Matrix Quattro Balanced Amplifier

After spending a lot of time with some high quality tube amplifiers, I thought it was time to revisit the world of solid state (using sound processing chips rather than tubes). Some headphones seem to pair well with tubes while others like solid state so it’s always nice to have both options available.

Matrix M-Stage (HPA-1): the Quattro's older sibling

Matrix M-Stage (HPA-1): the Quattro’s older sibling

The amp I decided on is the Matrix Quattro amplifier which offers balanced and unbalanced operation (which I’ll explain later) and pairs really nicely with the Matrix X-Sabre DAC I bought a little while ago. I was fortunate enough to also be able to buy a second hand Matrix M-Stage (HPA-1), the Quattro’s baby brother (although it’s been around longer). The M-Stage is renowned as a great bang-for-buck entry level amplifier (around $300) so how would the more expensive Quattro compare at its $450 level? Let’s find out…

Overview

The Quattro builds on the success of the famously affordable and excellent M-Stage amplifier, but brings improved design and balanced operation. It was the balanced operation that hooked me because I love the idea of it from my days working in car audio where I often designed systems with completely separate left and right channels, but let me explain the concept a bit better.

Every speaker (or driver in a headphone) requires a positive and negative connection or an active signal and a ground connection. In unbalanced systems, there are two active outputs that deliver the stereo signal  – one to each driver – and there is a single ground connection that is shared between both drivers. This setup can produce very, very good sound, but there is also the risk of the ground connections causing some leaking of sound between the left and right channels which can result in the sound becoming less defined and less controlled. I’m sure there are much better explanations of these circuits out there if you’re interested, but hopefully this paints enough of a picture to say that balanced circuits have the potential to provide cleaner, better defined sound.

Specifications

  • Max power:  1 W (balanced mode)
  • Power per impedance:  800mW @ 60 ohms / 400mW @ 300 ohms (balanced mode)
  • Inputs:  1 pair RCA, 1 pair balanced 3-pin XLR
  • Outputs:  2 x stereo 6.3mm headphone jacks / 1 pair balanced 6.3mm headphone jacks
  • Signal-to-noise ratio:  >98dB via XLR / >95dB via RCA
  • Distortion:  <0.001%

Just to explain some of these specs, the power of the Quattro in balanced mode is twice that of its unbalanced mode because it’s essentially 2 amplifiers working together when running balanced versus just a single amp when running unbalanced. Also, there is just one set of outputs that are used for both balanced and unbalanced operation, but I’ll explain that setup a little later.

The specs of the Quattro don’t really tell us a lot about its performance and there was nothing in that list which excited me more than any other amplifier on the market, but for the price and with its offering of balanced operation for my beloved T1 headphones, I had to give it a run.

Design & Compatibility

01170021The Quattro is a simple design that’s been described as two M-Stage amplifiers sandwiched together. That may or may not be true as there are definite similarities under the hood, but also some differences in terms of the components used.

Perhaps the most obvious differences are the combination of unbalanced and balanced circuits as well as the use of different op amps. Op amps are the chips that amplify the sound and lend the amplifier a significant dose of sound signature (how warm, cool, bright, dark, bassy, or tinny the amp sounds). Where the M-Stage uses the OPA2134 chip, the Quattro uses the OPA604 and OPA2604 chips for its balanced and unbalanced circuits respectively.

Inputs / Outputs

01170020The Quattro has a pair of RCA (unbalanced) inputs and a pair of 3-pin XLR (balanced) inputs. Unfortunately, it doesn’t get any line level outputs which is a shame. It’s always nice to have the option to use headphone amps as pre-amps or to have a straight pass-through to connect other amps in a chain, but for the average consumer who doesn’t stockpile audio gear, the Quattro offers everything you need in terms of these 2 input options.

For output of sound, the Quattro comes with a pair of 6.3mm sockets on the front which are labelled Solo 1 / Balanced R and Solo 2 / Balanced L. It’s only as I write this that I realise that the left socket is on the right side and vice versa!? Oh well, doesn’t really matter. The point is that this pair of sockets is multi-functional which is both good and bad.

The Good

01170018Having 2 jacks means that you can use 2 pairs of headphones simultaneously which is great if you’re comparing headphones or if you want to listen with a friend. It ‘s amazing how often I would like to be able to switch between headphones without having to plug and unplug leads all the time so the Quattro is great in that regard.

