Not enough power?


Hi everyone,

I'm trying to sort through an issue with my system as I have it configured.  I've added a couple of pieces recently, and the results have been quite good.  However, there is one major problem - I don't seem to be able to generate reasonably high SPLs.  The system is as follows:

Source: VPI Traveler with Clearaudio Maestro V2 (4.2mv output)
Phono Stage:  LFD LE/SE (39db gain, not adjustable)
Integrated Amp: Sony TA-A1ES (80wpc into 4 or 8 ohms, switchable between the two)
Speakers:  KEF LS50 (84.5db sensitivity, 4 ohms min.)
Listening room 15x12ft.  relatively easy to pressurize.  

The system sounds fantastic.  However, I am using the volume of the Sony set between 70-80% of max, and I'm still only generating peaks of 80db (avg around 65db) at the listening spot (7 feet away).  If I push it much higher than that the sound starts to thin out quickly.  Interestingly, I had a similar problem a couple of years ago when I first tried the KEFs (and returned them) with a Hegel H80, which also puts out 80 watts per channel.  My initial thought is that the KEFs just need more power.  However, the various reviews of the LS50 use similarly powered amps with no comment about power problems.  

Don't know whether I should be looking at a more powerful amp.  The sliding class A sound of the Sony is phenomenal, but perhaps the topology just doesn't draw enough current?  Maybe the KEFs just need more kick?   I will be trying a pair of MM De Capo BEs, which in theory should be much easier to drive (although I just read a review where they were measured at just 86.7db sensitivity rather than their 92db as claimed).  

Any thoughts would be greatly appreciated.

Thanks, Scott
smrex13
I think I agree with your suspicions in saying some of what your describing may lie in the Sony’s power section being less than adequate for the Kef’s. However I noticed they match it with the same Kef’s during one review I read, they speak more positively about the mating. I was not able to find detailed specs but was less than highly impressed with the Sony's power amp from what I did find. I have De Capo’s and while they sounded quite good on one of the NAD 326 BEE integrated amplifiers they really came alive when I got a larger Bryston hooked up to them.
Meerizistar - yes, I noticed that review, too.  They didn't seem to have any problem with the Sony driving various speakers, including the LS50s. 

Leads me to believe that gs5556 is probably on to something.  I checked the Clearaudio website, and the output of the cart I'm using is only 3.6mv, not the 4.2mv I listed above (that was for V1 of that cart).  I would imagine a higher output cart might be just what I need, or a LOMC with an appropriate SUT. 

Will bring my CD player home from my office system and give it a go with the Sony to see if I have similar issues.  

Thanks for the help,Scott
According to the KAB phono gain calculator, you're right on the money with the phono pre-amp.  Which suggests that either the LFD is not putting out enough voltage (defective) or the amp/speaker interface is the issue.  The fact that the Sony is spec'd at the same wattage for 8 or 4 ohms, plus your experience with the Hegel, and the low sensitivity of the KEFs all point to the amp/speaker match-up not being optimal.  The S-phile measurements show impedence dips to 4 ohms at the low end and 5.3 ohms at the high end and also notes " the combination of 5.3 ohms and –41° at 135Hz, a frequency where music often has high energy, will make the speaker work at its best with a good, 4 ohm–rated amplifier."  I'm no techie, but most solid state amps put out more power into 4 ohms than 8, the "more robust" being able to double their power output as Ohm's Law suggests.  No idea what is happening with that 4-8 ohm switch, but you might try it at the 8 ohm setting.  If that does not work, I think you need a beefier amp that "doubles down" into a 4 ohm load.