Solo & Duo Phono Preamp Review
Company & Product Overview
Over the last few years, Cambridge has produced a constant stream of top-rated products, from amplifiers to Blu-ray players. The Cambridge team has an incredible talent for producing great-sounding audio products at affordable prices. Their gear is always extremely musical and easy to listen to for hours.
One of the secrets of Cambridge is their focus on power. Since their origins in developing the toroidal power transformer, they have always focused on making sure the power being supplied to their units is as good as it can be for the price.
Today we’ll be discussing two new phono preamps from Cambridge -- necessary components for any high-quality turntable system. While many entry-level tables have phono preamps built in, any true audio enthusiast can speak to the benefits of an outboard phono stage. The new Cambridge Solo and Duo, at $179 and $299 respectively, are both built for performance and value.
Let’s dive in, see how they stack up and help you determine if either one might be a good fit for your vinyl playback system.
Design & Build Quality
At 7” wide and 9” wide respectively, the Solo and the Duo are both smaller than a typical component. They come in simple metal cases, like most Cambridge products.
The front panel of the Solo is minimalistic, with only a power button and the Cambridge logo. The Duo, on the other hand, includes the same power button and logo stamp but also includes a button to select between a moving coil and moving magnet cartridge (more on this in the next section), a large volume knob, and a headphone jack.
One unique design choice that we love about Cambridge products is the way they do their back panels. They print all of their input labels both upside down and right-side up, so that they are easy to read, even while leaning over the units from the front.
Build quality is way above what you would expect for the price -- especially in the Solo. When you pop the cover (like we always do), you’ll see a surprisingly stuffed circuit board with a great internal layout to keep the power supply separate from the very low-noise phono stage parts.
Even to our critical eyes, the quality of the parts quality used and the board layout is top notch and way beyond what one would expect for this price. The Duo is very similar but adds some features not found in the Solo.
Features & Technology
Our readers and customers come from all different points in the audio spectrum, from beginners to seasoned audiophiles. Considering the price point of these phono stages, we think it’s worthwhile to take a second to dig a little deeper into phono stages and cartridges before we dive into the features.
The first thing to know is that all turntables have a cartridge on the end of the tonearm. The needle (or stylus) in the cartridge is what touches the grooves in your records. The job of the phono stage, also known as a phono preamp, is to amplify the tiny signal coming from the stylus and through the cartridge so that it can play as music through your system.
Phono cartridges are typically one of two types -- moving magnet (MM) or moving coil (MC). Properly designed moving coil cartridges can usually extract more information from your record grooves, but they come at the cost of a much lower electrical output. This means that a phono preamp for a moving coil cartridge needs the ability to amplify the signal a lot more than one for a moving magnet.
Most entry-level to good turntables under ~$1,000 will come with a moving magnet cartridge. The Cambridge Audio Solo is made specifically for moving magnet cartridges.
For those of you who have moved up to a moving coil, the Duo supports both moving magnet and moving coil. Plus, the Duo gives you the added bonus of a headphone amp with volume control.
Phono cartridges can produce a signal produce that is 1,000 times lower in output than a CD player. When you are dealing with such a minuscule signal, you really do not want any noise at all getting anywhere near that tiny signal. The designer of a phono stage is faced with this conundrum: The phono stage actually needs power, and really clean, stable power to properly amplify that tiny signal. However, if any noise from the power stage leaks over into the signal path, you’ll not be able to hear all the subtle nuances of your music.
Cambridge Audio took a whole new approach to solving this problem with the Solo and Duo by developing a special switch mode power supply that has an extremely low noise floor. The entire power supply section sits off to one side of the unit and is even isolated by a metal divider and shielding material that wraps it completely. The three prong power cord only has about ½” of wire before it hits the power supply circuit board. They even came up with a new circuit board layout to further reduce the noise. The layout design is perfect. The critical input where the signal is at its lowest level is on the far side of the unit, away from the power supply. The final output stage, which is not as sensitive to noise, is next to the supply. All for a $179 phono preamp!
