- Oct 18, 2009
This has been a bit of an odd review for me to write, because the character of this amp changes quite a bit with the tubes being used. So I will offer some bits and pieces, but then the rest is just going to devolve into a short tube diary.
Here's the webpage with information and specs:
A little bit about Wolf Ear Audio: This one man show is run by Andrew Rintoul, by day a mild mannered pencil pusher, by night a solder slinging superhero... but really now, he's just an ordinary guy like the rest of us who started his headphone journey back in the day with an impulse purchase Denon D5000.
A student at the time and on a shoestring budget, he starts mucking around and modding existing gear and soon after starts building his own amps, discovering a love for tubes along the way. Years later, he decides to take his passion a little bit further. So he starts up his business with his own pocket money, designs and builds everything from the circuits to the art/website to the chassis etc, and wonders just how much longer his wife will put up with him cluttering up the house with all the parts and prototypes (this last part should be a familiar story to those of us with the DIY bug). Wolf Ear is based out of Alberta, Canada, and to my knowledge is the only Aboriginal Canadian business dealing in high end audio amplifiers.
First of all, you're not going to get awesomesauce pics from me. For one thing, I'm a terrible photographer. Secondly, I'm getting really tired of reviews that look like a product placement ad. I'm gonna shove in pictures I took with my decrepit barely-a-smartphone, on a messy desk with wires everywhere. Eventually.
Secondly, I'm just gonna start with the TL;DR of this review: OMG I've descended into tube hell and am having way too much fun experimenting and kicking back with tunes. Somebody pry this thing away from me before I descend into even greater head-fi neurosis...
With that out of the way, this really is a lovely amp and pictures won't do it justice anyways. It looks very simple and box like, but the textured red surface is quite beautiful in person. It is also heavy beyond its looks. Know why that is? Lots of good 'ol fashioned iron inside. You really have to try and pick it up yourself to appreciate it. In the audiophile world, a quick and dirty estimate of quality can often be gauged from its weight, and boy howdy that's what we've got. In the digital age we can shrink things down to components the size of ants, but you've gotta deal with the electrical hash as a result (a gross oversimplification I realize, just work with me here). In the fully old school analog realm, there's no substitute for big heavy pieces of inductive metal. There are five notables inside. The first is the big toroidal transformer, followed by two chokes for filtration. On the other end are two large output transformers for the headphone outputs. There's no cheating for size with these things. At very high frequencies you can shrink them down, but at audible or mains power frequencies, you have to go big (and big = heavy) to maintain linearity and performance.
Total power output is impressive, at a rated 4.5W into 32ohms. I'm one of those nuts with a Hifman HE-6, which is basically as abusive as you can get in terms of sheer power requirements. Now most of the time I drive my HE-6's from the speaker taps of a dedicated speaker amp, but the Makoyi has never left me wanting for more power. I can push it to more than adequate volume levels before I hit distortion, and even then just barely. On any other headphone this would be deafening, so I don't recommend it.
As for the topology itself, this is a class-A SET amp with transformer coupled outputs. In the high efficiency speaker world, SET amps are often prized for their, well, let's just dispel with the audiophile jargon and say that they do what they do very well and have earned their place.
Here's some random reading for you if you want to get an idea of what the topology means:
They have the advantage of being "simple" and are considered more "pure", yadda yadda. Now of course SET amplifiers have the disadvantage of low power and high output impedance... but that's for speakers. Power really isn't an issue for most headphones which operate at literally a thousand times lower output than speakers. As for output impedance, that is hardly an issue either as headphone impedances are typically several times higher than speakers, and what more increase at difficult points rather than drop lower which is where the speaker problems come into play. That said, here are a couple specific output impedance values provided by the designer (values vary depending on tube used):
6L6 - 4.8 Ohm
EL34 - 3.6 Ohm
KT88 - 3.7 Ohm
So we're averaging around 4ohms. If we abide by the old rule of x8 for load, that puts us smack into the 32ohm range of most typical dynamic headphones. Many audiophile headphones average significantly higher than that. Those of you with multi driver iems... you are playing in the wrong ballpark (get the right tool for the job people; don't use an impact driver when you need a jeweller's screw). Now if you happen to have a headphone which swings an impedance peak, yes there might be a slight variation to the frequency response, but we're talking maybe a decibel at most in variance at one very specific point. In my experience though, this typically doesn't even make a palpable difference until the output impedance approaches 10 ohms or higher, and the rest of the amp design makes more of an impact on sound than this single specification anyways. The only headphone that I would pick on here would be the Sennheiser HD5xx family, as this is singularly the oddball where base impedance sits at 50 ohms but swings up to 250 ohms in the midbass. In this worst case scenario, it will generate a whopping 0.3dB difference. Whoopdeedoo.
