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Integrated Amplifier Project

Raspberry Pi Amp Intergration

DIY Audio Streamer Conversion

In recent years integrated amplifiers have evolved from the simple device with a preamplifier & power amp to something all singing and dancing like the NAD M10

From a “Do It Yourself” standpoint, especially in the audio community it is always considered that DIY is cheap and better compared with an OEM products.

So here at Solid State Audio Equipment, we will explore the possibilities of what an integrated amplifier could be today and how to start going about such a project. It’s bewildering if you think about it, the age of digital content has spawned a whole wave of components from Digital Signal Processors to Audio servers.

Raspberry Pi

Jumping right in the thick of it whilst trying to keeping it simple, could the GSJ be converted to a simple media streamer? Well yes, it could be rather simple. One of there favourite devices for most DIY’ers like to use when making a media streamer is the Raspberry Pi. The community for this device is immense. The flavour of audio player software is so vast, you can get bogged down with deciding which one to choose.

Image of Raspberry Pi
Adding a Raspberry Pi to make a audiophile Media Player.

DAC

Armed with an RPi you’ll now need a digital-to-analogue converter. Though the Pi is great at processing data on a budget (£45ish), it’s onboard sound card is pretty poor. So we need a “DAC”, which is a way to converts a digital signal (IE your source – MP3, FLAC, etc) to an analogue signal which an amplifier module can amplify the signal sufficiently to drive your speakers.

Again, the choice of DAC’s is huge, it’s amazing that such a device with a simple job can come in a vast number of flavours. There everything from USB sticks like the AudioQuest DragonFly to a portable device which Chord MoJo seems to have conquered. This choice isn’t limited with the RPi either!

Luckily Leo at Orchard Audio came to the rescue, he loaned one of their Pican Pi DAC’s. Its a HAT, which means it sits directly on top of the Pi using the GPIO pins. It’s a shame to enclosed this DAC in the GSJ Amplifier Chassis, you won’t appreciate the engineering gone into this PCB board but I guess who cares providing it does the Job?

Raspberry Pi DAC HAT
Using a Raspberry Pi DAC from Orchard Audio. The Pecan Pi DAC.

Leaving reviews to the professionals, all we’ll say about the Pican Pi is that this is a serious bit of kit for any DIY streamer. For detailed information about its capabilities & for those into “jitter noise”, here is the link.

Items used

  • GSJ Amplifier Enclosure
  • Using a pair of Pascal S-Pro2 Amp modules
  • Analog VU meters
  • Raspberry Pi – (Switching between Version 3 & 4)
  • 128Gb memory card
  • Pecan Pi DAC from Orchard Audio

Keeping It Simple

For the moment the RPi is running headless, which means there’s no screen directly attached. Instead all controls are done using an app on a smartphone.

It’s shocking at the number of media player software out there, they’re all rich in features and depending on how brave you feel the number of ways you can connect is endless.

For simplicity, Volumio (free) was chosen as is was designed for an “Audiophile” being dedicated to music only. Its connectivity includes DNLA and Airplay allowing you to play Spotify titles or even stream via you iPhone.

FINAL THOUGHTS & FUTURE PROJECTS.

As you have seen an integrated amplifier can be anything you want it to be. This example was only the tip of the iceberg, however on reflection it does make you wonder where the possibilities end? DSP integration configurable via a touch screen? Digital VU meters measuring both RMS & Peak? Multi-channel distribution?

Currently we’re investigating and doing a little design & research checking the feasibility of adding an option for replacing the front panel of the GSJ amplifier chassis. The idea is to replace the VU Meter windows from analogue to digital screens. This has the potential to enable an infinite number of possibilities whilst retaining control in a neat and tidy package.

Touch Screens on Power amplifier
Digital touch screen to control your Amplifier
Raspberry Pi touch screen conversion.
Product idea for adding Raspberry Pi with touch screens to the GSJ Amplifier Enclosure.
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General Enquires for the “GSJ Amplifier Case”

A general enquires came in asking “if and what modules can be used”. For example, Stefan from Canada wanted to know if the “GSJ Amplifer Case” could house & become a 4 channel amp using parts he’s already acquired.

Part list Stefan provided –

Luckily in this day and age computers are efficient at construction management. This means using Computer Aided Design “CAD”, all the parts can be arranged to verify what’s possible. Most Vendors provide the relevant files for their components as CAD files (.STEP), Hypex is one such brand who offer this.

Example of the CAD model. “This may take time to load”

Back to Stefan, as you can see, everything fits. However, additional machining for source terminals would be required as this is 4 channels. In addition to this, a new Aluminium plate would be needed to act as a heat sink for the SMPS.

So no major changes, just a pillar drill.

We would like to thank Sami at Micro-Audio for providing the Step files. Nice chap and quick to response via email. Keep up the good Work.