Harrison D510r

With up to 10 module slots on board, and both Dante converter and mixer expansion cards available, could this rack widen the appeal of the 500‑series format?

The D510r is a 500‑series chassis with a difference. It can, if you wish, be used pretty much like any other 10‑slot chassis: you can pass analogue signals into and out of the modules hosted within by using the rear‑panel XLRs. But this rack also has expansion options. Currently, there’s a Dante interface card and a mixer/headphone amp, but also firmly in Harrison’s plans (the launch date is yet to be announced) is a USB and ADAT converter card. In combination, I reckon these expansions mean this rack has more potential applications than almost any other, including for large‑scale use of networked 500‑series modules in a live sound context, or in analogue‑digital hybrid studios as an expandable computer audio interface system.

Overview

Sent for review was a D510r fitted with the optional D510mx Mixer Interface and D510Dante card. As you can see from the photos, it also came loaded with Harrison’s own 500‑series preamp, EQ and compressor modules, but while I was reminded that there’s plenty to commend those, we reviewed them in SOS October 2024 (https://sosm.ag/harrison-500-series) so I won’t revisit them here.

The smaller faceplate you’ll see on the front when the Mixer Interface isn’t installed — when this is fitted, channels 9 and 10 act as conventional 500‑series slots.The whole ensemble is housed in a 3U, 19‑inch rackmount steel box that extends 85mm (7.25 inches) behind the rack ears (these form part of the enclosure so can’t be removed). While there are plenty of ventilation holes on the top, bottom, sides and rear of that box, these don’t compromise the impressive robustness of this chassis. Top marks for that. Physically fitting and removing modules was just as I’d expected, given my experience of many other 500 series chassis, which is to say that it’s usually a breeze but seating a module in that final slot is always a fiddle! There aren’t many controls on the standard rack, but there are plenty on the Mixer Interface card, of which more below. The need to pack so many knobs in such a small place has left that feeling a tad cramped — not inoperable by any means but, for example, when turning a headphone level knob my thumb always brushed against the adjacent controls.

Viewed from the front, module slots 1‑10 are laid out from left to right, and to their right is a faceplate, the standard version of which carries the brand name and model number, and has four buttons with some indicator LEDs along the bottom. A red LED indicates power on/off, and the other buttons and LEDs are currently “reserved for future functions”. These appear to include the ability to select the sample rate and clock settings manually for an installed converter card, and to indicate the status of USB, ADAT and clock connections (during the review period, I could only set the sample rate remotely, using the Dante Controller app).

On the rear, the 10 pairs of XLRs carry analogue audio into and out of the rack (balancing is performed by the 500‑series modules themselves). To the left, an IEC inlet with on/off switch feeds mains power (100‑240 V, 50/60 Hz) to a built‑in switch‑mode power supply. The 10 500‑series slots share up to 1700mA of current, the average of which is comfortably (40mA) above the VPR Alliance spec. The Dante card and planned USB/ADAT card fit into a slot in the lower portion of the rear panel, and on the Dante card’s own panel are two RJ45 connectors, for Primary and Secondary Ethernet connections, as well as a BNC word clock connector and a recessed Reset control (that I never had cause to use).

The headphone outs have a Blend knob, to set the balance between the stereo mix and a separate stereo feed for each headphone amp.

The Mixer Interface card occupies channels 9 and 10, and extends to replace the standard faceplate. The XLR analogue inputs 9 and 10 feed this 10:2 summing mixer directly, and it takes the other eight inputs from the first eight module slots. The stereo mix is routed in parallel to the main mix out (channels 9 and 10), whose large Main level knob has unity marked around the one or two o’clock position, plus two front‑panel quarter‑inch TRS headphone jacks, each with a smaller level pot. The headphone outs also have a Blend knob, to set the balance between the stereo mix and a separate stereo feed for each headphone amp that can be sent from a computer or other Dante device when a converter card is fitted.

The optional Mixer Interface card, with individual level and pan controls for each channel, sends a stereo mix to XLR outputs 9 and 10, as well as to two headphone amps.

Mixer channels 1‑10 each have a level and pan pot, and a red button with red indicator LED to route that channel to the mix bus (or not, as you prefer). These controls are arranged in two columns, with odd‑numbered channels on the left and evens on the right, such that each row controls the five obvious stereo pairs (1+2, 3+4 etc.). Beneath this are the same buttons/LEDs as on the standard card, the only difference being that the Mute button lights at power up to indicate a lack of connection of the Dante interface to a network; at the time of writing this feature was still in development.

Internal Options

With no 500‑series modules fitted, much of the internals are open to view, and some of what can be seen deserves our attention. As with most 500 racks, a large, main PCB is mounted inside the back panel, and its most obvious features are the 10 card‑edge connectors. Adjacent to each of these, though, are two switches...

The first switch determines whether that slot receives its analogue input from the rear‑panel XLR or from the D‑A converter. This gives you the welcome flexibility to, for example, route from a DAW to a multi‑module channel strip and back, using only a single Dante input and output, avoiding the need for several stages of conversion and the cumulative latency that would entail. Less welcome is that these physical switches on the inside are the only way to change this setting — if you wish to change it after the initial setup, then you must power off the rack, remove a module and use a ‘long pokey thing’ (in my case, a wooden chopstick!) to push up a latching button. A task best done while shining a torch inside, since there’s no external indication of the status. In most traditional Dante network setups this is unlikely to be problematic, as you’ll likely configure the device once and leave it that way. But those, like me, working in a music production environment would be justified in wishing for more flexibility. I’d have preferred to see external switches (there’s space on the standard faceplate) or maybe remote‑switching options, such as using MIDI over MADI.

