Digital direct – from cassette to smartphone

Analog is cool. Hell, analog was always cool. If you grew up any time during the last quarter of the last century, you’d remember the compact cassette.

We all knew well enough not to buy albums on cassette if you wanted the best audio quality, but for creating the ultimate mix-tape, cassettes totally rocked.

Dutch giant Philips may have invented the Compact Cassette in the early 1960s, but by the late-80s, brands such as Nakamichi and Marantz using clever tech from dbx and Dolby pushed home-recorded audio quality to high levels.

By the end, ‘metal’ tape could achieve an impressive 80dB signal-to-noise ratio (SNR) – it’d be ten years before CD burners were cheap enough to improve on that in the average PC.

If you think about it, the compact cassette was the world’s first globally-successful mass storage device.

According to USA Today, we hit ‘peak cassette’ in 1990, when we bought 442million pre-recorded music cassette tapes – you can imagine the music industry yearning for those glory days again.

Still, it’s funny how what goes around, comes around and old-school analog is making a comeback. Vinyl is hot and bands can even create new music on cassette – Dex Audio in Melbourne still does cassette duplication.

But if you think there’s no cross-over in the analog and mobile digital worlds, think again. We’re used to thinking any analog conversion requires a PC, but there’s enough low-cost tech available now to turn your Android smartphone or tablet into a stereo recording deck.

Stereo ADC

Most smartphones and tablets have a basic MEMS (micro-electromechanical system) microphone on-board, but it’s not exactly ‘high fidelity’ and certainly not stereo.

If you want maximum audio quality, you need a wired way to capture that awesome stereo analog sound – and that means a stereo analog-to-digital converter (ADC). Its job is to sample the audio at regular intervals and turn it into a stream of 16-bit stereo soundbites.

Smartphones and tablets typically don’t have this tech on-board – but virtually every Android device since Ice Cream Sandwich/4.0 has a USB host port, either directly or more commonly through a USB OTG port.

Since our last article, we’ve found a couple of new low-cost options that work with Android smartphones and tablets and, with the right software, capture analog stereo audio.

USB cassette player

casOne of the big problems with cassette decks today is maintaining them – not the electronics, the main issue is deterioration of the drive belts.

They age, go brittle and just fall apart. In an age where nothing is repaired any more, you either have to become your own electronics repair technician or just walk away.

But eBay being the Aladdin’s Cave of Tech that it is, we’ve found something of a simple compromise. The Super USB Cassette Capture is a one-stop shop cassette player with built-in stereo ADC and USB output.

It’s no Nakamichi CR-7 (if you’re used to pitch-perfect digital, this low-cost player has a bit of wow and flutter), but there are some nice touches.

First, you can use it as a Walkman – two AA batteries and you’re away. If you’re desperate, it even comes with a pair of earbuds.

But more cleverly, the rotary volume control is set before the stereo ADC, allowing you to vary the audio level before sampling if you need to. There’s also a 3VDC socket for external power.

For $18 including shipping from China, it’s not bad.

Connecting it to your phone

otgThe Super USB Cassette Capture comes with a USB Type A to miniUSB cable, so all you need is a USB Host port or, if necessary, a USB OTG cable.

Plug the USB OTG cable into your Android phone, plug the Type-A plug end of the USB cable into the OTG port and the other end into the USB cassette player.

We’ve looked at it a couple of times now, but our go-to app for this job is USB Audio Recorder PRO from eXtream.

It’s a bit pricey for a mobile app at $10, but it’s easily the best at what it does. You’ll find it on Google Play and it should work a treat. To test before you buy, grab the free trial app from here.

USB audio capture

ezBut if you’re a bit of an audio purist, the last thing you’ll want to do is put your pristine cassettes through an unknown player.

And to be honest, the mistake most people commit is thinking they need a playback device with a built-in USB port to digitise the sound.

To get the best audio quality, stick with your highest quality audio device – your Nakamichi CR-7 if you have one – and convert the analog audio to digital externally.

Personally, I use my old Creative Sound Blaster Audigy 2 NX and Extigy USB boxes for this, but depending on how fussy you are, there is a $13 option that might do the trick.

This ezcap cable features a USB Type-A plug on one end and your choice of two RCA female sockets or a 3.5mm stereo male plug on the other with a little black box in the middle housing the stereo ADC.

As for the cables, get your own stereo RCA cables to connect the line-out outputs of your cassette deck to the ADC cable and again, plug the USB end into the USB OTG cable on your phone or tablet.

recUSB Audio Recorder PRO had no trouble picking up this one, either, offering 48kHz/16-bit stereo capture straight off the bat – that’s thanks mostly to its own built-in USB Audio Class device drivers.

Android only began offering native USB Audio class drivers as of Lollipop/5.0, so having its own USB drivers means USB Audio Recorder PRO will work on just about any Android device from ICS/4.0 and up.

The one drawback with this audio capture cable is that, unlike the USB cassette player, it has no on-board audio level adjustment – and USB Audio Recorder PRO’s mixer slider doesn’t seem to work here.

That’s a bit of a problem because the cable ADC is set to handle a maximum 2Vrms CD-level input, which gets the digitised audio level up to 0dBFS.

Using a cassette deck delivering the usual but lower 775mVrms line-out level however, it ends up a bit lower on the scale than you’d ideally like.

