KEF Reference 1 Meta with Class A amp

If your posted specs are correct it looks like your amp prefers 4 ohms and 40 watts should be enough, often it's more the current availability more so then watts anyway in driving lower impedance.

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Tomster66 said:

Hello all.

I have a Sugden integrated amp which runs pure Class A.
The specs show 40 watts into 4 ohms and 30 watts into 8.

My question is do you think this amp will run the KEF Reference 1. It’s rated 85-86 db sensitivity with nominal impedance at 4 ohms.

They will be placed in a relatively small room and I generally listen at about 80-85 decibels.

I understand the amp is underpowered in a technical sense but does Class A even the playing field.

P..S. This amp creates more than enough power for my Merlin floorstanders which are 89 db efficient.

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Can I ask which Sugden amp you have? I ask because their Masterclass FPA-4 was amongst the dozen amps I home demo'd with my own speakers when I was moving from tube amps to ss. Although I was expecting a Class A to win me over, sadly the Sugden was one that seriously disappointed, though your amp may well be better with your speakers.

My own view is that the primary item that needs careful selection to suit your room and listening preferences is speakers, and only then should you be looking for the ideal amp to power those speakers. That's why I was demo'ing all those amps. These included other Class As (Accuphase A-36, etc) and a number of Class AB and D. The best Class A was the Accuphase, but it was just a little too "polite" so I reluctantly sold it after a year or so.

Whether Class A is likely to get the best from the KEF, I would suggest unlikely in my view, although the only Sugden I've had first-hand experience with is the FPA-4. Do you really like Class A or the Sugden in particular?

Have you bought the KEFs yet? If so, you can answer your primary question (is the Sugden powerful enough) without our help, but I suspect it will be. However if you are still deciding on your speaker purchase, I would suggest you give preference to this decision over the suitability of an existing amp.

PS - The only KEFs I've owned were the big Reference 107s (from the mid 1980s) and great speakers they were. Sensitivity was 90 dB and impedance 4 ohms. I had 100 watt mono amps at the time, but I learned (after selling the speakers) that those speakers needed an amp with greater current delivery than my AVIs could deliver. So I probably never heard the speakers at their best! This experience has contributed to my view that speakers need to be chosen first, then get the best amp to power them.

My KEF ref 5's love being over powered and sound best when they are.


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Phishphan said:

My KEF ref 5's love being over powered and sound best when they are.


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Well I typed out a lengthy response but for some reason it didn’t post and now it’s gone.
The Readers Digest version is my amp is the Sugden A21se.

Tomster66 said:

Well I typed out a lengthy response but for some reason it didn’t post and now it’s gone.
The Readers Digest version is my amp is the Sugden A21se.

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I think that Sugden's A21 series has stood the test of time and it has a lot of fans. I suspect that the "higher spec" and more costly Masterclass FPA-4 that I had on loan wasn't popular as it seems to be discontinued now as it's not in their main website, although a Google search comes up with a Sugden page describing it as "the latest member of the Sugden Masterclass Family." How odd!

I'd still keep an open mind after buying your new speakers whether to stick with the Sugden or use a different amp. It's well worth trying a few options, including Class D. Rather against my expectations when I tested a dozen ss amps, I found the best of the Class D amps offered the best sound out of all of them - perhaps tied with the GamuT D200 Mk III (Class AB). Good luck anyway.

I found an old Stereophile review of the A21 where it was mentioned the amp could drive Quad ESL's which have a very difficult load due to impedance and, in fact, Sugden uses the Quad's as a listening reference. Then I found information that says the A21se has double the power supply of the standard model. So I've never owned the Sugden but I'd say it would drive the Ref 1 with no issue.

Decibels are logarithmic however the Merlins's will play nearly twice as loud with the same signal input. If you have plenty of volume left when listening to the Merlin then this may not be an issue for you with the Ref 3.

It confounds me that I can use less than a single watt peak yet hear an obvious difference between a 300/525 wpc amp and 600 wpc amp? 1 would think such a small draw would make amps impossible to tell apart. There’s obviously more to an amp than its wpc output. If the model 1 reference is anything like the Blade you’ll know pretty quick.

Tomster66 said:

Hello all.

I have a Sugden integrated amp which runs pure Class A.
The specs show 40 watts into 4 ohms and 30 watts into 8.

My question is do you think this amp will run the KEF Reference 1. It’s rated 85-86 db sensitivity with nominal impedance at 4 ohms.

They will be placed in a relatively small room and I generally listen at about 80-85 decibels.

I understand the amp is underpowered in a technical sense but does Class A even the playing field.

P..S. This amp creates more than enough power for my Merlin floorstanders which are 89 db efficient.

Click to expand...

These speakers' efficiency is on the low side. What kind of music do you listen to? If it's classical and your 80-85dB is an average listening level, my answer would be 'no.' You would get sound, but dynamics would be compromised.

I have had KEF speakers since the early '80s. I have driven with both SS (First Watt) and tube (Audio Mirror) Class A. Never an issue... but I don't ever approach concert levels . If you like to play at modest levels to lower-high levels then you should be fine. I would love to get a pair of Ref 1's.