THE MISSING LINK
Reimagining the DI for a Modern Era
In the modern squeaky clean digital world we often feel something is missing, a warm, musical color and depth of tone that is just not fully emulated. While there are numerous DI box solutions designed to be ruler flat, we find something is still missing from the equation, but what is the missing link?
The Missing Link is a series of premium analog direct boxes that are made with the same analog components of those beloved analog consoles of yesteryear, designed to restore the sonic color, weight and depth lost to the digital age, going way beyond what we generally expect from our DI boxes and makes plugging in direct sound and feel more inspiring then ever!
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The Missing Link accomplishes this through using the same analog component equation tried and true for generations, a high quality discrete opamp, running on high voltage driving a quality transformer. This isn't really a secret receipt, as some form of this is in nearly every high-end studio console and many famous microphone preamps, practically defining the "sound" of every professional recording since the transistor was invented, however, this sonic receipt has never been applied to the preamps little brother, the DI box, until now!
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AUDIO SAMPLES
Check out some audio samples below comparing industry standard DI boxes with the Missing LINK series DI. While this is not an effect box and the differences can be subtle at times, on most decent speakers or headphones you should be able to hear how the LINK boxes impart a sense of weight and warmth to the signals and makes them sound and feel more organic and analog!
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A Deeper Dive into the Missing Link!
There is a saying in pro audio that I learned as a young aspiring recording engineer, "your tone is only as good as the worst link in your chain". Over the last 22 years of recording, mixing, mastering, running live shows and designing pedals, I have found that to be nearly universally true, and I have found that many peoples weakest link is actually their direct box. Let's dig into why that may be...
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Digging in on DIs
To understand the problem with standard DI boxes, we have to first discuss the two main types, being active and passive and their shortcomings. The goal of a DI box is to simply balance an instrument signal (High Impedance) to a balanced signal (low impedance) in order to send it long distances without degradation or excessive noise, usually over XLR cables.
Active DI boxes use some form of electronics to balance the signal, usually powered by 48v phantom power of the sound board. The best of these boxes tend to be very clean sounding, but most are made with cheap components and usually sound harsh or outright sterile and even worse if driven with a loud signal close to clipping. The advantage with active boxes is you can get a very high input impedance of 1Mohm or higher which limits parasitic loading, making them sound more consistent from source to source.
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Passive Direct boxes, while being convenient not requiring any external power, are usually also full of electrical compromises. Passive direct boxes utilize a transformer to balance the signal, which introduces a number of questionable factors into the situation. Not only is this transformer often of questionable quality usually degrading the sound, the use of high winds ratios to attempt the impedance match is less then ideal resulting in input impedances usually on the order of 100-200k ohms, which is especially low for anything besides active pickups, resulting in audible tone sucking due to loading and impedance mis-match. The best passive DI boxes use high quality transformers but still suffer with inconsistency of tone from impedance loading.
Our solution to these issues is to bridge both designs to optimize for the strengths of both and cover for the weaknesses, utilizing a high impedance input stage comprised of a discrete opamp driving a passive, studio-grade transformer made by either Cinemag or Jensen selected for their warm, smooth sound quality with ultra musicality. In fact, this is actually a circuit lifted straight out of the DejaVu studio preamp released in 2022 by Stephen Pettyjohn's studio company Ethereal Analog, which is now also available in 500 series format here: DejaVu500! The Link Studio variant is a 1 to 1 exact lift from the DejaVu, including the ability to run any "big box" 6 pin discrete opamp.
Why a Discrete Opamp?
An active high impedance input buffer/ gain amplifier is composed of a modernized version of the famous 990 discrete opamp made for us by Sonic Imagery Labs. This 990 discrete opamp is the same one we first used in a guitar pedal via the original PreDrive that came out a decade ago and has been further optimized for the low current draw in the 48v versions of the LINK boxes. The main advantages to using this 990 discrete opamp is that it exhibits extremely low THD and noise specs, below standard opamp specs, along with the ability to run on higher voltages, up to 48v for extremely high headroom, and perhaps most importantly, it can source the current needed to properly drive a transformer without loading issues.
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Transformers, the Magic of Magnetics!
Transformers were used in early designs for balancing audio signals because their wasnt really any options. Once modern opamps came into play in the 70s and 80s the cost and size of the transformer was seen as excessive and transformers started to disappear from all but the most premium products. The issue was that using transformers was actually imparting something to the sound quality that opamps alone can not, in fact its the non-linear nature of transformers that imparts glorious harmonics to the signal, which increase as the signal level pushes high enough to start to saturate the core of the transformer. This is called saturation and our ears love it. In fact this thing called saturation is actually a feature of magnetic based circuits and found in nearly everything well loved for its tone in audio. Magnetic saturation is responsible for a majority of the tone we love in so many devices from tape machines to tube amps, from mic preamps to recording consoles, so why not explore this in our DI boxes? For a transformer to sound its best it needs to be properly driven by an active circuit like a tube or discrete opamp stage that can source the power required. This is why just strapping a passive transformer on isn't enough to fully activate the mojo, we need to drive it! Only now can we properly impedance match and properly drive a high quality, carefull chosen transformer into the sweet spot and achieve the warmth and depth of tone we know and love.
