| elnec |
hi to all
i'm designing a 5.1 channel amplifier project 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. |
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| AndrewT |
Hi,
most single channel amplifiers can be made to work well when the transformer is rated so that VA=1.5*W @ maximum output.
A multi-channel amp could be set up the same way. However, I believe some economy can be achieved without reducing the music playing ability of the completed amp.
I suggest total VA = 1.5*LargestW+1.0*(totalW of all others).
Each amplifier has it's own rectifier and smoothing bank.
Use a single 25A 200PIV rectifier for each amp.
Use a smoothing bank with 2mF/Apk to 3mF/Apk for each amp.
eg.
200Winto4r +100Winto8r(times 5) transformer voltage for all 6channels will be the same.
VA=300+500=800VA.
200W uses +-20mF and 100W each use +-10mF. (total capacitance=180mF@63Vdc- not bridged, see note).
However, to achieve 200W into 4r requires 40Vpk into 4r and 100W into 8r also requires 40Vpk into 8r. These will require supply voltage of about 95V to 100V. Can LM4780 survive these supply voltages?
Solution;
bridged-parallel can achieve these powers but at the expense of doubling the number of chipamps required and doubling the number of PSUs required.
Do you want to consider discrete? or reduce your target spec? or aim for lower quality? Decision time. |
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| elnec |
thank man
but can this be possible to go discrete i.e power supply for sat channel(all 5 channel) & separate supply for sub
plz revert for this & also please help me avoid schematic(as i'm not a expert in psu design) |
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| AndrewT |
Hi,
you have selected the chipamp and suggested a power target, but I see no speaker selection.
This brief is incomplete.
How do you know what power might be suitable if you don't have a speaker specification?
Have you revised any of your targets?
Do you know what impedance and sensitivity each of your speakers/drivers are? |
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| elnec |
ok
there goes the spec.
for sat
sensitivity about 92 dB
impedance 4ohm
for sub
sensitivity about 89 dB
impedance 4ohm / 8 ohm
& regarding my target
for sat (no target change) using lm4780 in parallel mode(100w)
but for sub (plz recommed amp providing 150 w to 200w power)
plz provide psu for this
thank |
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| AndrewT |
Hi,
for 100W into 4r you need 28.3Vpk and 20Vac.
This can be achieved with supply rails of about +-35Vdc from a transformer wound to achieve 25-0 & 25-0Vac when fully loaded.
A pair of paralleled chipamps can get you to that target. Follow the manufacturers direction carefully and don't skimp. Each amp requires a minimum of +-6800uF, or maybe +-15mF for the paralleled pair.
The 200W into 4r requires 40Vpk and 28.3Vac.
Chipamps can only achieve this if bridged.
The spec for each half of the bridge beomes 100W into 2r. That is just about achieveable if you use three or four chipamps in parallel making six or eight chipamps and PSUs for the parallel-bridged amp for just the sub.
There's why I think you would be better going to discrete. It will be simpler and cheaper. One PCB and one PSU
Chipampers,
is it possible to get you to 200W into 8r from bridged-parallel chipamps.? |
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| elnec |
thank
plz any u give detail on sub part
also plz can u provide me schematic(as i'm not good at designing psu) for both discrete section
thank |
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| AndrewT |
| You should wait for the chipampers to come in to get a balanced view. |
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| awpagan |
| quote: | Originally posted by elnec
ok
there goes the spec.
for sat
sensitivity about 92 dB
impedance 4ohm
for sub
sensitivity about 89 dB
impedance 4ohm / 8 ohm
& regarding my target
for sat (no target change) using lm4780 in parallel mode(100w)
but for sub (plz recommed amp providing 150 w to 200w power)
plz provide psu for this
thank |
100w amp into 92db sat's is a lot of volume
impedance for the sub, is it 4ohm or 8ohm at 89db
also 89db at what Hz's? 1kHz??
what's the rolloff and frequency range for the sub?
Decent sub amps need a fair bit of power due control the driver at low frequency's
As andrew alluding to, this will give an idea of chipamp or discrete.
allan |
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| burnedfingers |
Solution;[/QUOTE]| quote: | | bridged-parallel can achieve these powers but at the expense of doubling the number of chipamps required and doubling the number of PSUs required. |
[QUOTE]
There may be a another solution.. You could use chip amps to drive bipolar output stage to obtain high power. |
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| elnec |
| quote: | Originally posted by awpagan
100w amp into 92db sat's is a lot of volume
impedance for the sub, is it 4ohm or 8ohm at 89db
also 89db at what Hz's? 1kHz??
what's the rolloff and frequency range for the sub?
Decent sub amps need a fair bit of power due control the driver at low frequency's
As andrew alluding to, this will give an idea of chipamp or discrete.
allan |
as for sub, i'm using sony "XS-L122P5"
& for sat, i'm using sony "XS-GT6938X" |
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| elnec |
| quote: | Originally posted by burnedfingers
Solution; |
| quote: |
There may be a another solution.. You could use chip amps to drive bipolar output stage to obtain high power. |
plz give some detail |
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| AndrewT |
Hi,
I think it is the LM4702 that is DESIGNED for exactly this.
A chipamp without the output stage.
It can be scaled from 20W all the way to 200W into 8r. |
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| awpagan |
| quote: | Originally posted by AndrewT
Hi,
I think it is the LM4702 that is DESIGNED for exactly this.
A chipamp without the output stage.
