Audio Note OTO SE Amplifier


Valve Integrated amplifier

Product name: Audio Note Oto SE Amplifier
Manufacturer: Audio Note - Great Britain
Cost: 3146.77 GBP (Currency conversion)
Reviewer: Graeme Budd - TNT France
Reviewed: May, 2020

Over the last 10 or 15 years there have been some interesting developments in the integrated amplifier market with the arrival of digital output stages bringing small, powerful amps into the forefront. And why not  - we at TNT Audio have a few favourites and they can be a fine base for a system - hey even my Dad has one! What we're dealing with today is the total opposite since it has been around since before the digital invasion and in contrary to the qualities I eluded to above is neither small nor on paper high powered. So for those that hadn't guessed yet the object we're talking about is a single ended valve amp.

Audio Note has been building the Oto for a fairly long time and it's available in a variety of guises. Firstly you can have either a line only version or one with a built in phono stage. As I already had a R Zero II Phono in house, Peter from Audio Note suggested the line version - which is fine by me. Then you can either have a push pull version, an SE (single ended) version (the one we have here) or SE signature and SE signature silver versions which feature upgraded components. As you can see only the SE versions get signature versions which reveals Audio Note (UK)'s preferred single ended output topology. The single ended versions qualify for Level 2 status in the AN(UK) hierarchy due to the components and output topology so we're on the way up the ladder but the next four rungs are very far spaced apart... As it is the Oto SE costs 3146.77. Don't ask me why this isn't UKP3149.99. Either it's some very honest pricing on AN(UK)'s behalf or there is some mystical significance to 46 and 77. Personally I'd have priced it at 3141.59 (no prizes for guessing the significance of these numbers).

The amp is of conventional size and appearance and certainly ticks all the boxes in the practicality stakes. There are no valves sticking out making it family friendly and it's not overly heavy at 17kg. The front panel sports a selector switch for the 4 inputs, a tape monitor rotary switch, a balance control and a volume control. Two of those are certainly rare enough to raise a few eyebrows. I was almost tempted to dig out my old Nakamichi but in the end decided to stick with vinyl and CD. The front panel can be had in black acrylic or brushed aluminium depending on your aesthetic preferences. I love the black but I admit it's difficult to photograph without you unfortunate people getting my reflection thrown back at you. Round the back there are some rather nice speaker sockets with both 4 and 8 ohm options and similar perceived quality continues with the phono sockets. There are also signal and chassis ground sockets. The former I presume is due to a shared chassis with the Phono versions and the latter allows easy connection to grounding systems  - not something I have but that I'm tempted to try at some point in the future so that's another tick in the box if I can get something rigged before the Oto goes back. There's also an on/off switch and whilst this may indicate that the amp could be left on all the time (it doesn't get overly warm) it's not something I'd suggest from an electrical consumption point of view. Just remember to switch it on a bit before any serious listening sessions to give it a bit of warm up time.

Valve complement is 1 x ECC82 and  2 x ECC83 in the preamp and 4 x EL84 in the power section. All of these are easily obtainable at reasonable prices making future valve changing an easy and relatively inexpensive process. Of course you can go over the top and buy a load of expensive valves if you want. We're not quite in Single Ended Triode pricing territory here but let's get down to business and see what a single ended Pentode configuration can do.

System wise I used both the Linn Axis/Akito/Etile and AN TT2 Deluxe/Arm II 2/Io1 Turntables and either the CEC PH53 or Audio Note R Zero Phono II phono stages. My Naim CD5i provided CD player duties and the Living Voice IBX RW3s made the required noises at the back of the system. I also had my Canary CA 608 LV on hand for amp comparison duties.

OTO SE rear

Rear panel


The Oto SE does take some time to run in and as this one was built brand new for the review (as is the case with every Audio Note component - there's no reviewer privileges or any other such malarkey going on here) it did change over the run in period. It started off well immediately showing impressive flow and musicality and kept getting better except for a couple of days where it just sounded a bit boring and dull (this is relative). Strange indeed but I can now report that it's back on song.

So what does it bring to the party and how does it compare with my usual Canary 608LV reference which if made today would likely cost the same amount? Well it's very nimble and has a wonderful ability to follow a tune. But this following a tune isn't what Linn fans would get excited about. By that I mean there isn't a beat dominating the rest of the presentation at the expense of everything else. It's quite a disarming sound as everything is there but isn't forced at you. It's detailed without being forward or bright. The music has time to happen  - you don't get the impression the performers are in a hurry to finish. There's bass but without boom and there's imaging without it being finely etched in space. You could definitely find individual amps that do any of one these hi-fi qualities better but it would appear Audio Note have steered the fine line of getting the musical aspects spot on without creating any obvious flaws. Not the easiest thing to do but very satisfying when you get in right.

