Is it possible to from scratch build a home power amp which could deliver 250 watts RMS into 4 Ohms? This of course without explosive amps, million dollar budgets or 50%THD levels...
I know this is asking ALOT. All power figures are ideal and may vary.
It would run from 240VAC outlet, with line outs from my stereo. The only other needed components would be an on/off switch (i do know how to put those in...) and a volume knob. I may put in a switch for bass/treble filter, if i find it needed, but I can manage that.
-Eli, willing to be yelled at if its relevant.
PS just making sure of something. If for example i wired 400 watts RMS at 2 ohms, into two 4ohm subs in parallel, would they each get 400 watts rms?
I know this is asking ALOT. All power figures are ideal and may vary.
It would run from 240VAC outlet, with line outs from my stereo. The only other needed components would be an on/off switch (i do know how to put those in...) and a volume knob. I may put in a switch for bass/treble filter, if i find it needed, but I can manage that.
-Eli, willing to be yelled at if its relevant.
PS just making sure of something. If for example i wired 400 watts RMS at 2 ohms, into two 4ohm subs in parallel, would they each get 400 watts rms?
> Is it possible to from scratch build a home power amp which could deliver 250 watts RMS into 4 Ohms? This of course without explosive amps, million dollar budgets or 50%THD levels...
You can scratch-build anything you want. Egyptian Pyramid, the InterNet, the 1903 Oldsmobile: all built from scratch. (And Mr Olds did it in a barn.)
However... 250W in 4Ω is a VERY common rating for rock-n-roll PA amplifiers. Most of these have impecable specs, sound that does not suck, and the prices are super-competitive. It works right out of the box, no flames, or if not they will give you another one on warranty. Unless you have an unusual spare-parts box, the price of a complete assembled warranteed PA amp is little more than the price of your parts, and people have been known to work months or years to assemble large power amps from scratch (and many abandon the effort). That's months of un-paid labor, some of it pretty dull (chasing back-ordered parts), and you need a pretty spiffy test-bench to smoke-test and verify a big power amp safely and meaninfully.
There are lots of things that DO make sense as DIY scratch-built. But you need a pretty specific reason to justify building high-power amplifiers in a range where commercial competition makes fine low-price power-monsters.
> If for example i wired 400 watts RMS at 2 ohms, into two 4ohm subs in parallel, would they each get 400 watts rms?
Each would get 200 watts.
You can scratch-build anything you want. Egyptian Pyramid, the InterNet, the 1903 Oldsmobile: all built from scratch. (And Mr Olds did it in a barn.)
However... 250W in 4Ω is a VERY common rating for rock-n-roll PA amplifiers. Most of these have impecable specs, sound that does not suck, and the prices are super-competitive. It works right out of the box, no flames, or if not they will give you another one on warranty. Unless you have an unusual spare-parts box, the price of a complete assembled warranteed PA amp is little more than the price of your parts, and people have been known to work months or years to assemble large power amps from scratch (and many abandon the effort). That's months of un-paid labor, some of it pretty dull (chasing back-ordered parts), and you need a pretty spiffy test-bench to smoke-test and verify a big power amp safely and meaninfully.
There are lots of things that DO make sense as DIY scratch-built. But you need a pretty specific reason to justify building high-power amplifiers in a range where commercial competition makes fine low-price power-monsters.
> If for example i wired 400 watts RMS at 2 ohms, into two 4ohm subs in parallel, would they each get 400 watts rms?
Each would get 200 watts.
Yes you can. As an example the Opti-MOS kit from www.sealelectronics con probably be configured to do that with double-die L-MOSFETs.
I think there is aqn outfit called AssieAmps that has something on that order.
H*o*w*e*v*e*r that is biting off a major, major project if this is a first amp project. The currents would most definately be lethal! The guage of the power supply and output wiring woulds have to be scaled up from what one finds in more modest amps. PCB traces would need to be made large enough to hanle the current. Even power on/off would need some additional circuitry.
I think there is aqn outfit called AssieAmps that has something on that order.
H*o*w*e*v*e*r that is biting off a major, major project if this is a first amp project. The currents would most definately be lethal! The guage of the power supply and output wiring woulds have to be scaled up from what one finds in more modest amps. PCB traces would need to be made large enough to hanle the current. Even power on/off would need some additional circuitry.
My first power amp was 200W / 2Ohms
Do your math with respect to current supply from your power supply and current supply through your output devices. Control your bias well with temperature tracking and limit the closed loop gain to less than 20. Yes, use thicker wire / copper on circuit boards and watch your ground circuit for high current in signal paths. Analog amplifiers cannot be greater than 70.7% efficient, so make sure your heat sink is large enough. All the usual safety features when powering up...a variac for first time or a 100Watt bulb in series with the line...fuses can save components going into thermal runaway.
have fun
Do your math with respect to current supply from your power supply and current supply through your output devices. Control your bias well with temperature tracking and limit the closed loop gain to less than 20. Yes, use thicker wire / copper on circuit boards and watch your ground circuit for high current in signal paths. Analog amplifiers cannot be greater than 70.7% efficient, so make sure your heat sink is large enough. All the usual safety features when powering up...a variac for first time or a 100Watt bulb in series with the line...fuses can save components going into thermal runaway.
have fun
Available in Aus
Mad,
Try this one from Jaycar
URL=http://www1.jaycar.com.au/productView.asp?ID=KA1760&CATID=&keywords=ka1760&SPECIAL=&form=KEYWORD&ProdCodeOnly=&Keyword1=xxxxxxxxxx&Keyword2=xxxxxxxxxx&pageNumber=&priceMin=&priceMax=&SUBCATID=]Jaycar KA1760[/URL]
I have built one or two and they perform really well. Just a big inrush current at turn on.