Neither good nor bad is the fact that the twin sockets are used for balanced output via normal stereo 6.3mm headphone jacks which are easy enough to buy from most electronics shops if you need to make an adapter. Please be aware though that you specifically need to use stereo jacks. Mono ones won’t work with the Quattro’s auto-detecting circuit which I’ll explain shortly.

The Bad

In my experience the twin 6.3mm arrangement is one of the least common ways to connect to a balanced output with 4-pin XLR being a much more common choice. That means you’re most likely going to need an adapter lead to connect your 4-pin terminated headphones to the Quattro’s 6.3mm sockets. It’s an easy DIY build if you can be bothered, but you can also buy this type of lead if you prefer so it’s not the end of the world, but an XLR socket would have been better I think.

The other thing I’m not a total fan of is the auto-detect circuit on the Quattro’s outputs. Although the concept of the amp switching modes for you is nice, the reality is that the process isn’t seamless and sometimes leaves me with a balanced connection to an unbalanced output. This is because the Quattro detects the status of the connection with the contacts on the 6.3mm plugs. It seems that sometimes, the plugs touch the wrong contacts on the way into the socket and make the amp think it’s connected to an unbalanced headphone. The only solution I’ve discovered is to unplug and reconnect the headphones or to switch the amp off and on again. It’s not the end of the world, but I would have been perfectly happy with a third button on the front panel to select my output type.

Other Design Elements

In terms of size, the Quattro is about twice the width of the M-Stage, but is shorter by about 15-20% and a hair lower in height. It’s a nice compact size.

On the front right of the unit is a nice large aluminium volume knob with a rough texture around the side. It looks good and feels good and it’s attached to a high quality Alps motorised volume pot so you can also use a remote control with the amp if you want. The remote is an optional extra, but it’s very well priced.

Also on the front panel are a power button and source button to switch between the RCA and XLR inputs. I was pleased to note that both inputs are able to provide output to balanced and unbalanced phones so you don’t have to use a balanced source to enjoy balanced ‘phones. Not only that, but the difference between the sound from the balanced / unbalanced input is near enough to identical that it makes no difference which you use.

01170017Finally, on the left side of the amp’s fascia are lights indicating mute status (only available using the optional remote control), input in use (RCA / XLR), and output status (balanced / unbalanced).

Compatibility

The Quattro’s power output means it will drive most headphones other than difficult-to-drive planar magnetics. I’m hoping to try it with some Audeze LCD 2s soon so I’ll update if there’s anything notable to share. Unfortunately, the Quattro has an output impedance of around 10 ohms which is quite high and may negatively affect the frequency response and tightness of sound from lower impedance headphones depending on their specific specs. Testing the Quattro with my 32 ohm headphones showed some variation compared to the M-Stage with its 5 ohm output, but it was very much a case-by-case thing. The one thing I can say for sure is that it will not match ideally with low impedance, multi-BA IEMs like the Miracles. The sound is really clean and hum is negligible, but the frequency response is altered slightly by the impedance mismatch.

Other than the minor issues with output impedance – and I do consider it minor because it’s an amp designed for desktop headphone listening, not IEMs and portables – the Quattro drives all my phones really nicely and I love the fact that it can run unbalanced / balanced in and unbalanced / balanced out. There’s plenty of versatility in how you use the amp and with what.

Sound

01170022Having been excited to buy the Quattro, I was initially disappointed with its sound. It was a bit harsh with the T1s and I felt like it wasn’t significantly better than the much cheaper M-Stage. The balanced output was definitely an improvement, but I was still left no really enjoying what I heard. Although I’m still quietly skeptical about the effects of burn-in, I decided to leave the Quattro running for a while to see if the sound changed at all. I didn’t listen to it during this time so I know I haven’t adjusted to its sound, but I can definitely confirm that I now thoroughly enjoy the sounds being produced by the Quattro in both unbalanced and balanced modes.

For the review of the sound, I’m referring to the character of the sound in both balanced and unbalanced mode. The balanced circuit is just 2 of the unbalanced circuits running in parallel so the character of the sound is identical. I’ll explain the audible impacts of balanced versus unbalanced output separately.

Treble

Treble from the Quattro is present and extended, but smooth. Even with the sometimes edgy Beyer T1s, the Quattro produces very listenable treble that’s easily on par with the treble produced by other amps in this price range or slightly above.

