# What does High Current mean?

I am confused. I know that the Sim Audio W-5 goes from 190 W at 8 ohm to about 1200 watts at 1 ohm. It has two 1 KW transformers for each channel....and then, I saw this YBA amp, called HC for HIGH CURRENT that barely produced 80 watts at 8 ohm, 170 watts at 4 ohm and then 1.2 KW at .7 ohm. How is this possible? If you double the wattage at halving the resistence, then the math would not work. Can someone explain this to me? Thanks!

PAUL
bemopti123
2 responses
 11-11-2001 8:29pmActually the math does work. A constant voltage source would double the power delivered to the load each time you halve the resistance.Power = Voltage squared divided by resistance (P=EE/R), so if we halve the resistance:EE/((1/2)R)=2(EE/R)=2P, or twice the power.It is difficult (i.e. expensive) to build an amp that functions as a constant voltage source. Many amps fall off the curve as impedance drops below 4 ohms.If the Sim Audio amp operated as a constant voltage source it would generate 380 watts into 4 ohms, 760 watts into 2 ohms, and 1520 watts into 1 ohm. The YBA does follow the doubling and operates as a constant voltage source down to 1 ohm.So what does this mean? It tells you how to match the amp with a speaker. The YBA can handle a load that drops to 1 ohm over part of the frequency range, if 80 watts at 8 ohms is enough for sufficient volume.The Sim Audio amp provides more power at 8 ohms, but may have trouble with difficult loads whose impedances dip below 4 ohms.Check the impedance vs frequency curve for the intended speaker. 11-12-2001 2:05pmA beautifully clear and succinct explanation, Ghostrider45. This is seldom emphasized or explained well by reviewers. What we frequently hear instead -- often from sellers -- is, "this amp is much more powerful than it's output rating suggests," or words to that effect. Unfortunately, few readers or prospective buyers seem to believe the claim.But, I know from personal experience that the statement can be amazingly true when you have a very difficult, low impedance speaker to drive and can use a well-designed, well-made amp that doubles down all the way to 1 or 2 ohms. A seemingly insignificant output at 8 ohms can easily translate to BIG output at 2 ohms if it's the right amp. Surprised the heck out of me!