YourITronics

Here is a project for music lovers. Although electronic tube or valve era is long passed, these devices are still used in high quality audio applications. It is true that you won’t wont find them in every home because their regarded as obsolete or too exotic. Guitar players are the ones who know and appreciate their sound as many famous guitarists use tube amps to drive their instruments. Stereo amplifiers built with tubes for hi-fi applications are still being made today and their cost can be pretty high as these amps are though to deliver high quality sound.

The reason tubes have a specific sound has to do in my opinion with the fact that tube distortion is mainly second order which is more music-friendly than the 3rd order distortion that solid state devices have. Some say this is because in tubes you control the flow of electrons and only electrons carry your information unlike transistors.

Depending on their output stage configuration tube amps can be single ended ( using only one tube working in class A) or push-pull ( like with transistor using two tubes working either class A or class AB). Because of the high output impedance of tubes they need an impedance transformer to drive the speakers. This is also the reason of their low damping factor which in combination with their usually low power output makes these amps suitable for certain types of speakers. From my experience you will need speakers with big woofers and very efficient (high SPL per watt). Also i have found that single ended amplifiers ( in class A of course) with high anode voltages applied are best when tube-like sound is desired.

Returning to the project at hand, it is a push-pull design using 6v6 pentodes connected as triodes. If you get an ultralinear output transformer you can use the 6v6 as pentodes.  The input stage using a 5965 double triode is as simple as it gets. It amplifies the signal in order to attack the final stage and provides phase inversion necessary for push-pull. The power supply uses semiconductor rectification which i find a bad thing for a tube project. There are tube diodes available for this task.

As with most audio high fidelity projects  the quality of the sound is in strong relation with the quality of the build. If you do this project just for fun then you will be happy with it just working, if you build it to experience tube sound you should take greater care at layout and components you use. Using multiple transformers is a bad thing as they introduce noise. Using one transformer with many output voltages is alot better. And screening of the transformers is a must. In the project link you will find many advices on how to build it even though the builder didn’t follow all of them.

Another thing, and a reason that keeps many diy-ers away from tubes, is that you will be dealing with high voltages. Be very careful with that. And to close this presentation with another advice don’t use it to amplify your iPod.

Hi-Fi Tube Amplifier: [Via] – [Link]

This is a AVR based joystick that connects to the PC via the USB port. The device utilizes the ATmega8, the 8-bit microcontroller from Atmel and is capable of movement on 8 axis with its analog inputs. The joystick also has 28 buttons for various uses and is fully plug and play, being immediately recognized when connected (no driver is needed).

This project is based on the Mjoy16, designed by Mindaugas Milasauskas, with a few adjustments. It is open source, both hardware and software, and the schematics, Gerber files, parts list and source code are all available for free, just follow the link below.

USB Joystick: [Link]

As i said in part 1 of this project i wanted to build a 2.1 system with good sound using most of the components i already owned and keeping the costs as low as possible.  Since the satellite speakers are not going to be used below 100Hz you can fit almost any 6.5″ woofer in there and since the box is closed. You can also use speaker filling to match the Qtc of the satellites with the subwoofer’s low pass filter. However you need to focus on voicing. Crossover between woofer and tweeter is very important and many times i found it’s making a big difference in sound. If you open most mainstream commercial speakers you will see a only a capacitor and/or resistors or something like that.

Now the subwoofer, since i don’t have much information on the drivers i have, i had to do some measurements. I found a Qts of about 0.76, Fs – 46Hz and Vas – 36l. Yes, i guess it’s made in China. No matter, it will fit a 60l (internal) box very well. The box will be sealed because the woofers are not that good and i will place it in a corner this way i will gain up to 6db in output. The thing about rooms is that their dimensions equals the wavelength for low frequency and this leads to room modes and room gain. If you have a subwoofer you might have experienced that in the room there are certain places where the bass seems to disappear. Take one step away and the bass appears again. This is due to room modes. Going lower in frequency there will be no more waves in the room and the room starts to pressurise and you have a gain going 12db per octave.

This is a generic box. You can fit in there a couple of 10 inchers too. What you must look at is strong motors in the woofers. Big magnets, thick top plates, big diameter voice coils all this will help the woofer perform in a sealed box.

Now to the build itself, first i cut the material i need using a circular saw.

After all the wood boards are cut, i use glue the boards together. Use of clamps makes things easier. Bracing the box and making the joints as solid as it possible will lead to best results. Heavy is good in subwoofers! After the glue is dried i applied the carpet on the box, corners protection, handles and connectors.