The Quattro produces brighter treble than the M-Stage, but manages to do so without getting cold or harsh. The treble can be a little dry, but the overall signature is slightly warm so it balances the treble nicely. Fans of sparkly treble may want to look elsewhere for an amplifier because there’s not a lot of sparkle in the Quattro’s sound, but don’t mistake that for a lack of treble or extension. The treble’s there, it’s just not enhanced or lively – instead it’s smooth and easy to listen to. To my ears, the Quattro strikes a really nice balance by presenting a sound that’s not as thick as the M-Stage (which is a great amp) while still keeping the smooth and musical presentation that makes the Matrix gear so enjoyable. I was really impressed with the Quattro’s rendition of the detail present in the sound of a solo violin during the listening I did for this review. The Quattro was able to accurately recreate the subtle rasp of the bow being drawn across the strings sounding completely accurate and lifelike. I think that’s a benefit of the slightly dry sound – it allows details like this to come through where a lusher, smoother sound might cover them over.

Mids

The Quattro’s midrange is accurate and clean. It’s got good presence in the overall presentation and strikes a nice balance between musicality and accuracy. Once again it’s drier and cooler sounding than the M-Stage, but still enjoyable and slightly smooth. I really like the presence of the midrange created by the Quattro. Even in busy, active tracks, the vocals are always clean and separate, but not enhanced or pushed in your face in any way. THey are slightly forward compared to the rest of the spectrum, but only to a degree that you notice if you’re listening for it.

Bass

The Quattro produces bass that is largely accurate, but possibly a bit behind the rest of the spectrum. I wouldn’t say it’s lean sounding at all, but the mids and treble overshadow the bass ever-so-slightly. The quality of the bass though is very good. There is texture and impact as well as body on sustained bass notes – it’s just that all of this happens slightly behind the rest of the spectrum. Extension of the bass is really good all the way down and is probably more balanced in the lower ranges than around the mid-bass.

It’s hard to be sure because of the time taken to switch, but I think bass impact and present improves slightly when running in balanced mode. This could simply be a reflection of the power output doubling and therefore having more energy to apply to bass notes.

The Quattro’s bass presentation pairs really nicely with bass-tilted phones like the Fischer FA-011 LEs and I imagine it would also really suit some of the Sennheiser models with a bit of extra mid-bass warmth.

Signature Summary

I don’t normally do this, but I wanted to clarify the descriptions I’ve provided of the bass, mids and treble. I found myself struggling to describe the Quattro’s sound in this review and I think it’s because the Quattro is largely neutral and accurate to the source with a slightly dry, but musical presentation. The comments above reflect very subtle impressions only and should not discourage anyone from considering this amp because it’s very, very good for its price and the evidence of that fact is the difficulty I had trying to really dissect its sound signature.

General Presentation and Staging

Matrix Quattro AmpIn unbalanced mode the Quattro produces a good-sized soundstage (or headstage) with decent width and depth, although I would say it is wider than it is deep. There’s not a lot of vertical layering or vertical space so the result is that all of the sound seems to be placed across a narrow stage extending side to side. The stage sounds open and in no way congested, but it’s not expansive and spacious like some amps I’ve heard, although those amps also cost significantly more (e.g. $200+ more). Staging is definitely more open and more accurate than the M-Stage so the Quattro is a definite upgrade.

Beware: moving to balanced mode makes a significant difference to the soundstage! Switching over to use the balanced outputs of the Quattro lifts the sound to a whole other level. The overall signature is unchanged, but staging resolution is dramatically increased. Everything becomes more sharply defined, gains extra presence and weight and just generally gets better. This is why you buy a Quattro!

In balanced mode the stage is deeper and taller while retaining the same side-to-side space. The accuracy of placement is improved and the ability to hear vertical layers in the sound is improved as well (i.e. vocals now sound higher than a guitar being played by the singer). In balanced mode, the Quattro’s stage and presentation is outstanding and highly enjoyable. It’s still not expansive and massive, but strikes a good balance by placing the listener “a few rows back” from the stage while keeping the music close enough to be engaging.

Summary

For its $450 price tag, the Quattro is definitely an amplifier worth considering if you’re running balanced headphones (or if you can get a cable to make them balanced).

