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Endless Analog CLASP

Tape Recorder Integration System
Published May 2012
By Hugh Robjohns

What's better, a DAW or real analogue tape? Both, of course! We take a look at an ingenious system that seamlessly integrates the two.

Endless Analog CLASP

As I'm sure most Sound On Sound readers will already appreciate, the age of the computer DAW has brought countless benefits to the musician, professional and amateur alike. Amongst the major advantages is the phenomenal speed of operation, particularly the ability to jump instantly back to the start of a take, or session, or around looped sections. The convenience of being able to navigate instantaneously around a DAW project at lightning speed is probably taken entirely for granted by many readers, but those who remember the tape era will recall that working with analogue tape was (and still is) slow, tedious and cumbersome by comparison, with the inertia of large and heavy reels on a multitrack machine inevitably taking an age to fast-spool and then slow down again.

Moreover, the physical wear on the tape's recording surface through playing over the same section repeatedly when performing overdubs and drop-ins caused audible deterioration in the quality of previously recorded tracks, and the continuous tape shuttling put considerable strain on the machine's transport. It's no wonder that, back in the heyday of tape recording, studios needed an on-site maintenance department! Having said all that, though, there's no denying that recording to tape often does something musically attractive to the overall sound, and many DAW users either miss that character or are desperate to find a way of achieving it in some way.

Of course, there's nothing to stop any studios still equipped with multitrack tape machines from recording a set of raw tracks directly to tape in the old-school way, and then transferring that material afterwards to a DAW for editing, processing and mixing. Indeed, this is precisely what many studios are doing. However, the problem with this approach is that it is a very time-consuming — and therefore expensive — process, and all the more so if it is later decided to perform some overdubs after the initial tracking, because it would involve bouncing to tape and yet more transfers, and potentially require chase-synchronisers and other technical complexities.


There's a lot of clever routing going on, but it's pretty easy to get your head around it with the help of this chart.There's a lot of clever routing going on, but it's pretty easy to get your head around it with the help of this chart.

This is where Endless Analog's CLASP system comes in, because it offers an innovative and deceptively clever way of integrating up to three analogue tape machines (providing potentially anything from one audio track on a mono machine to 72 audio tracks on three linked 24-track machines) seamlessly with a computer running regular DAW software.

In essence, the CLASP system passes the incoming audio onto analogue tape and, via the repro head, straight off again to be recorded permanently in a DAW. Cleverly, the system automatically compensates for the inherent off-tape delays, and it also manages the source and replay track monitoring to suit the task in hand — including providing completely latency-free monitoring when tracking. The end result of this intelligent technology is that it retains all the speed and convenience of working in a DAW environment, while simultaneously capturing all the audio character of tracking to tape.

I think it's worth mentioning at this early juncture that although the CLASP system might initially appear to be quite an expensive option, it is a complex system, it is truly innovative and, currently, it is totally unique. Also, while the concept and technology is, as I said, complex, in practice the CLASP system is almost trivially simple to configure and use, and it works astonishingly well. It even permits some novel and creative ways of working that are virtually impossible (and certainly impractical) with conventional tape tracking techniques. Yet more factors help to explain the cost: the CLASP system is built by hand in small batches; it incorporates 'mastering quality' relay-switched audio circuitry; it brings a superb level of convenience and seamless tape-machine integration; and it dramatically reduces the costs normally associated with analogue tape recording! So, assuming you are already using tape, what's not to like?

What's In A Name?

The CLASP in action with a Studer A810 stereo tape machine during our tests.The CLASP in action with a Studer A810 stereo tape machine during our tests.

CLASP stands for 'Closed Loop Analog Signal Processor'. In fact, there's no 'signal processing' in the conventional sense: the input audio is recorded directly onto analogue tape with the real-time replay head output being recorded into the DAW. As the off-tape signal is delayed relative to the input signal, the audio files in the DAW are automatically time-aligned and re-allocated with the appropriate time-stamping. The CLASP system doesn't require or use SMPTE timecode, as there's no 'chase synchronisation' element in the usual sense. Each recording pass is recorded sequentially on the next available section of tape, and there's no shuttling of tape back and forth to maintain synchronisation between different overdubs on tape. In effect, the tape is merely a consumable resource used to provide some audio character, and the permanent recording and construction of the whole audio project is done entirely within the DAW in the usual, modern, way. Usefully, though, the CLASP system keeps track of how much tape is left on the spool, and will rewind it automatically before it gets close to the end. Any subsequent takes are simply recorded over the previous takes, extending the useful life of the tape reel at the same time as reducing its effective cost!