It can be scaled from 20W all the way to 200W into 8r. |
Andrew
the XS-L122P5 sub is a 12" 4ohm car audio woofer
the XS-GT6938X is a 6*9 car audio speaker (probably 4ohm also)
http://www.latin.sony.com/corporate...del=XS-GT6938X#
is possible
depends on how they are utilised
makes a difference to the amp thought.....
allan |
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| AndrewT |
Car audio drivers!!!!
What are the Q values?
Are they suitable for cabinet loading?
Suit vented or sealed or open baffle? |
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| elnec |
| quote: | Originally posted by AndrewT
Car audio drivers!!!!
What are the Q values?
Are they suitable for cabinet loading?
Suit vented or sealed or open baffle? |
sealed cabinet is used here for sat & suit vented for sub & for Q values plz refer to sony's website |
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| elnec |
hey guy
pz help me this as without psu i can't finsh my project |
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| AndrewT |
Tell us what decisions you made.
chips?
voltage or voltages?
discrete?
Target power?
speaker impedance? |
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| elnec |
| quote: | Originally posted by AndrewT
Tell us what decisions you made.
chips?
voltage or voltages?
discrete?
Target power?
speaker impedance? |
for sat: target is same (using lm4780 in parallel mode) but for sub. one can go discrete with 150w of power into 8ohm subwoofer as lm4702 isn't available here |
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| gmphadte |
For your Sub, u should go for a discrete amp. As a beginner, u may find this proposal a bit too much but as far as parts availability is concerned, u will not suffer a bit.
Take it from me, U SHOULD consider this as the first priority at "in my house lol"
The options could be Quasi's amp (350W is a bit higher) but is all explained.
The Symasym is a bit lower in power but can u krank your sub so high where u live. If not should be OK. I am worried of your neighbourhood.
If u want to go for discrete, then we can help u.
Google for it and ask.
Knowing where is "in my house" will get u better help
Gajanan Phadte |
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| AndrewT |
Hi,
we have a brief for the sub, 150W into 8r.
That requires a Vpk=49V.
Assuming losses of about 10V the supply rails will be about 59 to 60Vdc.
150W output requires about 225VA
Peak output current is 6.1Apk
Use 41Vac to 42Vac 250VA transformer. It can be dual secondary 42-0Vac + 42-0Vac or centre tapped 42-0-42Vac
This voltage is difficult to obtain, so you may have to use 40-0-40 and reduce your output target to 130W into 8r.
The rectifier should be 25A 200PIV.
The smoothing caps should be +-12mF to +-18mF 75Vdc.
If you reduce your transformer to 40Vac you can reduce the smoothing caps to 63Vdc, these are easier to obtain and much cheaper.
If you decide to use a 4ohm driver on this amp you need to double the transformer VA to 450VA and double the smoothing caps to +-24mF to +-36mF.
Are you going to give us a brief for the rest of it? |
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| bijenk |
I guess this document will help you. Keep me informed of your project.
Enjoy......... |
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| elnec |
thank for your help
as for my project i am looking for amplifier that suit my need for sub
plz help me find it
can u give me idea what will be power req'ment for same so that i can get a supply for same
rest every thing is build & will be completing the project if sub amp is avaiable
peace |
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| AndrewT |
Hi,
what is the amp power and speaker sensitivity for the mains?
What is the sub-bass sensitivity AT the FREQUENCY you require matching maximum SPL? |
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| elnec |
| quote: | Originally posted by AndrewT
Hi,
what is the amp power and speaker sensitivity for the mains?
What is the sub-bass sensitivity AT the FREQUENCY you require matching maximum SPL? |
hi andrew
i don't know abt this stuff & plz don't take wrong but in my project i don't want these type of complexity plz provide me the simple solution for my subwoofer amplifier that can give o/p of 150w & suplly voltage should be in range of 35 to 50 v
plz read the whole thread one more time
thank in advance
regards elnec |
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| AndrewT |
Then I can't give you a useful answer.
Maybe someone else can guess? |
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| geminni |
I am sorry, but don't think that those speaker will survive 100wats!!
Haven't seen woofer but those car speaker... Don't know... Bad idea.
Second thing, do you mean +-35 to +-50 volts or just single 35 to 50v?
Why don't you make all with TDA7294? 60-80wats will be enogh shure, as for woofer in bridged mode maksimum 150w allso with TDA7294. |
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| elnec |
| quote: | Originally posted by geminni
I am sorry, but don't think that those speaker will survive 100wats!!
Haven't seen woofer but those car speaker... Don't know... Bad idea.
Second thing, do you mean +-35 to +-50 volts or just single 35 to 50v?
Why don't you make all with TDA7294? 60-80wats will be enogh shure, as for woofer in bridged mode maksimum 150w allso with TDA7294. |
as for power supply it's +-35v to +-50v
& can u suggest the speaker & woofer for this project as i want to make this project with above given spec i.e for sat 100w & for sub 150w or more
thank for your help
regards
elnec |
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| elnec |
| quote: | Originally posted by geminni
I am sorry, but don't think that those speaker will survive 100wats!!
Haven't seen woofer but those car speaker... Don't know... Bad idea.
Second thing, do you mean +-35 to +-50 volts or just single 35 to 50v?
Why don't you make all with TDA7294? 60-80wats will be enogh shure, as for woofer in bridged mode maksimum 150w allso with TDA7294. |
as for tda 7294, there inductor used for this & i don't want to use them as i don't like to install inductor in my project as i can't handle them efficently
but thank for your advice
regards
elnec |
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