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Portable Digital Audio Recorders

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Summary

A guide to choosing and using a portable digital audio recorder, covering everything from digital dictaphones to professional field recorders. If you need a self-contained device for recording audio on location, audio note taking, or for any other scenario where recording with a computer is impractical or inconvenient, this document examines the alternatives.

Introduction

In this document we look at self-contained portable digital audio recorders - the modern equivalent of the dictaphone or field tape recorder. These recorders can vary widely in cost, features and quality, and here we compare a few representative models, and give some general guidelines and comparative specifications to help you choose a machine suitable for your needs.

Many of the new generation of smart phones also offer the ability to record audio, and we'll consider their performance when compared to purpose-built devices.

Key Facts

Portable recorders self-contained and powered by batteries

Flexible usage in many differing scenarios

Many have built-in microphone(s)

Range of recording file formats and resolutions (WAV, MP3 etc)

Varying methods, formats and capacities for storing and transferring audio data

Ideally paired with good quality monitoring headphones

Who are they for?

Portable audio recorders are an excellent tool for generating podcast material, capturing interview footage, recording seminars, lectures or group sessions, and making field and location recordings of all kinds of material. There are many potential uses in education both for teachers and students, including podcasting, recording audio feedback, recording lectures, interviews or group sessions etc.

Sound quality will be dependent on the type and features of the device you use, and its price range. The most basic handheld ‘dictaphone' style machines are fine for many types of voice capture, and for audio notetaking, as are some mobile phones; midrange all-in-one recorders can capture at surprisingly high quality, and are convenient and easy to use; top quality field recorders can deliver broadcast quality audio when paired with suitable microphones.

One of the key benefits of the portable recorder is that it frees the recordist from the PC, as well as the visual and technical distractions which can accompany it, and can thus often help capture more relaxed and spontaneous performance and voice-over, delivered in varied locations. For location recording, these machines are usually quite small and discreet, and powered by batteries.

The disadvantages include their limited on-board editing and processing features, and the extra stage of the workflow (when compared to recording directly into audio software) required to transfer recordings to a PC audio workstation. They also generally have more limited storage and audio resolution - again when compared to a fixed workstation.

For many users the advantages will outweigh the limitations, and certain projects require location recording, and hopefully this guide will help to make an informed choice when picking a recording device.

Anatomy

Portable recorders generally share these common elements:

Built-in Microphone and/or Microphone input(s)

Analogue-to-Digital (AD) converters

Storage media - built-in and/or removable

Audio output(s) (inc. headphones)

Data connection

In addition to these, there will be controls for the interface, and other features particular to specific devices.

Built-in microphones can be mono or stereo, and will have (like any microphone) particular pick-up pattern(s), frequency and dynamic responses, and ‘sound', all influenced by different factors in their design.

Microphone Inputs for external mics can be on a stereo TRS minijack (3.5mm) connection, as found on many consumer stereo microphones (e.g. Sony ECM range), or on separate XLR or jack connectors for each channel (L&R for left-right stereo)

The device's Digital converter is a significant factor in determining the resolution and quality of the recorded signal, converting the microphone's signal into digital audio, and will determine the sampling rate, bit depth etc of the recorded digital data stream.

The Digital file storage medium can take several forms: internal hard disc or solid-state memory, or removable media in the form of a memory card. The amount of storage space available (measured in Gb or Mb) will determine the total length of recordings which the device can hold

Audio outputs for monitoring recordings and listening to results, can be for headphones and/or line level output for plugging into an external amp and speakers. Some devices additionally have a small built-in speaker for playback.

Data interface - usually USB, although some devices (again mostly phones) have wi-fi and other wireless data transfer interface...

Accessories can include carrying case, microphone stand mount, windshield, memory card(s), USB cable, tabletop stands, external microphone(s), headphones

Recording formats

Most recorders offer a range of recording formats, which balance sound quality with file size.

