how are 'cheap' amps built differently?

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i sell car audio stuff, every manufacture has their reason for being the best. what is it, on the electronics level that is different in the cheap amps? im talking about amps that can actually do what they claim but maybe at a .5 or 1ohm load vs some expensive amps that do the same powers but maybe at 2ohm and are not 1 ohm stable?

i guess im trying to understand why anyone would pay for a 2000W 2ohm stable amp when you could run at 1ohm and save quite a bit of money on amps. (just as an example)
 
i sell car audio stuff, every manufacture has their reason for being the best. what is it, on the electronics level that is different in the cheap amps? im talking about amps that can actually do what they claim but maybe at a .5 or 1ohm load vs some expensive amps that do the same powers but maybe at 2ohm and are not 1 ohm stable?

i guess im trying to understand why anyone would pay for a 2000W 2ohm stable amp when you could run at 1ohm and save quite a bit of money on amps. (just as an example)


I will be a bit provocative and state that cheap car amplifiers are mainly made as cheap copies of more expensive amplifiers such that they at best perform similar to the more expensive amplifiers. The difference in stated performance is with the marketing where power values are often heavily exaggerated, and for the cheap amplifiers much more than for the expensive amplifiers.
You mention yourself 2000W in 2 Ohm. That requires a 90V supply rail and handling of 45A peak for each channel for what we call the "clipping point". Where does the 90V rail come from with nominally 12V (actual 13V) in ordinary cars and nominally 24V in trucks? Do the amplifiers include a 2000W+ voltage booster?
 
Fauxfrench, all car audio amplifiers of significant power have a switched mode boost converter for the power rails.

Component choice allows for a huge range of prices on similar products. A single cap can vary from pennies to many pounds depending on the quality. Not to mention cheaper Chinese silicon being readily available these days.

And take all car amp specs with a pinch of salt... a 2kW continuous power output, assuming the amp is running at 100% efficiency pulls 166A. Managing that kind of real power is never cheap!
 
well all amps have transformer coils, the 12v @ xxxA gets drawn up to 60/80/120/... Volts at lower amps and then goes to two rectifiers to give continuous +/- rails. not all car amps work this way but most do and certainly the cheap ones in my experience do.

what im getting at is you have a hifonics (for example) that mgiht do 1500W @ 1ohm. now its tested to do this and it really, really does do rated power. maybe the amp costs 200.00

then you have a rockford that is rated at 1500W but at 2 ohm and the amp can not run at 1ohm. this amp might be 850.00.

if we assume you will buy a sub to match the rated ohm load of the amp - why spend the extra 600.00? what do you get out of running at higher ohm load?

along those same lines, why do so many cheap amps require a 1ohm load to put out max power? the industry is moving away from 2//4 ohm as standard and going to 1//2 ohm it seems. ive seen many 2 ohm door speakers and more than 3/4 of amps that customers bring in are all rated at 1ohm (some even at .5 ohm).

i know running a 2ohm rated amp at 1ohm will decrease efficiency but if a mfg is building a 1ohm amp surly they have similar efficiency to the 2ohm variants?
 
Sorry for my ignorance. I have only had very trivial (Clarion, Pioneer, Alpine, JVC, Sony) car-amplifiers typically rated at 4x45W and without a voltage booster. Without being explicit, these amplifiers assumed a speaker impedance around 2 Ohm (for 4x45W) though it was obvious that 4 Ohm would be the most frequent speaker impedance. Many customers only read "4x45W" and do not think further. Also thermally, I doubt if I could pull 4x45W for some minutes if I had tried.
I believe that for 850$ it is possible to construct a (permanent) 1500W amplifier (with a voltage booster) though I personally cannot see the need. But for 200$, I am surprised. It is an old trick to state the "power" in a very low load impedance. With less impedance, the peak power depends on the current-surge that can be pulled from the decoupling capacitors. The problem is to maintain such an output power for more than a short moment. The currents handled for >1000W in 1 Ohm are huge and hardly indicating a good reliability.
In the "class D" threads we occasionally discuss PA amplifiers with >1000W output power. Expensive items may be rather reliable but cheap items frequently suffer from reliability issues from high temperature and huge current handling. For 200$, I am surprised if a manufacturer can provide a power booster + amplifier that can deliver >1000 Weff for just 1 minute.

