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845/211 tube amplifiers with kef reference 5?

Hi, am seeking for advise from those who have the kef reference 5 or have 845 or 211 tube amplifiers.

I personally own a pair of kef reference 5, driving them with primaluna dialogue HP integrated tube amplifiers with EL34 tubes at 70 watts. Am liking the sound but cant help but wonder if playing with the bigger tubes like 845 or 211 will give it even more tube magic, sweetness/softness, musicality and wider soundstage.

However, those amps typically are lower powered around 20-30watts, and would like to ask for advice of those are suitable to power a kef reference 5 which is 90db at 8 ohms and minimal impedance of 3.2ohms? Recommended power is 50w to 400w but i know tube watts can be more powerful than solid state. 

For those of you who have matched a system like that or heard set ups of these forms of amplifiers with the kef ref 5, or have similar experiences, would like to seek some advice/get some experience from you

Thank you!
Regards
Ben
thegreenman

Showing 4 responses by georgehifi

georgehifi's avatar
georgehifi
10,312 posts
 
thegreenman OP

Don't listen to Ralph, it won't be a disaster like he's making out, he's got a bee in his bonnet, over something.

They will work up to a point as verdataudio and I outlined.And very good if you just use them for the mids and highs, with a cheap class-D on the bass.Maybe he's got some sort of other agenda with his soon to be released Class-D and got you in his sights.
Cheers George

georgehifi's avatar
georgehifi
10,312 posts
 
That will ne be the case with the Reference 5s. You will have peak output of about 100dBs before the amp clips. This is going to mean VERY flabby bass.
Yes as I also said the bass is the problem unless there’s a 4ohm tap, then ultimate loudness is reduced 

Seriously, wouldn’t it make more sense to bi-amp. Get a great 845 for mids and treble and power the bass with a nice, SS amp. Get a used Krell or Chord power amp, even Musical Fidelity to pair with it and the net result will be brilliant.

Yes this would be the best way, put his 845 on Ref 5’s mid/highs terminals, and just a cheap Class-D for the bass, a number of configurations could be done being able to even triamp.

Cheers George
georgehifi's avatar
georgehifi
10,312 posts
 
What George is saying here is bad advice.

That’s wrong

you’ll encounter a tonal issue
That’s just what sets do, look at ANY SET into the Stereophile simulated speaker load frequency response graph, most sets act like tone controls.

thegreenman OP
As I had 805 sets drive just that same speaker off the 4ohm taps, like I said the max loudness wasn’t quite there, but it sounded great, for tube set. The Kef looks like a benign 4ohm load to an amp when impedance and combined -phase angle is taken into account.

Cheers George
georgehifi's avatar
georgehifi
10,312 posts
 
thegreenman OP
845/211 tube amplifiers with kef reference 5?
You should be fine with P/P 845 or 211’s, or even SE ones with the speakers being 90db, and if the amps have a 4ohm tap, and you don’t want to go too loud with the SE’s.
The 8ohm tap will give more watts but "could" a problem in the bass.
https://www.stereophile.com/images/1017KEF5fig01.jpg
The impedance peak at 2.5khz will be bought back down by the increase in -phase angle around there also, so a fairly flat 4’ish ohm impedance will be seen by the amp

This is what Stereophile had to say
Fig.1 shows how the impedance and electrical phase vary with frequency. While the impedance lies above 8 ohms in the low treble, it remains between 4 and 5 ohms throughout the midrange and bass and in the top octaves. The minimum value was 3.3 ohms between 90 and 100Hz, but as the phase angle is generally benign, the Reference 5 should work well with tube amplifiers from their 4 ohm output transformer taps.


Cheers George
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