I probably wouldn’t specifically recommend the Quattro if you’re only using unbalanced headphone connections even though it’s a good amplifier even in unbalanced mode. With the new M-Stage (HPA-2) out now, I would expect it to match the Quattro for unbalanced performance and you can always change op amps (see below) to upgrade the sound of either amp so I’d probably choose the M-Stage plus an upgraded op amp for unbalanced use, but it’s a no-brainer for balanced headphones – the Quattro is excellent!!

Just like its older brother, the original M-Stage, the Quattro offers outstanding value for money with good power, an enjoyable sound that’s more neutral and detailed than the older M-Stage, and the opportunity to wring every last bit of performance out of your headphones with balanced cables.

A Quick Note on Op Amps

01170024I’m new to op amps, but having come from recent experiments with tubes in amplifiers, I look at these little “chips” kind of like digital tubes. What I mean by that is that you can tweak the sound of your amplifier by using different op amps. In the image to the right, the op amps are the black, rectangular things – there are 4 along the top and one in the bottom left corner.

The Quattro uses a single, stereo op amp for unbalanced operation and uses 4 mono op amps for balanced operation. This can make it an expensive prospect to upgrade because you need to buy 5-6 op amps depending on the versions you use, but it can also provide some relatively cheap fun because you can pick up decent op amps from as little as $5-6. You can also spend up to nearly $100 each if you want to spend that much, but it’s not necessary. You do need to make sure the op amps you buy are suitable for your device, but it’s not too hard to work out with a bit of online reading and asking on forums.

I’ll be posting an article specifically on op amps soon so subscribe if you want to know more. I’ve ordered a bunch to plug into the Quattro and a couple of other amps I’ll be reviewing soon and I’ll have impressions of the different op amps and how they influence the Quattro, M-Stage and a Fiio E12DIY portable amp.

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Aside

I’ve been quiet for a while here on the Passion for Sound blog due to a little personal project I’ve been working on over at Head-Fi. Some of you will have read my review of the assembly and performance of the Bottlehead Crack DIY tube amplifer and you might have also read my assembly review of the Bottlehead S.E.X. amplifier too. If you’ve been waiting for the performance review for the S.E.X. then you’re in for a treat! Not only have I completed a thorough review of the S.E.X., but I’ve also built and reviewed Bottlehead’s premium, top of the line amplifier, the Mainline. I’ve compared each of the three amps to each other as well for anyone who’s unsure of which amp is for them.

Rather than post the same reviews here or take the time to redo them, I’m going to share links to the review on Head-Fi. Don’t worry, you don’t have to be a member to read the reviews, but you will need to sign up if you want to comment (it’s free to sign up and it’s a great community). If you have any questions or comments, please feel free to post them here.

Bottlehead S.E.X. full review prior to the C4S upgrade

Bottlehead S.E.X. review post C4S upgrade

Bottlehead Mainline full review

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See you soon for more reviews including:

  • Matrix M-Stage amplifier – the classic entry level performer
  • Matrix Quattro fully balanced amplifier
  • Fiio E12DIY portable amplifier with swappable components to tailor the sound
  • Signature Acoustics C-12 IEMs

Where I’ve Been Lately

Bottlehead S.E.X. – “The Build”

Some time ago I built the Bottlehead Crack amplifier and reviewed both the build process and the resulting sound. After thoroughly enjoying the Crack for over a year, I decided it was time to enjoy the next step up in the Bottlehead range for both a challenge and a new step towards audio nirvana. The next step in the Bottlehead range is called the Single Ended eXperimenter kit (or S.E.X. for short). It’s a different design to the Crack as the S.E.X. uses output transformers to work with a wide range of headphones. (The Crack is an output transformerless (OTL) design which will only work effectively with high impedance headphones.)

The S.E.X. has a lot more wires than the Crack (partly due to having two output transformers) so it’s a slightly more complex build, but it’s still fairly simple point-to-point wiring with no circuit boards or finicky micro components.

The Kit

S.E.X. kit contentsWhat arrived at my door was a moderately sized box containing a couple of plastic bags of components and wires, 4 pieces of wood which make the base, 5 cardboard-wrapped power components (transformers, etc.), an aluminium chassis plate, a list of parts, and a CD containing the manual in PDF form.

At first glance I actually thought the S.E.X. was going to take only a tiny bit longer than the Crack… oops!

