Line level attenuator and voltage needed to drive amplifier to full power

[holbob]

So I have a passive line level attenuator connected to the RCA inputs of my ncore nc502mp. I've had this for a while - I have an unpredictable 8 year old so this makes sense.

The thing is, I was reading an old thread and I checked with AI what wattage I would receive at 4ohms from my minidsp flex with the attenuator in place at 10db. The AI told me only 30 watts and encouraged me to remove it.

Does this sound about right?

The Flex is 2v btw and the amp needs 2.3v.

I can post the AI maths if somebody is interested.

Thank You

 

[Blumlein 88]

Minus 10db is about 1/10th power. So without attenuation you would get nearly all the power.

 

[holbob]

Ok, that tallied up with what the AI said. I'm sure I've read something on this forum that says if you connected it directly to the RCA inputs, it would negate this? It is entirely possible I am misremembering so apologies if so.

 

[bmc0]

Without the attenuator, the MiniDSP unit's maximum output voltage is 20×log10(2V / 2.35V) → -1.4dB relative to the amp's input sensitivity (2.35V). The maximum output power is then 500W×10^(-1.4dB/10) → 362W. With the -10dB attenuator, it is 500W×10^(-11.4dB/10) → 36.2W.

Whether you should remove the attenuator depends on whether the MiniDSP unit ever clips. If no, there's likely little or no benefit to removing it.

 

[holbob]

Or even having a 500watt amp I guess??

 

[DVDdoug]

If it goes loud enough for you, why remove the attenuator?

Or even having a 500watt amp I guess??

Most people don't need 500W in a domestic setup. Bass can require lots of power if you want to shake the walls, and power requirements go up exponentially as you go louder, or if you need to fill a larger space with sound.

 

[bmc0]

Or even having a 500watt amp I guess??

Power requirements are a bit unintuitive since perceived loudness is roughly logarithmic. Surely 500W is way louder than 36W, right? Well, it's at most only a bit more than twice as loud. Add in power compression and it's likely not even twice as loud.

500W is certainly a bit overkill for domestic use with all but the lowest efficiency speakers.