THE ORRONOCO AUDIO DIY

Continue from the previous post about the introduction of this great affordable vacuum tube amplifier, so in this post, I will share my first modification to the layout of this amplifier. This layout modification is quite radical, because I will put balanced headphone out via 4 pin XLR in this amplifier and defeat the speakers out. The reason for this is this amplifier dimension is small enough for the headphone amplifier compare if I am using the KT88 amplifier  here . We never see Reisong build amplifier for headphones, so I should make one with this unit. Keep reading.

This Reisong A10 is a very popular vacuum tube amplifier. This is because the price is very cheap consider to it's high built quality. I got one in this second hand condition for about US$250. The amplifier condition is like new. In my opinion, it is a great small amplifier. It weight about 7 kilos and the casing is all stainless steel, beautifully mirror finished, and well arranged components inside out. In this post, I will make a review about what this amplifier gives for the price. I think, this could be the entry point for anyone who want to explore the excitement of do it yourself  audio, especially for vacuum tube amplifier. So let's begin.

This is the second implementation of the GIC filter in the DAC circuit. Previously I have using this GIC filter in the non-oversampling TDA1541 DAC and the result is smoother sound and micro detail reveal. The sound quality from this TDA1541 DAC is now extraordinary. Then in this today post, I will do the same in my Ultimate AD1865 DAC that I've previously built   here . This DAC is oversampling using CXD1144 and the low pass filter using unity-gain Sallen-key LPF. Because this Ultimate AD1865 DAC built is intended for future upgrade, so the board inside are separate into 4 module. What I will do right now is built the new analog output module using the GIC filter and replace one of the board with this new module.

My previous post is the explanation about General Impedance Converter (GIC) filter which have been long forgotten. This could be, first it is because more complicated design compare to common low pass filter and second, the digital oversampling already took the job for smoothing the audible frequency range and it doesn't require too much filter slope at the output anymore. But I really want to implement this GIC filter on my DAC built. I want to experience the result by my own. So in this post, I will make another DAC. This is the same TDA1541 non-oversampling DAC using PCM2706 as USB input to I2S converter. Then the analog output would be the GIC filter. This build schematic will be the same just like my previous TDA1541 USB DAC  here  and  here  but at that time the analog is the unity gain Sallen-key filter and this new build will be using the GIC filter. They both will be compare directly.