I've had a go at speaker ratings "now vs then", now I'll pose a question for the amplifiers.

Something like a HCCA225 has a 35-40amp fuse for 2 x 25w @ 4 ohms(1x500 @ .5ohm mono) , a SS Renoir amp has 1 x 25 watt fuses for 50wrms x 2.

Something like the Audison LRX-2.150 uses a 20amp fuse and gives over 100wrms x 2 @ 4ohm stereo. I don't know what it bridges to, or it's max rms output.

Is this increased efficiency?

This isn't having a go: this is a "teach me" thread. I'm expecting a more plausible response for this one than speaker "marketeering".

PLEASE SEE BELOW FOR *ACCURATE* POWER RATINGS AND FUSE SIZES. BAD WAYNE: SHOULDN'T POST WHILE DRINKING!

I would say no, the efficiency of Class A/B amplifiers is generally similar. It won't vary by anywhere near the amount that those fuse values suggest.

One of the other problems is the fuse size is there to cater for maximum current draw (usually when bridged at low impedance), so it is not terribly accurate to try and work out the 4 ohm unbridged output or efficiency from the fuse size. Obviously some manufacturers like to over cater, others like to under cater. :wink:

I find it very hard to believe a the Orion HCCA has a 40-amp fuse but can produce 500WRMS at 0.5ohms with said fuse. 40-amps times 14.4-volts is 578 amps going in, making the amplifier around 85% efficient - which is unheard of for a Class AB design. You would have to run a larger fuse at low impedence loads.

Similarly, the Audison would be around 70% efficient to make 200WRMS from its outputs when the fuse limits the input side to just 288 watts - and that's not even bridged yet!

Are you sure of your claims?

Not any more! Just talking to a friend who is "borrowing" my amp for a while, via ICQ. I will return.......

As stated: not having a go, just wondering if there was something simple to explain it (apart from me just having it totally wrong. :mrgreen:

Meh - he's offline.

OK - until I get confirmation of the actual fuse rating: work on the Audison vs Soundstream amp: very similar fuse ratings: double the rated output.

???

This will teach me. Research first! Sorry guys: I was close, but not close enough. New figures:

Orion HCCA-225. 40watt fuse (yep).

2 x 25wrms @ 4 Ohm stereo. 12v
400watts @ 1 ohm mono 12v. Grab google: people are claiming over 500w @ higher voltages, but I can't verify this.

It does bridge to 0.25ohm, but generates no more power.

Soundstream: 50x2wrms @ 4 ohm stereo. 25amp fuse.

The Audison amp was slightly out too. Now list two models:

LRX-2.150 - 20amp fuse
2x70wrms@ 4 ohm stereo. 12v
2x80wrms@ 4 ohm stereo. 13.8v
220wrmsx1@4ohm mono. 13.8v


LRX-2.250 - 30amp fuse
2 x 100wrms @ 4ohm stereo 12v
2 x 120wrms @ 4 ohm stereo. 13.8v
1 x 420wrms @ 4 ohm mono 13.8v


I won't edit the figures in the first post: it's not fair on the respondees. I'll put a disclaimer to look here, though.

OK - The SS and the LRX2.250 are a good example of my question. Both designed mainly to run at 4 ohm stereo, 25 amp fuse vs 30 amp fuse: 50wrms vs 100wrms @ 12volt.

Ok, there seems to be a commonality that I have noticed (not just with these amps) - the peak current draw may be around 30% more than the fuse rating. (I believe I have brought this up several times before, but who knows where the threads are..)

So 12 x 40 x 1.3 x 0.6 ~ 375w close to 400w
13.8 x 20 x 1.3 x 0.6 ~ 215w - close to 220w
13.8 x 30 x 1.3 x 0.6 ~ 320w - getting a bit small, perhaps be a bit cautious about the rating..

But the problem is, you are trying to work out the 4 ohm stereo output from the fuse rating - and as I said earlier this will not be accurate, since the fuse is designed to cater for the peak current draw, not the 4 ohm stereo current draw.

Cool - did a bit of a search, found a few topics that edged around the subject, but nothing specific that I could find.

Without getting too far into to, as I think it is a bit of a moot point, Class AB amplifiers that I have reviewed have been measured (at full power output) to be between 40% and 60% efficient - which is quite a wide variance. This is a simple way of explaining the variances you have found in fuse ratings versus output ratings.

Its can be simple put that the newer amps use higher voltage comonents, this means that inside the amp there can be greater voltage swing,however the current capacity of the newer amps are less.

To get 100wrms at 4ohm requires alot higher voltage than 100wrms at 1ohm. However at 1ohm the current is much greater so its the same power at the end.

The audison LRx amps can only be loaded down to 2ohm per channel, this is because any more and too much current will be able to pass through the amp. The maximum power is where the voltage swing is reached.

In the older amps such as the HCCA225 the voltage swing that the amp can produce is less, but the current it can pass through is far greater.

So like the Audison is running at 100volts RMS at 1amp to produce 100wrms, where as the older amps run at 25volts RMS at 4amps which equals 100wrms.

you're forgetting maz - that power is a relationship between Voltage and load (P=(V^2)/R)- HENCE to produce 100WRms - requires exactly the same voltage from any two amplifiers to produce the same amount of power into the same load. Hence your theory is all cocked up really...


we are comparing amps into the same load aren't we? (ie all at 4 Ohm stereo?)