Mad,
Try this one from Jaycar
URL=http://www1.jaycar.com.au/productView.asp?ID=KA1760&CATID=&keywords=ka1760&SPECIAL=&form=KEYWORD&ProdCodeOnly=&Keyword1=xxxxxxxxxx&Keyword2=xxxxxxxxxx&pageNumber=&priceMin=&priceMax=&SUBCATID=]Jaycar KA1760[/URL]
I have built one or two and they perform really well. Just a big inrush current at turn on.
I do like the sound of one or two of those kit amps on www.seaelectronics.com as they have very nice power levels, though I also like the idea of simply buying one. I will enquire at the big PA places and see what I'll be up for. Thanks!
ive just built slones amp design of 11.8 in his high power amp book 250watt 4 ohm, cost me about £150 for EVERTHING (two monoblocs), yes I bought the caps and sinks of ebay but there is no reason you cant either. They sound fabulous driving my dads speakers better then a Quad 77 and a musical fidelity A1. Anyway, building these is really simple it took me less then a week and I had university to attend at the same time.
If you choose to build them good luck.
Matt
If you choose to build them good luck.
Matt
You'll never find heatsinks and capacitors on the australian ebay... and even if ya did, I'd win them anyway... I need heatsinks.. ok, SO BACK OFF BUSTER!!! THEY ARE MINE!!! ALL MINE!!!
anyone got any heatsinks in AUstralia I can get for cheap? lol I'm looking for like 15cm high, 5-6cm "thick" and 35-40cm long.. lol AND I need 4.... I was originally going to get 4 heatsinks total from Dicksmiths... these are 30cm long, 7.5cm high and 4.8cm thick.. and bolt a block of aluminium onto the back of each... but that would cost $80 total... and thats the most expensive part so far.. and I'd rather find something cheaper..
anyone got any heatsinks in AUstralia I can get for cheap? lol I'm looking for like 15cm high, 5-6cm "thick" and 35-40cm long.. lol AND I need 4.... I was originally going to get 4 heatsinks total from Dicksmiths... these are 30cm long, 7.5cm high and 4.8cm thick.. and bolt a block of aluminium onto the back of each... but that would cost $80 total... and thats the most expensive part so far.. and I'd rather find something cheaper..
try looking at hamfests...I got some really cool heatsinks that cost me arund USD$12 only...but it's only good for a channel...so I'll need 2 for stereo operation...and it's HEAVY....for a good amp schemmatic...try this site. I'm sure you can make a PCB urself right?? If not go for a kit.http://www.astro.uu.se/~marcus/private/m250.html
Also try this site.
http://www.audio-circuit.dk/LYNX_main.html
He's a member of our forums (ACD) you might wanna try trading some stuff for his PCB..that's how I got them...
Also try this site.
http://www.audio-circuit.dk/LYNX_main.html
He's a member of our forums (ACD) you might wanna try trading some stuff for his PCB..that's how I got them...
That week included the case, v simple, holes in front top and side of heatsink, tapped fir 6mm screws, panels screwed in. But then again I have made loudspeakers bfore and an amp case in a similar way, my dad also makes acoustic guiltars, so Im not short on tools or help. Which I didnt need anyway excpet where two pairs of hands are not enough. wooo long sentence.
Yes I used slones artwork, works fine. Dead easy to etch too and solder.
Good luck with whatever you choose, and feel free to ask more q's.
Oh and skinny I bough heatsinsks from conrad in Aussie and it cost me a lot less then buying here, that including air freight took about 4 days to arrive.
Yes I used slones artwork, works fine. Dead easy to etch too and solder.
Good luck with whatever you choose, and feel free to ask more q's.
Oh and skinny I bough heatsinsks from conrad in Aussie and it cost me a lot less then buying here, that including air freight took about 4 days to arrive.
5th element said:
http://www.conradheatsinks.com/welcome.htm ???
that the place??
just comparing the same size/disipation of some of the heatsinks to the ones Jaycar sells...
okay... Jaycar sells a diecast sink... 200 long, 75 wide and 48 high...
Conrad has the same heatsink, same rating.. (0.55 degrees celcius per watt)
From Jaycar it costs $23.50
From Conrad it costs $19.62 (including GST) and then you gotta add postage to that...
and another example...
one from Jaycar costs $14.95
same one from Conrad costs $14.05
http://www.conradheatsinks.com is the place you were talking about, wasn't it??
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