Customisation

Having built the Crack completely stock in all ways except for staining the wooden base, I decided I would express myself a little more in this amp. I love the Art Deco period and I thought that style would match the vintage tubeyness of the S.E.X.

To achieve the vintage look I decided to paint some of the visible metal parts and my fiancée convinced me to anodise (rather than paint) the aluminium chassis plate – thanks Lisa!

Painting

Painting the metal elements of the S.E.X. required a lot of careful preparation. The top of the main power transformer and the brackets on the plate chokes (the things on either side of the transformer) needed thorough sanding to remove the varnish that they are coated with during production.  The plate choke brackets had a lot more varnish than the transformer bell, but both were tricky to sand and took multiple attempts to get right.

I was using an etch primer to ensure a good finish on the metal parts, but my first priming attempts didn’t go well. Despite fairly thorough sanding, there were small patches of varnish left on the metal and the varnish reacted with the etch primer to create a crinkled look that would have really messed with the final paint finish. Having failed once, I stripped all parts bake to 100% bare metal before starting again.

WP_20130910_09_00_51_ProIn this image you can see the metal parts all sanded and masked for painting. This image was actually before the first, failed attempt. You can see a dark patch on the top left corner of the front piece (the transformer bell) which is some of the left-over varnish that I failed to fully remove.

It’s worth adding at this time that masking the plastic parts on the plate chokes is VERY difficult. There are a lot of small sections that are tricky to mask and I found that using lots of small pieces of tape was more effective in the cramped spots than large pieces of tape.

Once correctly masked and sanded, the metal parts were relatively easy to prime and spray. The only other issues I had were keeping dust out of the fresh paint job and paint quality issues. I dealt with the dust by lightly sanding the blemished coat and lightly respraying. The paint issue was solved by changing paint brands and actually led to a fortuitous change of colour from off-white to cream which better suited my desired colour scheme.

Anodising

Chassis plateI was worried that the anodising was going to be expensive and possibly time consuming. It turned out to be neither once I found the right provider.

After a few calls I came across Riga Crafts who were located fairly close to me here in Melbourne and were able to work with a small scale, single-piece project like mine. I delivered to them a simple aluminium plate (as seen to the left) and received back a strangely Anodised platemottled looking brassy coloured plate. I had ordered the bronze colour, but expected something much more brown, much less yellow, and much more consistent in colour. Before you think Riga did a bad job, please read on because their work was wonderful!

I don’t fully understand why, but for some reason, the colour on the chassis plate became uniform over the next few days and went more brown than yellow (as I had wanted). The finished product perfectly matched the sample Jimmy at Riga had showed me and was a perfect match for my design idea.

Assembly

Assembled chassisSo far everything I’ve discussed I did on my own, but I actually bought the kit with 2 friends (1 kit each) and we agreed to build them together.

The first stage of building was a night of assembly where we screwed all of the components to the chassis plate in preparation for a separate wiring and soldering adventure.

The assembly stage of the S.E.X. is very straight forward, much like with the Crack. It simply involves clicking into place the various plastic power parts, screwing on some terminal strips and installing the volume control, headphone jack and tube sockets. All straight forward except for the tube sockets which were a little fiddly to get centred and well secured.

At this stage, I also had to make sure to create a good earth point on my anodised chassis. The anodising process creates an inert layer on the surface of the aluminium which means it no longer conducts electricity. That’s a slight problem when you want to create an earth on the chassis, but it’s easily solved by just taking a file or a piece of sandpaper to the chassis plate around the earthing screw hole (see silver screw to the right of the black box on the chassis near the far left corner).

After just a few relaxed hours, the underside of our chassis plates looked something like the image to the right.

We could have installed the plate chokes and output transformers at this stage, but this involved a tiny bit of soldering so we left it to be done at the same time as the other wiring and soldering.

Wiring & Soldering

I mentioned earlier that there are more wires to work with in the S.E.X. compared to the Crack. We allowed a day and an evening to do the wiring and soldering, but we should have split it over 2 days. It’s not hard as such, but it IS time consuming so please allow plenty of time and some breaks to ensure an enjoyable build process if you decide to buy and make the S.E.X.

SAMSUNG CSC

To do the work, we setup a table with a sheet of thick cardboard to catch any solder drips and prevent damage to the table we were using. This turned out to be a great move because we were able to fold up the cardboard at the end of the night and easily dispose of all the little wire and insulation off-cuts we’d created. I can highly recommend this approach!