The car-audio threads may be visited by members with much better understanding of how these ultra-power amplifiers are constructed and what can be expected from them.
 
its hard to talk about these things in car audio forums i feel. all too often it seems that people who dont understand the electrical side of the circuit are just talking about how amp A will do power all day long and no need to pay for amp B.

seeing as im trying to learn about how the circuit topologies differ i figured a place like these forums would be best.

so its worth noteing that when pushing amps in teh 2 or 3KW range (or more) we are almost always talking about multiple large batteries and high output alternators. while its not always the case lets set aside the power demand and just assume the car can give how much ever current is needed to power the amps.

so one thing i have not done is taken an amp and run it for any real durration. the way we often check amps at work is to put a hall effect clamp on teh power lines, play a sine wave at 30-40hz and measure the voltage output. this is over maybe a 10 second (at most) durration. then we can do the math and see power. most recent was an orion that we tested this way @ 6750W output. the amp cost about 600.00. it does this power at 1ohm.

compare this to a rockford fosgate amp i used to own - it was rated at 2500W 1/2 ohm and about 2000W 4ohm. its birth sheet was 3800w and i got about 4400w out of it at 2ohm. again i never measured it with a straight sine wave over a minute or more, i think i may try that and see how hot they get.

the rockford is a 1700.00 amp and is built to not dish out power at 1ohm but rather hold things pretty steady. where as the cheaper amp shoves power out the lower ohm you go. now its worth noteing that the orion is a class D and the rockford is a class BD
 
I understand, you like to discuss how it is possible to get KW outputs with rather cheap car amplifiers. I got curious from your posting (and my own ignorance) and watched a Hiphonics (Brutus) test on YouTube. It was interesting and I may have picked up something useful.
I may use more consecutive postings as I sometimes loose what I just wrote from "cannot find server".

We (the HIFI-nerds) define an amplifier as capable of delivering an almost constant output signal in the full audio band (20Hz-20KHz). Am I right in that the Hiphonics Brutus is used to produce low bass signals up to a couple of hundred Hertz only (a sort "bass-kicker")?
For HIFI, low THD is very important and accordingly we use a separate power supply to deliver a stable rail voltage followed by a low THD amplifier operating from this rail voltage. Is my impression that your "bass-kicker" (if correct) is less focused on THD in the higher frequencies because your sub-woofer by nature will reproduce very little of higher frequency, correct?
If you only need to produce high power signals at low frequencies, the more complex design used in HIFI amplifiers may be simplified a lot such that you may use only one conversion and not two and with a much lower carrier frequency (a sort variably controlled SMPS).

If you told me to identify problems in a KW PA-amplifier, I would say heating and current handling. If you only need to produce signals up to a couple of hundred Hertz, the switching losses (heating) can be reduced importantly. The current-stress remains.
 
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Tried to look at specifications for a 1500W Rockford (T1500) and the 1100W Hifonics (BRX1116).
For the Rockford the specifications are: frequency response 20HZ-250Hz with a THD below 1% (I believe it).
For the Hifonics the specifications are: frequency response 10Hz-50KHz/10Hz-250Hz, THD less than 0.1%. The 10Hz-50KHz sounds unlikely for an amplifier that is shown to be used with a subwoofer - the 10Hz-250Hz must be valid. The THD is measured how? (I do not believe it is measured the same way as for the Rockford.)

The price for the Hifonics is 350$. What is really strange about the Hifonics specs is that they use a 60A fuse. Rockford use a 200A fuse. A 60A fuse will only allow some 750W, amplifier losses not taken into account.
 
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its hard to talk about these things in car audio forums i feel. all too often it seems that people who dont understand the electrical side of the circuit are just talking about how amp A will do power all day long and no need to pay for amp B.

seeing as im trying to learn about how the circuit topologies differ i figured a place like these forums would be best.

