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ampsandaound Bigger Ben Amplifier

04-21-2020 | By Sam Rosen | Issue 109

ampsandaound Bigger Ben Amplifier

The Bigger Ben has 5 impedance outputs

Let's get one thing out of the way before we begin this review, I am a big fan of ampsandsound. I have owned, or had in home trials of pretty much every headphone amp that, Justin, the owner of ampsandsound, and his team have produced. I have purchased several of his amps over the past few years. Throughout that time I have gotten to know Justin, and we have become friends, which means sometimes I get to hear about new products or new raw materials before others do. In this case, one day I got a picture from Justin of a brand new 20-watt custom wound single ended output transformer with five output impedance taps (8, 16, 32, 100, 300). Interesting, I thought to myself, I think I want one.

Justin is a man who believes that big output iron makes a major difference in performance. You can see that throughout his entire amplifier lineup, the Kenzie and Mogwai use 5-watt transformers, even though they output 300mw and ~1.5-watts respectively. The Mogwai SE, which I owned, outputs ~3-watts (~8-watts with a 5AR4), but is equipped with a 10-watt transformer as well.

The question that came to my mind was: how would the Mogwai SE sound with these new 20-watt transformers? Would they make a substantial difference? Either way, I wanted to find out. So I called Justin up and asked if he could build me a custom headphone power amplifier with no volume control, and no source selection. I wanted it to be based on the Mogwai SE, and use these fancy new 20-watt output transformers. During that phone call the new Bigger Ben was born. As Justin and I discussed the final specs of the amp, he suggested using a bigger choke and massive pre-broken in Jupiter caps in place of the standard Auricap coupling capacitors. Four weeks later the Bigger Ben was on its way to my house, and my original Mogwai SE was sold.

ampsandaound Bigger Ben Amplifier

The new 20-watt output transformers dominate the plate of this amplifier

It is important to know that the Mogwai SE is easily one of my favorite amplifiers. I found that it consistently punched well above its weight, and drove every headphone I threw at it. It worked well with extremely sensitive headphones such as the Focal Utopias and Stellias, but it was also able to drive the Hifiman Susvara with relative ease.

I expected the Bigger Ben to be a slight upgrade over my Mogwai SE, instead what I got was a holistically different amp, that dug deeper, extended higher, and provided details and spatial cues that the Mogwai SE could only dream of. The transformation was shocking, and I can say that I have never heard a SET amplifier that sounded like this. It was as if the output transformers simply vanished. If you want to skip the rest of the review, I'll spoil it for you. If you can afford the Bigger Ben, go buy it! I would bet that the vast majority of people out there will never buy another headphone amp, or maybe even speaker amp, again. Yes, it really is that good. Let's jump in!

Review Equipment

  • Custom Built Roon Core
  • Pro-ject Stream Box S2 Ultra
  • Chord MScaler
  • Chord Dave, Chord Hugo 2, Schiit Gumby
  • Core Power Deep Core
  • Custom Built Balanced Power Conditioners
  • Final Touch Audio USB Cable
  • Wireworld Platinum Starlight BNC cables
  • Moon Audio Black Dragon RCA Interconnects
  • Schiit Freya S Pre-amp
  • Wywires Platinum Headphone Cable
  • Hifiman Susvara, Hifiman HE1000SE, Focal Utopia, Focal Stellia

Arrival and Unboxing

This amp is all about iron. Big output transforms and a massive choke

The Bigger Ben ships in a massive plastic hard case, so massive in fact, that when I picked it up at FedEx I had to think about how to fit it in my car. The shipping weight was north of 60 pounds, and my back was thankful for the wheels on the back of the case. Sadly, getting it up to my 2nd story condo required patience and some grunting. It was worth it, and no backs were thrown out in the writing of this review.

Once in the house, I opened the case. Inside was the tube compliment, which consists of a new production 6SL7, 2x new production KT88s, and a NOS Russian 5u4g rectifier. I also found a power cord and the hand written bench report showing both power output and noise output for each of the headphone taps. Once I removed the top layer of foam, I finally saw the top of the Bigger Ben. Pulling the amp out, it became clear where all the weight was. The amp itself has to weigh at least 35-40 pounds thanks to the larger output transformers and the massive choke.

For those who have seen the Mogwai SE, the Bigger Ben is a physically larger amp. It uses the Agartha chassis, which was ampsandsound's largest headphone amp. Looking at a top view, it is clear why the amp needed the extra space, and I am quite fond of the final layout for the tubes on my unit (which has all four tubes centered across the front of the amp). 

