Just a quick question about amps.
Say you have an amp that has a 80 amp fuse, so it would draw 60 amps at 2/3 power at 14.4 volts or whatever. If this amp is set to run at 2 ohms or 1 ohm instead of 4 ohm, would the amp be prone to draw more amps quicker?
So, if you had headlight dimming, and de-bridged the amp, it would draw less current?
Thanks.
Derek
Replies (9)
Relax_The_Mind on 06/3/2003 12:54:50
dflock,
Current draw is more directly connected with the first stages of your amp. The later output stages of your amp put out power depending on the impedance matching of your amps output and your speakers inputs. It is very it isnt an exact science to go by the volume but it will only draw power when it needs it at any volume level.
An amp will draw about the same amount of current at 4ohms 2ohms or 1ohm at any specified power level.
Theoretically, the only difference you may see at using a lower impedance(2 or 1ohm) is that the internal cicuits may run hotter than the more stable 4ohm configuration which in turn can cut down the efficiency level of the amplification stages making it draw more current to acheiuve a stable output.
So basically to answer your question. Bridgeing or de-bridgeing will not have much affect on current flow. As far as an amp goes the only way you will cut down current draw is to keep the amp as cool as you can, beyond that is a whole other story (alternator/battery issues)
RTM SMILE
dflock on 06/3/2003 14:30:33
Thanks!
That is exactly what I needed to know. I figured I'm close to my total current draw with my alternator. But wanted to run my amp at 1 ohm instead of 4 ohm. Wasn't sure if that would suck even more juice from it.
Swez on 06/5/2003 23:18:55
RTM is pretty much on it.
There is some math (Ohm's Law) to consider when calulating power output... regarding sub ohms loads. The lower the ohms load from subs, the more current will be drawn by a given amp, at a specific output setting. Depends on the amp design. (Class A/B or D amp designs) The voltage into the amp is generally fixed in range between 12.0-13.5 Volts, depending on the elelctrical system load. The current draw is variable, based on system voltage, sub impedance and watts output demand on the amp.
Also, amp fuses will only allow so much current to be drawn by the amp (regardless of sub impedance) , before the external amp fuses blow... bridged or 2 channel. Once that current draw value is reached the amp fuses will blow or the amp will go into protect mode.
If your headlights are dimming on big bass hits, there is not enough current available from the primary electrical system, (ALT. BAT) to supply all power demands on the electrical system. There are a few tricks to eliminate this... but more details on your system are needed:
1. Amp used (make & model... web link is great)
2 Subs used... same
3. Present ALT rating you have now
4. CCA rating on present battery
With additional details, can help you figure out a good fix here.
QUOTE: "If this amp is set to run at 2 ohms or 1 ohm instead of 4 ohm, would the amp be prone to draw more amps quicker" ? YES and NO.... depends on the amp design. Class A/B amps will draw more current but Class D amps work off voltage mutiplication.
The problem most guys have when using larger amplifiers, they can draw large amounts of current, right off the ALT/BAT at higher ouput levels. Turn on the lights, fogs, A/C blower and a few other accessories and what happens??? A sizable Voltage drop in the electrical system has now been activated. (electrical load on system is changed) This makes the ALT work harder, the BAT is called upon to make up the lack of current and the entire electrical system goes into distress mode.
To compensate for this shortfall, more output power from ALT/BAT, (to feed the new load) is required.
Hard subject to explain, but an easy fix... larger CCA rated BAT, higher output ALT and larger gage wires to carry more current from ALT/BAT & BAT/GND.
Hope this helps , more than confuse,
Swez
Swez on 06/6/2003 07:45:11
To get a better understanding of how an amplifier works, read this link:
http://pub51.ezboard.com/fcaraudioknowledgefrm7.showMessage?topicID=42.topic
Sky Pilott is a EE and had broken the subject down into managable details... if you can hang in there on the technical details.
Swez
Relax_The_Mind on 06/6/2003 13:12:12
nice link ... hehe
That guy speaks my language. Im an EET major myself, but that guy is straight up "theory" oriented. I used to talk like that a while after graduating but I got too many of those "what in the world does that mean!" looks.
