I’ve been waiting to get a good Power Bank so I can recharge my iPhone 6 Plus and my iPad when on the go. I didn’t want a too small Power Bank. I use my iPad quite a lot, so one of the main feature it needed was the ability to quick charge at 2.1 Ampere. After comparing the different choices I decided to get a TP-Link TL-PB10400mAh Power Bank. It didn’t take long before I had to test it out by measuring the capacity and the efficiency of the boost converter in it.
With the resurgence of good Hi-Fi, where more and more people buy good headphones and listen to a lot of music thanks to streaming, it’s sad to see the things the mastering engineers (and in the end the artist) do to music. Yet, the recordings are getting worse. Even old records that gets the “Remastered” or “Expanded” treatment doesn’t sound as good as the original. Why?
A friend of mine bought a new amplifier but he wasn’t pleased with the sound. He likes the aesthetic of older things, so he called me and asked if I could recommend a good old amplifier that could drive smaller speakers. The first one that I could think of was the venerable NAD 3020B. When I was young, this was the first affordable amplifier that actually sounded good. It’s not a power house by any means, putting out a (very conservative estimate) 2 x 20 watts. But the phono stage which is switchable for both MM and MC pickups is good, and the sound quality is excellent. So he scoured the used market and finally found a NAD 3020B. Unfortunately when he got it home, there was a loud hum from the output. So I told him to send it to me so I could fix it.
I haven’t had time to update the blog because I’ve been busy designing a new headphone amplifier. There’s been a lot of development when it comes to operational amplifiers and I was curious about how well I can get an amplifier to measure using the latest technology. The op amp I’m using still hasn’t got a development board, so I make one myself. The op amps are 5x5mm in PVQFN-20, so you need to use an SMD soldering gun or oven to be able to solder them. I simulated the circuit with both LTSpice and TINA90, but left biasing resistors and some other stuff in good old fashion though-hole components for easy testing.