VII. Analog-to-digital conversion

1. In-house or outsource?
2. Equipment and software
3. Outsourcing and evaluation
4. Technical guides to conversion

If you haven't already, read the "Project Planning : Why go digital?" section of this site. The first question to ask when considering analog-to-digital conversion is whether it makes sense to commit significant resources and staff time to do it in-house, or whether outsourcing to a vendor would save time, money, and hassle. Both options are presented here to help you make an informed decision. Begin by asking the following questions:

1. How big? How many recordings will be converted and what is their total recording time? Will analog-to-digital conversion be an ongoing need, or is this a one-time project? Analog-to-digital conversion is rather labor-intensive because it must be done in real time, and the digital recording should ideally be monitored during and/or afterward to ensure sound quality and an accurate transfer.
2. Are you experienced? How familiar are you and/or your staff with working with audio and computers? How much time are you willing to invest in learning the necessary skills? Does the size and expertise of your staff match the size and degree of difficulty of the project?
3. What's the raw material? What is the sound quality of the original analog recording(s) and the format(s) and condition of the recording media? The improvement of poor sound quality in original analog recordings is a major justification for digitization. Although sound editing software includes features that enable non-professionals to increase sound levels and remove distortions and unwanted noise, some analog recordings will require more complex sound engineering. You may want to consult a professional sound technician or outsource the conversion to a vendor if the original recordings are poor quality (excessive background noise and/or low sound levels), the original playback device is no longer functioning or available onsite, the recording was made at variable or undetermined speeds, or the recording media is fragile, damaged, or in a very rare format. Richard L. Hess' website is a good resource on professional-quality tape restoration, repair, and mastering as well as archival sound engineering for a wide range of analog formats.
4. What's the final product? What are your expectations for the quality and purpose of the converted digital files? Do you want broadcast-quality audio preserved at professional archival standards, or do you just want to convert standard audio cassettes to .mp3s for streaming web audio or podcasts?
5. Do you have the right stuff? Given the number and quality of original analog recordings, as well as the level of expectations for the sound quality and long-term preservation of the converted digital files, do you already have the right computer and audio equipment and software or can it be obtained from another organization or institution? If not, are there resources to buy new equipment?

For more information on in-house versus outsourcing A/D conversion, see Daniel J. Cohen and Roy Rosenzweig, "Becoming Digital: Who Does the Digitizing?" in "Digital History: A Guide to Gathering, Preserving, and Presenting the Past on the Web".

Basic recommended equipment for analog-to-digital conversion (in order of importance for determining the quality of the final digital audio):

1. computer with internal sound card (which means the computer has speakers and audio input ports) or an external audio input device with an analog-to-digital converter (connects with USB or FireWire). The computer should have at least 256MB RAM and enough hard disk space to store large audio files (CD-quality audio in mono creates files of 300MB per hour of recording time).
2. analog audio playback device
3. connecting cabling (see the VFC guide for details on different types of audio jacks and how to connect them
   [http://www.vermontfolklifecenter.org/archive/res_digitalediting.htm#4b])
4. sound editing software (enables the computer to record audio). For more details on sound editing for oral history, see Recording interviews digitally: Software and Vermont Folklife Center, Digital Editing of Field Audio.

   Optional but recommended (in order of importance):

1. quality sound card or external audio input device
2. quality playback device, such as a cassette deck, with 1/4" RCA or other better-quality output jacks (1/8" mini-jack is lowest quality type of connection)
3. additional RAM and/or disk space
4. amplifier
5. external hard drive for storage and editing
6. audio mixing board with internal analog-to-digital converter (makes #1 unnecessary and provides a variety of analog and digital input/output options as well as easy manual control of recording and monitoring levels, and is usually packaged with good editing software)

Depending on your budget, here are some possible suggested configurations (prices checked Nov. 2007):

No budget:
Use your analog recorder as the playback device (it must have an audio output jack, even if it's just the headphone port). Use the factory sound card in your PC (it must have audio input jacks and be able to transfer to digital at a minimum rate of 16bit/44.1kHz for CD-quality audio; otherwise, you'll need an external input device). Find cabling with connectors that match the playback output and computer input jacks. Download Audacity sound editing software free.