The gain of the amp varies on tubes used as well. The input stage puts in around x19-20 of gain, but then the output stage incurs a bit of loss, so in the end it averages out between +18 to +22dB of gain overall. The input stage is fairly robust and can handle about 3.4V before clipping occurs. Clipping on tubes is generally more forgiving on tubes than on solid state, but still not something you should do (obviously). Most consumer gear will top out at 2V on their RCA outputs, so there should be nothing to worry about here. It is also worth noting that if you're cranking 3.4V through the input and amplifying that into into your headphones, you will most likely blow your ears out. As all Makoyi's are built to order, the input gain can also be lowered by roughly 6dB but the tradeoff will be slightly higher distortion.
The inputs and outputs of the amp are single ended. The XLR4 jack on the front panel is simply there for convenience and shares ground on the L- and R- pins. Since the outputs are transformer coupled though, technically they could be left floating if you really wanted to remove ground from your output entirely (Andrew does say there is no benefit to this in the circuit, thought the *crazy* part of me kinda wants to try anyways). Do note that this also means you can't have a 1/4" output anymore.
The Makoyi can also be wired up for 230V voltage; please inquire directly before ordering.
Andrew offers several upgrade options for his amps in the form of nicer Teflon film/foil coupling capacitors, and a stepped attenuator. While my unit was stock, his prices for the upgrades are surprisingly cheap (I'm a DIY guy and I'm not sure if I could even match that pricing by doing it myself). The stepped attenuator is especially appealing considering they are all hand-built ladder types, which is in my opinion is the best kind but *very* labour intensive (there 92 resistors that have to be clipped, bent, placed, and soldered in; I don't care how good you are, that takes a ton of time). In fact, Andrew believes so strongly in stepped attenuators that some of his other amps come standard with a series type stepper, but of course has the better ladder types available as an upgrade.
From my conversations with Andrew, here are some more notes from him on the hows and whys of his design:
- KISS - keep it simple, stupid - stick to good parts and linear design
- use film caps where possible because they measure better and have longer lifespan, despite taking up a lot of space and increasing the chassis size
- going "overkill" on the power supply noise, using a large toroidal transformer with magnetic shielding, two chokes, and only high quality film caps; use FRED rectifiers which are the closest thing to tube rectifiers but without voltage loss and current limits
- use CCS (constant current sink) for both loading the driver tube and biasing the output tubes - this maximized gain and tube linearity over their lifespans; measures much better than standard resistor loaded designs and allows for higher gain with lower distortion
- CCS also allows a wide range of tube rolling options as the current bias is kept consistent (p.s. do not try 6V6 output tubes, they will die a quick death)
- output transformers were used to maintain a low output impedance while keeping the amp at minimal negative feedback
- for those interested, a new OTL amp (Natayo) has also just been recently released
The noise floor is adequately low, and with the majority of headphones that I tried (and I have a lot), it was mostly a non-issue. Perhaps with super sensitive iems I could find noise, but What are you doing pairing a piddly little thing with a brute like this? Again, pick the right tool for the right job to do it well. Now, my main headphone happens to be the Hifiman HE-6. Yes, this is the power hog that most of us nutters run off speaker taps. With these I heard no noisefloor at all. Switching to the HD650, there was no noise floor either. With the Focal Utopia, which is a moderately sensitive headphone, I could hear a tiny bit of noise with the volume up all the way and no music playing.
By Andrew's own admittance, this is his most "tubey" amp and I am wont to agree with him. The Makoyi presents this immediate sense of "warmth" and "fun"... all the stereotypical good stuff that we expect from tubes. As an interesting comparison, I also have a Neurochrome HP-1 in house (that I reviewed quite recently here: link) which is a perfectionist solid state design. Comparing these two was a literal night and day affair. I had several friends listening to the two back to back, and it was almost universally agreed upon that the HP-1 was the more technically capable amp, yet the Makoyi was much more "fun".
