Bruce Heran writes:
It has been a while since I did anything really crazy in DIY and had it work out far above my expectations. Such is the case for the Mini Blocks. I had a lot of extra parts lying around (really a huge amount of them) and tried to figure out what I could build. Two small chassis about 5 inches by 9 inches by 2 inches (12.5 X 22.5 X 5 cm) were just begging for a project. They are just the right size for lots of things. I first thought of a pair of SET amps. But since I didn’t have any suitable single ended output transformers I nixed that idea. A preamp perhaps could be built on one of the chassis. Since I have many preamps now that didn’t really get the nod either. A pair of small push-pull amplifiers was next on the list. Maybe, but I have so many amps now that it doesn’t make sense either. Since this hobby doesn’t always have to make sense, that is what I built. Clever observers will note that each of the mini blocks is a whole lot like half of a PoddWatt amplifier
Mini Block Push-Pull EL84 (6BQ5) Valve Amplifiers - [Link]
The TDA2003 has a better performance than the TDA2002 using the same pin configuration. Additional features compared to TAD2002, requires few external components, easy assembly, is a low cost solution to an audio amplifier. A mounted amplifier with TDA2003 features protection against short pins to ground.
TDA2003 Power Amplifier - [Link]
Amplifier with TDA7294 of the ST microelectronics, you can get power up to 100W in a single chip.
TDA7294 Power Audio Amplifier 80W - [Link]
This circuit is a complete 2.1 amplifier for two satellite speakers and one subwoofer.
TDA2030 Audio Amplifier with 2.1 – 3 x 18 Watt – Subwoofer - [Link]
This is a PDF in English published in 1947 and features 45 complete schemes of tube amps, including diagram drawing material list and description of operation. Ideal for anyone interested in old amplifiers (Vintage) and the supporters as well as a modern valve amplifier. The power of the circuits presented in the book ranges from 1 to 75 Watts.
Practical Amplifier Diagrams – Tubes Audio Power Amplifiers - [Link]
Matt Renaud writes:
It’s time for a little confession: I don’t always spend as much time on my power supply designs as I should. Sometimes I get excited about my latest circuit and after looking for just the right tubes, output transformers, coupling caps, and low noise resistors, the power supply design becomes almost an after thought. Sometimes things turn out ok and there are no problems. Other times I end up with bad voltages, unacceptable power supply sag, channel crosstalk, or worst of all, a hum that I just can’t seem to eliminate. It’s at these times that I always wish I had taken a little more time to get it right.
The truth is, there is no reason to suffer power supply set backs like this. The design of basic tube power supplies is actually very straight forward. And, if we rely on the excellent work of those who’ve come before us (O. H. Schade, N. H. Roberts, D. L Waidelich, H. J. Reich), we don’t even need to tackle any advanced math or taxing mental gyrations to arrive at some truly excellent power supply designs.
Power Supply Design for Vacuum Tube Amplifiers - [Link]
This is so cool, and it has enormous potential — think nanotransponders for the Internet of Things (or sub-dermal radios). From nanotechweb: [via]
The first graphene device capable of significant voltage amplification (more than 10 dB) has been fabricated by researchers in Italy. The result confirms that the “wonder material” could compete head-on with silicon as the material of choice in electronics and is not simply limited to niche, low-voltage gain, high-frequency applications as currently thought.
The voltage amplifier (a device capable of amplifying small alternating voltage signals) is the main building block in analogue electronics. Thanks to its unique electrical and mechanical properties, graphene (a sheet of carbon atoms arranged in a honeycomb-like lattice just one atom thick) should be ideal for use in a host of technological devices – such as high-speed transistors – and in photonics. However, many scientists believe that it cannot compete with silicon in applications requiring voltage amplification, like analogue amplifiers and digital logic gates.
Even though it is their first graphene amplifier, it already shows “remarkable performance”, according to Sordan and colleagues – with a flat frequency response well exceeding the audio range (>20 kHz) and a very low total harmonic distortion (<1%).
Using Graphene to Build Nanoamplifiers - [Link]
I’ve finally gotten around to assembling a breakout board for the Skyworks SKY65116 UHF amplifier. It’s really amazing how the state of the art in RF ICs has advanced. They can still be on the expensive side ($6 at digikey), but still relatively cheap when you consider the cost of all the support parts that it takes to build an amplifier from a RF transistor. This particular amplifier has a 50 ohm input and output, and 35dB of gain. It works from 390Mhz to 500Mhz, which means its perfect for the 70cm ham band. The breakout board is stupid simple, copied directly from the evaluation board schematic in the datasheet, but I’ll include schematic and design files anyway.
SKY65116 Amplifier - [Link]
I made this portable speaker in the summer. It mixes the stereo input into a mono signal, which is then amplified. It’s powered by a six pack of AA batteries. The batteries are held in an external battery pack, so they are easy to change on the fly, without the need of a screwdriver.
Portable speaker for MP3 player - [Link]