So, we also have another device with a name as cryptic as with the speakers. It’s IAP-01. And its description may actually not only be really astounding, but also reading more than once. The IAT-01 is actually a “Photovoltaic Conditioner”. It is a device that can be connected to your audio gear, to mains, to batteries and also to the PV cells. From what I know, no one in the audio industry makes similar thing. And even if those exists somewhere, they actually belong to the realm of the DIY world rather than being in real manufacturing. So, Divaldi is a definitely an interesting case.
Because one thing is that those are ambitious products, and the other is that they also make stuff that nobody else seems to be even trying to do. However let’s go back to our amplifier and take a look at what it has to offer. AMP-05 SE is an amplifier that sports three headphone outputs, two balanced and one unbalanced (we can use only one at a time), has two line inputs (both of single-ended nature) and works in Class A (to this we will get soon enough). It’s also priced at roughly three thousand Euros. Looking through the prism of its size of the fact that it does not have XLR inputs, the asking price may seem a bit steep. Yet it also happens so in this whole audio circus that sometimes these small devices with limited functionality turn out to be really great sounding. Let’s take the Chord Qutest as a great example. Small, pricey, but when you start listening to it, it turns out to be good enough that even the price is really justified. Will this be the case with the AMP-05 SE? Let’s find out.
Divaldi AMP-05 SE – design and some interesting design choices.
Let’s start off with how it looks. Design will obviously be a matter of preference, yet what I would like to mention – the volume know that is facing upwards is really convenient to use. It’s also lit with soft white glow, which also adds to the feeling of luxury. Looking more objectively, this one particular amplifier is really well-made. Everything is perfectly fit together and it has a sturdy feeling to it as a whole. There are three headphone sockets in the front, so it seems a bit minimalistic there. On the back it’s actually much more crowded. Because apart from the two line inputs (one RCA and the other mini-jack) we can find the selector between them, power socket and power switch. And also gain switch that is presented as actual power switch. The amplifier also has some kind of an anti-vibration feet and on the bottom we will find a balance knob. Yet what’s the most interesting, we will find inside the device, since as I mentioned, the AMP-05 SE works in Class A. However this is not a Class A as many are used to, where the bias current is set to one value, but rather something else. The designer of this amplifier, Mr. Waldemar Łuczkość has quite an explanation for us here:
“The amplifier does not have a set bias – that would be typical for a simple circuits operating in Class A. Power stage here is a bridge of PNP/NPN transistors with a dynamic bias that tracks the voltage changes in the power stage output. This design choice itself widens the possibilities as for the linearity and non-linearity of the amplifier, which when used with shallow negative feedback makes a complete whole. Additionally, the circuit is complemented by the existence of artificial ground for the power stage where the loading is not galvanically connected to the power supply ground”
I even asked more regarding that bias and got another, and this time really, really elaborate answer:
“The amplifier works in Class A with a dynamic bias, with low saturation of current – compared to the classic circuits that are deeply biased. The problem starts in the classic circuit where, after exceeding a certain current (pumped into load), there’s a shutting-off of one of the transistors and ordinary change to working in Class B. AMP-05 amplifier, having dynamic bias, moves the operating point far away form the area of shutting off of any of the power transistors (compared to the classic circuits), and with additional solutions is free from typical drawbacks that many of the amplifiers on the market today have.