Regulated amps??

[neonrt 10+ year member]

Got a small question. they put out the about same through 1- 4 ohms, but what kind of power can one expect at 8ohms? just curious. i have never owned one, but may here soon, and should the need arise to run it at 8ohm wondering what it would put out compared to its 1-4ohm output. thanks.

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[the727kid 10+ year member]

Half?

 

[iceteebone 5,000+ posts]

it would be nice to know which amp

 

[neonrt 10+ year member]

it would be nice to know which amp

i dont really have a specific amp in mind, but lets just say for example

phoenix gold x400.1. puts out about 400rms 1-4 ohm.

i was just wondering if it is like other amps and puts out about half at 8ohm like the guy above said, or if it would be closer to ratings at 1-4ohm, since the amp is regualted.

 

[jdawg 5,000+ posts]

half of 4ohm power

 

[thch 10+ year member]

Regulated amps normally refer to the power supply. the prime example is JL RIPS (regulated intelligent power supply). the "regulation" is nothing new, and means that the power supply will boost 11-15V up to some amount, and that this voltage will not change when the battery voltage changes, or the load has a transient.

The "Intelligent" part is what you are refering to. From my best guess, the power supply senses what is attached, and tells the power supply what voltage it needs to regulate to in order to work best for the speaker's attached.

the difference is that MANY amplifiers have regulated PSU's, but very few have intelligent PSU's.

Now the real question is how far the regulation extends to, or how its even implemented. I would expect some power output from half power to full power would be the answer. eg, maybe the JL amp will produce full power @6ohm as well, but this was left off as some 6ohm speakers might be detected closer to 8ohm after tolerances.

 

[thylantyr 10+ year member]

Optimum power, at any impedance between 1.5 ohm and 4 ohm per channel, at any vehicle voltage between 11V and 14.5V.

http://mobile.jlaudio.com/products_amps_pages.php?page_id=46

From this you can make a good guess that if optimum power is only

from 1.5 - 4 ohm, then optimum power is not when the impedance > 4 ohms,

therefore that implies the power supply rails are maximum at 4 ohms and scale downward, maybe a multi-rail power supply.

Googling reveals a Carsound test here;

http://www.carsound.com/review_archive/amps/jl_3004.html

The 300/4’s rather unusual power ratings are attributed to the fact that the amp has three internal DC rail voltage settings, which are approximately 57 volts, 50 volts, and 43 volts. The upper range is automatically selected when the amp is turned on, then, based on the amount of current drawn, one of the lower ranges may be engaged. Of course, the amount of current being drawn depends upon the load. So there you have it, three different loads with the same power rating - good old Ohm’s Law in action again. I have a feeling that most of the criticism surrounding this rail-switching feature stems from the fact that it switches down rather than up.

but what kind of power can one expect at 8ohms?

If it was a RIPS power supply then you get 1/2 power.

If the other amps copied this idea, the result is the same.

 

[thch 10+ year member]

PG Xenon appear to do load sensing at startup. There is a mod where disconnecting the speaker until after the amp is full on will cause the amp to put out more power with low impedances. given that normal users do not change speakers while the amp is in use...

since its a regulated SMPS, there's no reason for multiple rails, especailly over a +-20% range. just change the regulation setpoint based upon load.

I would have thought the simplist method would be to regulate only against line variatons, and set up a slow load current feedback to reduce the amp rails based upon current (thus simulating a resistive source with a large capacitive bank).

 

[thylantyr 10+ year member]

I remember that conversation now on the other forum. Someone wanted to do

the relay mod to bypass the funny load sensing circuit, to get the higher power

at a lower impedance and obviously, putting the amp at risk for failure, hehe.

 

[joetama 5,000+ posts]

Instead of modding an amp, why not just get one that does what you want it to do?

And, what speaker config are you going to be running 8ohms in a car?

 

[neonrt 10+ year member]

Instead of modding an amp, why not just get one that does what you want it to do?
And, what speaker config are you going to be running 8ohms in a car?

if this is for me, i never mentioned modding an amp at all. i was just wondering what kind of power one would expect at 8ohm since they put out roughly the same between 1-4ohms. i have never owned one of these amps, or knew anyone that has either, so i am looking to find out more about them.

btw thanks for the replys guys.

 

[thch 10+ year member]

this was in regards to the ways this intelligent regulation feture is implemented in various amplifiers. one of the arguments against regulated amps, and especially ones that sense the speakers and adjust themselves, is that the output power is lower then it could be. regualted amps will not put out much more power if the battery is brought to 16V. intelligent amps will also limit power based upon speakers.

in the case of the PG Xenon, the amp was apparently overbuilt and could work at these higher power levels, at least according to the people who did this mod.