Simulating Dolby decoding

dolThe USB cassette player also has a potential drawback – given its price, there’s no Dolby noise reduction on-board, so anything originally recorded with Dolby B, C or dbx is going to sound quite a bit ‘trebley’.

Now Dolby is (still) a heavily patented technology and there are no free Dolby decoding filters available for apps like Audacity.

Even Dolby B, the most common consumer-grade version, is quite complex and uses signal-amplitude compression filtering techniques that are difficult to replicate manually.

But thanks to Georgia State University for the basic specs, a simple, crude solution is to run the captured audio through a graphic equalizer app on your Android device.

You need something like a 6dB-per-octave low-pass filter starting at 200Hz or so with a bottom of about -10dB thereafter. It ain’t ‘genuine’, but the result gets you somewhere near the same postcode.

The cassette player also has something of an azimuth adjustment – a tiny screw to correctly align the replay head’s horizontal axis with the actual tape.

But annoyingly, the plastic shell holding the head in place covers the screw when the tape drive is in play mode, making it mostly pointless, unless you’re prepared to cut/drill some of the plastic away and then it’s all getting a bit much.

Ideally, the best option will always be to run your tapes through the deck they were recorded on, or failing that, play them back on a deck with the correct Dolby standard to get something like the original frequency response back again.

That’s where the EzCAP cable is a more workable solution. If it just had adjustable output audio level, it’d be perfect for phone use as opposed to being just ‘reasonably good’.

Still, for something that costs $13 and works with your Android smartphone or tablet, it’s not a bad result.

Audio playback app

If you’re looking for a decent Android music player, give Onkyo’s free HF Player app a go for two reasons.

First, it has a customizable graphic equalizer you can draw your desired frequency response (nice). But second, it supports playback through USB devices, so if you have something like the Burr-Brown PCM2704C USB DAC we looked at in the last article, it works a treat.

Just look up ‘Onkyo HF Player’ on Google Play. You’ll need Android 4.1/Jelly Bean minimum, though. We tested the app on our Lillopop’d Galaxy S3 and it worked nicely.

Expensive storage box

Hopefully, you can see that your tablet or smartphone is simply now just a glorified digital stream recorder and storage box.

Once the ADC process is complete, it doesn’t matter whether you plug the cable and record that stream into a PC or smartphone, the audio quality recorded via that ADC is exactly the same.

Powering the USB cassette player

There was one interesting thing we found with the cassette player – although it supports two AA cells, they don’t make the slightest bit of difference once that USB cable goes in. Whether those cells are there or not, the player consumes approximately 170mA of current measured from the USB cable.

If you have a tablet with separate power, that current load shouldn’t be a problem. Nor did we have any trouble powering the cassette player from the USB OTG cable on our Samsung Galaxy S3 smartphone and its battery.

The problem, though, is that without external power, a 170mA-drain will cut battery life by anywhere up to half, depending on your device’s battery capacity, so it’s something to keep in mind.

Recording from analog source direct to smartphone

Dubbing from an analog source to your smartphone is easy. Here’s what you do:

Step 1

Get USB Audio Recorder PRO – it’ll cost you $10 on Google Play (test the free trial app first).

You need at least ICS/Android 4.0.3 on your device, a USB OTG port and a USB-OTG cable with microUSB on one end and a Type-A USB socket on the other.

Step 2

Grab either of the stereo ADCs we’ve talked about. If not one of those, there are many USB ADCs supported by USB Audio Recorder PRO – check the web site here.

Step 3

If using a line-level ADC, connect the line-out outputs from your audio source to the ADC and plug the USB end into your phone via the USB OTG cable.

Step 4

Launch USB Audio Recorder PRO and you should see the ‘access the USB audio device’ prompt. Select OK and basic ADC specs should appear on screen.

Step 5

monPress the Monitor button on USB Audio Recorder PRO and start playing your source audio.

Select the Mixer tab on the app, try to locate the loudest passage of your source audio and set the mix level so that the peak-program (VU) meter gets close to the 0dBFS (full scale) without hitting it.

This should give you the cleanest, least-distorted sound.

Step 6

Ensure you have sufficient space for the running time of your audio source.

For WAV-format recording at 48kHz/16-bit stereo, you’ll need around 700MB per hour.

Once you’re ready to go, begin recording by hitting the red button on the app and start your audio source. Once complete, hit the stop button.

Step 7

Press the green Play button on USB Audio Recorder PRO to play back the file you’ve just recorded and check the quality.

The benefit of line-level recording is that you shouldn’t get any interference from other sources, so the quality should be as close as possible to the original.

Mixtapes live on

Nothing brings back the sounds of the 80s and 90s as you remember them quite like your old mixtapes, so if you have yours still in a box in a cupboard somewhere but nothing to play them on, $30 for a USB cassette player and a stereo audio recording app will have you rolling back the years in no time – and with no PC in sight.

What about Apple devices?

Apple has baked in support for USB audio class-compliant devices into iOS.

If you have an iPad that’s ‘pre-lightning’ (meaning it uses the old 30-pin connector), you need the iPad Camera Connection Kit, which you can pick up from Apple for $45.

And of course, there are plenty of knockoffs on eBay for under $3 including shipping.

That said, we haven’t tested the Apple side of things, but the hardest part is getting the USB host port sorted – provided the stereo ADC is class-compliant, it should work with your iPad, but your mileage my vary.