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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
onhwy61's avatar
onhwy61
5,270 posts
 
I do not think your current set up has any gain mismatch issues. If you are listening at the 9 or 10 o'clock position, it is okay. I would say you have a problem only if you are always below 8 o'clock.

The factors involved are the output of your digital source, input sensitivity of your preamp and amp, preamp and amp gain and speaker sensitivity.
Please describe what you mean about the loss of sound quality when the preamp -20dB jumper is used. The fact that your unnamed preamp has this feature means it could be modded to other values. You might want to contact the manufacturer.

Your unnamed speaker are not such a tough load unless their impedance varies wildly. They may not be the current monsters you think they are.
sebrof's avatar
sebrof
837 posts
 
>>"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."<<

What's the problem??
xti16
1,525 posts
 
I had a similar problem when I use balanced ic's. Except I could not even get to 11 o'clock which is why I bought the rca version.

As far as tube power I had a Bryston B100 rated @ 100w into 8ohm and 180w into 4ohm. My speakers are Dyn C1's rated at 85 db but a steady 4ohm. Then I bought the Octave V70SE rated at 70w into 4ohm. The Octave has everything all over the Bryston especially the control of instruments and vocals. 2 things I would consider when looking at a tubes is a soft start to make the tubes last longer and a good output protection circuit (all tubes will eventually fail) and you don't want to have to have it repaired after a tube failure.
charles1dad's avatar
charles1dad
10,250 posts
 
Great comments from Onhwy61! I agree that you need to know the voltage out put of your digital sources as they can often exceed the 2.0 volt standard. Preamp gain plays major role also. I had rhis same issue a few months ago. My DAC has 3.1 volt output,preamp had 20db of gain, amp input sensitivity=0.7v and speakers are 94 db sensitivity. I solved the problem by having Coincident reduce rhe preamp gainfrom 20 to 10db, problem solved completely.
Good Luck,
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.
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