It should be noted that if you order the standard Bigger Ben from ampsandsound, the layout will be slightly different to accommodate the volume control and the speaker jacks. Since I have a Chord Dave and a Schiit Freya S acting as the preamp, the built-in volume control seemed redundant, and removing it allowed for a more streamlined signal path. Likewise, when I eventually add speakers to this setup, I will use a quarter inch adapter to make it easier to switch between speakers and headphones. Deciding between my headphone power amp version and the standard version with volume control will come down to personal taste and surrounding equipment, but sound quality should be identical between the two units.

Looks, Layout, and Build Quality

I really like the way ampsandsound amps look. They match my decor (midcentury modern, clean lines, and walnut wood), and I love when the tubes and transformers are displayed on the top of the chassis for all to see. Everyone who walks into my house and sees the Bigger Ben immediately asks what it is, and it has become a conversation piece for both me and my wife.

Each tube socket is clearly labeled from behind the tube, giving the amp a clean look when all tubes are loaded in, but ensuring it is clear which tube goes where. The five input taps are positioned on the left of the amplifier starting with the 8 ohm tap and scaling up to the 300 ohm tap in the back. Looking at the amp from the front, the RCA jack is on the left side, and the power cord socket is on the right. The power switch is on the right side and is not blocked by a transformer making it easy to turn the amp on and off. If this were a standard Bigger Ben, you would also see 8 ohm speaker taps on the back of the chassis and a volume knob on the front left side of the chassis.

The amp itself is built onto a thick aluminum plate that is set into a walnut wood box that forms the base of the amp. The fit is pretty much perfect. I did unscrew the top plate when the amp arrived since Justin recommended I admire his team's work. Removing the plate exposed nothing but clean and well thought out wiring. As this amp is based directly on the Mogwai SE, the Mogwai SE's circuit board is at the center of the show. Some people do not like circuit boards in tube amps, but when speaking with Justin, he chose to use circuit boards to create consistency and repeatability. Their boards are also of incredibly high quality and well-spaced. I have a few amps built with point to point wiring, and this amp is still my favorite in my collection, so I do not think the circuit board is anything to worry about. It is also worth noting that ampsandsound stuffs the entire board themselves. All wiring is nicely braided and wound, and the giant Jupiter capacitors are soldered into place onto the board. The tube sockets are ceramic, with the exception of the rectifier tube socket, which is a high quality plastic that I have seen consistently used for rectifier tubes both from ampsandsound and other manufacturers.

I always appreciate the effort that goes into building these amps. Justin and his technician clearly take great pride in their work. The amp is manufactured in the US and uses parts exclusively sourced from US suppliers. The feel is boutique, but the execution is at the level one would expect to see only in truly custom builds. Justin does not want ampsandsound to take over the audio world. He does not want to build thousands of amps a year, he wants to build quality products that last a lifetime. To do that takes time, skill, and patience. This is what ampsandsound is all about.

Do Transformers have a Sound?

There are two major differences between the Mogwai SE and the Bigger Ben. The larger output transformers (10 watts vs 20 watts), and the coupling capacitors (Auricap vs Jupiter). There are of course other things, but these are the primary differences. With this in mind, one would expect that the Bigger Ben is a step up in performance. This is fortunately incorrect, the Bigger Ben sounds like a completely different amp when compared directly with the Mogwai SE. It has better extension in the bass and a smoother treble. I was also shocked at the amps ability to retrieve micro-details from the recording. One could read what I just said and conclude that maybe the Mogwai SE is a slouch, and that would be a very incorrect interpretation. I have personally compared to the Mogwai SE to some of the best tube headphone amps in the world, and the Mogwai SE has come out on top every time. The Bigger Ben is just substantially better.

So the question becomes, do output transformers have a sound? I believe they do, and that bigger tends to be better and more transparent. This makes logical sense, bigger means more bandwidth before saturation, and the farther you are from saturation the more linear the output should be. Justin proved this to me with the Suolo Monos, which are mono block version of his famous Kenzie amplifier. The Suolo Monos use 10-watt output transformers where the Kenzie uses 5-watt output transformers. The result was that the Suolo Monos put out noticeably better bass, both in weight, quantity, and clarity when compared to the Kenzie. It is also important to note that the 5-watt transformer for the Kenzie was already significantly oversized (the Kenzie only outputs around 250 mWatts). By comparison, the Mogwai SE's output transformers were only over spec'd by 25%, therefore, doubling the output transformers size for the Bigger Ben was much a larger update and easily explains the performance gains.