I'm trying to come up with words to describe my overall sonic impressions of this amp (before getting into the tube rolling portion of this review), but the more I try the more I feel like I'm just cutting and pasting keyphrases from every other tube amp review I've ever read. Things feel "laid back" yet "full bodied" and "warm" with a hint of "buttery goodness". Yeah, that doesn't really tell you much does it?
If I could perhaps pick out on two specific aspects that I noted, although again this changes with the tube complement, but draw some conclusions/inferrals from them: 1) upright bass string plucks come out very clear and seem almost like there's a stronger initial impulse, and 2) deep bass impacts are conversely softer but have a deeper rumble. Overall definition is quite strong particularly in the midrange. Lower range stuff is a touch looser but still fulfilling and meaty.
Notes on some specific headphone pairings:
Hifiman HE-6: This well known power hog played reasonably well with the Makoyi. While not fully tamed, I never felt like I was running out of steam either. Tonality was actually somewhat similar to my Bryston power amps, though without the headroom obviously. Where the Bryston won was in some better texturing and an increased sense of air. The Makoyi did however deliver a deeper sounding tone, despite not quite reaching as low.
Sennheiser HD650: Actually this was a fantastic pairing. I've been fortunate that I've had some really nice amps cross my path recently, and the Senn is a rather nice team player once you climb the ladder. It has a very warm tone and somewhat soft edges; "easy listening" is certainly the phrase that comes to mind. As mentioned earlier, Andrew designed the Makoyi to be his most "tubey" amp and with that deliberate intention in mind he certainly succeeded. Back in the day I had a Bottlehead Crack + Speedball, and from memory I would say the Makoyi beats it handily. Comparing vs the Neurochrome HP-1 that I recently just reviewed, it was with this headphone that generated that stark "night vs day" feeling, and I honestly can't quite tell you which I would prefer. I would say with the HP-1 that the HD650 was the most lively that I had ever felt, yet with the Makoyi it was a bit fuzzier, a bit groovier, a bit smoother, a bit... humpier. Yeah just work with me on that.
Focal Utopia: There's an element to the Utopia sound that bugs me a bit; what I call a "papery" upper mid section. With other amps like the Chord Dave or Neurochrome HP-1 this characteristic jumped out further and I didn't like it. With the Makoyi there was a smoothing over that troublesome spot and I felt myself relaxing with the Utopia that I couldn't before.
Hifiman HE-1000v2: The HE1k and the 560 were two amps used by Andrew to voice the Makoyi, and in my opinion the HE1k is a great match. There was a quickness to the sound that almost made me think I was listening to an electrostat.
Sennheiser HD800: Similar to the Utopia, the HD800 gained a bit of oomph and a relaxation of the upper end. It actually seemed to draw the sound halfway towards the HD650 without losing it's characteristic nimbleness.
Oppo PM-2: I've always liked the Oppo planars for their relaxed attitude and great combination of comfort and aesthetics. That said, this was not my favourite pairing that I've heard with the Oppos. Not bad by any means, but at a recent meet with numerous amps on the table, I found myself prefering the Oppos matched with the various solid state amps available.
Okay, that's enough of me squirreling around words here. Scroll down to the bottom for the tube portion with more sound impressions.
I'll admit I wasn't really a fan of tubes before. Nothing against them, and the glow is nice, but previous experiences didn't exactly leave me aching for more per se. The Makoyi however has really turned my eyes around. When I review audio products, I get into a certain mindframe and it's really kind of like work with all the critical listening and note-taking. Not so with the Makoyi; for the first time in a long while I really started to have fun while reviewing. I found myself wanting to let my mind and my ears drift off instead of paying attention (which is partially why this review is a month late, lol)
So at some point we have to talk about cost. Well, I rambled a lot about the heavy iron in the beginning. Unfortunately, good iron doesn't come cheap, and there's five big pieces in there. Andrew also decided to go with all film caps for power and coupling purposes. They measure better, but again those costs add up fast. They're also quite large, which necessitates a larger and more expensive chassis. Now have you guys ever tried making your own custom chassis? A plain off-the-shelf box will run you into three digits and that's without considering the panels and machining required. Now go custom, add the paint job and finishing, and... well, you get the idea.