The 'closed loop' aspect of the title relates to the way in which the CLASP hardware surrounds the tape machine's audio signal path, and takes care of all the monitoring switching automatically, so that the musicians and engineers hear what they need to hear when tracking, overdubbing and mixing. Although the CLASP system concept is based very closely on a traditional studio's operating paradigm, with the audio being sourced from and monitored through a large-format console, it's versatile enough to be integrated with a more compact system if required.

CLASP Hardware

The CLASP's recently redesigned plug-in interface, used on the test session with a Pro Tools system.The CLASP's recently redesigned plug-in interface, used on the test session with a Pro Tools system.

The CLASP system involves a closely-related combination of hardware and software elements. The 2U, rackmounting hardware device deals with the audio signal-path switching between console, tape machine and DAW, and also with the tape machine's transport control functions, communicating bi-directionally with the software using a combination of MMC and HUI protocols via MIDI. The CLASP hardware unit handles 24 audio channels, but up to three units can be chained together for larger track counts if required.

All the necessary tape-machine transport control and track-arming functions are accessed via a bespoke interface cable that plugs into a 15-pin D-sub connector. Different cables are available to suit a variety of common professional studio tape machines from 3M, Ampex, MCI, Otari, Scully, Sony, Studer and Tascam. An optional optical sensor is also available, which can be fitted to tape machines without one of the supported transport interfaces, so that even vintage tape machines can be used with the CLASP system. A pair of three-pin XLR connectors provides the send and return test signals used for calculating the head-offset timing during the system's initial configuration.

The CLASP's audio routing arrangements are designed effectively to envelop the tape machine, and all the audio connections are via standard 25-pin D-sub connectors, wired to the balanced, eight-channel Tascam standard. In a normal setup, the console's 24 tape sends or bus outputs (or the record signals from an alternative front-end configuration) are connected to the CLASP's line inputs. These signals are routed internally to the corresponding tape recorder inputs, as well as being made available at the CLASP's monitor output selector for latency-free monitoring.

The tape recorder's off-tape replay outputs are connected directly to the DAW's input A-D converters for recording. The corresponding DAW channels' D-A converter outputs are returned to the CLASP hardware as 'DAW returns' and the signals are made available at the CLASP's monitor output selector. The outputs from this selector are connected to the mixing console's tape returns for monitoring and/or mixing.

This all-analogue signal path and built-in switching arrangement allows the CLASP hardware to toggle the console's monitoring feeds between the recorder input signals and the DAW outputs as necessary, on an individual channel basis, when tracking, overdubbing and mixing.

The hardware front panel is surprisingly simple, with just five chunky buttons and a large numeric time display. The latter is used mainly to show the duration of tape remaining, while the buttons allow the hardware to be configured and the machine controlled locally. The 'RTZ' button probably has the most obvious function, which is simply to rewind the tape back to the zero point at the head of the tape. Most of the other buttons are for system configuration and are rarely used once the system is up and running. For example, the 'IPS' button informs the CLASP system what tape speed has been selected on the machine, while the 'Post' button adds a post-roll period after each recording pass. The 'Sync' button is used to calculate the head offset timing, and the 'Mon' button forces the audio path switching to provide direct (latency-free) input monitoring.

Building Bridges

For those who are curious, we thought we'd lift the lid on the CLASP... and revealed neat, tidy construction.For those who are curious, we thought we'd lift the lid on the CLASP... and revealed neat, tidy construction.

The software side of the system involves two deceptively simple plug-ins: the 'bridge' plug-in and the 'machine' plug-in. The 'bridge' can be inserted into any convenient DAW channel and provides a simple means of monitoring and controlling the tape machine's status. The CLASP system has to measure the timing offset required for the specific tape machine and tape speed before you can start using it in earnest, of course, but this is controlled from the 'bridge' plug-in and requires only a few button clicks at the start of a session. The transport and track arming follow the normal DAW operations, and the audio path switching is automatic. The plug-in communicates with the hardware via a MIDI interface, and Endless Analog recommend various M-Audio USB MIDI interfaces if the DAW system doesn't already have available MIDI ports.

