While not the world’s most demanding IT test and certification, I was pleased to pass this G-Suite Administrator’s course, to prove that I can administer G-Suite. Nice!
Here are ten rather obvious steps to maintain and extend your Kindle’s battery life.
- Turn off wi-fi and or 3G when not needed
- Turn down the back-light, if you have one
- Turn off automatic page refreshing
- Put your Kindle to sleep when not in use
- Ensure your Kindle firmware is up to date
- Keep your Kindle in moderate temperatures
- Lithium-ion polymer batteries like slow, regular charges
- Don’t fully discharge the battery as a matter of course, recharge at 30 – 60%
- Take the opportunity to add or sync your books while charging
- When the Kindle is nearly fully or fully charged, remove the charging cable
As a Kindle is essentially a Linux based computer, it’s a good idea, once in a while, to power off and or restart it. The IT two-step, “switch it off and on again” works for so many things, including Kindles, if they start misbehaving.
Here’s a view of a Kindle Voyage’s battery in the process of being replaced, courtesy of ifixit.com.
I was preparing to write a long review of my newest and most favourite thing, my Kindle Voyage. However, having read Joe’e review I needn’t bother. He’s said it all and that was back at the end of 2014.
Simply put, if you want an excellent e-book reader, within the Amazon ecosphere and don’t mind paying £170 for it, then you will unlikely be disappointed.
I’ve bought a couple of valves for my new Rift Amp. I’ve played it extensively and although I don’t doubt the ones it came with will last a while, it’s always sensible to be prepared for the inevitable day on which they will fail. The amp contains a 6V6GT-STR power valve and a 12AX7 pre-amp valve. Thanks to multiple viewings of Uncle Doug’s YouTube channel, I now have a better understanding of how these little marvels work and how they’re classified.
Here’s a shot of a Tube Amp Doctor 12AX7, which is the most prevalent pre-amp valve used in guitar amps. It’s a duo-triode valve which means that it contains in one glass vacuum tube, two separate triode valves, each comprising a cathode, a control grid and a plate. You can see the gap between the two triode’s dark plates in the middle of the valve. The round “halo” at the top of the valve is the getter which collects waste products and ionized gases omitted when the valve is operating, the purpose being to keep the vacuum as clean as possible.
The 12AX7 is used as a pre-amp valve because of it’s low distortion, high quality sound reproduction, comparatively high amplification levels and production of 2nd order harmonics which are pleasing to the ear. In other words it sounds good. Many amplifiers use more than one 12AX7 in the pre-amp section to provide phase inversion, basically splitting negative and positive halves of the input signal and sending each half to a distinct power amp valve, thereby increasing the overall amplification when the circuit recombines the signal and sends it to the speaker.
Next up is a 6V6GT-STR, the power amp tube.
The shot below shows the connections from the valve’s electrodes to the pins set in the base below the glass tube, which in turn are plugged into sockets which connects them to the amplifier’s circuits. Thanks again to Uncle Doug, I now know that the 6V6GT is a beam tetrode valve. These were designed in 1930s American in part to bypass a UK patent created by a company called Mullard who had produced Pentode valves which successfully solved the problem of secondary emission. This is where the electron stream bounces off the valve’s plate, bringing about undesirable effects such as noise and oscillations.
The diagram below shows how the charged electrons flow from the heated cathode through the control grid and are bent by the beam forming plate so they pass through to the anode, in a beam tetrode.
Obviously you’ll remember your Ancient Greek and spot that a Pentode has five electrodes and a Tetrode has four; being the cathode, the control grid, the screen grid and the anode. Pentodes use a fifth element called a suppressor grid to prevent secondary emissions, while the tetrode uses the beam forming plates. The replacement of the suppressor grid, which was the patented element, with the beam plates was another successful method of removing secondary emissions. Why these are not actually counted as a fifth electrode, I’m not sure but it may have been due to the need to distinguish the valve from the copyrighted Pentode.