We have some very knowledgeable members in our car audio forum, including seasoned techs and engineers. Some with decades of experience, don't sell them short.
 
hey, i think fauxfrench has learned how decieving the car audio world can be... lol.

yea, the differences in measuring specs makes it near impossible to drill down to how the amps will actually preform. this is one of the reasons why i want to learn how the circuitry works as opposed to "what specs to look for".

ive seen some car audio amps that rate at "maximum thd" instead of minimum, easy for a a consumer to miss that.

i guess ive never thought of an amp to do 20hz-20khz. in the car audio world we often use 1 amp for sub, 1 amp for mid and 1 amp for high so everythign is crossed over. its getting difficult to even find a/b amp anymore as mostly all of it is class D.



i have not been to this forums car audio side, wasnt aware there was one. ive been to other places such as SMD and the like
 
I guess the car-audio specialists may tell you that one difference between an expensive and a cheap ultra power amplifier is that you can rely on the specs of the expensive amplifier.

With a frequency range up to only 250Hz, you can lower the class D switching (carrier) frequency a lot from the 400KHz-600KHz we use for HIFI and reduce switching losses enormously. Perhaps to some 2KHz-5KHz. Further, you may get away with a single-step conversion of the battery voltage directly to the AC signal output. That will lower power losses and costs as well.

I noticed a documentary from somewhere in central America. People would meet outside of the cities with their vans. The vans were equipped with KW audio installations that made doors vibrate like under a powerful earthquake. All persons had to stay outside and at a distance from the cars and listen from there. Inside the vans the sound level would have caused permanent hearing damage on the spot.
For HIFI-freaks and in particular audiophiles a very different kind of logic.
 
so im repairing a 12000W amp right now, i think its more around 6500W rms. the switching frequency from the driver board is 41.2Khz. is this the switching frequency you are referring to? this is the frequency on the power side of the amp.

there is an audiophile (sound quality) section to car audio. i dont think its worth it however. a car is perhaps the worst place to reproduce music that we find our selves in on a daily basis. there is something to be said for quality speakers and amps but to spend 10, 20, 30 thousand on ultra low THD, high sensitivity, low distortion products in a car is a waste of money imo. in a house you can setup your room to take advantage o such things but in a car... you have your blower fan, your road noise, the large panes of glass all around you, to say nothing of engine and wind noise at 70mph down the high way...
 
OK, 41.2 KHz is higher than I expected. For Hifi we use some 20-30 times the highest frequency we want to reproduce. Perhaps the ultra power amplifiers have another concern that make them switch outside of the audible range - the fear that the magnetic components will generate audible noise directly.

The amplifier you are repairing right now, let's assume it is "only" 6500 Wrms. My 100Ah 12V battery will be drained from fully charged in some 10 minutes. At least I would have that "fun".

Here in Europe we have small cars compared to the US. Those who wants the loudest music are often young persons with a more moderate economy - thus, the smallest cars. Sometimes I hear such a small "boom-box" on wheels. My guess is they have installed amplifiers with a power in the order of some hundred Watts. They hardly have space for double batteries and horse-powers for a larger generator. And, they remain inside the cars.
Is it your impression that cars are frequently equipped with KW audio gear in the US?
 
Voyager:
At this point in time, I listen to music in my car about 1½ hours per day. At home, I'm lucky to get to listen 5 minutes per week.

Totally agree that there's a limit to fidelity in a car, but the point of diminishing returns depends on your wallet and desire.

FauxFrench:
Car stereo contests are common here in the US, and have evolved quite a bit since the 1980's. The SPL competitions now reach levels of insanity, and have absolutely nothing to do with fidelity. I suppose the ultimate SPL system would reduce the vehicle to a pile of rubble.
I don't really know what's out there now, but a couple decades ago even 2x20W car amplifiers used DC-DC converters to step up voltage to the appropriate level.
 
most audio systems we install is between 500-850W in the budget range. that being said it is quite common to install 1500W systems in the average/every day automotive setups.
as a rule of thumb we install 500-1000w systems with out additional alternator setups and some times up to 1500 in suv's.

its not uncommon to push the 2500w range on the more expensive systems, we frequently recommend alternator upgrades in these setups.

my own personal vehicle i have 6 group 49 batteries and two 420A alternators. these is more on the outside edge of audio systems we work on but to install a couple batteries and a 280-320A alternator is fairly standard.

one issue we run into is the idle vs cruise rpm and people who want to blast full volume at a stop light and drain voltage so much that their engine will shut off.
 