I hate trying to answer the question of "is it worth the price?" It's a bit of a trap when you're into the boutique manufacturing realm. So let me posit the question this way. I myself am reasonably skilled at DIY and have even built a few amps in my makeshift lab, some from kits, some of my own (albeit rudimentary) design. Can I build a Makoyi to equatable quality and sell it at a cheaper price? No, not even close. In fact, were I in Andrew`s shoes I would vie for even fancier parts and bump up the price further, but that way lies (even greater) madness.
Ok, with all that out of the way, let`s move on to the...
Tube Rolling Diary
Because it is simply not practical to comment on each and every single possible combination, what I will do instead is present my thoughts in a stream of sorts. I will alternate switching out input or output tubes. So each new tube(s) mentioned should be considered paired with the previous mentioned tube in the block above, and subjective remarks should be compared with the corresponding same tube type mentioned two blocks above. Input tubes marked as blue, Output tubes marked red. If I repeat a set of tubes, I will denote with an asterisk (*).
Listening impressions were done primarily with my Hifiman HE-6, although at times I did also switch to a Sennheiser HD650.
In a very broad sense, I find the input tube has a greater effect on sound compared to the output tubes, but both are important obviously.
Tung Sol 6SN7
- Everything seems to come out stronger
- almost feels kinda V shaped?
- more euphonic-ish, but I feel a pressure build up
- fatiguing from pressure
Electro Harmonix EL34
- a bit too much weight
- gives the impact but a bit muddled
- fatiguing from weight
- way too much when combined with Tung Sol 6SN7
- more neutral sound
- cleaner, like a bit less haze
- nothing really sticks out about this one
- I can breath again, took off the weight
- bass has depth but not the cleanest edge
- I like the nice blue glow from the tube though
Psvane CV181-T II
- separation and resolution is better
- but still a hint of fatigue
- sadly no glow
- interestingly doesn't get hot to the touch on top
Psvane KT88-T II
- weighty, immediate sense of that presence/heft
- better pulse of energy rather than blob
- but more air/uppermids at the same time, which is odd
- bass impact slightly veiled, but upper end clearer
- staging feels compacted
- resolution murkier
Psvane 6CA7-T II
- lighter but more forward
- stage wider and taller but shallower
- softer transients
- less kick
- not the best detail but gentle
- zero fatigue
- a nice brighter glow
- supposedly a higher tolerance version of the EL84, but sounds very different to me
*Psvane CV181-T II:
- ok I came back to this one because I thought it would be a good match...
- yes this is good, bass is rich and clear
- no fatigue here
- excellent resolving ability and staging
- tactile on the soft parts
- though staging feels a bit lower
Tung Sol 5881
- hard and tizzy compared to the smooth 6CA7
- at first it feels "detailed", but it comes across as heavy
- metallic aftertaste
- tones down with some burn-in
- good tactility
- slight blue glow
*Tung Sol 6SN7
- just going for the Tung Sol combo; wonder if it would accentuate the stuff I didn't like...
- yup still has that metallic tint
- more forward
- fast pressure
- do not like this combo
Svetlana 6V6L 6GC
- smoother/softer (but that 5881 was so bright... anything will feel mute in comparison)
- but a hint of sibilance/grain
- better belly rumble
- ok air
- staging is floaty around my head
NOS 6SN7 W/U (USA)
- more shimmer
- lighter feel; easy listening
- resolution average, less than or equal to the Tung Sol before, but lower than the Psvane
- detailing feels flatter
- soundstage is a bit closer in
*Psvane KT88-T II
- decided to come back to this, see if the weight balances out the lightweight feel of the 6SN7 USA
- not quite, still slightly mellow
- yet at the same time individual notes feel more energetic
- but somewhat blurred together
- better thump
NOS 6SN7 GTB (Japan)
- a mostly relaxed sound
- very slight burr in the upper mids
- a bit pushy at the faster transients
- slightly rolled in the bass?
*Psvane 6CA7-T II
- impactful with body but not super defined
- stage wider and behind
*Psvane CV181-T II:
- last rotation through this one
- clarity improved
- upper mids move forward
- stage comes back to the front
- gripe: still doesn't have a big kick
- plays very very well with acoustic and vocals, not so much with rock