Unclipped Amp Output Database

[Eric D]

I didn't know that since I never do this.

So at that point you know that no matter if you slap a 8 ohm stereo or a 4 ohm stereo load that it is tuned? what if you bridge it?

Sort of...

If I had a perfect amplifier, and by that I mean perfect in theory, this would hold true. As you keep lowering the load the amp would keep the same voltage but the current would increase. But we know that is not true in the real world, since a dead short would be no resistance and the amp would have to supply infinite current, which just won't happen.

If you look at some amps they may be rated like this, 100W into 4 ohms, 200W into 2 ohms, 400W into 1 ohm. Well, it is hard for the amp to do that. PG tends to rate a bit different. An amp may be 100W into 4 ohms, 180W into 2 ohms, and 220W into 1 ohm. What happens is as the load decreases the current is so demanding it draws the voltage rails of the amp down, and the amp starts to clip.

But all this talk is with sine waves or test tones, not music. I am a big believer in unclipped voltages because I know PG amps have big capacitor reserves and overbuilt output stages. They may not be able to sustain their voltage continuous, but they can do it for short periods of time, which is what music demands of an amplifier.

Now just because I say this MS250 will do 17.5V a channel unclipped, does not mean it will do it with stereo 1 ohm loads. In that case the amp may choke. But, if you run 4 ohm stereo loads, like components, I am certain the amp will be able to hit any note which demands the 17.5V output.

When you bridge an amplifier all you are doing is adding the voltage of the channels together. So, the MS250 would be 35V, or 17.5+17.5. Again, if you took that 35V bridged output and ran it into a 2 ohm load, there is no guarantee it will do it without clipping.

I am probably not doing a very good job explaining this. It is not something I can really cover in a few posts. It took me long enough just to understand this all myself. I guess my only point here is knowing what your amp can do is a useful bit of data, and it is also very useful for system planning when you wish to compare different amp models.

[bogart]

Hmmm....I for one am lost....I want to get it...something just isn't clicking.

I am still nervous about the scope...era 60's big and 200 million knobs. I still can't find the right probes for it honestly.I have wondered often how this is calculated and generally ask the manufactures for the info. If not I tune by ear....the only amps that I would be interested in really tuning per ac voltage is my sub amps...as I have popped a few subs and I have cooked a few amps via shameless abuse.

Tuning by ear can be a pain in the ass. Distortion from clipping can be very hard to hear sometimes if the system is running hard and when subs are running 150s acoustically it is nigh impossible to hear what the front stage is doing as so much high frequency noise is canceled...so in a comp setting tuning per ac sounds ideal. Now this is not sq based for me...for sq I would tune via ear and rta....

I want to learn how to do this though....

Fluke make some of the best dmm's on the market and I've been told by several techs that they trust them implicitly. I have one and it has never done anything wonkie to the best of my knowledge.

I am interested in hearing more folks...this thread has my vote of approval...for what it is worth...

Thanks Eric