Once subwoofer construction was completed i focused on it’s amplifier. I had a car amplifier with it’s smps busted and i thought it’s just what i needed because it already has adjustable low pass filter. The corner frequency can be selected from 40Hz to about 200Hz. So i removed the defective smps and i installed a mains transformer rated 150VA which gave me +/- 35V dc after rectifier bridge. Also used 10’000uF caps for filtering. In most car amplifiers the case is used as a radiator so i had to put new radiators for the power transistors. All this and the amp board i put in a deceased Pioneer Cd player case.

Here’s the 2.1 speaker system:

Time to power the system. The satellite speakers are amplified by a JVC integrated amp and the subwoofer by it’s own amplifier with each channel to its woofer. Set the subwoofer low pass filter to about 100 – 120Hz. Sound was good however some tweaks were still needed in satellite crossover, it sounded bright. Waveguides rule! Here are frequency response graphs. Between two horizontal hard lines there is a 3db difference divided into 5 other thinner lines. The roll off after 10Khz is caused by my old mic.

– satellite speaker                           – whole system

I compared the sound of this 2.1 system with a pair of Cerwin Vega CLS-12. On the high mid-range and highs my system has more detail. I think that tweeter with the waveguide is too good to be used with this system haha. Ofcourse the CLS goes deeper and with a couple dbs louder and the big difference is seen when you turn the volume up. The 8″ woofers from my sub can’t keep up with the 12 inchers from the CLS but they do have a fair amount of excursion as you can see from this small video:

Here are the dimensions of the speaker cabinets and the crossover schematic with one modification the 6.8uF cap from the tweeter high pass filter must be changed with a 4.7uF cap.

This is it for now, I’m sure there will be more changes to the crossover and probably i will test other drivers for subwoofer as time goes by but for now i’m pleased with the result. I wanted a 2.1 system to use with my PC because the two CLS-12 speakers are too big to be placed near my desk.

Anyways if you have some woofers, drivers, tweeters, horns my advice to you is to get your tools and try and build a speaker for them and you might be surprised with their sound and you will have lots of fun in the process specially when you will blow your friends’ commercial setups.

The N97 touchscreen smartphone from Nokia was announced at the end of 2008 and was released earlier this year. With quite an impressive set of features that would satisfy even the pickiest of mobile phone users, the N97 has its share of flaws that can be very disappointing when counting on the phone to get your job done. Such a flaw is the N97′s GPS performance, which is rather poor, especially with this kind of feature-rich phone – it’s worse than N95, which is already an old model for those who follow the mobile phone industry closely. But this unfortunate defect can be remedied with some minor adjustments.

The idea of this hack is to improve the GPS performance of your N97 with ease, dismantling it with care and adding some copper wire to its antenna. Because half of the antenna wire is covered with glue, you will need to peel it first, until you get to the metal. Then, you add a copper wire (you can easily find it in all sorts of broken stuff you may have laying around) that should be placed under the GPS antenna. And that’s it, your N97 will now be more reliable since the antenna received the special high-tech upgrade presented – the addition of the copper wire!

On a side note, as the author of the original article says, I’m also baffled by the terrible performance of some of the high-end smartphones. I’m not a big fan of the GPS, but something is definitely wrong when you pay hundreds of dollars for a device that performs so bad in environments in which it was meant to function. How all of this eludes the people in charge of testing is a mystery.

Nokia N97 GPS Upgrade: [Link] – [via]

If you’re an amateur photographer and own an entry-level Nikon DSLR, you might be dissatisfied with the lack of certain features these models have, which can be quite disappointing since high-end cameras are pretty expensive. But there is something that can be done. The cameras have an infrared sensor that can be utilized with great success using a remote control, so you are able to take pictures and control your camera from afar. And here’s where the programmable remote control for Nikon comes along, enhancing the capabilities of your camera.

This project is a small remote control based on the Atmega168/328 microcontroller from Atmel. It also has a bunch of 3mm LEDs (one of them is the power LED, the rest are for different programs for the camera), capacitors, resistors, 3 switches, a battery holder and an IR LED. The device ends up using all GPIO pins of the MCU (you can find detailed schematics and a complete parts list in the link).

The code is available for reading and download and is neatly commented so you can understand what it actually does. The code makes use of Cibo Mahto’s Nikon Library. Gerber files and Eagle files are also available for download. A nice device to have when taking difficult shots with your DSLR, the programmable remote control for Nikon can be a great addition to your photo gear, helping you make great use of your DSLR.

Programmable Remote Control for Nikon: [Link]