Thanks for giving me a glimpse of a tradition we do not really have here in Europe.
Just for fun I will show you a typical car for youth where I live: the Peugeot 207 (Peugeot 207 : essais, fiabilite, avis, photos, prix ). Cheap, quite pretty, well driving, economical and easy to get in at the small parkings in the old villages and city parking houses. Typically 80 horsepowers but a torque of only some 160-200. The luggage part at the rear may be replaced with a solid wooden plate for the speakers but then no luggage. No extra battery and standard generator. This is why we cannot follow your tradition. We do not have space and size as you have. But, we can remain inside our cars when we use our car audio equipment and some of us even have some hearing left when we get elder.:D

Out of curiosity, about how much horse-powers do you have in your car? Your system sounds WILD!

Also here we see high quality audio systems typically supplied in up-market cars. BMW, Mercedes, Volvo, Bentley etc. may be equipped with audio gear from Bose, B&O, Harman Kardon etc. and the sound quality can be impressive. Their competitive edge is rather sound acoustics than raw power. True, if you spend most of your idle time in your car why not put the good stereo there. I guess these up-market systems offer some hundred of Watts and are seldom used to the limit anyway.
 
this one is mine. not a typical vehicle but i use it for work (hauling heavy things) and play (driving through rivers, rock crawling, drag racing, and sled pulling).

JO0aDF3.jpg
 
my own vehicle is as follows, its a work in progress so i dont have everything listed here.

5.9L cummins turbo diesel - stroked and bored to 6.4L: shortened/cupped pistons, ARP rod bolts/main studs/head studs. hamiton long duration cam, compound turbos with 93 wheel. coolant bypass kit to relieve pressure at higher rpm's.

full billet 48RE transmission with high energy clutch packs, kevlar shift bands, billet servos/rods/accumulators. shift kit to vastly increase line pressures. teh case has been machined to hold extra clutch packs and bolt together parts that other wise have no positive retention.

axles are dana 60/70 with dana 70/80 internals, electronic locking differentals and 4.11 gearing. over sized axle shafts, external fluid cooling, and upgraded skid plates.

tires are 37" toyo open country MT's. in this picture its got hte smaller 35" nitto grapplers on however.

the body is swapped from another truck due to rust, the interior is from yet a 3rd truck, the bed is original (to be replaced this summer).

the electronics are fully custom. ipod on the dash to control fueling/timming/display gages, statistics, data logging, and allow for on the fly power level changes.

last dyno had 780HP and 1,650 ft/lbs of torque at the wheels.

truck has 567,800 miles on it

weighs in at 10,100 Lbs unloaded (4,581KG)

i started rebuilding this truck about 4 years ago, i have done nearly all the work on it personally and solo. from engine to axles, to body swap... just me for 95% of it. i figure i have about another year or so till im done.

audio so far is: full spray on damping from cascade audio, black hole tile/peel and stick damping, two layers of 3/4" MLV from cascade audio that goes form bottom of windshield to bottom of rear window. single layer 1/2" MLV on inner doors and roof. also a lead seperated base with 5Lbs density rests over the transmission tunnle/firewall/rear wall area.

dual hybrid audio 8.8" lagatias in each door for midbass, 1/4" aluminum plate to cover holes in doors, single 4.75" lagatia mid range in each door, single 1.25" tweeter also in each door. 1000/4 T series rockford fosgate for mid/high, 1000/2 rockford for midbass, both class A/B. sub amp will be a T2500.1 rockford class BD. powering a isobaric mounted pair of Fi audio SP4 3500W (rms) 18" subs in a 6th order 22 cubic foot box in the back seat. finially a mosconi 6-8 aerospace DSP for the processing. i plan to install a 17" touch screen LCD into the dash adn run either linux or windows 8.1 off a mini desktop ryzen/vega system for the radio.

if your looking for some build porn here are the links to my build log of this truck: rebuild of my truck N7 part 2 - Dodge Cummins Diesel Forum
 
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