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A New Generation of DI
The Missing Link is not your father's DI box. It is more accurately a studio mic preamp optimized for unbalanced high impedance input from a variety of instruments. Now this is a fully optimized impedance matching solution that fully transfers the core tone of your instrument to the transformer, which imparts it's magnetic magic to the sound while driving the signal up to 300 feet over XLR cable with zero quality loss and very low noise. ​
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We are calling this a "Direct Instrument Preamp", which can still be a DI box in short but it does more then just the utility of balancing an instrument signal. The circuit hass been voiced with careful transformer selection chosen to add "that" analog warm sound without sacrificing detail. Every version of the MISSING LINK shares a common topology and sound quality, imparting extra depth in the lows, warmth in the low mids and a smoothness in the mids and highs that EQ alone cant accomplish. Perfect on just about everything and anything unbalanced, examples include:
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BASS: Increase depth and impact of lows along with great note focus.
DRUM MACHINE: Increase punch and weight to any drum machine or samples along with smoothing out "digitis"
ACOUSTIC INSTRUMENTS: The Link is incredible on any sort of acoustic pickup where any "ice pick" tone associated with piezo pickups gets simply smoothed out leaving a natural acoustic tone left.
SYNTHS: Analog or digital synths gain new life when sprinkled with analog goodness.
DGITAL AMP SIMS & PROFILERS: One of our favorite use cases for the Missing Link family is balancing digital "direct in" amp solutions that have become popular in the past 5 years. We feel like any final bit of digital flatness gets melted into analog oblivion and simply sound even more like a real amp again!
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The Thru Jack & An Inconvenient Truth
A common feature on direct boxes is a thru jack, which passes through the unbalanced signal, supposedly un-effected. Unfortunately, most if not all of these do not provide a true clean through signal, but tone sucking from loading effects are common making these thru jacks un-reliable at best, as far as delivering consistent sonic results. We have made our THRU outs fully buffered, abolishing tone sucking and loading effects forever.
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NOTE: Not every Missing LINK box will have a "Thru" buffered jack, specifically some of our 48v stereo box doesn't at this time due to current and space limitations.
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The "Level Problem"
Many direct boxes, especially most passive DI boxes, have another issue we address in the Missing Link Series, that is the -18dB issue. Yep, most DI boxes reduce the signal by 18dB, which just needs to be made up by the preamp gain at the sound board. While this is not a huge deal if you have a very loud signal say a keyboard outputing near line level, most instruments have very low signal level output, with passive pieazo or magnetic pickups being among the lowest. When a DI box knocks this level down another -18 dB thats another 18dB of gain needed at the sound board, which brings up noise. The Missing link series is build around a Unity Gain buffer and 1:1 transformer. We have provided GAIN and PAD switches that allow the user to optimize for the signal needs, including a classic -18dB mode, but also adding gain can be down to further optimize the signal to noise level or to creatively drive the transformer for more analog mojo! Mix and match the PAD and GAIN levels and optimize to your needs.
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Powerful Options
DC Pedal Power or 48V Phantom Power?​
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The Missing Link Series offers several versions of both mono and stereo direct instrument preamp boxes. While they all share the common discrete opamp driving a quality transformer design, one of the main differences and factors in which model is right for you depends on how you would like to power your LINK.
LINK 48V Models: The 48V models are powered via 48 volt phantom power on the sound board preamp, and do not require local DC power supply. This can be very useful for live stage stations that don't have power close by. It is also a limiting factor as phantom power is industry wide specced at 8mA, so while there is just enough to power our custom Low Current Discrete Opamp but not enough to power another opamp needed for buffered Thru jacks. Also, it limits the Discrete Opamp to the one low current model, so no opamp swapping is possible. Big advantage here is the Discrete Opamp can run directly off the 48v power, with no scaling for massive 48V of headroom on the active stage, making it nearly impossible to clip.
LINK Standard Models: Utilize DC power via 9-18v, 100mA, center tip negative, standard pedal power adaptors. Require quality, isolated power. Input power is inverted for a negative power rail, effectively doubling it, delivering 18-36v to the discrete opamp, naturally we recommend 18v here for max headroom and performance. This is perfect for any pedal board or stationary setups where DC power is readily available. The advantage here is we can design with more current, and thus we can use other active stages to create a buffered THRU output. Also, it allows for using the standard current draw version of the 990 discrete opamp.
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LINK Studio: Utilizes our proprietary dual rail internal supply, that delivers 36 Volts to the opamps from any isolated, quality 9-15v DC power supply, minimum 100mA of current rating, with center tip negative barrel jack. This is our most beefy power suppy and allows this version to power standard 'big box" 6 pin discrete opamps beyond our 990 Enhanced opamp and enables opamp swapping for other studio discrete opamp flavors, virtually erasing the line between studio and live gear once and for all. Finally, you can take your favorite discrete opamp on the road!