The increased micro-detail between the two amplifiers is likely due to a combination of the much larger output transformers and the Jupiter Coupling Capacitors. While I have personally not experimented as much in this area, I have read that coupling capacitors in cathode biased single ended amplifiers can have a major impact on the resulting sound and detail. Assuming that is true, this would help explain the noticeable increase in detail that this amplifier provides.


My goal is to have audio equipment that is extremely flexible, especially when it comes to amplifiers. Right now my primary headphone is the Hifiman Susvara, which requires amplifiers with a ton of output power. Before the Susvara my primary headphone was the Focal Utopia which, simply required quality amplification but due to its high efficiency could not be paired with noisier amplifiers.

Before the Bigger Ben, my high efficiency headphones were driven by my Suolo Monos, and my Susvara was driven by my Mogwai SE. The Mogwai SE did not render details and spatial images as well as the Suolo Monos, but the Suolo Monos just were not capable of driving my Susvaras. I am always looking for ways to consolidate, partially, because when I find something I like more, I tend to ignore and not use the equipment. The Bigger Ben offers me the flexibility I was looking for, as it provides all the detail and spatial benefits that the Suolo Monos provide, along with the power output and ability to customize the power output to best suit the transducers.

If I want to use lower efficiency headphones, I can run the amplifier with a 5AR4 rectifier and a 6SL7 or a 12AX7 (with an adapter), and it will drive whatever headphone I throw at it with ease. If I want to use a headphone that is reasonably efficient (93 - 98 dB/mW), I can swap the rectifier to a 5u4g, which easily reduces the noise floor below audible levels for these headphones. If I want to use the Focal Utopia or Stellia, both of which are 104 dB/mW efficient, I can simply change the input tube on the Bigger Ben to a 6SN7 or a 12AU7 (with adapter) and enjoy those headphones. Finally, if I want to drive high efficiency speakers, I can swap the tube rectifier with a solid state module and tap into 8+ watts of output power, which is plenty of power for speakers such as Zu, Tekton, and Klipsch. I sadly do not have any high efficiency speakers on hand to test this last configuration, but it is likely that some will be coming in the future.

Listening Experience and Setup

Before we get into how the amplifier sounds, let's talk about the setup. The vast majority of this review was conducted with either a Chord Dave, Chord Hugo 2, or Schiit Gumby serving as the source. All sources sounded excellent, and the overall quality went up more or less with price, as one would expect. The volume control was either handled by the DACs (Chord Dave or Hugo 2), or by the Schiit Freya (Gumby and Hugo 2). Critical listening was conducted using the Hifiman Susvara (low efficiency), and the Focal Stellia (high efficiency). Both the Focal and the Hifiman headphones were cabled with a 20ft Wywires Platinum headphone cable. All critical listening was performed with a 5AR4 rectifier, though, I will say 5U4g rectifiers sound great on this amplifier as well. I just prefer the stiffer sound of the 5AR4.

When listening to the Susvara, the Bigger Ben is simply a dream. When driven directly from the Dave, the background is inky black. The thing that jumps out at you right away are dynamics, which is saying something considering I am listening on the Susvara. You can just tell that the amplifier has power in reserve, and is not afraid to show it. When listening to "Mr. All" from the album We No Be Machine by ONIPA, the drums sound lively and fun. The singers voice is fixed about three feet in front of me, and I can feel his mouth moving. This last statement may sound funny, but I am trying to get across the micro detail retrieval. I have noticed when components within a system are transparent you can get enough information to truly imagine the movement of a singers mouth. You can visualize the angle of their mouth in the air, and the resulting position of the microphone. Extracting this much detail is quite challenging, and I have only experienced it a few times in my life. However, now whenever I use the Bigger Ben with the Susvara and the Dave I have that experience, and it is awesome.

This experience also occurs when using the Hugo 2 and the Schiit Gumby, it is just a little less pronounced. This brings me to my next point, the Bigger Ben is incredibly transparent, it highlights the good in your source chain, and the bad. You can clearly hear the difference between the above three DACs, and you can tell when external volume control is used (Schiit Freya S), even if its passive. This is a level of transparency that, in my experience, is fairly rare in tube amplifiers.

