit, but as of now need your inputs for getting it up and running.

And please also suggest which rectifier should i use....for the bridge. Should i put one polyster cap in parallel to each diode? I can make abridge unregulated, but do i need a regulated one. If yes, then will LM 78XX Series will do................?

Sorry - lots of questions this time !!

Thanks in advance.

 

[sarith]

A simple way is to sell your existing trafo and custom build one trafo with all the necessary winding/volts. Normal bridge and ultra fast diodes, either are okay. Putting caps is not a bad idea. Using regulators depend on the application. If you need to use LM 78xx, then you gotta use it..

 

[subro99]

I really really don't want to buy another traffo set as this will make the set too bulky and lot of EMF issues. Moreover contrary to what is suggested above, i cannot go back to the traffo shop and ask him to extract a tapping at 30-0-30 level. . . .

Hence, i am now thinking which voltage needs more amperes. The 60Volts rail or the 45 Volts rail. I have heard one is for actual power feed requirement ( the actual lunch & dinner for the amplifier) while the other is for "control" purpose. Which means this would be the "sweet dish/dessert" stuff. So this would not require so much of "amperage".

Is this the correct line of thought? Well, for the Gurus, how will they say, if they are not shown the X-Ray plate...

So here it is.....in my next post.

 

[subro99]

Well, this is the Chinese schematic that i have received. Please let me know if i can have a minimalist approach to one of the supply voltages....

 

[omishra]

According to schematic, 45V need actually more ampere. 60V is for preamp section.

For more current needs 78Xx are useless. It has limited current capability.

 

[saheb11123]

Is it safe and wise to implement a voltage divider circuit?
Or is there a way to bypass the preamp section of the amp and use the power section of the amp, that way the +/-60V will not be reqd.

 

[sashijoseph]

@Subro99

Simply use the transformer at hand to power both the o/p and LME stages.

With ~ +-48V (considering ~15% sag at full load) to the LME,you'll get an o/p of ~ 120W into 4 ohms.

Enough to get you up and running.

 

[diesel engine]

I think those output trannies can handle +/- 60V
Alternatively use the circuit attached. well documented. PM me for the PCB file.

 

[diesel engine]

sorry, the atchmnt failed to upload. the same is available in Elektor website. search for Q Watt power amp in the site. or contact me to - [email protected]. I will try uploading it here later.

 

[diesel engine]

here is the schematic. the pcb pattern is also a large file. which failed to upload.

 

[saheb11123]

@Subro99

Simply use the transformer at hand to power both the o/p and LME stages.

With ~ +-48V (considering ~15% sag at full load) to the LME,you'll get an o/p of ~ 120W into 4 ohms.

Enough to get you up and running.

Seems like a good idea to me.

 

[subro99]

Thanks everyone.......

i will take the most common and popular advice. Will build a bridge circuit with the available traffo................

 

[subro99]

These were assembled in a hurry. FM Saheb suggested to remove the boards and join the capacitors directly.........

Thanks buddy - much appreciated.

Hope i am on the right path......................

 

[subro99]

Should i go for "snubber capacitor" across each diode.......?

 

[saheb11123]

Should i go for "snubber capacitor" across each diode.......?

You should 0.01uf will suffice i guess...

please advise other members.

 

[saheb11123]

I can build the psu for you if you would like, i have lots of free time now, since exams are over.

 

[sashijoseph]

Instead of discrete diodes,a 35-Amp bridge could also be used and bolted onto the chassis for keeping it cool.

sth like here : http://www.flickr.com/photos/97860410@N03/9105146409/in/photostream/
from Hydrovac's build thread here : http://www.hifivision.com/diy/45380-300-watt-hi-fi-power-amp-project.html

 

[saheb11123]

The Mur series rectifiers are better i guess

 

[omishra]

Snubber cap, 0.1 uF will also work but voltage rating should be at least 3X of secondary voltage.

 

[shaan]

So we met and then this happened!