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USB Audio DAC with Slow Down Mode

Updated: Oct 16, 2023

This is quite different to my previous few posts around neuroscience but it is related in some ways from a personal perspective in terms of tools I use for mindfulness like music. I've worked on a few audio projects just for myself over the years.

I’ve been working on a USB audio DAC (Digital to Analogue Converter) & Headphone Amp that can be used for better and more powerful listening quality than a host device - these kind of things are quite common but this also has an added feature to slow down streaming audio in real-time with reduced pitch. I’ve always enjoyed listening to a lot of music slowed as it can dramatically change the dynamics of a song and how you experience it.

The way the device works is fairly straightforward and involves storing incoming audio onto a memory chip and then replaying it out at a slower rate. The key is doing it with limited impacts to audio quality and I’ve gone through several hardware and software iterations to get it to where I’m happy.

Below are some more details on the project. I’ll be planning to launch a KickStarter campaign so I can reduce production and end-user costs mainly for early adoption and then it will be available more generally. I’m not expecting huge amounts of orders on this as it’s a very niche product so I’ve taken that into account when designing the case etc. And there's still time for changes based on feedback.

History of Slowed Down Music

Originally made popular in Houston in the 90's by DJ Screw, slowed down music has seen an increase in recent years across multiple genres where playback is often reduced by 30-40% and songs re-shared online in SoundCloud and YouTube.

Documentary on DJ Screw

I think in it's original form where songs are 'chopped' in addition to slowing them down, it's more polarizing for sure and isn't for everyone but I personally always liked it.

Example below of a song simply slowed down, people sometimes add reverb or other effects. I've also noticed slowed down music in other genres are popular now and not just hip-hop:

Although you can find selected songs online where people have altered the speed and re-uploaded there own version like above, I wanted to make something that allows for all music to be slowed down in real-time that can be used with a PC or smartphone with any streaming platform or playback software being used e.g. YouTube, Soundcloud, Spotify etc basically all audio that is output.

There are some great software approaches to doing this but they don’t cover all platforms and that coverage can vary over time, for example Spotify has recently stopped support for third party apps like Amazing Slow Downer, which has angered quite a few users as you can see in this thread on their community forums, which is now 45 pages with ongoing discussions on the topic since last August!:

The module I’ve made can be connected to a PC or smartphone (Android & Apple IOS via relevant USB to lightning adapter), and you can choose to listen to music either slowed down by 30% (not adjustable) or normal speed. The module includes a 1.5W headphone amp and a separate DAC so even at normal speed the audio sounds better than host laptops and smartphones where sound quality is often compromised for more space and inadequate spacing of the audio components.

The device is low power so does not include or require it’s own battery – it is powered by the same USB port the audio data comes from.

I’m not aware of any consumer listening device that does this kind of thing – the only product which I could think of was Kanye West’s Stem Player as it has a feature to slow down or speed up MP3s but the playback rate is much slower than what you’d normally listen to and also it can’t be used with streaming audio, you need to upload MP3 files first via Bluetooth.

For casing, it has a CNC milled aluminium top cover for durability and a high-density plastic plate underneath with good thermal properties. There are also physical mute and volume control buttons along with a button for speed change. The shape will be modified to remove sharp corners and some other minor detail changes around the look.

If you’re interested in this product or have any questions feel free to comment here or email me.

I will give more updates on the project in the coming weeks.

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