In radio astronomy, a key limiting factor to observations made is the available bandwidth of the system. This thesis looks at two different approaches to building ultra-broadband correlators for use in radio astronomy. The first was a 2-20GHz double-sideband complex analogue correlator that was constructed before the work of this thesis. Characterisation tests are performed and a basic calibration is attempted. Both these sets of experiments show good results, with the basic calibration successfully being able to compensate for gain difference between the lags over a reduced bandwidth range used in the testing. The second approach was the investigation into different techniques for high-speed digital sampling, capable of providing equivalent bandwidths to the analogue system. The use of FPGA high-speed serial interfaces as direct 1-bit 3.125 GS/s samplers was investigated. Single-frequency sampling showed that a signal-to-noise ratio close to the theoretical maximum across the band was achieved (≈ 0.8 effective bits). Techniques were also identified to use multiple transceivers to generate a single interleaved stream at higher effective sampling rate. Two different methods were also explored for producing greater-than 1-bit sampling. A hysteresis approach was shown not to produce the desired results and a reference based sampler in the end was adopted. Finally, the interleaving and multi-bit techniques were combined to generate a single 1.5-bit 6.25 GS/s sampler. This was seen to have reduced signal-to-noise compared to the expected values. This was believed to be caused by the poor method of RF signal injection causing cross-talk between the channels and large amounts of loss. As a comparison to the direct sampling method, an external 1-bit high-speed Hittite comparator was also examined. The single-frequency experiment was repeated with a slightly higher signal-to-noise ratio found compared to the direct sampling method. This was again believed to be due to the RF environments used. From the sampling setups a four-input, six-baseline lag correlator was constructed using the direct sampling method. The entire correlator, as well as the sampling transceivers, was incorporated into a single Xilinx Virtex 5 FPGA. This was shown to have the expected response to single-frequency, broadband and noise signals. The thesis concludes with a characterisation of the RF devices used throughout the testing procedures. Several new devices were developed through the course of the experiments with the designs being documented. All the necessary components to construct IF chains for both the analogue and digital correlators described are present. This leads to simulations being made of complete IF chains, with the expected responses shown.

Digital sampling, wherein excerpts from pre-existing recordings are incorporated into a new recording, has been a vibrant and innovative manner of artistic creation since the 1960s. However, this practice has engendered complex infringement litigation, blurring the commonly understood lines that separate the musical "composition" from the "recording." The has been exacerbated by conflicting articulations as to the status of these entities as "works" within musicological discourse and conceptions of copyright law such that they would warrant protection from infringement. Furthermore, sampling has complicated the application of previously utilized principles of copyright law, such as de minimis and substantial similarity, and has not occasioned much, if any, consideration in litigation as to the artistic or creative purposes for which samples were used. This thesis considers Grand Upright Music Limited v. Warner Brothers Records, Inc., the first notable case involving digital sampling. The first two chapters offer an historical overview of the development of American copyright law and its musical purview, and proceeds to the facts and ultimate judicial ruling in this case. Through the interpretive lens of "democratic experimentalism," the remainder of the thesis proposes an alternative method for handling digital sampling cases than that of the Grand Upright court and other courts in subsequent cases. This is offered with a view to taking a more comprehensive account of the materially quantitative and artistically qualitative aspects of particular acts of sampling.

The socio-musical practice of sampling is closely associated with the re-use of pre-existing sound recordings and the technological processes of looping. These practices, based on appropriation and repetition, have been particularly common within the genres of hip-hop and Electronic Dance Music (EDM). Yet early digital sampling instruments such as the Fairlight Computer Musical Instrument (CMI) were not designed for these purposes. The technologists at Fairlight Instruments in Australia were primarily interested in the use of digital synthesis to imitate the sounds of acoustic instruments; sampling was a secondary concern. In the first half of the thesis, I follow digital sampling instruments like the Fairlight CMI and the E-mu Emulator by drawing on interviews with their designers and users to trace how they were used to sample the sounds of everyday life, loop sequenced patterns of sampled sounds, and sample extracts from pre-existing sound recordings. The second half of the thesis consists of case studies that follow the users of digital sampling technologies across a range of socio-musical worlds to examine the diversity of contemporary sampling practices. Using concepts from the field of Science and Technology Studies (STS), this thesis focuses on the ‘user-technology nexus’ and continues a shift in the writing of histories of technologies from a focus on the designers of technologies towards the contexts of use and ‘the co-construction’ or ‘mutual shaping’ of technologies and their users. As an example of the ‘interpretative flexibility’ of music technologies, digital sampling technologies were used in ways unimagined by their designers and sampling became synonymous with re-appropriation. My argument is that a history of digital sampling technologies needs to be a history of both the designers and the users of digital sampling technologies.