AUDIOSCAPE PROUDLY INTRODUCES THE MK-609!
AudioScape proudly introduces the MK-609 Precision Diode Limiter/Compressor. Well known as one of the most classic bus compressors ever made, the original 33609 was based on an older design, the 2254, dating back to 1969. The 2254 bus compressor was integral to some of the most iconic British consoles of yesteryear. Utilizing a diode-bridge circuit topology, this design controls dynamics by constantly listening to the side-chain, whose control voltage is used to adjust the amount of compression applied; as the control voltage increases, the output gain decreases. This design allows for subtle compression as a stereo bus compressor when one is just looking to grab peaks, but can become much more aggressive when used on more dynamic tracks, like vocals and drums.
MODERN UPDATES FOR THE MODERN WORLD
Featuring two independent channels, each has a discrete LIMIT and COMPRESS section, either of which can be bypassed, both with their own Threshold and Recovery controls. The COMPRESS section also has a makeup GAIN control and variable RATIO switch. Normally used in the STEREO mode, QUAD mode activates a connection on the rear panel that allows multiple AudioScape MK-609s to be linked together.
The new MK-609 improves on the original design by adding a few new features making it more versatile in the modern studio workflow. AudioScape has included a high-pass filter on the sidechain, allowing more precise control over how it triggers compression, with settings at 50 and 100 Hz. Also new for this iteration is an additional “Super Fast” attack setting on both the limiter and the compressor that gives the MK-609 the ultimate control in any application, including kick and snare! Optimized for more subtle bus compression, the original was excellent for that and vocals, but not useful on faster attack, more percussive sources, the MK-609 corrects for that. It’s designed to have the harmonic richness so associated with the original British maker, whilst being a much more versatile tool in today’s recording studios. The character of compression is altered in a very useful way. Users can really ‘dig in’ to both the compressor and limiter sections now. AudioScape found ‘super fast’ to be the MOST useful mod they could add to this circuit, and they tried everything under the sun!
One other upgrade AudioScape has added is having the makeup GAIN available even when the compressor is *switched out*. Which means that if the MK-609 is being used as a limiter-only, with the compressor out, makeup gain is still available for the limiter, a function not available on the original versions. AudioScape actually made this feature reversible back to the original design by way of an internal user-accessible jumper, if that’s your preference.
Please note:
The mods on every AS product are curated and well thought out, with the idea of preservation and respect of the original design. Everything you add takes something away, so that is very much in the front of their minds while designing every product. Simply put, they’re after purity of tone, devoid of distractions.
THE RARE BITS THAT MAKE IT GO!
A deep dive into the original Metal Knob revision of this circuit revealed a lot of unique parts that weren’t used in later revs. AudioScape also discovered that there were parts added in later revs that aren’t even in the “Metal Knob” iteration of the 609. They had to trace and account for every part. So in true AudioScape fashion, AudioScape scoured the surplus market here in the USA. Having access to these original parts is one of the advantages of building products here.
Let’s break some of these down:
- U410 silver can Dual FET (pictured). This is a decades-old obsolete dual FET used in the originals; others just pop a pair of J109’s in place of them and call it a day. But this is an important component in the compression section. It took some time, but AudioScape secured a good lot of them. One could even argue that it’s not truly a “Metal Knob” version without this part!
- Original issue BC184C NPN transistors (pictured). This is the most used transistor in the old school 609 compressors and old N style preamp designs. This is why AudioScape uses these BC184C’s exclusively in their MK-609 and the V1290 preamps. If you want that vintage sound, you have to get the right parts. Plain and simple.
- BC214C PNP transistors that were also originally used, no corners were cut. AudioScape searched them out and nailed it.
- BC441 and BC461 silver-can transistors. Used in the original. AudioScape searched them out and found NOS ones for the main amp cards and BA440C discrete amps in each channel.
- Original JAN blue 1n4153 diodes. These were in AudioScape's Metal Knob compressor, so they searched them out and found a healthy stock in the UK.
- AudioScape even went as far as to find the original locking power toggle switch and the identical power jewel bulb as the original vintage Metal Knob they have here. These are military-grade parts and come at a great expense (like buying another transformer).
- Notice the component layout on the original Metal Knobs, it is quite different right before the meters. This control layout is unique to the circuit design of the metal knob revision itself. Don’t be fooled by someone popping metal knobs on a modern control layout and then chucking small SMT parts( like in your phone) on the pcb (which is game over for tone)
THE STORY?
The only real story is that this particular legacy piece is so loved in the industry that it took Chris more than four years of development to create a unit worthy of the classic British original. Painstaking care was taken to recreate the original “Metal Knob” version as faithfully as possible. Like all of AudioScape’s legacy builds, NOS parts are used throughout when available, new parts where it makes sense for reliability, and in-house built recreations of the original PCB, transformers and other components as needed.
The creation of the MK-609 started with you. Every die-hard AS follower has been clamoring to experience our take on this for years, so they answered the call!
At AudioScape Engineering Co., they believe in creating boutique analog hardware for a reasonable cost. No Compromises. No BS. Many years of research, development and experimentation have gone into each product resulting in units that can be your daily-driving, rock-solid workhorses for years and years to come. Each and every unit they sell is hand made in small batches, one at a time in the USA - right here in our Daytona Beach, Florida facility!
