Clipping? why not build amp with twice rms needed and only use half volume?

Hello Everyone,
I always read about amplifiers and the damage done to speakers by clipping when the volume is turned up to high.
It seems to me that all you have to do is build an amplifier with twice the rms wattages you need and set up the volume pot with an additional resistor to only make 1/2 that wattage avaliable to the user. Hopefully never allowing the Amplifier to clip?
What do you think and is there any amplifier being made that does this? Or have someone on the forum done this
 
Hello Peranders,
My family is used to over engineering everything we build from sheds to electronics, So using components rated at half the load they would normally be used at can't be a bad thing as a side effect to setting up an amplifier to only give half its rms watts and prevent clipping. That's the logic behind the idea.
 
Firstly, you will be paying for capacity that can't be used, both financially and in size and weight. Secondly, you can't actually stoip people running the amp into clipping because input sensitivity is not really a standard, there will always be some source or pre-amp that can put out more voltage and drive the amp into clipping.

If you buy a decent pro amp it will have a 'soft' clipping limiter in anyway ;)
 
John Biles said:
Hello Everyone,
I always read about amplifiers and the damage done to speakers by clipping when the volume is turned up to high.
It seems to me that all you have to do is build an amplifier with twice the rms wattages you need and set up the volume pot with an additional resistor to only make 1/2 that wattage avaliable to the user. Hopefully never allowing the Amplifier to clip?
What do you think and is there any amplifier being made that does this? Or have someone on the forum done this


I don't think there is anything to built. Just figure out the absolute max output level and buy/built an amp that can do that.

Jan Didden
 
Well your thought is very valid, in fact it is used by professional amp manufacturers already for something they call "dynamic headrooom".

You could build an amp that can say deliver 200 watts of music power (real music power) and only say be capable of 100 watts RMS.

Lets imagine a stereo amp with the following

A ransformer with the following ratings; 40v 0 40v and 200va
100,000 uF of capacitors for each power supply.
This will provide DC rails of around +/- 55 volts DC.

In theory this amp could deliver 150 watts per channel of music power into 8 ohms but only say 80 watts per channel of RMS power as the transformers voltage would collapse under sustained power conditions.

But music is nothing like RMS and the average power delivered by the amp (and transformer) over a few minutes may only be 50 watts.

Indeed this amp coud provide music power of almost 300 watts per channel into 4 ohms and do this quite comfortably without any strain on the transformer at all. (Except if you listened to organ music or severe classical tracks, but for pop, rock disco, etc ...no problem).

But most DIY's (like me too) go for a big transformer because, like hot cars etc... we gotta have it.

Cheers
 
John Biles said:
I don't run my amp into clipping as i only use half the volume. this post was just a thought i had.

Just because the volume dial is at half way doesn't mean you are at half volume. Amps have an input sensitivity which is the voltage input required to achieve full output, this varies between amps. Sources have an output level, again which varies between sources. So the chance of you having a source with perfectly matching output level to your amp input sensitivity is very small. Unless it's all professional kit which works to a standard level.
 
Hello RichieOOBoy,
Most of the CD Players, DVD Players, Tape Recorders and Video Recorders I have brought have a output of 1 volt peak to peak.
So my idea was for amplifier to run at half volume (Half Output Power) at this level.

The comments about the amp costing more are true, but if you are going to only use half of the avaliable rms power, then the heat sinks could be smaller and you could have a thermal cut off circuit on those heat sinks to turn off the amplifier if someone did over load the input overheating the amplifier. I imagine that there would be other components that could be changed to make saving in cost in the design of the amplifier as well, knowing it's not going to be stressed to its normal levels.
 

tlf9999

Disabled Account
2005-05-25 2:25 am
none
the biggest problem is the crest factor in the signal that the amp sees. Music and human speaches tend to have a very high crest factor (10:1 isn't uncommon).

So in order for the amp to have a reasonable chance of not clipping, it has to handle 10x of the average signal (or 100x of the average output). In that sense, you will need to have a 1kw amp to listen at 10w average volume.

That is if the 10:1 crest factor holds true. What if you encounter a music signal with 100:1 crest factor?

I don't think overengineering is a practical solution. Soft clipping, as tubes do so well, is.
 
Well thinking back to when I was about 14, I plugged my electric guitar into my dad's fancy Kenwood amp and proceeded to totaly blow his set of AR speakers, the cones literaly tore loose right around....

It is not a bad idea when you have other people in the house!

Dad if you can read this from up there, I'm realy sorry, had no idea it would cause damage...