effect of hot CDs and soft CDs on amps?

Does it make a difference to your amps or preamps when you play loud or soft CDs to the same loudness? Does the amp stress more to play a soft CD loud? Or does the preamp do the heavy lifting in these cases? I'm not really sure how these things work.

 

You know, i'm leaning towards the opinion that hot signals can affect the sound of the amp if there isn't sufficient dynamic headroom. My reciever also has a swtich that allows the user to attenuate the line input from very high output sources to avoid distortion.

My very compressed CDs don't sound as stressed by my new amp as the old one.

 

I think you may possibly encounter a problem with cheap preamp, but it would have to be a pretty poorly implemented circuit to overload.

For a normal 2v CD output the preamp will attenuate the signal for most power amps. The preamp is not amplifying - that's why folks can skip the preamp and just stick a pair of attenuators in there. Here's the most minimal design courtesy of Ric Schultz:

 

Geoff, that looks like the plumbing beneath my kitchen sink!

My SET amp (a Decware Zen) was designed so that you don't need a preamp. The 2v CD signal feeds directly into the amp, which has an attentuator built-in.

Yes, I realize this in no way answers Cwon's question...

 

I know. And if that's not minimalist enough for you, Ric goes one step further with fixed resistor attenuators. I've heard these at his place - there's just one volume level, so you can't turn it up or down. The balanced version looks like this (without the resistors to ground):

 

If you think about this logically then what Grant said is wrong. A hot, compressed CD actually has less dynamic range than a lower volume non-compressed CD. Thus you would use less of the amplifiers "headroom" to reproduce an overly hot and compressed CD. To reproduce an average 90 db/spl volume with a hot CD your amplifier will need to only run at 1 watt constant (if your speakers are rated at 90 db/spl per watt for example), and very seldom would it have to double its output to 2 watts. But a CD with a lot of dynamic range requires your amplifier to really work to achieve the same volume level. A CD that has a 10 db dynamic range might be played at an "average" 90 db/spl only by setting a quiet passage at 85 db/spl, which would require your amp to put out about .5 watts of power. This same CD would then pump out a 10 db louder passage which would require you amp to play at 10 X .5 amps, or 5 watts. Of course this is just a simple scenario, imagine a CD that has a 20 db dynamic range or more. Your amplifier really takes a work-out to reproduce those dynamic peaks compared to running constantly at the same volume to reproduce a hot, compressed CD.

 

Well, no, what I was getting at is the fact that such a CD has LESS dynamic range that could stress the amp, and certainly the drivers in the speakers!

 

Well, I can make an argument that if a signal is overly compressed it may be harder for a sound system to reproduce. Granted uncompressed audio has higher peaks, but with a compressed signal the average signal level can be higher and more steady state. Peaks generally are transient in nature and occur for short times.

This reasoning is somewhat similar to that of power in amplifiers. Most of us agree that is is easier to destroy tweeters with low power than with high power. If the amplifier distorts it is more likely to put out square waves. A square wave is basically a very compressed signal, actually more like a totally limited signal. There is a brick wall that the signal can not exceed. .