To use the CLASP with your DAW, the DAW project has to be structured in a specific way, but it's not a particularly onerous requirement. Essentially, each DAW output channel has to have a copy of the 'machine' plug-in inserted in it, as this implements the necessary time offset associated with the tape recorder's record/repro head spacing and tape speed combination. In Pro Tools, this requirement means inserting master faders in each output channel, but that's easy enough, and once set up, these master channels can be hidden from view and forgotten about.

The time-alignment between tracks already recorded or generated directly within the DAW and those captured through the external tape machine is sample-accurate, although in Pro Tools HD systems it may be necessary to manually 'tweak' the offset value to accommodate the latency. This shouldn't be necessary with the native version of Pro Tools, or, for that matter, Cubase, Logic or Nuendo.

The software plug-ins are currently compatible with Pro Tools, Nuendo, Cubase, and Logic 9, but compatibility with other popular DAWs, including MOTU's Digital Performer, is also being developed. For Pro Tools systems, Endless Analog recommend at least an HD2 system running Pro Tools version 7.3 up to the latest version of Pro Tools 10 (Mac only), and for sessions at 96k they recommend an HD3 system.

In Practice

The rear panel is dominated by D-sub connectors. The system pictured is hooked up to a Studer A801 stereo tape machine.The rear panel is dominated by D-sub connectors. The system pictured is hooked up to a Studer A801 stereo tape machine.

A key strength of the CLASP system is that the tape-machine operation is totally seamless and almost invisible: it's just not something you need to think or worry about at all, because all the complexities are taken care of automatically in the background. The creative workflow is no different from any other DAW session, but you have the benefit of capturing inherently 'analogue-rich' source tracks via the tape machine. Other than loading a reel of tape at the start of a session, you never need to touch the tape machine's controls at all if you don't want to, and you always know how much tape is left on the reel before you start another take, regardless of the machine's speed setting. Once you're set up, it really can be that simple.

One of the really nice and uniquely innovative things about the CLASP system, though, is the ease with which you can experiment with different tape-machine settings for different takes within the same project. For example, switching recording speeds is trivially simple, so it's incredibly easy to record the initial tracks at 30ips, say, for maximum quality, and then capture some overdubs at 15ips, so that the lower tape speed introduces some extra weight and body at the bottom end, and maybe a more obviously saturated high end. Such creative shenanigans would be virtually impossible in a normal old-school multitrack tape recording session, because to achieve the same thing would require multiple machines and lots of track bouncing. Similarly, it's just as easy to change record-drive levels, EQ curves or bias settings between takes if you want to, allowing you the kind of creativity and instant experimentation that just wouldn't be practical with conventional multitrack techniques. That really is quite empowering!

For any studio with a dusty multitrack machine lying, forgotten, in a corner of the control room — or perhaps for one with a hankering to invest in a pre-loved machine — the CLASP system offers the truly exciting possibility of integrating the desirable sonic qualities of tape recording with the fast and convenient world of the DAW.

Better still, despite the headline price, it greatly reduces the costs associated with analogue multitrack recording because there's no need to store and archive reels of expensive multitrack tape for each project, and each reel can actually be used several times over many different projects. There is also no need for complex SMPTE chase-synchronisers, and no need for a dedicated timecode track (and adjacent guard track), so you can record as many tracks simultaneously as the tape recorder (and the DAW's converters) can cope with. The built-in monitor switching provides automatic zero-latency monitoring, which is a nice bonus, too. So for a studio doing a lot of work with tape, it might not take so long to recoup the investment cost.

Endless Joy?

In a nutshell, then, and depending on your point of view, the CLASP is designed to make a DAW sound like an analogue multitrack tape machine, or to make a multitrack tape machine work as quickly, flexibly and conveniently as a DAW. Either way, the end result is remarkably easy to use, very appealing on a musical level, and completely removes the time and expense that would otherwise be involved in transferring tracks from tape to hard disk! Expensive, yes, but it provides a fabulous and ingenious solution to a problem that many people hadn't even thought about!  


There are no other products that can match the CLASP in terms of integration, speed, simplicity or convenience.

Published May 2012

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