Jun 04, 2012 The Bottlehead Crack amplifiers arrived a little over two months after having ordered them on Bottlehead’s website. We ordered a couple of Cracks right before the price increase was announced (more on that later) so that probably explains the long waiting period. The Bottlehead Mainline is the top of the line DIY headphone amplifier in Bottlehead’s range. Unlike other products in the Bottlehead range, the Mainline doesn’t have any “standard” upgrade options like the Crack‘s Speedball or the S.E.X.‘s C4S kit so the review that follows represents the stock Mainline kit which is also the peak version of the Mainline without getting into.
Recently I posted a review of the construction stage of my Bottlehead Crack amplifier. The amp’s been in action for a few weeks now and I’m ready to share a review of my impressions. I’m not going to start with the normal list of specifications for the Crack because it’s so variable due to the massive range of modifications you can make to it.
What does matter are the following details:. Tube driven amplifier for headphones. Designed for high impedance headphones (ideal with Sennheiser and Beyerdynamic cans). Buckets of power Overview The Bottlehead Crack is a DIY kit sold by Bottlehead in America. It costs around $350 fully shipped to Australia and takes a couple of days to put together if you take your time, but could be completed in a day of assembly, committed soldering and testing. If you want to know how easy it is to build one of these for yourself, you can check out the build post here: For $350, this amp is simply incredible. To put it into perspective, the Crack performs on par or better than products like the Woo Audio WA3 ($580) and Schiit Lyr ($550).
Because of its DIY nature, you can get brilliant performance for a very low price. On top of that, building it yourself means you know what’s going on inside and can easily add to it and improve it either on your own or using the add-n “Speedball” kit from Bottlehead. Tubes, Glorious Tubes The Crack uses 2 tubes in its design – a small 12AU7 model at the input and a larger 6080 model to provide the output power. Don’t worry if you don’t know what that means, I didn’t either when I started. Actually, I still didn’t know even after I had finished building the amp – it’s only been in recent days of research and reading up on the great Bottlehead Forum that I’ve learned more about it. Using tubes means two things.
1 – the sound from the amplifier is smooth, liquid and magical. 2 – it’s very easy to adjust and upgrade the sound by simply swapping tubes. The 12AU7 and 6080 combo that’s supplied with the Crack do a great job. The sound from the Crack was an instant and significant upgrade over the output from my Audio-gd NFB-5.2 and it’s not a slouch. After building and listening to the Crack for a while I became curious about upgrading the tubes (or valves as we call them in Australia).
This was compounded by some minor issues with the supplied tubes which likely resulted from the trip from America to Australia. I found a local supplier called Evatco who were able to offer a selection of replacement options. I ordered a Mullard 6080WA, a Cleartop RCA 12AU7, and a Mullard ECC82 which is an alternative to the 12AU7. After a bit of playing around, I found that the combination of the Mullard 6080WA and RCA Cleartop 12AU7 tubes provide the sweetest sound and the upgrade only cost around $50!!
Sound Quality This is why you’d bother buying an amp in the first place. This is what matters and it’s where the Crack really delivers. I’m running my Crack (yes, plenty of humour available with this amp) from the line outs of my NFB-5.2 which is connected to my laptop via USB and is running 96kHz / 24-bit sound. My headphones of choice with this setup are the s. Admittedly, the choice of headphones is simple given the need for high impedance headphones with the Crack, but more on that later. The most immediate characteristics of the Crack’s sound are openness and smoothness. The sound is liquid and creamy, but never slow or veiled.
It’s just real. The music flows out of the Crack like it would flow straight from the instruments. There’s space and depth and separation between the instruments, but again it’s delivered naturally – nothing artificial. I had heard talk about analogue sound being smoother and more natural, but had never really paid much notice. Moving from the solid state sound of the NFB-5.2 over to the Crack immediately showed me why analogue sound has such avid fans. I’m not suggesting that tube amplifiers will always outperform solid state because there are some truly amazing solid state amplifiers out there, but they cost a whole lot more than this $350 gem. I feel pretty safe suggesting that you will not find a better amplifier for the same dollars as the Crack.
In fact, I think until you’re spending in excess of $700-800 on solid state, you will have trouble finding better sound. Clarity Without realising it, I somehow didn’t expect high levels of clarity and detail from the Crack because of its simple and analogue design. It certainly surprised me. It’s not analytical in its sound like a solid state amp might be, but there’s no lack of detail and the beautiful separation of different sounds and layers means you can really enjoy the music and the details, not just pick the music apart to hear separate details.
Sound Signature The Crack’s sound is basically neutral, but perhaps slightly warm. It doesn’t add significant colouration to the sound that I can hear, but it does bring out the extended bass more than my NFB-5.2. The Crack makes the bass from the HD650s sound fuller and meatier, but it doesn’t make the sound significantly warmer overall, just fuller at the bottom end. Top end sparkle and air is still great, mids are well-balanced, liquid and smooth, and the bass is full and solid, but not forward of other frequencies. Overall, I think it seems a little warmer because everything is so smooth. Of course, the signature can change with a simple swap of tubes (valves).
