Life of Pi

[despearce]

Personally I'd save my money and get a linear 2.5A psu (either kit or built) and get a real step up in performance. I've heard one that cost about £45 delivered off ebay that sounded good with a Pi...

[Fretless]

Yes, a 'real' psu is the obvious next step. Wall-warts are cheap n' easy to compare for what effect the extra wattage gives. Something with a good, solid transformer ought to improve things even more.

Will check ebay out. How are your power supplies progressing, Terry?

Edit: interesting powerbank available from TP-link, model TL-PB10400. Has 2 USB outputs, of which one is a 2A supply.. Big capacity. Maybe i'll try it, could come in usefull anyway as the holidays are approaching.

[terrybooth]

How are your power supplies progressing, Terry?

The power supply (inspired by others here) is currently a 240 v to 9 v Torroid transformer feeding the Audiowind PSU which is set to output 5v DC (this is rated at 5 amps)
http://www.ebay.co.uk/itm/161379188572? ... EBIDX%3AIT which is connected to the Pi via a USB type C connector (this doesn't look like it works with the later/current models). I did play around for a bit trying to split the power to the Pi and the Dac board but gave up. Others have succeeded despearce for one.

[Fretless]

Geek news: there is an announcement of the forthcoming Volumio version 2. The audiophile Pi OS has been rewritten from scratch and will be faster and better (they say).

Info here: https://volumio.org/introducing-volumio-2/

On another note; I have found an alternative Windows Phone 7.5 app that will control the Pi via MPD. I have been using MPDi up to now - but have just discovered 'SevenMPC' which is simpler and faster but has a handy 'Wait for Wifi' function that delays sending commands until a stable wifi connection is made.

Waiting for delivery of a 2A powerbank (5V DC battery supply) and hope to be able to report on it by the end of the week.

[Fretless]

It was a comment from Terry that got me wondering about a DC supply for the Pi. "Batteries?? " i thought, "Don't they run down??". So I started digging about a bit for some info. The problem with cheapo wall-warts is that they provide a DC supply that is 'fizzy' because the things try to compensate for the 50Hz alternating current and so the direct current that comes out is not a constant 5V but fluctuates a tiny bit along with the mains.

Powerbanks. Now if you had asked me 2 weeks ago what a powerbank is I would have given you a blank stare and guessed that it was some instrument of physical torture used in a gym. Not so, a powerbank is a rechargeable battery-pack that you carry around on your travels and use to recharge your tablet/smartphone/whatever when there is no convenient mains supply around. A nice, fat 5V, USB-friendly DC source. Further investigation led me to the TP-Link TL-PB10400, with enough capacity to recharge the average iPhone about 4 times, or an iPad once. This thing is small and has 2 USB sockets, one for a 1A supply and one for 2A, Hallelujah! Also handy for those camping trips is a built-in LED lamp that allows you to use it as a powerful(ish) torch. And not very expensive - time to try it.



So here it is running the Pi. Using the 2A mains adaptor it took about 8 hours to fully charge (there are 4 small LED's that tell you how much charge it has) and I estimate that it will power the Pi for 16-20 hours usage on a single charge. Only snag is that you cannot use the powerbank while it is charging (more expensive devices do have this possibility).

What does it sound like? Well - it feels quieter, less punchy and in-yer-face. But far more relaxed, small details come through better, more 'life', more analogue-like. I am into a serious retrospective of Krautrock pioneers Can at the moment, their wild and convoluted musical adventures become far easier to follow and understand, tracks that I used to find bizarre and incomprehensible now begin to make some sort of sense.

It came to me that this is the sort of effect that a BMU probably offers in far greater quantity. A stillness and silence that allows the electronics the rest and space to just let the music flow through.

Early days - but we're getting there slowly.

[Fretless]

One of the great/weird things about having a hobby is that every little step you take is accompanied by a certain retrospection in which you try to work out what you are doing and why it is going right or wrong.

Hifi involves a particular awareness where listening becomes the tool for judging improvement (and lack of) and the emotional impact that goes with this (the love of music) can be most addictive.

Okay then - digital audio. Anathema to some, who regard it as dry and soulless in comparison to the analogue reproduction of vinyl. Let's just forget how many current LP releases have been either recorded or at least remastered digitally. What is digital audio?

