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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

Showing 6 responses by 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.
dgaylin OP
255 posts
 
Daverz, thanks very helpful....by sensitivity, you mean input sensitvity of the amp, right?
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?
dgaylin OP
255 posts
 
Yes that's probably right...just helpful to keep all this in mind as I think about what tube amps to get.

Thanks so much.
dgaylin OP
255 posts
 
All --

Thanks for the many helpful comments.

Specifics are as follows: speakers are Wilson Benesch Curves; pre-amp is Nagra PL-L. Sources are EAR Acute CD player (yes very high 5V output) but also Northstar DAC (2 volt ouput).

Here's the experience:

with the Northstar into the Nagra, volume on the Nagra was at 8-10 o'clock. Over 10 too loud. When I changed the jumpers on the Nagra to -20db, the volume needed to be at 3-6 o'clock (7 is maximum). But the sound was noticeably less clear -- sort of compressed sounding.

with the EAR into the Nagra, the EAR's volume is set at 12 o'clock, and the Nagra then has a nice range of volume control (10 o'clock to 2 o'clock). Seems good. BUT...

The very best sound of the system, despite the fact that the Nagra is an absolutely wonderful pre-amp, is to connect the EAR directly to the amps. Surprisingly much better: more details, greater warmth, greatly improved soundstage.

In this set-up, the EAR's volume control is between 8 and 11.

Sebrof -- the problem is that fine volume control is difficult with such a small range, and as I understand it with volume controls, using them at the extreme range is not good in terms of sonics.
dgaylin OP
255 posts
 
Yeah the EAR has no fixed volume option. Yes it does sound warm, which I like, and while the Northstar is good, the EAR is substantially better. Agree that tube amps may be too much of a good thing. Also agree that maybe I have less of a problem than I originally thought. Will probably try some attenuators since it is an easy and relatively low cost experiment.

thanks all!
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