Beam tetrode valves were first introduced way back in 1933 and but are still widely used as power tubes in guitar amplifiers. The 6V6, as used in my Tweed 5 amp, was introduced by RCA (Radio Corporation of America) in 1937 and is used primarily because, like the 12AX7 produces a good clean sound which when pushed distorts pleasantly. My amp based on a Fender Champ circuit with its single 6V6 produces about 5W – easily enough for jamming sessions with other musicians and recording in studios and more than enough for practice for us flat-dwellers. Amps with two 6V6s used as a pair, usually push out about 15W.
Traditionally Fender used the US designed 6V6 valves, while in the 60s Marshall and Vox used the equivalent but Pentode based EL84 valves in their power amp stages. This gave rise to the still applicable main distinction for general amp sounds, into American or British sounds. US Fenders excel at bright clean tones, while Marshall have a much more woody basic tone. However it’s not an exclusive or fixed arrangement, for example my Fender Blues Junior has two EL84s which like the paired 6V6s produce about 15W.
There’s bound to be errors in the above but I find it fascinating to read about and try to work out the physics and science which enables the “art” of producing music from some wood, magnets, wound steel, resistors, capacitors, valves and controlling the electricity which binds it all together.
On checking the efficacy of my WP database tidying, I was pleased to see these graphical representations of my efforts.
This first chart shows the amount of strain my Linode installation of Ubuntu 12.04 LTS was undergoing, coping with a MySQL database weighing in close to 50 MB. The default Linode alerts caused daily warning e-mails, as the virtual drive struggled with the large amount of disk input/outputs. Removing the obsolete wp_statpress table and deleting ancient posts of little interest or merit, has clearly placed the server under less strain.
Similarly, the CPU’s processor has been having an easier time of it since the change. The increased activity at the end of the reporting period were caused by a reckless attempt to try out another theme. This was not successful for a variety of technical and aesthetic reasons, so I decided to amend the existing theme, Atahualpa.
I do like a line graph.
I’ve written before how incredibly impressed I was with Linode’s virtual servers. Well, I had a work task today which required me to flatten a CentOS installation and create a new Debian 7 install in order to provide a base for an nginx web server and a Phusion Passenger application server. It took all of 5 minutes to achieve that on the Linode. Twenty five minutes later I had upgraded the server, read, learnt about and installed ngenix and PP. All ready to go in half an hour.
Having moved my WordPress install to my Linode, on my day off, I spent some time investigating means of improving it’s speed and reducing the size of my SQL database, which had reached the humongous size of nearly 50MBs.
Looking at a number of tidy-up plugins, I realised that my site was 10 years old, had numerous entries which at best could be described as being “no longer relevant” and at worst “simply embarrassing.” So first thing I did was have a cull of posts from the first 5 years. So with 2005 – 2009 having been reduced to a slimmed down non-embarrassing selection, I optimised my database and saw that it had indeed reduced by about 3MB.
This was still rather annoying. More research lead me to a plugin called Plugins Garbage Collector. This interrogates your database and references a list of plugins. It then produces a table of the database’s contents, shows their size, suggests what plugin may have created the table and indicates whether it’s active or not. This was just what I needed. It showed me that 40MB of the database was a table called wp_statpress. This seems to have been created by Statpress plugin which tracks information about every visitor to your site, including real people and every web bot who happens to crawl through your posts and pages. Even though I long ago disabled the plugin, the table continues to track connections and continue to grow.
Garbage collector allows you to select and delete tables within your database without having to resort to the command line or applications such as PHPMyAdmin. So having already taken a back up of my database, I selected the wp_statpress table together with a few other tables I recognised as remnants from previously deleted plug-ins and clicked the delete button.
Once I’d opened my eyes again, I could still login to my site and everything seemed fine. I backed up my database to a new directory and was pleased to see that it was now down to a manageable 7MB. My server and I are now happier with the lean and speedier database.