Category Archives: General

The Raspberry Pi 4 Model B: Game changer for audio?

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About a month ago the Raspberry Pi 4 was announced, pretty much blind-sighting everybody.

For the last (many) years, since the announcement of the RPi 2, we had been used to relatively minor incremental upgrades every time a new RPi came out.

Usually the new processor was a bit faster, we got WiFi and BT, then better WiFi, then faster (almost) GbE network, etc. But until now, all of these connectivity options had to be accommodated by a single USB 2.0 port on the SoC.

But this year everything changed. We got a new SoC (the BCM2711), one that finally supported an RGMII interface for a true GbE port, plus a PCI Express port that is used to give USB 3.0 & 2.0 connectivity at useful speeds.

We also got more processing speed and more RAM options, up to 4GB of fast LPDDR4 memory, dual HDMI outputs, etc.

So, all of the above specs mean that the RPi is definitely faster and more capable than ever as a desktop replacement. But is it indeed a better audio streamer for us audiophiles?

For starters, it’s been almost a month since its announcement and availability (I got my unit delivered just 3 days after its announcement) and AFAIK the well-known audio distributions do not yet support it.

Then there is the increased system complexity and power consumption that comes with the new architecture. More power consumption and more ICs usually mean more noise. More noise is never good news for audio.

So I had to do some testing. The idea was to compare the RPi 3 that I had for a couple of years now to the RPi 4.

To keep the playing field as level as possible both of them were running the exact same software (Raspbian Buster Lite, since ATM that is pretty much the only OS that supports both of the platforms) with MPD loaded and were powered by the same (excellent) Salas L-Adapter power supply.

Connection to my DAC (DIY dual AK4493, very detailed) was through USB 2.0.

The music streamed from a NAS box over Ethernet.

I had a friend over in order to at least try to have a bigger sample size (of ears).

The music used was a handful of tracks that we always use for such comparisons (well known material).

We listened using the RPi3, then shut it down and booted up the RPi4, listening to the same material.

Much to our surprise, we actually preferred the sound of the RPi3!

The RPi4’s presentation had something of a “fatiguing” effect. The sound was a bit more “coarse” that that of the RPi3.

We are not talking about big differences here, but they were there. Note that my system is pretty resolving, every change to any component is audible, so YMMV.

I’m not saying that my (our) results are 100% conclusive, but in any case it seems like I’ll be going ahead with my “Audio Pi” project after all (I was considering waiting for the Compute Module 4 to come out).

Ideon Audio 3R USB Renaissance

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OK, so this small Greek company comes up with a USB regenerator gadget targeted towards audiophiles.

They claim that it improves audio dramatically. It uncovers lost detail, enhances dynamics, etc.

We’ve heard all that hi-end mumbo-jumbo before, right?

Problem is, this time the gadget actually works. I didn’t believe it either until yesterday, when I was invited to a friend’s house. Also invited were a couple of friends and this little guy:

It was accompanied by its designer, Vasilis of Ideon Audio. Mind you, this is the same Vasilis that is behind the Mamboberry DACs.
I’ve known Vasilis for the better part of 10 years now. We have exchanged some pretty sharp remarks over the years, in regards to our shared hobby, but this time I must admit that he’s really on to something.

The 3R contains a TI chip with a low jitter clock and a bunch of LDOs. It is powered by an SMPS wall-wart (rumor has it that it works even better powered by a linear power supply).
What happens is that the 3R is detected by the PC as a USB device which essentially passes-through the DAC that it is connected to. It works like a USB hub – it’s an active device but it needs no drivers.
It works its magic by regenerating the USB signal using its own low jitter clock and low noise LDO regulators.

The end result is that the DAC manages to literally extract more detail from the music stream, be it from a PC or a Mac based transfort. It doesn’t matter what your DAC is – it will make a positive difference. We tested it with a Buffalo III dac (Amanero as receiver with no isolation) and with an Aune S16 (XMOS receiver, isolation, and FPGA doing FIFO and reclocking). In all cases, introducing the 3R into the chain made for better bass definition, more resolution, and better sound stage.

This is some upsetting stuff. This made me feel the same way I felt a few weeks back when I was auditioning Salas’ system and I could hear audible differences when we changed Foobar’s buffer length from 400ms to 1000ms. This shouldn’t happen, but it does.

I don’t know.. Perhaps this is a sign that I should switch to another hobby.

In conclusion, here is a picture of Darth Vader on the 3R:

If you have a half-decent USB dac and you’re serious about audio reproduction (a.k.a. you’ve already invested in a good sound system) you should get one. Not Darth Vader, the 3R.

uRADMonitor KIT1

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About a year and a half back, while watching a mailbag clip from EEVblog, I learned about the uRADMonitor project by Radu Motisan.

The idea was to build a network of monitoring devices all around the globe that would measure radiation levels and display the results on a global map.

I noticed that there existed no data for Greece, so I thought I would fill that gap in the map. I enquired about a uRAD measuring unit but realized that it was kind of pricey (~$200 for a finished unit) so decided to wait for the Indiegogo campaign that had already been announced.

The campaign ran successfully, so I ended up owning a uRADMonitor KIT1. These are the contents of the kit:

uRAD_KIT1_01

The smaller components come nicely sorted and taped to a piece of paper:

uRAD_KIT1_02

The PCB itself is of typical quality:

uRAD_KIT1_03

You might notice that there is no silkscreen detailing the names of the components. I hope Radu changes that in future revisions of the KIT1.. It would make building the kit a lot easier.

The kit comes with a pretty nice manual. In the manual among other useful info you can find a parts placement diagram:

uRAD_KIT1_04

..and a BoM:

uRAD_KIT1_05

You will notice that I have added a couple of transistors to the bottom of the BoM. They appear to have been left out of the BoM by accident. No biggie.

To actually build the kit one has to correlate info from the parts placement diagram and the BoM. It’s not really difficult to do, but it might trouble a novice in electronics.

We start by soldering on the lowest-profile components. That means the resistors, the diodes, the inductors, the ceramic capacitors, the IC’s socket, the crystal and the push-button.
We continue with the transistors and the voltage regulator IC. Take care to follow the instructions here – R7 should be left open (no component) and R13 should be shorted.
Next up is the on/off switch and the terminals that will hold the Geiger tube.
We then move on to the piezo speaker (be careful, it is polarized!), the pin headers for the display and the ethernet board and the power input jack. Regarding the ethernet board, you will need to take care to mount it properly on the first try because it will be soldered in place. You are supposed to mount it in such a height and angle so that it is perpendicular to the main board:

uRAD_KIT1_06

You can power the board with the supplied power supply or any 5VDC power supply. The power switch turns on when it is toggled towards the Geiger tube:

uRAD_KIT1_07

The Atmega328 that comes in the kit is already pre-programmed with a unique identifier for your unit so all you have to do is connect the kit to your router with an ethernet cable and it should get an IP from your DHCP server. Once that is done, it will automatically appear on uradmonitor.com:

uRAD_KIT1_08

Here is my unit powering up:

uRADMonitor may have begun with measuring radiation levels but it is evolving into a more diverse platform, measuring several other pollution factors. I’ll be happy to incorporate more sensors into my KIT1 in due time.

New section: Στα Ελληνικά..

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No, it is not a Greek version of my blog (sorry..).

Even though I am Greek, I chose to publish this blog in English. I made that choice because I believed that its target audience would be better served this way.

Since then I have realized that I would need to occasionally post some information in Greek, and thus came to be the Greek section.

Its first page is a guide to installing the Arduino IDE for novices: Εγκατάσταση Περιβάλλοντος Arduino Για Αρχάριους