I guess some musical examples would be best here so here goes.

Take as an example Go Go Penguin's Hi Rez. Play it on my Canary 608LV and it's pretty impressive. The left and right hands of the piano are clearly demarcated in space. The double bass goes low and the drum fills have power, body and realistic tone. Swap the Canary for the Audio Note and whilst there's less low end the musical flow takes over and the interplay between the instruments somehow makes more sense. The left and right hands of the pianist are somehow more human. If that sound's weird stay with me and I'll try and explain it further.

I've recently found a copy of Four Tet's New Energy album  - playing the opening two tracks through both the Oto SE and my Canary 608 also proved interesting. Both amps are very enjoyable  - the Canary tends to favour the stage depth and the lower registers. You'll hear things off in the distance that are present with the Oto SE but less obviously so. The Oto SE trades off a bit of stage depth and width and some low end for the presentation of the instruments and the touch of those that played them. It will tell you what the players intended you to hear. In essence I think the amp is adding the strict minimum of its own character to the music. It's not trying to be impressive and as a result manages to be.

I put the Stone Roses Second Coming on the deck and cued up Ten Storey Love song. Now this is a great track with a bit of a Byrds feel (a definite plus in my books) but it's not particularly well recorded. There's little instrumental space and you don't get the feeling of being there. Move onto the next track and all of a sudden the drums sound like reals drums with obvious resonance and presence in space. The guitar is off to the left and the central staged bass guitar just sounds like it's being played through a decent (probably valve) amp. A quick bit of geekery on the internet and it turned out I was right. Now what does this tell us? Well firstly I should get out more and secondly the Oto SE will also show you when the engineer had an off day and when he was on his game.

Similarly a quick play of Jamiroquai's Morning Glory allowed the Oto SE to impress further. It's ability to portray even subtle shifts in the way a snare drum is hit and the way Jay Kay sings particular phrases - things I'd never really noticed before. Again the word human is what springs to mind. I guess this is what some refer to as microdynamics - whatever you wish to call them the Oto SE is capable of resolving the tiny differences that differentiate real players from samples or loops.

Single ended advocates would explain that this communicative character is due to the amp design. Due to the necessity that I remain as impartial as possible and my lack of electrical engineering qualifications I'm not in a position to comment on the technological choice compared to others. What I will say is that the Oto SE has been the first single ended amp I've had at home but I have a feeling it won't be the last. It certainly hasn't put me off.

So is single ended working for you and your future upgrades? Anti single ended critics would no doubt point to the lack of power the designs produce. On paper I'd be tempted to agree but lets do some real world comparisons of the amps mentioned above. The Canary is an ultra linear design with 4 EL34s and is capable of going stupidly loud if required (for the guitar players among you 4 EL34s are what power a 100 watt Marshall). It throws out around 35W per side and the volume control rarely goes above 8:30. It works wonderfully with the Living Voices (and has been no slouch with other speakers) and that's why I have no intention of parting with it. The Oto SE manages 10W per side but frankly it's amply sufficient for normal listening especially if you value the communicative qualities I alluded to above rather than being forced into your chair. Yes the volume control tends to be used closer to 11:00 for involved listening but frankly who cares - its just a number! It manages to be both delicate and forceful when required and works equally well with my choice of speakers. My local hifi emporium even told me they have sold systems with the Oto SE an LS3/5a speakers with their meagre 83dB/W sensitivity. I've not tried this combination but it's certainly food for thought. Maybe best to avoid Wilson Audio MAXXs though...


It would appear that Audio Note have been onto a good thing for quite a while with the Oto SE. Despite it's low on paper power I feel it could be the answer to a lot of people's amplification questions. It's reasonably priced and built to last a good few years - during the review period it never put a foot wrong with no pops, crackles or buzzes. It manages to generate a level of realism that is a pleasure to live with - I'd be more than happy to. My only reservation in terms of recommendation would be for those who swear by infra bass but you never know - the essential is to approach it with an open mind and let it work its magic. It might make a Single Ended Disciple of you yet.

DISCLAIMER. TNT-Audio is a 100% independent magazine that neither accepts advertising from companies nor requires readers to register or pay for subscriptions. After publication of reviews, the authors do not retain samples other than on long-term loan for further evaluation or comparison with later-received gear. Hence, all contents are written free of any “editorial” or “advertising” influence, and all reviews in this publication, positive or negative, reflect the independent opinions of their respective authors. TNT-Audio will publish all manufacturer responses, subject to the reviewer's right to reply in turn.

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