The headphone jacks found on most Cambridge products drive just about any pair of headphones very well, so we suspect they used a similar design for the headphone amp stage of the Duo. The full-sized headphone jack on the front has a volume control, allowing you to listen to your vinyl through headphones without having to turn on the rest of your system. A nice, eco-friendly touch.
As an interesting twist, the Duo has separate inputs for both moving coil and moving magnet. The moving coil and moving magnet inputs follow a completely separated path until they go to the final output section. This means that technically you could connect two tables up -- one with MM and one with MC and play DJ. There is even a switch on the front of the Duo to change inputs!
You really get a lot for $299.
However, you don’t get much in the way of adjustability. In the world of phono cartridges, there are slight differences in almost all of them. Various brand and models have different output levels, and many of them like to see a different load. The load is the resistance that the tiny signal sees and it can make a pretty big difference in the sound. Most all moving magnets like to see 47K ohms, but moving coils can vary from 100 ohms to about 1000 ohms. Cambridge took what is typical for about 60% of moving coils and made the load fixed at 100 ohms and gave us 60 dB of gain (again on average).
For moving magnets, their settings handle about 95% of the models out there with settings at 47K ohms and 39 dB of gain. When you move up into the world of more expensive phono preamps, you can usually adjust these settings. For instance, our favorite phono stage brand, Sutherland Audio, offers gain settings of 40, 46, 52, 58, and 62, and load settings of 100, 200, 475, 1000, and 47k. You’ll typically begin to see this type of flexibility in the $500 and up price range, so it’s not surprising it is missing here.
We are being picky here, but we think these settings are much more useful than the balance control on the back of each of these phono preamps. Almost every amplifier has one of these already, so we would rather they put that money into some adjustability.
With that said, overall these are both incredibly feature-packed, solid units for the price. We just like to help our brand partners push the boundaries and produce the absolute best products they can for our customers.
For our testing, we used a Rega P6 with their Exact MM cartridge as well as Rega’s Ania MC cartridge. Since it appears that the circuit boards on the MM circuitry are exactly the same, we used the Duo to test. For listening, we used a pair of Focal Elear headphones.
We listened to three 180g vinyl pressings of some classic music from the vinyl heyday. Gilberto and Getz’s Girl from Ipanema, Fleetwood Mac’s Rumors album, and Pink Floyd’s Dark Side of the Moon. You can’t get much more classic than those three!
When we first popped on Rumors, it sounded a little dirty. We ran it through the Vinyl Cleaner Pro from Audio Desk and it made a huge difference. We don’t think most sub $500 phono preamps would reveal such a difference.
These preamps are super quiet. Even with the volume all the way up, you hear silence when nothing is playing. You can hear deep into the layers of a piece of music. “Dreams” from Fleetwood Mac sounded fantastic.
We would describe the sonic character of these new phono stages as warm and musical. You get a good amount of detail, but we have heard more information out of the much more expensive Sutherland models. “The Girl from Ipanema” is always a great test of rhythm and pacing, and these phono stages passed with flying colors. Bass definition is also very good, but if you spend more for something like a Sutherland KC Vibe ($895), you will definitely get more bass extension.
The headphone amp on the Duo is also very good. It pushed the Elears as loud as we wanted to hear them. Some people who like to really crank up the volume might not find them loud enough, but we recommend protecting your hearing. If you are into vinyl, you’re probably listening more for the detail and enjoyment of the music anyway, and this amp is capable of getting good levels out of around 90% of the headphones on the market.
Both of these are as good as we have heard for their price. At $179, the Solo is an absolute steal. If you have a receiver or turntable with a built-in phono stage, either of these will be a big upgrade.
We would like to see more adjustability on the Duo, but even if you have an MM cartridge and want to listen to headphones through your turntable, the extra $120 gets you a great headphone amp. We think the person who has spent the extra money on a moving coil cartridge will probably choose a higher end phono preamp. Therefore, we suspect your choice should come down to whether or not you want the headphone amp functionality.