Review: Sony PCM-D50 Portable WAV Recorder
Pages: 1, 2, 3, 4

Got a Map?

The D50 shares something called Super Bit Mapping (SBM) with its more expensive sibling. Here's the scoop: when you select 16-bit recording, the D50 records at 20-bit resolution in order to increase the dynamic range. Normally, the extra four bits are discarded.

The side-mounted analog input and output jacks also work with mini-TOSLINK digital optical cables.

Engaging SBM recodes the data to squeeze 20 bits of information into a 16-bit word. The idea is to use a higher bit rate to reduce quantization noise and then employ noise shaping to move any grunge away from frequencies we can hear. To test this, I recorded two short clips of my guitar at 16/44.1 — one without SBM, one with. To my ears, there is a difference: the SBM track is more detailed and has less grit.

Here's an uncompressed WAV file so you can hear it for yourself. Pay attention as the guitar trails off into silence — it's smooth as silk.

• Acoustic Guitar with SBM (7.3MB WAV)

Super Bit Mapping is a great addition to the D50, but it makes one wonder: why not use it for all 16-bit files? According to Sony, it's best to turn SBM off if you'll be editing the recording in your computer. The manual doesn't explicitly state why, but it stands to reason that reprocessing the processed signal could create unwelcome artifacts as the computer wrestles with the complex math, accumulating rounding errors. SBM is a shaped dithering process, and digital gurus like Bob Katz (who is very good at math) assert it is best to not dither at each stage, but to wait until the file is ready to be mastered. In practical terms, though, I doubt most folks could hear the difference caused by this extra step.

Super Bit Mapping is disabled when you select 24-bit recording.

Menu, Please

As with most digital recorders, you'll need to dig into the menu structure sooner or later. Navigation starts with a silver button labeled with a tiny folder icon and the word "Menu." A quick press puts you in the Folder screen. Here you select one of ten folders to store your recordings — up to 99 files per folder. This makes it easy to group recordings, but you can't change the names of the folders. Keep a pencil handy so you'll be able to find things later.

Holding the Folder/Menu button for one second or more accesses the Menu ... errr, menu. Use the Fast Forward and Rewind buttons to scroll, and the Play button to make a selection. Here's a nice touch: although you set such functions as Limiter release time, Digital Pitch Control (more on this later), and Low Cut Filter cutoff in software, tiny hardware sliders on the sides or back of the recorder engage or disengage these functions. Albeit miniature, the switches are easy to find and remarkably solid. I applaud Sony's engineers for making so many vital functions accessible.

The RM-PCM1 remote ($49.95) lets you control the D50 from six feet away, simultaneously eliminating handling noise.

The Menu offers most of what you'd expect, including options for sample rate and bit depth (see the specs sidebar for types and recording times); internal or removable memory (sadly, you can't set the recorder to automatically write to both in sequence if space gets tight); clock; and formatting options. Track editing is extremely limited: the only available options are Delete All (for tracks in a selected folder) and Delete (for the currently selected track). There is no way to rename tracks, reorder them, or move them to a different folder.

However, you can split long tracks manually during recording or playback with a dedicated button on the face of the unit. Of course, if you are using the built-in mics, you run the risk of adding unwanted handling noise, as well. Sony has an optional remote control that would be useful here, but I didn't have a chance to test it.

All in all, navigation is about average. I found I constantly got the Folder screen when I wanted the Menu, and vice versa. Worse, if I accidentally backed out of a menu item, my previous choice was not retained. However, the most important functions do not require re-entering the menu once you've set the initial parameters. I'd rather put up with the D50's minor quirks than the endless menu archeology I've encountered in some other recorders.

iPlayback

You can also import MP3 files from your computer for playback. Be aware that placing your playback-only folders anywhere but the root directory renders them invisible. You also have to follow Sony's strict naming conventions and 99-song limit, although you can have up to 500 playback folders. The D50 displays album and song titles just like any other MP3 player, but you can't peek inside the folders to select individual songs. Instead, you select a folder, and then scroll through the titles one at a time using the Fast Forward and Rewind buttons. Given Sony's vast experience with personal music playback devices, I find this lack of finesse surprising.

The Outer Limits

One of the most talked about features of the expensive Sony PCM-D1 is its unique limiter. It works like this: the recorder creates two audio files during recording. One is written to memory, another — recorded 20dB down — is held in a buffer. If peaks exceed zero (i.e., maximum digital level), the recorder grabs a portion of the safety track and writes it to memory. I am happy to say that the D50 shares this feature.

Fig. 1: Instead of distorting when you record too loud, the D50 deftly swaps in a parallel safety track captured at a lower level and then normalized to zero (top arrow).

How does sound? To be honest, it works so well I didn't know it was engaged. I'm so used to hearing poorly implemented dynamics processors drastically ducking the audio and then sucking the levels back up that at first I thought my review unit wasn't functioning properly!

To test it, I purposely slammed the levels, causing the red LEDs to flash like Rudolph's nose (hey, it was just before Christmas). Listening back, I didn't hear any clipping, but I didn't hear any pumping, either. So I imported the files into my DAW and inspected the waveforms under the microscope. I expected to see a 20dB drop whenever the limiter wrote the safety track to memory; when I didn't, I contacted Sony. It turns out everything was just fine; when the safety track kicks in, it's boosted until its peaks are just below zero. (See Figure 1.)

Sure, slam the level too hard and you'll clip the waveform. And with no user-selectable threshold and only three release times (153ms, 1 second, and 1 minute) you have limited control. But the PCM-D50 limiter isn't a conventional limiter (dynamics signal processor). As a result, it doesn't require extensive parameter controls (threshold, release, hold time, etc.) to operate transparently, and that makes it easy to use. This is far and away the most useful limiter I have ever encountered on a portable device.