Uncompressed - usually WAV - the native Windows uncompressed audio format - or BWF (Broadcast WAV), a suitable high-quality archive format, which is also WAV compatible. Higher bit depth and sample rates give higher audio resolution and better quality, but produce bigger files per minute of recording.

Where possible and practical within your workflow, recording in uncompressed formats and performing compression only at the final stages of preparation for delivery will preserve sound quality. More details on choosing a suitable uncompressed audio format are available in our advice document Uncompressed Audio File Formats

Compressed - usually MP3. Smaller files, but some audio degradation, especially noticeable at lower bit rates (sub 128kbps). Once on computer, MP3 files can be easily tagged with ID3 metadata.

For detailed information about the MP3 format, including its audio and metadata structure, read our User Guide to MP3

Note: Some devices (again usually phones) record to unusual audio formats such as .amr, which may not be compatible with your editing software, or easily converted to a standard format. Make sure that you choose a suitable format, or test your phone's format before using it for anything important.

Types of portable digital recorder

There follows a small selection of portable digital audio recorders, with a simple comparison of some of their specifications and features. This is by no means an exhaustive list, but hopefully is representative. JISC Digital Media do not endorse any manufacturer or product, and no endorsement should be inferred.

Digital dictaphones

Designed primarily for handheld voice recording, digital dictaphones feature built-in microphones, simple interfaces, and often extended long-play (though reduced quality) recording modes. Their emphasis on voice capture means that they are generally less suited to critical audio work, but if informal voice recording and note-taking are your main needs then they offer good value and ease of use. Note - not all dictaphones offer easy transfer of files to computer.

Olympus VN-5500PC DNS

A simple but flexible digital dictaphone and note-taker. Different quality/file size modes to suit different applications. Also includes a voice-to-text feature which claims 99% accuracy in generating text from voice recordings, though we have not had the opportunity to test this claim.

Olympus VN-5500PC DNS

Max sample rate / Bit depth: Not given - record modes HQ/SP/LP (High Quality, Short Play, Long Play)

Record formats: WMA

Inputs / outputs: Built-in mono microphone. External microphone input, headphone out

Storage: internal 512Mb

Data transfer: USB

Additional features: Voice-to-text technology, integrated speaker, adjustable playback speed

Guide price:£40

Sony ICDB600

A simple digital dictaphone with quite limited features, but which is easy to use. No data transfer facility to computer, so recordings would have to be manually re-recorded to allow editing and use within the computer domain. Most similar in this sense to a traditional tape-based dictaphone.

Sony ICDB600

Max sample rate / Bit depth: Not given

Record formats: Native (?)

Inputs / outputs: Mono microphone, headphone out

Storage: internal 512Mb

Data transfer: none

Additional features: Voice activation mode, integrated speaker

Guide price:£40

All-in one portable recorders

While generally retaining an all-in-one design, mid range portable recorders such as those listed below feature improved sound quality, stereo microphones, higher resolution recording, and often higher build quality. These machines are better suited than 'dictaphones' to capturing stereo location recordings for inclusion in projects where sound quality is more of a priority.

Edirol/Roland R-09 HR

Edirol's handheld recorders have a flexible set of features and a reputation for excellent sound and good build quality, and are popular for music recording and critical audio material.

Edirol R-09

Max sample rate / Bit depth: 48kHz /24bit

Record formats: 24-bit or 16-bit WAV; 64/96/128/160/192/224/320kbps MP3

Inputs / outputs: stereo pair of omnidirectional condenser microphones, stereo microphone input with 5V phantom power, line input (both on 3.5mm mini jack)

Storage: SD card

Data transfer: USB drag&drop

Additional features: add digital reverb to recordings (4 preset types)

Guide price:£250

Zoom H2

The Zoom H2 is a flexible recorder which has a couple of unusual features, primarily its 4 channel recording mode, using two stereo pairs of microphones, whose directionality matches the 90° forward spread, 140° rear spread of the 5.1 surround format, making it a good tool for capturing surround recordings as well as standard X/Y stereo. It can also capture in archive-standard Broadcast Wave File (BWF) format, or a range of compressed MP3 resolutions, offering extended recording time. It also offers voice-triggered recording mode and continuous pre-roll, where it will include the two seconds of audio before the record button was pressed, allowing capture of those surprise moments. A versatile set of recording options.

