How to calculate a proper amplifier gain?

[Hanalee]

Good day all,
I swopped my Rotel 200W power amp for a Cambridge Audio 200W power amp and at the same relative volume on the preamp, the volume was considerably louder on the Cambridge. From this, I deduced that the 200W is a lot more powerful than the 200W on the Rotel, which to me doesn't make any sense.

So now my questions :
Can the same wattage amp but with a different gain really have such a large impact on loudness?

But if the gain results in a much louder sound from the same relative position along the volume pot (according to amp gain formulas), and both amps have similar power output, then wouldn't the amp with higher gain reach full output sooner than the other?

I guess I'm just trying to understand what's going on here. I always assumed that two power amps of equal power output would have equal loudness as the volume was turned up, but I guess my assumptions are inaccurate or incomplete.

Anyone have ideas of it? Thank you in advance.

 

[LarryFine]

Two amps can have the same rated output capability, but have a different gain, or input sensitivity. A different input signal voltage may be required for the same 200 watts.

The Rotel might requires a greater input voltage for a given output level, while the Cambridge could be driven into clipping with a lesser input signal voltage than the Rotel.

Imagine that you replaced the preamp instead of the amp, and found that your system was louder at a given volume control setting. Would that make the new preamp "louder"?

It's similar to replacing a thermostat and finding you need to set the (indicated) temperature setting slightly different to achieve the same comfort level (actual temperature).


By the way, you've found a kindred spirit. Audio has been a hobby of mine since I was a kid, and I now have a home theater system with a total audio power of 2,200 watts (cont.).

 

[junkhound]

such a large impact on loudness?

the amp with higher gain reach full output sooner than the other?

trying to understand what's going on here. I

Yes

Yes

'electronic engineer' ? something surely missing when you covered feedback and gain theory.
BTW, what type amps, did not bother to look at the brand names, but going from class AB to class D with same preamp a whole other subject by itself. Look at input specs on your amps, etc.....

 

[romex jockey]

I really don't have a prayer of touching the 'math' here>

Introduction to Amplifier Gain in dB and Calculation

www.kynix.com

But i do have some 'sound' experience , not much to brag about really

gain control through multiple amps and instruments into and out FOH can be a b*tch

one just can't have settings of <2> <9> <2> <9> in the chain, gotta all be leveled out....

~RJ~

 

[steve66]

Sorry, can't resist:

Spinal Tap Goes to 11 - Search Videos

www.bing.com

 

[synchro]

Compare the amplifier's input sensitivity spec, which is the input voltage necessary to get to full rated output. Also, what is the output impedance of your preamp or other source? The Rotel might be loading down the preamp output if its impedance is not sufficiently low. For example, the output might be a potentiometer and not an active stage.

 

[ggunn]

Another thing to consider: audio equipment manufacturers are infamous for overstating specs.

 

[grich]

...But if the gain results in a much louder sound from the same relative position along the volume pot ...

Keep in mind that not all pots are the same. Some are linear taper, and some are logarithmic taper. A linear 1000-ohm pot will be 500 ohms (wiper-to-either end) at half-scale, while a log-taper pot may be only 200 ohms (wiper-to-"low" end) at half-scale. Log-taper pots are most often used in audio applications, but don't assume.

 

[LarryFine]

And then there are the high-end units with separate volume and loudness controls. You're supposed to turn the loudness control all the way up, set the volume at the most-likely loudest, then use the loudness after that.

 

[hbiss]

Compare the amplifier's input sensitivity spec, which is the input voltage necessary to get to full rated output.

This is exactly it. Read the manual!

-Hal

 

[Speedskater]

Unless the amps are tested using the same protocol and test conditions, specs like rated power and distortion are rater meaningless.
Some major manufactures are known to test their different price lines using different protocols. That's because the internal circuit is the same in both products, but then the specs look different.