REVIEW: ROGERS e40a TUBE INTEGRATED AMPLIFIER Jun 13, 2009 0:52:11 GMT 7
Post by on Jun 13, 2009 0:52:11 GMT 7
Designed and built for digital era, the Rogers E-40 and E-20a Class 'A' Stereo Integrated Amplifiers truly represent digital sound the way it should be heard and appreciated. These superb fully integrated, all-valve, handmade amplifiers are guaranteed to send tingles down the spine of the most discerning of audio aficionado's. Recommended for use with a wide range of the highest quality transducer or electrostatic speakers. When partnered with Rogers' LS3/5A and AB1 speakers, the result are truly spectacular! The E-20a is recommended for smaller listening rooms using standard transducer speaker systems. "The merging of digital and valve technology is the perfect marriage between source and loudspeaker"
Power : 40 watts per channel class 'A'
Valve Output : Push Pull Cathode Follower
Self Bias 6L6GT x 8
Phono Stage : 2 x ECC83/12AX7
Line Input Impedance : Phono: 47K ohms, Line: 100K ohms
Of all the many subjects discussed in the LS3/5a yahoogroups mailing list, the subject of which amplifier to use with the LS3/5a has been the most controversial. A look through the group database shows members using Quads ancient and modern, old Leaks, Radfords or modern M.F. Nuvistors, the list goes on and on. If there is any consensus at all it is that the LS3/5a sounds terrible with some solid state amplifiers. Many of the group members think LS3/5as should only ever be driven by tube power.
I was intrigued then when Doug Stirling from Stirling Broadcast rang me to offer the loan of the Rogers E40a. This amplifier's pedigree is impeccable. It was designed and manufactured by none other than Audio Note for Rogers UK before they went belly up (Rogers that is). Doug bought out Audio Note's stock and has been steadily selling them to happy customers ever since, several of whom lurk in the LS3/5a mailing list. But what's especially interesting is that Rogers had this amplifier in mind as the perfect companion for the LS3/5a and AB1. To quote from the brochure, "Recommended for use with speakers that have an efficiency of around 86dB and, when partnered with Rogers' LS3/5A and AB1 speakers, the results are spectacular."
OK, so that's advertising copywriter's hype but then Rogers certainly knew what they were about and their early version of the LS3/5a remains among the most sought after. I used the E40a in my system for more than a month before Doug managed to prise it back off me. First let's get the technical stuff out of the way
The E40a uses a quad of 6LGGTs in each channel to generate 40 watts of Class A power into an 8 ohm load. In a Class A amplifier the output devices, tubes in this case, are biased so that they conduct continuously. There is no change in tube plate current with signal. Class A lovers say there isn't any other way an audio amplifier should work. The trade off is inefficiency. A Class A amplifier runs hotter when it is sitting silently than it does at full pelt. And does the E40a run hot! 40W of Class A is a substantial amount of power and in order to be able to generate it the 8 output tubes alone are going to need to dissipate at least 160W of heat at idle. In practice the E40a pulls a little under a continuous 300 watts out of a 240V mains supply.
The choice of 6L6GTs for the output stage is interesting. This tube was originally designed with the military in mind and modelled on the physically bigger and now horrendously expensive KT66, beloved of Quad II owners. The rest of the tube line up includes ECC83 line and phono stages, an ECC82 phase splitter and 6SN7 cathode follower.
Unbalanced inputs, on gold plated phono sockets, are provided for a phono cartridge, dedicated CD input, 2 line stages and a tape deck. Line level tape output is catered for. Speaker output uses very nice Audio Note gold plated binding posts to take either 4mm plugs or thick bare wire ends. Output transformer taps are provided for 4 and 8 ohm loads. What a shame a 15 ohm tap wasn't provided for the owners of old LS3/5as run sans AB1s. The E40a will drive them OK if the speakers are connected to the 8 ohm tap but the full power of the amplifier won't then be available.
As for the aesthetics? Well I have to admit that I like to see tubes sitting proudly above the chassis glowing merrily. For me, a Quad II is the model of function leading to pleasing form. And I even like the rather industrial look of the Leak tube amplifiers. In the E40a the tubes are mounted on a printed circuit board at the bottom of the black chassis, the top of which features a curved stainless steel perforated cover which was the subject of much comment by visitors. My wife drew an instant comparison with the UK Millennium Dome (how cruel can you get) but for me I'm afraid the E40a looked extraordinarily like an aerial view of a main line railway terminus! Unfortunately you can't run the amplifier with the cover off because it exposes high voltages on the board. And those knobs! Gold-plated with the control legends written on the stainless steel cover. The E40a does look much better in the dark, where the satisfying glow from those eight 6L6GTs will be a fine substitute for someone who hankers after a real fireplace.