The other ‘switch’ is a Stereo Link jumper, which uses (presumably) pin 6 of the 500‑series connector to sum the control signal of a dynamics module installed in an odd‑numbered channel with that of one in the even‑numbered channel to its right. Again, a welcome feature, but one that’s inconveniently placed for those wanting to change this setting after the initial setup, and there’s no external visual feedback on the current status.

Dante

When fitted to the D510r, the D510Dante interface can carry up to 14 channels to the rack and 10 channels from it, at your choice of 44.1, 48, 88.2 or 96 KHz sample rates, over a Dante network. The ‘additional’ four sends to the unit are the PC 1+2 and PC 3+4 signals that I alluded to above and which, with the Mixer Interface fitted, you can use to route DAW mixes or backing tracks/cue mixes to the headphone amps. All the inputs and outputs are combined by an Ethernet switch fitted inside the D510r so that it appears as a single device on the Dante network, with a primary/secondary redundant configuration.

The Dante interface occupies the lower half of the review unit’s rear panel. An alternative USB/ADAT interface is also planned.

There are other 500‑series racks out there with A‑D and D‑A conversion built in, Cranborne Audio’s 500R8 interface and 500ADAT expander being the most prominent examples. But I can’t think of one that also offers Dante connectivity, and the potential scale of setup into which you can integrate one or more D510rs without requiring separate converters or lots of analogue cabling is significant.

For instance, it means that you could create a network of several of these racks in a studio setting, with each and every channel directly accessible from your main DAW machine. Even though there’s a USB interface card on the horizon, a Dante setup could have some advantages in that context too, whether simply the reduction in cabling required around the back of your rack, or the ability to place racks of headphone amps, cue‑mix facilities and 500‑series preamps, processors and utility modules further away from a computer than USB typically allows. I could imagine that appealing to the sort of shared‑live‑room, multi‑control‑room setups that you find in higher education facilities. Alternatively, a single D510r rack with the Dante Virtual Soundcard software gives you an eight‑ or 10‑slot 500‑series audio interface that’s expandable and so, to some extent at least, future‑proof.

With Dante Virtual Soundcard software and the Dante expansion card, the D510r can serve as a computer audio interface.But while we’re increasingly seeing Dante and other networked audio in music studios, it’s already widely used in live sound, and there are definitely applications for bands and engineers wanting to take high‑quality analogue outboard out on tour. A rack like this, that’s relatively compact compared with 19‑inch processors and effects and can integrate with existing Dante setups without external boxes, could make a lot of sense.

I’ve used Dante devices previously, but this was my first time setting up a ‘network’ from scratch, and connecting the unit directly to my MacBook Pro (rather than a router) running Dante Virtual Soundcard initially caused some head scratching. My computer has access to multiple networks, and it took a while to figure out the settings needed to get the computer and the rack talking to each other (I didn’t find Audinate’s Dante troubleshooting documentation the most accessible!). But having cleared that hurdle and, in Dante Controller, set the D510r to the same sample rate as my DAW project, I could easily route audio from the DAW to the rack and back with impressively low latency. Setting up headphone cue mixes and balancing them with an analogue foldback was also a breeze.

Also pictured here, my routing tests in Dante Controller and Reaper, showing that it’s possible to route audio over Dante to a module, pass an analogue signal from that module to another, and to return an output from the second module back over Dante to the DAW.

Sound & Specs

Subjectively, the D510r sounds good, and I’d characterise it as ‘clean’. I wouldn’t expect the module slots themselves to add anything untoward, as there’s very little going on there until you plug a module in, but I’d include the mixer and headphone amps in that description too. I noticed no problems in terms of undue noise or distortion, and I found that my headphones of various impedances could be driven louder than I needed. It’s perhaps worth noting that in the ‘off’ position the headphone amps still pass a faint signal, but it’s not loud enough to leak onto a mic or be a bother.

The published specs perhaps don’t put the D510Dante converter card up there in ‘best‑in‑class’ territory, but it’s my sincere belief that people massively overthink converter specs today — for the vast majority of applications, converter quality just isn’t the issue it once was, and it’s unlikely ever to be the weakest link in your chain. In this case, the converters are perfectly capable of professional‑quality results, offering plenty of dynamic range for the sort of signals that will be run through this rack and, importantly, I couldn’t hear any problems. In short, I’d have no qualms about using this box with the Dante card for recording, mixing or live sound. Neither did I detect any of the problems I’ve observed in some host racks with the built‑in power supply compromising the performance of nearby preamp modules.

Verdict

So, Harrison’s D510r is a welcome addition to the 500 series. It brings convenient Dante conversion to the format for the first time. As well as being a 10‑slot rack, this device has the potential, with the right expansion cards, to be a summing mixer, an audio interface, to deliver two headphone mixes... the list goes on, and when the USB and ADAT card becomes available it will lengthen further. Sure, there are some things that I’d like to see done differently, not least those internal‑access switches. But there’s scope for future development here, and the convenience of having the converters built into your 500 rack rather than relying on standalone units should not be understated. Definitely one to put on the audition list.