2. tech-talk
  3. 1299805133

stupid question about sources, amps, and loudness

Okay, so I really should know this, but I don't, so your help is most appreciated.

My speakers are a fairly tough load to drive 86db efficient, 6 Ohms nominal.

That suggests that I need reasonably powerful amplifier(s). Currently I use solid state amps rated at 100 WPC.

The amps are Kharma MP150s. They drive the speakers quite loud, although they do start to "flatten out" at 95 db (which is much louder than I typically listen, even when I've turned it up).

I have some issues with not having enough range of volume control either with a pre-amp or with a CPD with a volume control -- that is to say, if I turn the volume control much past 10 or 11 it is too loud.

I know that I can use attenuators to fix the volume control problem, but that they also can have sonic consequences.

Here's the question: less powerful amps are NOT the answer right? It's input sensitivity. Right?

So, if for example, I am thinking of trying tube amps, I still need to be mindful of the difficult to drive speakers and thus need to get some pretty beefy tube amps (i.e., 100 WPC+). Because less powerful tube amps won't have enough current to drive the speakers effectively.

BUT: I would want amps with a lower input sensitivity?

Do I have this right?

Thanks for clearing the cobwebs for me.

--dan
dgaylin
dgaylin OP
255 posts
 
Ckoffend, thanks. I can't find a gain spec on the amps. They do have an input sensitivity of 1.2 V.

I actually tried the amps with a different CDP. Same issue. I can attenuate the output of the pre-amp with internal jumpers by 20 db. But the sound quality is reduced.

So there's gain, current, and input sensitivity. How can you ever know what components are going to work.
daverz
487 posts
 
The gain is probably the better number to pay attention to because it is not relative the the power rating of the amp.

If only the power rating and the sensitivity is given, gain in dB is related to the power rating (at 8 Ohms) and the sensitivity by

gain = 20*log10(sqrt(power*8)/sensitivity)
dgaylin OP
255 posts
 
Daverz, thanks very helpful....by sensitivity, you mean input sensitvity of the amp, right?
daverz
487 posts
 
Yes, input sensitivity of the amp. So your amps would have a gain of

20*log10(sqrt(100*8)/1.2) = 27.4 dB

Which is on the moderate side.

It would be nice if more amps had switchable gain like some Brystons or variable gain like the Parasound amps.
dgaylin OP
255 posts
 
Daverz, yeah that's what I got too (good to know I can do math even if I can't figure out component matching). Thank you.

So...back to my main question. As a separate issue, I am interested in trying tube amps (never had them before). So what I want are amps with good current 100+ per some of the Atmasphere technical papers and posts on this. But I want amps with a lower gain.

This way, not only will I have the ability to try appropriately powered tube amps, but I will have the added benefit of better volume control with the CDP or the preamp.

Do I have this right?
More to discover