Low budget (under $500):

1. sound card upgrade (comes with sound editing/mixing software)
   Soundblaster Audigy SE sound card, $30 (transfer rate up to 24bit/96kHz, but no RCA input jacks)
   or USB/FireWire external audio input device
   iMic , $40 (maximum transfer rate is 16bit/44.1kHz, no RCA jacks) or
   Edirol UA-1EX , $80 (transfer rate up to 24bit/96kHz, includes RCA jacks)
2. upgrade computer to at least 1GHz processor, 1GB free disk space, and 1GB RAM
3. good quality playback device (cassette deck with RCA outputs)

Medium budget ($500-$1,000):

1. sound card upgrade
   Creative Sound Blaster X-Fi Fatal1ty Pro Series PCI Interface Sound Card, $125 (24bit/96kHz, comes with sound editing/mixing software)
2. upgrade computer to at least 1GHz processor, 1GB free disk space, and 1GB RAM
3. medium quality playback device with amplifier
4. quality speakers and/or headphones to monitor recording

High budget (over $1,000):

1. high quality playback device
   Tascam Cassette Deck, 102 MK II, $330 or 202mkIV (dual cassette), $400
2. microcomputer with 200 GB internal disk, 1 GB RAM, and 2.24 GHz processor
3. USB recording/mixing board with internal 24-bit/48kHz A/D converter
   Alesis iMultiMix 8, $300 (has 8 channels and lots of knobs like a professional mixing board, variety of analog and digital input/output options, available in either USB or FireWire, has dock to record directly to iPod)
   DigiDesign MBox 2 Mini, $329 (simple to use, has RCA inputs and headphone monitor outputs, USB connection) or MBox 2, $500 (includes greater variety of analog and digital input/output options than Mini)

Sound editing software is discussed further in Recording interviews digitally: Software . Once you have all the equipment in the conversion chain set up and connected, open a new session window in the sound editing software and set the recording specifications (at least 16-bit/44.1 kHz sampling rate) and external input source of the digital audio. Begin digital recording and analog playback, monitoring the sound levels visually and listening with either headphones or speakers. It is helpful to insert time or section markers at intervals, either automatically or manually, to facilitate navigation in the digital file. This divides the recording into manageable pieces the way a music CD is divided into tracks. When you have finished recording, save the file in .wav format. See Preservation: Guidelines for naming files and subsequent sections for more information on how to archive and preserve digital files.

When selecting a vendor for outsourcing analog-to-digital conversion of audio recordings, the following questions are useful:

• How long has the vendor been in business? Are referrals available?
• What is the cost of conversion? Are rates per hour of staff time, per hour of recording time, or some other basis? If sound engineering is required, what services does the vendor offer at what additional charge? Will the vendor provide media for storing the digital files as part of the service, or is the customer expected to provide it?
• Converted digital files are typically created in .wav format. Will the vendor also create derivatives such as .mp3s for web delivery?
• What is the turnaround time?
• How will the analog recordings be safeguarded during transfer to and from the vendor and while in the vendor’s possession? What is the vendor’s policy regarding loss or damage to materials entrusted to them for conversion?
• What type of equipment will be used for the conversion? Depending on the format of analog recording, ensure that the vendor has access to the proper playback equipment and, in the case of older formats such as reel-to-reel tapes, that playback can be done at variable speeds and head configurations to accommodate variations in the original recording parameters.
• How will the digital file be monitored during conversion?
• How will the converted digital files be stored (e.g., on DVD, compact flash card, flash drive, or external hard drive)? What arrangements will need to be made for shipping or pick-up?

  An excellent detailed discussion of the pros and cons of outsourcing versus in-house digitization (and how they are combined in practice) is Robin L. Dale's "Outsourcing and Vendor Relations," available on the Northeast Document Conservation Center website. It includes detailed specifications for Requests for Information (used to identify potential vendors) and Requests for Proposals (the terms and conditions of the project used to solicit bids from vendors and to finalize a contract once a vendor is selected). There are also sample RFPs and criteria for evaluating bids from vendors and tips for working with vendors after the contract is signed. Another helpful resource on the NEDCC site is Janet Gertz' "Vendor Relations "Handbook for Digital Projects: A Management Tool for Preservation and Access".

  Whether digital files are digital-born or converted from analog, be sure to consider the question of how they will be archived, stored and monitored (see Preservation . The shelf life of CDs and other optical media is only a few years before they are very likely to deteriorate or become unstable, despite media vendor claims to the contrary. Cornell University's Lab of Ornithology offers a very comprehensive, state-of-the-art example of audio digitization and preservation methods that can be applied to oral history as well as field recordings of birdcalls.

Additional technical information on analog-to-digital conversion can be found on the following websites:

"Becoming Digital"(covers digitizing text, images, and audio) in "Digital History: A Guide to Gathering, Preserving, and Presenting the Past on the Web"

Council on Library and Information Resources,
"Capturing Analog Sound for Digital Preservation"

International Association of Sound and Audiovisual Archives Technical Committee:
http://www.iasa-web.org/IASA_TC03/TC03_English.pdf
http://www.iasa-web.org/pages/06pubs_03_new.htm

Andy Koslovos, Vermont Folklife Center, "Digital Editing of Field Audio":
http://www.vermontfolklifecenter.org/archive/res_digitalediting.htm

Library of Congress, "Audio Transfer and Image Scanning Specifications"

Matrix Oral History Tutorial, Audio Technology: A/D conversion

Eric Weig et. al, "Large Scale Digitization of Oral History: A Case Study" in D-Lib Magazine