The E40a is a big amplifier. Although only a shade wider at 430mm than a full-width CD player it is as deep as it is wide. This could cause a problem for an owner with an equipment rack although if you don't mind it hanging over the back some Vibrapods or similar will allow it to sit on the top shelf. It is also heavy, weighing in at around 20kg. I didn't have a support that was suitable and so ended up with the E40a on my wooden floor. Realising this isn't ideal and conscious of the information in the instructions about using a decent support, I experimented with vibration isolation putting home-made Silipads (silicone rubber pads), bean bags and juggling balls under the amp. Curiously all of these degraded the sound achievable by simply using the E40a's own feet. Tube amplifiers, because of their inherent microphony, are often more critical of what they stand on than solid-state amps, and this was the case here. It would certainly pay an owner to spend some time experimenting.
All tube amplifies need a long warm up period and the E40a is no exception. This amplifier sounds best when it is really hot! No problem there because that's just how it is designed to operate, the instructions caution about how hot the stainless steel cover gets and although I didn't try it because I thought Doug would object to the crumbs, I'm sure you could toast bread on the top!
After about an hour of warm up I couldn't resist the temptation any longer and put on a CD. In the past I have used Quad IIs and old Leaks and consider myself fairly familiar with the sound of tube driven LS3/5as. My particular favourite are the Quads which have been described as a marriage made in heaven when used with the LS3/5a. Although the Quads don't appear on paper to have enough power output to drive the LS3/5a-AB1 combination properly, in practice they can go satisfyingly loud. It's all due of course to Peter Walker's marvellous conservative design and the intrinsic ability of tube amplifiers to sound nice as they are driven into clipping.
I wasn't at all prepared for what I heard from the E40a. It was immediately clear that the E40a is a very good amplifier indeed. But it sounded nothing like the cuddly warm soft clipped sound I know from Quad IIs. Neither did it sound like my solid state amplification, modified Quad 405-II or home-made MOSFET amplifiers. The E40a sounded much better, rather like a very, very good solid state amplifier. Had I been listening blind I would have guessed that I was listening to some very classy and very expensive well-behaved solid state amplifier. Perhaps the giveaway would have been the just slightly light bass, although that got better and better as the amplifier got hot, "warmed up" seems an understatement here.
Then the penny dropped. I was listening to a modern tube amplifier. Not an old Quad or Leak. This amplifier was transparent. Forty watts of modern, pure Class A tube amplification with no added vintage tube extras. In many ways it does exactly what the LS3/5a does so well. The midrange was clear and analytical, so clear that I was able to understand vocals I had previously missed on well-known CDs. The stereo image was pin-sharp, very wide and deep.
I was so impressed with this amplifier that when Andrew Drummond, Derek Rumble and I ran the LS3/5a demonstration room on behalf of HiFi News at the 2001 London Show we chose the E40a as our amplification. Andrew loaned his own E40a for the show and it behaved flawlessly. Despite all the attempts of the desperately poor acoustics of our Novotel Hotel room we were able to throw up a convincing sound stage for the visitors. And the visitors were clearly impressed with comments like, "the best sound in the show" written in the vistors' book.
If there are any E40as left at Stirling by the time you read this (and I am sure some will have sold as a result of our activities at the HiFi Show) then a brand new E40a can be had for very much the same price as a decent set of Quad IIs. The choice is yours. Would I own one? Absolutely! Why don't I own one? Well only because, as an incurable romantic I'm looking for the right set of Quad IIs to come along. The problem of course with owning a vintage amplifier like the Quad is that you had better be able to fix it yourself. Because if you can't, then just like running an old car, you are going to be faced with frequent big bills from the repairer. My heart told me that I wanted to use Quads at the London HiFi Show. My head told me that it would be madness. To a rational rather than a romatic the E40a is actually a better amplifier and won't surprise you with the bangs, pops, hum, whizzes and farts that so often add to the listening experience of vintage tube amplification! The E40a will work when switched on and will go on working.
The E40a sounds great, generating a huge holographic sound stage. Forty watts of great Class A tube sound at a bargain price, what more could you ask for?