PSU for 5.1 amp

[jsandvik]

Hello

I am goint to build a 5.1 amp for my barebone PC

I will use 1 bridged LM4780 for the subwoofer and 2 LM4781 for the other 5 channels (not using 1 of the 3 channels in one of the IC`s).

Does a transformer rated 28V-0V-28V and 400VA sound resonable for this purpose?

Can I use only 1 rectifier bridge for all 3 chips or should I use 2 or 3 rectifier bridges?

How can I hook up 3 rectifier bridges to 1 transformer?

Cheers

 

[roibm]

I use 250VA(2x22V) for 2 channels...
There is a nice table, have a look:
http://www.tnt-audio.com/clinica/ssps3_e.html

I also have a question... Right now I am building a mono gainclone for my center channel(the most important), and I don't really know what transformer would be the best... Would a 160VA(2x22V) be enough? Better to go for a 250VA(2x22V)? If yes, what would be the diff? Would the 250VA be more efficient? The price diff between the two is minor, so that won't really matter.

Thanks...

 

[jsandvik]

Thank you,

Im still not sure about how many rectifiers I shall use!

 

[rnoble]

GC's don't tend to have that much headroom anyway, so you don't need helluva lot in reserve. I would think its more important to match your ps voltage with your speaker impedance rather than have an overrated transformer.

I would suggest a minimum of 80VA with anything over about 150VA being overkil. 100VA per channel is ample. 400VA for 5 channels is at the bottom end, I would consider 600VA. 160VA for a single channel is HEAPS - overkill really.

 

[jsandvik]

I was about to go for a 600VA but concidering that only one of the five channels are going to be feeded with frequencys under 100Hz (low frequency use more current) I thougth a 400VA was enough.

I am going to build it very compact, so size is an issue here.

I have to use a 8ohm speaker for the subwoofer sinze I am going to bridge the two channels in the LM4780, right?

I belive the other 5 spekars will be 4 ohms, but I have not decided yet.

Is one rectifier bridge OK?
What transformer voltage should I go for?

 

[demogorgon]

why, yes, you could use one rectifier bridge, but if you find the space for it, i would use one for eatch or at least let eatch chip have its own capacitance bank (kondensatorer).

jeg driver med samma greia jeg og.
vi kan jo holde hverandre oppdatert og utveksle erfaringer!

 

[rnoble]

What transformer voltage should I go for? [/B]

Check out the national specs on the amp. Particularly the supply voltage section.

link

 

[jsandvik]

What are the advantages/possible downsides of having one rectifier bridge for each chip or maybe even each channel compared to one rectifier bridge for the entire amp?

I am still not sure about how to hook up three rectifier bridges to one transformer...

Regarding voltage; I`ve been locking at the datasheets but I just wondered if anybody had some expirience or additional info around the subject.

This is my first electronics project except from building speakers, so I hope you can stand some silly questions now and then

Kjekt at flere roter med det samme!
Bruker du de samme IC`ene også?

 

[demogorgon]

well, the advantage of using one bridge for every chip is that the rectifier bridge dont have to handle a lot of current, and so they can do without a heatsikt.

another advantage is that every chip\chanel gets it's own ground source, so signal to ground ratio improves. (or so i'v heard )

well, about voltage, as i understand it you should use low voltage for 4 ohm speakers and both low OR high when using 8 or higher ohm speakers. dont ask me hwy, but it do seems to be the oppinion shared by most people here.

many say 30V is the compromise.

tengte jeg skulle bruke tda 2050 eller 2040 jeg, de koster mye mindre, kan bygges på veroboard, er mindre fysisk (bare 5 pinner) og har kraft nok til ampen jeg trenger.
den skal uansett inn i pc'n min sammen med en 160VA trafo så størelse teller.

 

[elnec]

hi to all

i'm designing a similer kind of project but using lm4780(in parallel mode) for satalite channel(100w each o/p power) & using two lm4780 chip(in bridge parallel mode) for sub (200w o/p power).so plz help me designing a psu for this project.