| D3 |
Hi, I am sorry to trouble this forum....but I would appreciate help right through the build process..........
I am a relative newby.....regarding power amps......however I have built preamps & power supplies in the past.
I want to build two mono block aleph-x's.......with an output of approx 60w into 4 ohms.
I have downloaded the parts list but I am aware that this amp.......requires differing values of components dependinging on
the setup.
Please can somebody help with the component list I require.....
also how many mosfets will I require per channel? what do you recommend.....and what type.....(ie IRFP240 or IRPF044????)
What sort of transformer volatages am I looking at ......ie 20-0-20
I hope there is somebody patient out there........I will be asking some pretty basic questions......
Richard Bolton UK
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| Luke |
hi D3
The best place to start is with calculator on post #267 of the high power x thread. It would also be a good idea to spend a couple of hours reading it.
http://www.diyaudio.com/forums/show...5&pagenumber=18
The yellow boxes are the variables you decide for your amplifier and it calculates what you will need.
If you choose 20volt rails with 4 amps of bias, and 4 fets you will need around 15 0 15 tx for something rated factor of 3 or more, or say a 16 17 for something rated with a factor of two.
With 4 fets you will dissipate 40 watts per fet which is doable i think but will need good sinking.
Nelson I think in his comercial offerings likes to keep things at around 25watts per fet.
A good fet is a cheap fet :D Irfp240, IRFP244 and IRFP044 are all good. I think mouser and digikey have good prices on these. I chose 240 for my aleps as they were cheap and did the job.
BOM materials is on the thread somewhere too for other things you will need. Keep in mind you will need alot of capacitance.
100000uF per rail for two channels would not be unreasonable I wouldnt think?
Good luck:) |
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| D3 |
Thanks luke.............good pointers.........still would like some guidance .........if possible......:cannotbe:
I will give the h-power threads a good read.........I have attached
my proposal for 20v rails and 8 devices per channel ..... what do you think???? Is this correct??? |
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| D3 |
| Gorden Bennit...........right here goes....have included xls file now ....sorry |
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| Netlist |
Hi Richard,
It appears to me you got the wrong spreadsheet.
There has been some confusion recently, resulting in the posting of a wrong xls-file.
Go to the WIKI. You'll find a lot of compressed info and a correct xls-file as well.
/Hugo :) |
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| D3 |
Thanks Hugo...................really appreciate your advice.....will check it out!
;) |
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| yoke |
Hi Netlist...
I have problem understanding this spreadsheet …
I have download X berekening v3 A and X nania v3B …
O.k. in X bereking v3A which is on wiki it says
voltage 20 volts
bias 4 amps
ac current gain 50%
number of fets 8
Peak current 4 amps
power 8 Ohms 64 watts
power 4 Ohms 32 watts
power 2 Ohms 16 watts
Dissipation 160 watts
Dissipation per fet 20,00 watts
Transformer secondaries 15,38 volts
16,67 volts
18,18 volts
20,00 volts
Transformer wattage 320 watts
480 watts
Bias per side 2,0000 amps
Bias per fet 1,0000 amps
Resistor to bias fet 0,5000 ohm
And X Nania V3b
voltage 20 volts
bias 8 amps
ac current gain 50%
number of fets 8
Peak current 8 amps
peak power 8 ohms 81 watts
peak power 4 ohms 128 watts
peak power 2 ohms 64 watts
rms power 8 ohms 57 watts
rms power 4 ohms 90 watts
rms power 2 ohms 45 watts
Dissipation 160 watts
Dissipation per fet 20,00 watts
Transformer secondaries 15,38 volts
16,67 volts
18,18 volts
20,00 volts
Transformer wattage 320 watts
480 watts
Bias per side 4,0000 amps
Bias per fet 1,0000 amps
Resistor to bias fet 0,5000 ohm
To me X Nania make much more sense … Diference is bias in Nania is 8A insetead 4A...So which one is correct
In X berekeing , voltage X bias = 20 x 4 = 160 W disispation ???
In Nania is 20 x 8 = 160 W
am I missing something ...???
Thanks
Regards Josip |
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| D3 |
Thanks Josip ..... I thought it strange as well......I assume as you do ......X Nania is more accurate..............I hope somebody will confirm our feelings on this
Thanks
Richard Bolton uk:xeye: |
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| Andypairo |
You are forgetting that the amp uses dual supplies, so 20V means 20+20.
Guess who is right now?
Cheers
Andrea |
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| Netlist |
Josip, Richard,
Andrea is correct.
Indeed, 20V and 8A per side makes 320W because AlephX has two sides.
20V and 4A accordingly gives twice 80W meaning 160W total.
The WIKI-version is the exact one, the Nania-version includes a RMS calculation which is handy but miscalculates the dissipation. :hot:
Greetings
/Hugo :) |
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| D3 |
Many thanks Hugo.......that settles it ......... I am after the 20v option at 8A.............I am building two mono blocks.
I asssume the 20-0-20 is after rectification as the nania ......if I remember rightly there is a rectification ratio .......... so assuming my target is 20-0-20 what should my transformer voltages be...are the ones indicated in the enclosed clip correct if so which one do I choose!!!.............advice/help would be appreciated |
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| Netlist |
| quote: | Originally posted by D3
that settles it |
You still have the incorrect spreadsheet. Don't know what's happening.
This is not the WIKI-one.
A nice program to calculate power supplies is PSU Designer. http://www.duncanamps.com/psud2/index.html
Try to make yourself familiar with it. It will give you very accurate results.
/Hugo :) |
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| yoke |
Thanks for the info,Hugo and Andrea...
Regards Josip |
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| D3 |
Thanks guys for supporting a newby.......................your advice is really appreciated .......when I get started ..........I will keep you all posted!!!
Thanks!
Richard Bolton Uk (nr Manchester) |
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| bigparsnip |
| yep, you will want to check those results with the other version of the spreadsheet (let me know if you can't find it an I'll mail you a coppy) as you will be dissibating about 320W per channel with that design rather than 160W. HOwever, if you are going ofr mono blocks, and using the large heatsinks from conrad as disscused a bit in the uk-order thread you should be quite ok, with only a 34 degree rise over ambient. |
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