For those who say SET amplifiers cannot provide thunderous bass, I highly suggest a call with Justin. In my experience, the vast majority of ampsandsound amplifiers have proven this stereotype wrong, but the Bigger Ben brings bass to a new level. The bass digs deep and is incredibly clean, especially with a 5AR4 and KT88 tubes. The drumming in MIKA's "Love Today" on his new live album Live at Brooklyn Steel is incredible. Switching to Torres's new album Silver Tongue the song "Two of Everything," just sounds incredible with the combination of synth and drums. The Bigger Ben and the Susvara does not skip a beat. It is impressive that the Bigger Ben is not only delivering its clean and clear bass, it is also delivering a wonderful and unclouded midrange.

Highs on this amp are exacting but not fatiguing. This will of course change based on the tubes you use, but in general the amplifier provides a top end that is both accurate and non-fatiguing. I expect nothing less from ampsandsound as this is a big part of their house sound. This is the first amplifier that I have been able to spend whole days (8+ hours) listening to with headphones on my head and walk away feeling fine with zero fatigue.

The Bigger Ben has the ability to make thin recordings sound full, but not overload well recorded pieces. Listening to Metric's "Help I'm Alive" used to be an exercise in fandom for me. I love the song, I love the band, but I hate how that song sounds on my HiFi system. The Bigger Ben adds just the right amount of warmth and weight to make the track a true treat to listen to. Conversely, listening to Melody Gardot's "Mira," which is a wonderfully recorded piece, sounds perfect. Not too much bass, not too much warmth, just the right amount of air and space with all the detail that you would expect. This brings me back to the point that I was trying to make above, the Bigger Ben is just incredibly flexible, and my guess is you will spend many hours rediscovering your entire library once you take possession of this lovely amplifier.

Switching to the Focal Stellia, provides much of the same. It is amazing how quiet the ampsandsound team has been able to get the Bigger Ben. The Stellia is 104 dB/mW efficient and the Bigger Ben is a 8 watt single ended tube amplifier with zero feedback. Using my KT88s, a 5751 (equivalent gain as a 6SL7), and a 5AR4, I have to press the headphones into my ears to hear anything. Replacing the 5AR4 with a 5U4g, or replacing the 5751 with a 6SN7 or 12AU7 will result in absolutely zero audible noise, and in my experience this is astonishing.

The Bigger Ben will still have quite a bit of gain, so you will likely need to use the volume pot or an external volume control, since I ordered mine without a volume pot, to remove any audible line noise. The Schiit Freya S (on loan for review) provides this functionality in my system, and I will  be sending my Bigger Ben back to ampsandsound to have a low gain switch installed so I can go directly from my Chord DACs to the Bigger Ben without a preamp in between. However you choose to handle line noise, the results will be the same: a black background with pretty much any commercially available headphone, and enough power to drive the most demanding conventional headphone currently available (Hifiman Susvara).

Listening to music with the Focal Stellia and the Bigger Ben is a lesson in immediacy. Drum hits are immediate, cymbals sparkly, and voices charge out of the darkness. Listening to Toto's Toto IV, I jumped out of my seat when "Make Believe" came on, and could not help myself but start to dance. I have never heard this song sound as good as it has on the Bigger Ben with the Focal Stellia, it was simply spectacular. Every point that I made above about the Hifiman Susvara carries over to the Focal Stellia, I can simply listen to this system for hours and hours no matter what headphone I am wearing.

So what don't I like? I don't love the fact that the amplifier did not come with a high/low input switch. While this is being remedied, I wish it was on the amp by default, especially considering its target use as a headphone amplifier. ampsandsound's purist and minimalist philosophy is what makes their amps sound so good, but at time it also leaves them lacking in convenience features. Is this the end of the world? No, would you require a high/low input switch if you order your Bigger Ben with a volume pot? No you would not. It is a really well built, quiet, and powerful tube amplifier, and I would gladly buy it again.

A Tube Rollers Dream

One of the reasons it took me so long to explore vacuum tube amplifiers was because of my confusion and fear of tube rolling. Three years later and I cannot imagine using amplifiers without tubes. Tubes not only sound wonderful, but the ability to customize the sound of your amplifier with tubes has become one of my favorite parts of this hobby.

