R4 Insert Routers

Powerful, comprehensive analogue signal routers for mastering studios

A 15 insert R4 Router

I can’t believe how much quicker I can work, and how much better I’m using my outboard. Well impressed!
James Clear

Complete control of analogue outboard

The R4 is a powerful insert router, packed with features to let you get the best out of your precious analogue outboard and chosen converters

It not only lets you choose which inserts you want, in the order you want them, but lets you A/B chains, level adjustments, different converters, and lets you listen to and meter the actual output, or the effect of any of your outboard, inside a record chain

Like all Crookwood routers, it lets you form a record chain, from any connected outboard, in any order. You can then A/B this chain instantly against other chains, adjusting and optimising levels into the chain and into your ADC.

You can selectively MS any piece or pieces of outboard, and form parallel chains and mix them back together (sum them) in the analogue domain, prior to sending them to the ADC of your choice.

You can save insert chains, MS and trim levels in the R4, or in a session via MIDI, and reload them by playing back the MIDI file.

We use balanced gas sealed relays for all switching, and all electronic gains are relay bypassable. If you want ot run the R4 completely passively you can do.

The R4 is ideal for mastering studios, that want’s to maximise the use of their analogue outboard, boost their creativity, while working to tight schedules.

The R4 is available in sizes of 7,11 and 15 stereo inserts.

If the R4 isn’t quite right for you, check out our other routers, or look at a full custom one – here


The R4 is a powerful router for comprehensively routing and assessing the effect of your expensive analogue outboard gear.

It uses Crookwood’s proven relay crosspoint systems to let you form any chain, as if you were patching it with a regular patchbay, but much, much quicker. Our electronics use similar relay based gain cells for low noise, high accuracy audio performance.

Integrated DAC and ADC routing

The R4 lets you work with up to 3 separate DACs and 3 ADCs, so you can choose the best converter for the job, on a track by track basis. As well as analogue routing, the R4 has an inbuilt digital AES router to route AES IO to and from your DAW. and your converters.

This means you only need one AES/SPDIF IO to your DAW to connect up to 3 DACs and 3 ADCs. Of course, if you only have one converter, or USB type converters, you can bypass the AES switcher, and just use the analogue selector.

Fast A/B Different Chains

The speed of routing means you can experiment with different combinations, or order of outboard and A/B two different chains to determine the best choice for a particular track. You can even have two identical chains, but adjust the input and output gains of each chain, to refine ADC clipping, or operating levels. As you A/B, the chain would stay the same, but the trim levels change.

In addition, the source and destination selectors let you rapidly choose different DACs and ADCs too.

Parallel Processing

As well a a single path, the R4 has Crookwood’s advanced parallel path technology. You can:

  • Choose which inserts are in the main path
  • Separately choose other inserts for the parallel path
  • Choose where to split off from the main path – at the start, end or middle of the path
  • Choose a completely separate input for the parallel path – for instance to add some reverb or ambience into the mix
  • A/B different parallel paths and mix levels to determine the best choice for that track
  • Mix together the main and parallel paths, with our summing mixer, adjusting each level
  • Solo each path to check the effect

Monitor and meter any insert

The R4 is equipped with our unique insert monitor. This lets you listen to and meter the output of any piece of outboard, no matter where it is in the chain. Great for working with vintage pieces with no meters.

In addition, you can engage our delta monitor. The delta system subtracts the input from the output of the outboard, so you just hear the effect of that piece of gear. This is great to be able to really tweak the outboard to maximum effect.

MS encoder and decoder

The R4 comes with a flexible MS system, presented as a piece of outboard. By wiring the MS to two inserts, our routing system allows you to selectively MS any piece or pieces of outboard, and adjust the S level too.

Store and recall settings to memory, or tracks

The R4 has 8 internal memories for storing and recalling all insert routing. In addition Store #1 is recalled on power up, so you can hit the ground running fast!

However the R4 can also respond to MIDI commands. This lets you send a dump to a session track, for storing the routing with the session. When you open and play the session again, the R4 will recall to the exact settings you used for the original session.

Pure passive routing

The routing and source selection in the R4 is passive, using precision, gas sealed, balanced relays. It has no inherent sound, no noise, no distortion, and no signal gain or loss, so you only hear the effects of the outboard you insert. Perfect for precision and repeatable working.

Our trimmers and MS are active designs for the best performance, but these too have full relay bypasses to take them out of the signal path. In the path however, our 30 years plus of audio experience shows – they are quiet and sonically neutral. Perfect for precision mastering.


A R4 is made up of these elements:

  • One or two 1U audio processing racks, depending on the number of inserts
  • A hardware remote, consiting of two panels, supplied with a wooden pod
  • A 5M long thin cable connecting the remote to the racks
  • A four stereo input source selector
  • A second stereo input selector for the parallel path
  • A four stereo output selector
  • A dual four to one AES source and destination selector, working in parallel with the source and destination selectors
  • A 7, 11 or 15 stereo insert matrix
  • A MS encoder and decoder
  • Two stereo trimmers, with individual L&R trim levels

Signals and Noise

  • Being truly passive, the noise floor is around -140dBu
  • The maximum signal level is recommended to be below 120V DAC, or about +40dBu
  • With the trimmer or MS electronics engaged, the noise floor is about -95dBu and the maximum level is about +28dBu ( S/N of ~123dBu, or 126dB A weighted)
  • The four trimmers have a range of +/-6dB in 0.25dB steps
  • In parallel mode, the parallel path trim has a range of -36dB to + 6dB


  • All audio is routed in remote, 1U air cooled racks that can be placed in a rack, or on the floor, in a machine room, or near to the outboard to reduce cable lengths
  • The control panel is compact, and can be moved easily when not needed, to maximise your rack area, and minimise reflections
  • The control panel is supplied in a wooden pod, with a raised rear for easy use
  • Panel buttons and encoders are rated for 1M plus actions
  • OLED displays can be seen at virtually any angle or lighting for instant feedback
  • All audio IO via 25w Dsubs, Tascam pinout
  • Control panel is about 110mm wide, 200mm high, and 50mm deep, when mounted in a wooden pod


  • Passive balanced relay based routers, the ultimate audio switch
  • Inserts can be placed in any order, in any path
  • A passive source selector selects the input and outputs to the router
  • An AES buffered router works in parallel with the analogue routers
  • Active trimmer gain stages are made with balanced relay gain stages, with full relay bypasses
  • Design is modular based, allowing for easy upgrades and sidegrades
  • All routes and levels can be stored and replayed for instant setup, either locally or by a MIDI file dump


  • Our 7 insert R4 router is GBP 3375, ≅ Euro 3,994 , or US$ 4,271
  • Our 11 insert R4 router is GBP 4195, ≅ Euro 4,964 , or US$ 5,308
  • Our 15 insert R4 router is GBP 5175, ≅ Euro 6,124 , or US$ 6,548
  • All prices are ex factory and do not include shipping or local sales & import taxes
  • Contact us for a quote with shipping to your country