When working in the office or studio, the H2 can be used purely as a USB microphone, feeding its audio signal directly to a computer DAW, avoiding the need for file transfer.

Zoom H2

Max sample rate / Bit depth: 96kHz (2 channel) 48kHz (4 channel) / 24-bit

Record formats: 24-bit or 16-bit WAV & BWF; :32/40/48/56/64/80/96/112/128/160/192/224/256/320kbps MP3

Inputs / outputs: dual stereo microphones (for surround recording)

Storage: SD card

Data transfer: USB

Additional features: Digital chromatic tuner, metronome, MP3 post-encoding

Guide price:£150

M-Audio Microtrack II

The Microtrack offers a flexible feature set. Most notably includes very versatile microphone inputs; there is a stereo mini-jack microphone input, compatible with many consumer and headset style microphones, as well as the 'T-Bar' stereo microphone supplied with the Microtrack (it has no built-in microphone); alternatively, there are two separate microphone inputs for left and right channels on full size (1/4") balanced TRS jacks, which also supply 48V phantom power, allowing the use of professional condenser microphones - the only recorder in its class to offer this facility.

Max sample rate / Bit depth: 96kHz / 24-bit

Record formats: 24-bit or 16-bit WAV & BWF; 32/40/48/56/64/80/96/112/128/160/192/224/256/320kbps MP3

Inputs / outputs: 2x 1/4" TRS Jack mic/line inputs with 48V phantom power. Stereo minijack microphone input, with mini T-bar stereo mic included. SPDIF digital I/O. Headphone out. RCA phono out

Storage: SD card

Data transfer: USB

Additional features: Analogue input limiter (prevents input overload)

Guide price:£150

Field recorders

For professional and broadcast level field recording, a digital field recorder would generally be preferred. Rather than having built-in microphones, these usually have two (or more) inputs for external microphones, allowing the recordist to use their choice of microphones, suitable to the particular environment and material. These machines are typically larger and more robust than 'consumer' versions, with professional feature sets, accessories and sound quality. Their prices are therefore also correspondingly higher.

These are the sort of machines that would be used to capture location sound for commercial radio, or audio to accompany high quality video capture, live surround-sound capture etc. Microphone inputs will feature +48V phantom power, allowing use of professional condenser microphones. None of these machines have built-in microphones. For information on choosing microphones suitable for use with a field recorder, consult our Microphone Guide.

Marantz PMD671

Max sample rate / bit depth: 96kHz / 24bit

Record formats: MP3, MP2, WAV, and BWF Format Compatible

Inputs: 2x XLR microphone with 48V phantom power and individual record level controls. 2x RCA phono line level inputs.

Outputs:

Storage: Compact Flash, Microdrive cards

Data transfer: USB2

Additional features:

Guide price: £695

Fostex FR-2

Max sample rate / bit depth: 192kHz / 24bit

Record formats: BWF

Inputs: 2 x XLR microphone/line inputs with 48V phantom power and individual record level controls. SPDIF digital I/O

Outputs:RCA phono outputs, high power headphone out, integrated speaker (1W)

Storage: Compact Flash, PCMCIA

Data transfer: USB

Additional features: USB keybaord input (on second USB port)

Guide price: £1,120

Tascam DR-680

The DR680 differs from the other machines listed here in that it is a portable multitrack recorder. It can record up to 8 channels simultaneously, and with 6 microphone inputs is suitable for capturing for surround sound.