The music is stored as zeroes and ones on a CD, chip, harddisk and is read into a processor. This converts the raw data into a digital music signal (most commonly SP/DIF) and the most important thing that happens here is that the information is given a time code, allowing it to be synchronised in the next step.

CD's are encoded with a sampling frequency of 44.1 KHz - a recording sample has been made 44,100 times per second, and each of those samples has to be assembled in the right order and at the right moment for the music to be accurately reproduced.

So these chunks of data are then shunted along to a Digital-to-analogue-convertor (DAC) that reads the samples and their time codes and makes an analogue music signal out of them which is then transmitted along to an amplifier. Hey, presto. Music!!

Essential is the timing, tight synchronicity that will make the music sound 'real'.

The Rasperry Pi is a hobbyists dream; it is simple, you can muck about with it and it is very responsive to tweaking. SO why does a DC supply from a battery sound so much better than the same current from a wall-wart AC adaptor? I can only think that the (for us) tiny fluctuations as the wall-wart switches 50 times a second would be perceived in the data-stream world of Pi as enormous slow waves of interference that come along as it it trying to process signals nearly a thousand times faster.
Somewhere within the switching and transmission of data the AC-regulated pwer supply distorts the data-streams timing and we hear that as a little bit of noise/veiling in the final audio output.

A battery - or a solid linear transformer, gives a constant, non-fluctuating supply that gives the chips a clean current and allows them to perform their tasks properly.

And the music sounds really good.

Here endeth the lesson for today.

[terrybooth]

Interesting. (I really must get round to doing my own experiments ).
Can - Prog Rock or Krautrock (or both)?

[Fretless]

Interesting. (I really must get round to doing my own experiments ).
Can - Prog Rock or Krautrock (or both)?

How to describe the music of Can without angering rock critics around the globe??

Can are progressive in the same way that The Velvet Underground were - avant-garde, breaking open new spaces and creating a unique language based on their own personalities. The whole Krautrock movement was a deliberate shift away from post-war American radio pop and Rock n Roll, turning its back on those conventions. Other groups active at this time would include Faust, (pre-Virgin) Tangerine Dream, Kraftwerk and Neu!.

A more accessible Can number here: Vitamin C

Can were regarded by many Punk-era groups as a major influence and you can hear their approach in (amongst others): PIL, The Pop Group, This Heat, Pere Ubu and Sonic Youth. Recommended albums are: Future Days, Soundtracks, Ege Bamyasi, Tago Mago and Soon Over Babaluma.

Just found this - Can, live in a studio playing a track from Tago Mago. Holger Czukay should have kept his shirt on. Paperhouse - Live

[Fretless]

A question for those adept in the dark arts of 'electrickery': my Pi B+ has a 2A fuse to protect it. Is there any reason why I should try using a power supply of a higher amperage than the 2A that it will accept,?

There are 5V powerbanks available that give 2.5 and 3.1 amps (A-Solar Xtorm series) and I am wondering if there is any benefit to be gained from a higher current supply.

[Fretless]

Well - seeing as I didn't get an answer from any of the tech wizards .....

Wandered into Dixons this morning (yes, we have Dixons over here - it's not entirely the back of beyond). And spotted an A-Solar Xtorm 15000 mAh Free powerbank. "Go for it" I thought and soon had the thing home. Hey - it comes pre-charged so you can fire it up straightaway, and here it is.



Looks neat, less plasticky than the TP-link (now put into service doing what it should be used for, i.e. charging up portable things) and this one has a power button so it serves as an on/off switch for the Pi. Ha! No more fiddling with USB plugs.

This model Xtorm has 3 USB outputs, so up to three devices can be recharged/powered at the same time. Maximum output is a hefty 5V/3A (amperage drops if more devices are used) and the battery capacity is 50% more than the TP-Link which ran the Pi for about 20 hours on a full charge - so here I can expect 30 hours or so.

Difference in sound? First impressions are positive, feels like a deeper layer of 'solidity' has been achieved, even more restful and detailed. Hoping to have time this evening for a proper listen and some A/B testing. But if you are wanting to go the Powerbank route it looks initially that the more amps you can shove into the Pi, the better it will sound.