Your last post in that forum, I personally thought about starting one (i make crossovers all the time and I made a couple small amps). But, I would have to sell high wattage amps for like thousands because I dont have the buying power of high quality parts (not Radio Shack garbage) that Rockford or any other big company has.
Relax_The_Mind on 06/6/2003 13:25:16
Oh yeh and an important thing he left out was that the 4ohm and 2ohm rating on a speaker given its setup, is that it is only the nominal impedance of the speaker. The impedance of a driver (techies dont call them speakers or subs) is highly variable depending on many factors (heat, wear and tear, even at different excursion limits)
A 4ohm speaker's impedance can range from .5ohms - 24ohms in different situations. Many manufacturers have impemented new features such as cooling vents and new basket designs to cut down on the stress and variation that heat causes on a speakers imependance therefore altering the amplifiers performance.
RTM
Swez on 06/6/2003 16:08:22
Yepper, You are correct and I often substitute "driver" for speaker or subwoofer as well... but only to those who know the Buzz words of Techies... hehe
Yes, VC impedance is very dynamic based on frequency, thermal loads in VC, enclosure design and power compression, etc. Sky did not forget to mention it. He intentionally left it out so that most non-techies could understand the basics and some of the details behind driver/amp performance.
I too have a EET background, but much of what I learned, was a good many years back when transistors were just hitting the scene. Back then, Vacuum tubes were the primary option and there was no such thing as a 500 watt RMS car amp. We were lucky to get 50 watts in a car amp then, with transistors being a new device.
My, my... how things have changed, but some have not huh?
Swez
PS Of coarse, cars in my HS days had 300 + HP too. Big block V-8's , (396 SS Chevelle, GTO 400, Mopar 440 six packs and 500 cid + in a Caddy) dual 4bbl carbs, Tri-power, rear wheel posi-traction and the like. Yeah, they sucked gas when we put our foot in the carburators... but heck... could easily leave rubber 30 feet or more too. Then again, premium gas was 94 octane and about $0.35/gal. So, who cared.
Had a 455 cid Pontiac Grandville back than.... a real cruiser that could do + 130 MPH on the Hyw.... if I cared to, but think the highest I ever had her up to, was about 125 MPH... That was enough for my taste. GRIN 0 - 60 in ~6.5 seconds I think.. all stock too.
PSS BOY, WAS I FOOLISH THAN OR WHAT ???
Relax_The_Mind on 06/6/2003 16:49:39
Swez
oh my goodness...the only thing we talked about vacuum tubes was the 'history' of them haha. although have you seen the new amps i think that mcintosh and some other manufactures make that have vacuum tubes in them? havent heard a vacuum tube anything before. i worked with all solid state transistors and such...silicon everything.
$.35/gallon.... lordy a full tank for about $6... thats how much my riding lawn mower takes to fill it up nowadays. (hmm...premium in my lawn mower I did make a custom rack for my cd player made of a big sheet of velcro on the back of the seat)
RTM
Swez on 06/7/2003 18:19:18
See, I told you I've been at this a while... Vacuum tube amps are a dead givaway huh? Did you not believe me ???
Actually, for HIGH END SQ (Audiophile gear) tubes are the preferred devices as they are so warm and natural in sound reproduction. Mac, older Crown and some other elite brands still use VT technology. There is a VT based car stereo amp or two out there as well. Moderate power, but super clean and very $$$. Most are probably still hand made too.
VT's are also great for ultra clean, high power output amps used in Radio/TV broadcasting system. They are very reliable, can put out gobs of power and last a long time as well.
Gas prices noted, were in the early 70's, before the big oil crunch in 1974-75. But minimum wage was under $5.00/hr too, for summer jobs. Worked in a gas station (NOT-self-serve either) as Asst. Mgr (73-74) and made ~$6.50/hr than.
Graduated from HS in 1974, but worked after school, 6 days a weeks and pulled ~55 hrs/week. Great job for getting my homework done on time. Did start taking electronics classes as a Junior and have been at it ever since in one way or another.
Where were you in 1974? (A gleam in Dad's eye?) GRIN
Swez
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