The first step in the wiring of the S.E.X. was to install the plate chokes and power transformers. At this time we also had to decide on the impedance we were wiring the S.E.X. for. You can choose from 4, 8, 16 or 32 ohm loads and should make the decision based on the speakers you will drive with the amp (if you will ever use speakers), or on the power vs noise ratio you are after. Lower impedance wiring means a quieter amp, but with less power so it all depends on your usage. We all chose 8 ohm wiring because it suits most common bookshelf / desktop speakers and also will work with most headphones, except the most power hungry orthodynamics out there. You can also buy an impedance switch from Bottlehead which allows you to easily change the impedance setting later buy simply switching the unit off, lifting the chassis plate and throwing a switch. It’s a great idea for those wanting all options, but not necessary in my case.

SAMSUNG CSCOnce the chokes and transformers were all installed we were ready for the hardcore wiring and soldering. You can see the numbers written on the chassis plate in the image to the left and the wiring process is as simple as following Bottlehead’s brilliant and clear instructions. For each wire or terminal, there are numbered terminals to connect each end to. The biggest challenges in the wiring process are confirming the right parts are used the right ways, especially for the directional components like capacitors and diodes, and also soldering in cramped spaces as the circuit nears completion.

SAMSUNG CSCIn all cases, the instructions are extremely clear and every written instruction is accompanied by a clear picture of the connections being made. The instructions specify the correct orientation of directional parts and even remind you to double-check before soldering. With patience, care and attention there’s really nowhere to go wrong.

Hook-Up Wire

Unlike the Crack, which used single core wires throughout, the S.E.X. uses a mixture of single core and multi-core wire. This makes the build slightly more fiddly because stripping and preparing the multi-core shielded wire takes a little more care and time, but it has it’s benefits because the shielding prevents noise creeping into the wire itself takes up less space in a circuit where real estate is in relatively high demand.

Wire Lengths and Paths

SAMSUNG CSCBecause the finished product becomes an organised mess of wires and components (see left), it’s important to focus on tidiness as you progress the build. Even though mine’s not bad, if I had my time again there are some things I would do differently to ensure a much neater finished product.

Although the measurements in the instruction manual never once left us short of cable, it sometimes seemed to be too much cable. Thinking back this might be because we took a direct path between the 2 connection terminals when the better path may have been around other things to keep them clear. In short, if I were to build the S.E.X. again I would manually check and plan the path and length for each wire before I cut it.

As you can see in the image to the right, the S.E.X. can look neat and tidy if you get it right. That image is from the Bottlehead website and was no doubt built buy one of their wizards, but it’s definitely a level of finish to aim for.

The main thing at this stage is to be wary of soldering in close proximity. It can be easy to accidentally touch a wire or the side of a capacitor (for example) with the soldering iron and melt the insulation or destroy the component so take care and think about each step before you do it. I can very close to destroying one of the capacitors and I think we all disfigured some insulation here and there.

Those Bloody Rectifiers!

WP_20130923_09_47_35_ProPerhaps the trickiest part of the build happens quite early when you’re building what will become the power supply for the tube heaters. It involves the use of some rectifiers which have really thick, stiff leads and all go in a tight spot between the power transformer and a terminal strip.

In the image to the left, you might be able to see some small black cylinders in the bottom third of the image. Those are the rectifiers and you can see from this shot that they’re all smashed in together in a very cramped spot. This is made harder by the fact that you have to pre-bend the very stiff leads prior to installing so it’s pretty fiddly.

What makes it worse is that the rectifiers are directional so you have to get them oriented correctly. Getting this wrong (as one of us did) is a real pain because desoldering and changing them is very tricky due to the cramped space and stiff leads. My tip? Care, attention and patience!

Testing

Once all of the wiring and soldering is completed you’re almost ready to test. I say almost because it’s worth giving the whole circuit a once-over before testing because if you’ve missed any solder joints (we all missed at least one) or done a poor job of a joint it’s much quicker to find it visually now before you try to troubleshoot strange readings during your test. A good solder joint should have ample solder, but not too much, and should be shiny, not dull.

