power amps

The 104/2s are good, but an easy load they are not. My brother ran a pair for 6years... and while they are capable of great things, getting the best from them ain't always easy.

KEF called it 'conjugate matching' and claimed they represented a flat 4ohms impedance, but the truth is, the power amp has to be happy with a a reactive 3ohm impedance to get the best out of these speakers. While the claim was 90dB/w+, the truth is rather nearer 86dB/W. Yet I'd take low-impedance load-handling over total power output any day - for example, of contemporaneous amps, a Naim NAP140 drives them far more effectively than a Quad 405/2 although on paper it's about 1/6 the power output and rather noisier. I know, I've done the back-to-back...

I would not pair a valve amp with the 104/2s unless it was capable of extraordinary feats into low impedances. A solid,transistor design is the way to go, perhaps even a chunky Class D effort (Bel Canto?); the 104/2's slightly soft top-end will forgive a lot. For a 'under a grand' I'd look at the best low-Z driving amp you can secure; a big old Roksan, some Michell Alectos Monoblocks, one of the Exposure poweramps with fully regulated supplies or even an older pair of Naim Nap 135s would all squeeze in this budget and offer a range of flavours to choose from to start with.

 

thanks for the replies so far....very helpful indeed....Felix, thanks for your info on the kefs. this was very useful....andy..whilst on the subject of class d etc...can someone explain in very basic terms, what is the difference between ...class A? class A/B? class D? etc.....i havent a bloody clue what this means.....for example, i see alot on here..." 100 watts of pure A class??????? what is this?

 

I owned Kef 104/2 since 1986, replaced them 2001...

By the way, claimed efficiency is 92db...

I used an old transistor McIntosh, 100 watts, no problem, lately I used a mini Toshiba Aurex 50 watts, bought in 1979, highly recommended then, also no problem...

As for Rotel, I had problems driving Sonus Faber EAII with a RB-991 200 watts power amplifier, couldnt handle the bass at all, I would stay away from it...

 

No Antonio. That's the claimed sensitivity. You need to understand the fundamental differences between sensitivity and efficiency in order to discuss real world power requirements. We come back to that impedence curve again. Do you understand that yet? Lot's of people make the same mistake as you and get these two mixed up.

 

From wikipedia:

For me it is enough, go play with your toys, let others play with theirs...

 

http://en.wikipedia.org/wiki/Electronic_amplifier#Class_D

 

ah, wikepedia, the source of internut bullshit.

 

Says the wise guy... :SLEEP:

One more in the group that discusses about me on weekends...

 

Any of the lower powered MC2 Audio amps MC450 or MC750.These are classAB non switching power amps.
More current than you could ever need with a neutral transparent sound.
For most domestic conditions you'll never get out of classA.
Designed by Klark of Klark technik fame and designed to be ultra hifi(dont laugh).

 

I've just gone totally valve, sold my original 1988 104/2's last week.
The amp that moved them well (which is just about to be "listed") is my Alchemist Forseti Tim de Paravicini Signature ADP20A MK II power amp.

They sounded great with the Alchemist pre/power combo.
PM if you're interested.

 

it's always seemed pretty accurate to me - like this on class D..

D does not stand for "digital"

The letter D used to designate this type of amplifier is simply the next letter after C, and does not stand for digital. Class D and Class E amplifiers are sometimes mistakenly described as "digital" because the output waveform superficially resembles a pulse-train of digital symbols, but a Class D amplifier merely converts an input waveform into a continuously pulse-width modulated (square wave) analog signal. (A digital waveform would be pulse-code modulated.)