Tascam DR-680

Max sample rate / bit depth: 192kHz / 24bit (stereo track only), 96kHz/24bit (8 channel recording)

Record formats: BWF (8 channel), MP3 (4 channel simultaneous recording)

Inputs: 6 x XLR microphone/line inputs with 48V phantom power and individual record level controls. SPDIF digital I/O

Outputs: RCA phono outputs, high power headphone out, integrated speaker (1W)

Storage: SD card

Data transfer: USB

Additional features: Stereo real-time mixdown to high resolution (192kHz) master track

Guide price: £800

Monitoring

Monitoring the recorded signal before and during capture is a critical step to getting the best quality you can from your equipment.

The best tools for this job are good quality closed-back or in-ear headphones, which allow you to hear what the recorder hears, while isolating you (to an extent) from external noise. This helps when finding the best position for your recorder or microphone(s), level setting and choosing other appropriate record settings, and good quality headphones are an invaluable tool when making any type of audio recording.

Refer to our Headphone Guide for further advice on headphones.

Note (for advanced users): Off-tape monitoring

Field tape recorders often featured a third head, which allowed monitoring off the tape immediately after recording, allowing the recordist complete confidence in the integrity of the recorded signal. While a quick soundcheck and test recording, combined with input monitoring and keeping a close eye on input monitors will be fine for most uses, some sensitive environments will benefit from a digital equivalent of off-tape monitoring. This is quite an esoteric feature, and of the machines listed above, only the Fostex FR-2 offers it.

Setting levels

As with all audio recording, the ideal recording level is that which uses as much of your device's digital bandwidth as possible without exceeding it. In practical terms you want avoid the distortion caused by too loud a level, but also the excessive background noise and indistinctness of too quiet a recording.

Soundchecking with a representative sound source, combined with use of your meters to ensure a healthy signal level at the loudest points (say around 80%) should make sure that the level of your recording is in the right ballpark.

Transfer and editing

As simple recorders, these devices offer only very basic editing and re-encoding functions (if any), and realistically will need to be connected to a computer to transfer recordings for editing and delivery. Usually this is done via a USB connection. Files for transfer can be selected and transferred to the host PC, often by simple drag&drop, where the recorder appears as an external storage device.

Once on the computer, recordings can be edited and encoded in a suitable format for delivery, and tagged with relevant metadata. Tools such as Audacity can be used for these tasks, and MP3 files exported

For some informal uses, no editing, tagging or transcoding may be required, in which case the original MP3 or WAV file may be suitable for direct delivery. Be aware of file sizes when sharing audio recordings, especially high quality WAV, which can be quite large!

Normalisation

Even where no additional editing or processing of your recording is required, almost any digital recording will benefit from a process known as normalisation. Normalisation analyses the recording, and scales the waveform such that the loudest signal peak is at exactly 0dB, i.e. the maximum possible recording level. This ensures maximum loudness of playback (a desirable thing) without introduction of any distortion.

While all background noise will be similarly amplified, normalisation can go some way to fixing too quiet a recording, and will benefit even good recordings with small increases in volume.

Normalisation can be applied in Audacity, or to MP3 or AAC files with the open source tool MP3 Gain. Normalisation is a standard tool in almost all commercial audio editing software.

Smartphones - a viable alternative?

Many modern smartphones feature good quality microphones (though to date all are monophonic) and large internal storage, making them ideal candidates for use as basic portable audio recorders. Most have some facility for voice recording, and there are many third party applications for the various mobile operating systems offering audio recorders with different features, interfaces, and suitability for various applications.

If you are looking for equivalent functionality to a dictaphone style recorder, and have a smartphone, you may already have the tool you need in your pocket, with the added bonus of powerful sharing and storage facilities. Smartphones will not however match designed-for-purpose recorders for audio quality, nor do any currently offer a built-in stereo microphone.*

For more information specifically about audio on phones, read our advice document Using a Mobile Phone as an Audio Recorder

*In a quite recent development, one manufacturer now makes a good quality stereo condenser microphone - the Blue Microphones Mikey - for use with the iPhone and iPod, which, along with its matching stereo recording app Bluefire, appears to offer functionality rivalling and in some ways surpassing those of many mid-range recorders. We will be testing this system as soon as we can obtain a unit for evaluation.

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