Bigger Ben and the entire Mogwai / Mogwai SE family is a tube rollers dream. Justin is a great resource for advice as far as what tubes are compatible and NOS and new production tube recommendations. Since I owned a Mogwai SE before my purchase of the Bigger Ben, I had already acquired quite the collection of new old stock tubes. While you can sit back and enjoy the stock tubes, and I actually recommend you do for at least three to six months. After you get a sense for the amplifiers natural sound, I highly recommend dipping your toes into the wonderful world of tube rolling to see what you like.

The Bigger Ben uses three types of tubes. One input tube, by default this is a 6SL7, but you can roll in ECC35s, 6SN7s (however this will dramatically reduce your gain), and with an adapter you can roll in 12AX7s, 5751s, 12AT7s, 12AU7s, and their European equivalents. The amplifier also uses two power tubes, by default they are KT88s, but you can substitute 6550s, EL34s, KT66s, KT77s, KT90s, and 6L6GCs. Finally, you have a single rectifier tube which takes 5AR4s, 5U4s, or a solid-state rectifier plugin.

The end result is that there are hundreds of combinations, which may either be overwhelming or exciting. I found it exciting, and my personal collection of tubes that are compatible with this amplifier exceeds 100 tubes and includes pretty much every major combination. With that in mind, I thought I would provide some level of guidance. Obviously your mileage may vary, but don't be afraid to try new tubes. Below are two recommendation based on my personal experience. Each recommendation is categorized based on the use case.

Low Efficiency Headphones and Speakers

For this combination you will want to use a 6SL7, 5751, or 12AX7 as your input tube (the latter two require adapters). This will allow you to get the most power out of the amplifier. Personally, I really like the sound of 6SL7s. As far as new production goes, I think the JJ 6SL7 is actually fantastic. If you want to go new old stock, I suggest trying the 1940s RCA black plate 6SL7. This is an inexpensive tube that sounds a bit warm, but is really a lot of fun. For power tubes, I suggest KT88s, new production KT88s are the only practical option with this particular tube type. I personally like the new production gold lions. They provide a bit more bite in my experience. The new production JJs are also decent and smooth. For rectification you should swap the 5U4g for a 5AR4 or a solid state plugin. You will need the extra power that either of these options provide.

High Efficiency Headphones

For this use case, I am a big fan of swapping the 6SL7 for a 12AU7 (this requires an adapter, you can also use a 6SN7 but those are a bit pricey). I like RCA black plate 12AU7s personally, but there are many choices for quality old production 12AU7s still available. The 12AU7/6SN7 will substantially lower your gain, but it will also lower your noise floor. I like to match these with 6L6GCs or EL34s/KT77s. If you can find them the RCA black plate 6L6GC is a wonderful tube full of tone. I have a few of these but some are microphonic so be careful. For EL34s/KT77s, if using new production, I really like the Gold Lion KT77. If using old production and you like your system to lean neutral bright the RFT short base EL34s are great tubes that can still be had at a reasonable price. With this you can use 5U4gs or 5AR4s. Again, I prefer 5AR4s but if you like your bass to have a bit more bloom a 5U4g is the right move.

The above just scratches the surface and are just a few of the combinations I run in this amplifier. I suggest starting slow, finding tubes you like, and then enjoying them. What is great about this amplifier is that you can customize it's sound to your exact taste. If you like to collect things, you now have an excuse to collect some really interesting tubes. While some combos will sound better than others, you can trust that the amp will maintain it's signature sound. Engaging, neutral, and fun.

Wrapping Up

Built like a tank with attention paid to every detail

Wrapping this one up is a simple task for me. I bought the ampsandsound Bigger Ben before it was an official product. I bought it sight unseen with no promise of writing a review. I have done this a few times with ampsandsound, and each time I am been delighted by the results, (I am actually in the process of doing it again) and I have written a review. Not because I had to, but because I want people to know that this amp exists and to my ears, in my system, it is the best headphone amplifier I have ever heard and used. I have listened to it on average for two hours a day since it arrived in December, and I don't expect that to change anytime soon.

At $5000 it is not cheap, but it's a purchase that you will make once, and never need to make again. For me, the Bigger Ben is becoming that new center piece of my system. Components are being changed out around it and speakers are being selected based on their match to it. It is my end game single ended medium output tube amp and I could not be happier about it. As per usual, a big thanks to the ampsandsound team, my wallet dislikes you, but my ears are happy.

Bigger Ben

Retail: $5000