The Cleartop RCA 12AU7 I bought makes the sound a bit leaner and brighter, but does so at the expense of ambience and space within the music so it’s all a matter of personal preference. I guess the key here is don’t decide on the Crack because of a sound signature because that’s adjustable with simple tube swaps. Overall Presentation This is the smile-inducing part of the Crack’s sound. I don’t feel like the Crack dramatically enlarges the soundstage of the HD650s, but it’s placement and layering of sound is flat-out holographic. Individual instruments and sounds are perfectly separated and spaced around the soundstage to a degree that’s surprising at times and almost enough to make you look over your shoulder or second-guess if you’re alone in the room! All of this adds up to a sound that’s fun, addictive and realistic.
It’s probably not an amp for people who like to dissect music and analyse recordings, but it is definitely an amp for anyone wants to really enjoy their music in a way they might not have previously. The Crack brings music to life in all it’s amalgamated glory.
The music is presented as a whole, magical soundscape, not a series of analytically correct, but unrelated parts. It’s been quite a revelation to me and has me subscribed to the benefits of high quality amplification. A Note About Headphone Impedance The design of the Crack results in a high output impedance. In layman’s terms, this means that it doesn’t work particularly well with low impedance headphones.
Most headphones on the market are low impedance (. Thanks for reading! I didn’t get the Speedball. There is a really slight background hum that’s really only audible when you’re listening for it and I think adding the Speedball might rectify this – I plan to get it in the future, but was interested in getting the stock kit and getting to know it before upgrading. The 240V transformer is a different version of the normal unit they put into the kit – i.e.
It’s built into the kit (and looks exactly the same as the 110V one from what I can tell) – it’s the dark grey cube at the back of the amp with the curved metal top. Thanks for the compliment on the wood finish. I used Black Japan stain and put it on lightly and irregularly. I also sanded it a little irregularly in between staining and varnishing (and in between coats of varnish). I used a satin varnish.
Good idea on a group buy. Fantastic write up Lachlan.
The only reason i ended up here was that bottleneck have a offer on this weekend buy it & get the speed ball free and if you ask me that is a real bargain.& now just needed some more feedback on it and your writeup made my mind up so thanks to you and there offer i have got one but the wife is going to be a little pissed with me mind you. I was looking at the crack a while back last year & after spending weeks researching valve amps i was going to buy it but due to work never go t round to it until i received an email from bottlehead regarding there offer and guess what i could not say no who wouldn’t.there going to power my 650’s with high end rme converter 32 bit 192 khz.kind regards sy. Nice write up. My kit arrived today. (QLD) Just a Q on tubes. I’m not very knowledgable on tubes You state “I found that the combination of the Mullard 6080WA and RCA Cleartop 12AU7 tubes provide the sweetest sound” (aren’t these both the output?) But later “The Cleartop RCA 12AU7 I bought makes the sound a bit leaner and brighter, but does so at the expense of ambience and space within the music so it’s all a matter of personal preference.” Is it that you accept (prefer) the loss of ambiance and space.
Thanks for any clarification Simon.
A lot has been written about the magic of Bottlehead Crack headphone amps. I'm sure anything I have to contribute has already been said and written two hundred times, at the very least. So - I will not bore you with it. I will just load the pictures to show you the great job the builder did. The name of the builder is James Cruz, he is located n LA.
He sells his wares on eBay and Etsy.com under the handle of cshop87. On Etsy he is a bit cheaper, and will give you the opportunity to get your amp build to order, with the color scheme you choose. He will provide sample pictures of colors and wood finishes, and will let you pick your scheme, then build accordingly. I got mine through Etsy, and devised my own color combination.
To my eyes - looks great. The cost is $650, built and delivered to your door by FedEx Ground, tube complement included. I got a NOS JAN Philips 6080, and a 12AU7.
Tube complement will vary, of course, depending on what's on hand at the time of build. The only comment I will make regarding the sound, other than it obviously sounds magical, is that it seems to have eliminated the one issue that I used to have with the Little Dot MkII. Used with the LD, Senn's 600 sounded very good, but a bit bright, to the point of hurting my right ear with some high passages, whereas the 650's sounded a bit dark (though never hurt me). With the Crack, the 600's still sound different from the 650's, but there's no more pain, and the 650's, while still 'warmer' than the 600's, are not 'darker' any more. I always thought the pain was associated with just the 600's drivers, yet it seems the amplifier does play a huge role, as well.
All in all, a huge improvement all around, for sure. I am very glad to give James free advertising, as I am very happy with his work, and think that it can benefit a few more fellow audiophiles.