The instructions for testing are as clear as everything else in the manual so it’s fairly straightforward. Stage 1 is an impedance test without the power connected so you can’t hurt yourself at this stage. After checking the resistance across a range of terminals you can either troubleshoot or continue.

Stage 2 involves power and therefore extra care. Once again the process is straightforward, but there is now the risk of touching a high voltage source so patience and care are key.

If, like us, you find strange readings at this stage, the first thing to check (again) is your solder joints. A partial solder joint can create very strange symptoms in your circuit. It’s also very important to take care with your circuit even after unplugging the power. We had a scary moment where one of the guys touched a component that should have been safe because the power cord was unplugged, but the capacitors hadn’t discharged their power due to a dodgy solder joint. The result was a few hundred volts through the hand and a very unpleasant experience so please be careful!

Building the Base

The wooden bases are very simple, but allow for lots of customisation. You can build it early or wait till the end – it doesn’t really matter.

WP_20130924_08_22_44_ProI found that building the base is as simple as gluing the pieces together with PVA craft glue, but we discovered (the hard way) that some glues work better than other. One of the guys had a craft glue which is extremely strong and actually made it impossible to fix any assembly errors.

I found the PVA craft / hobby glue to be a really nice compromise between bond strength and flexibility. It gives you time to adjust the positioning of the pieces of timber before it dries too solid and can be pulled apart if absolutely necessary. My approach was to put a zig-zag of glue along the edge of one piece of the base and then sandwich it together with the other piece. While the glue was still wet, I gently slid the pieces of wood until the edges all lined up to a nice flush finish. Because the wood is all pre-cut with a ridge for the chassis plate to rest on it’s easy to identify which parts go together. Once again it’s a case of patience and care.

Stains & Finishes

The beauty of the natural wood base is that you can make it look however you want. On both my kits I’ve chosen to stain and varnish, but you could also paint the timber, oil it, or just sand it lightly and keep it natural – it’s all up to you.

For the record, staining is a fairly simple process of wiping or brushing the stain onto the timber and allowing it to dry. You can also do things like wiping off any excess or lightly sanding to create an uneven / aged look on your stain. Once stained, you can varnish or oil the wood to complete the look of the stain. I guess you could leave it just stained, but my experience with the two stains I’ve tried is that it didn’t look particularly good until varnished.

Conclusion

09280022Once the build is all done and you’ve tested the circuit you’re ready for listening and feeling the massive sense of satisfaction that comes from hearing your handiwork sing. Be prepared for a fantastic experience because this amp is a beauty!

I was unfortunate enough to have a faulty tube with major hum and noise, but the lovely folks at Bottlehead were quick to offer a replacement and I found a local supplier to buy some from in the meantime so I didn’t have any downtime (and will have spares for the future).

I’ll share a full review of the amp’s sound in the coming weeks so please subscribe if you’re interested in more!

Bottlehead Crack – “The Review”

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: Bottlehead Crack – “The Build”

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.

To read the full review please head over to the new Passion for Sound site. It’s sexier and there’s lots of great new content.

 

Bottlehead Crack – “The Build”

I’ve been quiet for a while – sorry regular readers! But thanks for visiting while I’ve been away.

As a little reward, I have 4 awesome posts coming up in the coming days / weeks starting with this one…

The reason I’ve been absent is that I’ve been unwell. I’m making a full recovery, but have had some significant rest time. Of course, that’s meant lots of time to play with audio gear including the amazing new Tralucent Audio T1 portable amplifier and the Unique Melody Miracle custom IEMs which should be arriving any day now. I’ll have full reviews for you as soon as possible, but today it’s all about Crack!

I ordered the Crack amplifier kit from Bottlehead (www.bottlehead.com) quite some time ago. The Crack is under large demand and they are basically packaged and shipped to order which means you can wait up to nearly 8 weeks (in my experience) before you get your hands on your kit. It worked out well because I got it just in time for some relaxing soldering while I rested and recovered.

By the way, I have absolutely no experience building electronics circuits. I am handy with a soldering iron (from many years of car audio installation and tinkering with speakers and hi-fi wiring), but can assure you that this is a kit that an absolute beginner could manage by applying some care and attention. There are also some great videos on YouTube about soldering including Tyll Hertsens from Inner Fidelity’s video of building this same Crack amplifier.

To read the rest of this review, please head over to the new Passion for Sound site. It’s sexier and there’s lots of great new content.