Understanding Mcintosh Meters?

Farjamed, first off in answer to your question about the 4 or 8 ohm concern, If you have autoformers then the meteres self correct for the impedance driven. I have own a number of Mc amps and find that the meters do indicate about how much power your are delivering at the outputs. How ever I emphasize "about" and really the appeal is the look. I think they are accurate as you can get in real world for what they are designed to do. The reason for the 200 on a 100 watt amp is to let you know when you are totally pegged and that is so close to the 100 watt mark that you won't really be able to decipher the difference between 100 and 200 while playing unless you leave it cranked all the way for anylength of time. At which point the Power Sentry will kick in and shut you down. Mc's power sentry /power guard circuits are designed to protect you from clipping and that is where you need to lose any concern about that occuring. As when you drive the amp to clipping the system will shut down the outputs and the lack of sound will get your attention far before the meters will ever indicate. I think the blue meteres are great to look at but I usually take my glasses off so I really can't see the needle. Have a glass of wine and relax and enjoy the music. They are much more romantic than a fireplace and never require cleaning ashes (unless you continue to crank it and the PG or PS circuits fail).

One last related question..

What about amps with a digital readout of the "volume" that shows a db reading. Are these accurate, in the sense that raising it from -35db to -32db is actually doubling the power?

Theo: I am with you, I can't see the needles from where i sit either, but i like the way they look.

Are these accurate, in the sense that raising it from -35db to -32db is actually doubling the power?

Yep, pretty much.

To be perfectly precise . . . it's actually the voltage gain that you're changing. So assuming that the input signal voltage and load impedance remain identical, than this is what happens.

“You said that as long as I am supplying less wattage than my speakers can handle I am fine. So does that mean if my amp is say 50-100 wpc (depending on speaker impedance) and my speakers are rated at 350w power handling, I dont have to worry about frying them with my amp? But then why does everyone say an underpowered amp is more dangerous”

The theory as to why an underpowered amplifier is potentially more damaging to your speakers than an adequatly powered amp is that the amp will tend to clip when "overdriven", and this will occur at lower volumes than for an adequatly powered amp. Clipped waveforms are waveforms that sit at the rail voltage of the amp (not an intended aspect of the signal). For example, consider a sine wave with a peak of 10 volts as opposed to a clipped sine wave with a peak of 10 volts. The greater clipping, the longer per cycle the waveform sits at 10 volts. In the extreme, the waveform becomes a square wave. Impressed across the same load, more power is dissipated by the clipped waveform than the unclipped waveform. More power means more heat dissipated , and at some point, damage may occur. However, that does not mean that an adequately powered amplifier cannot cause damage just because it does not clip. If the speaker draws more current than it can handle, damage can result.

They are put there to sell product. When I was a dealer I was often told that products with meters invariably outsold those without. My own experience bore this out, my best selling amp was a Hitachi mosfet power amp with large meters. I was quite a good amp, probably better than the Haffler I was also selling in many ways. But people bought it for the meters, not the sound. If you really want to track output LEDs are much better , but not as much fun.