Amp Designs That Are Able To Drive 4/2 Ohms Load

One thing that came out at the recent CES is that there really is no longer any argument for low impedance speakers anyway. It turns out that transistor amplifiers, while easily able to *drive* a low impedance speaker like 4 or 2 ohms, actually sound their *best* driving 16 ohms.

Steve McCormick, as one example, makes transistor amps that have no problem at all driving 4 ohms and less, but he discovered that the amp *sounds better* when using a set of ZEROs to drive 4 ohms, rather than directly, much the same way MacIntosh did years ago (the ZERO was loading the amp at 16 ohms). By better: smoother, more detailed, more authority, and something easily heard.

So Eldartford and Bob are right- there are many amp manufacturers that don't care if their amp 'plays' a 2 ohm load- more likely is what they are really interested in is how the amp plays 8 ohms.

The original Eagle could almost be used for welding in that no speaker load bothered it.

Doesn't distortion go up as impedance decreases? Why design an amp for a lesser performing speaker? How many speakers actually are a stable 2 ohms, outside of car audio which has much higher distortion tolerances.

My one tube amp is stable at 2 ohms, but the same wattage output as 8 ohms. My other mono block tubes are stable to 1.4 ohms but put out the same wattage as they do at 16 ohms or 70 volts. Does this mean I'm going looking for 2 ohm speakers, NO. I'm looking for the best sounding speakers in my budget but doubt it will be a 2 ohm speaker. 8 ohms will probably sound better, why push my amps to the extreme?

My one tube amp is stable at 2 ohms, but the same wattage output as 8 ohms. My other mono block tubes are stable to 1.4 ohms but put out the same wattage as they do at 16 ohms or 70 volts.

Pardon my ignorance. How do you know your tube amp is stable at 2 ohms? Is the amp capable of driving speakers at 2 ohm load or did the spec specify this? I am just curious on the differences in the output wattages for various amp manufacturers when the impedance is halved. As others have pointed out, the power supply is the critical factor in determining the power output. Now I'm more confused to hear of tube amps that will output a similiar wattage at varying impedances.

It's a little more involved than just the power supply being unable to provide the current to double the power as load is halved. You can design two amplifiers with the same power rating at 8 ohms and have one being able to double power at 4 ohms and the other with the power remaining the same. Yet the amp that doubles the power can sound worse regardless of its heftier power supply and yet have nothing to do with the quality of the components.

When a speaker draws current, the power supply gets taxed. If the power supply serves both the input and output stages, the voltage sag affects both. This will cause the input stage to distort which sends a distorted signal to the output stage which then gets amplified to the speaker.

However, if you split that power supply with two stages of regulation (expensive), then the current demanded by the speaker only goes through the output stages, leaving the input alone. The input signal is left undisturbed by voltage fluctuations but the output power delivery is limited. So that's one answer as to where the "missing power has gone".

Another answer is that the power supply may have the capability, but poor design (such as high impedance) may cause the power supply to waste heat, thus robbing the output stages of the ability to maintain voltage during speaker impedance dips. There are other reasons, but basically the missing power is either diverted for better fidelity, is wasted as heat or is simply a victim of the manufacturer's budget.