Hand Made Abbasaudio capacitors

Everyone knows that capacitors in audio are the most critical element of the circuit, along with tubes. If we keep in mind an LP preamplifier, capacitors in the RIAA circuits determine the level of the preamp. In a tube power amplifier, capacitors limit the overall sound quality. In a DAC, the voice is formed by capacitors quite significantly. And if electrolytic capacitors can only be selected from products on the market, then you can try to make output capacitors yourself. Until now, I have used proven products from German manufacturers Bosch and Siemens, and they generally satisfied me. There are several offers of copper capacitors on the market, but experiments convinced me that they are inferior to German capacitors from 50 years ago in terms of musicality. Sometimes modern products demonstrate weak energy, sometimes just a lack of subtle nuances. Therefore, for the time being, I was in no rush to change my approach to choosing such critical elements. However, the time has come to move up to the next level of sound quality. I already had experience making wire copper capacitors for RIAA correction circuits, but this year I decided to go further and try making foil ones. I came across an old copper tape 60 mm wide at an auction, and I decided that it was a sign of fate. I checked the sound properties of this copper and it turned out to be quite euphonious.

The second problem that I had to resolve is that the possibilities of making a capacitor are limited by capacitor paper. I was lucky to buy a roll of old Soviet paper, 0.1 mm thick, of good quality, and this will be enough for a small batch, but in the future, I will have to look for other options.

The quality of the paper is determined by its homogeneity and impurities, and this is the second most important element of the capacitor.

The third element is impregnation. The question arose of what to impregnate the paper with after winding. Long-standing experiments with coatings led me to the conviction that wax is far from the best option, as are various types of transformer oil. Both of these impregnation methods soften and alter the sound, whereas I would like to have capacitors at the DAC output that minimally interpret the signal.

Previous comparisons of varnish and wax showed that dried varnish, composed of natural resins, meets these requirements to the maximum extent — after drying, high frequencies regain their original sharpness and clarity, while the timbre of the sound becomes more noble and beautiful. But here another problem arises — the varnish can be driven into the roll only in a vacuum chamber in the form of an alcohol solution. After this, the capacitor must be thoroughly dried, otherwise it will have a huge leak or even be damaged in first attempt to use. Drying in a conventional oven turned out to be ineffective. I had to buy a vacuum cabinet. And even in a vacuum cabinet, I had to dry the first batch for a month so that all the alcohol evaporated. Some of the capacitors still went to waste. But the rest turned out to be excellent.

However, the resulting product also has its drawbacks — so far, the maximum voltage is limited to 200 volts, and the capacity is no more than 1 μF. In my DACs, the voltage on the plate of the output stage tube in most cases does not exceed 100 volts. Therefore, this suits me today.

The final listening also showed the need to tune the capacitors — since my winding method involves the use of a hollow sleeve, there is a cavity inside that can be filled with various materials. This turned out to be extremely useful, since the capacitor can be additionally “tuned” to the sound by using inserts made of materials other than copper.

The capacitors are packaged in acrylic tubes and sealed with epoxy on both sides. I am still sure that the case of an ideal capacitor should be smooth and transparent, and the material is a secondary thing. On top, the capacitors have an additional rubber seal under the epoxy one, sealed with a special glue. A brass screw is installed at the bottom, since I am used to the German method of fastening — vertically, with a protruding screw on the bottom.

So far, the number of manufactured capacitors is only enough for use in the PSYCHE and HERMES Signature DACs. The future will show whether this project can be further developed.

In addition to copper capacitors, I also took care of a simpler product based on tin foil — the winding and assembly technology is the same, but it is impregnated with oil. These high-capacity capacitors are packed in wooden boxes sealed with epoxy resin; they do not need to be dried, which is a big plus. I use them in the new Hephaestus preamplifier.

As for wire capacitors of small values, they turned out to be an extremely useful tool for upgrading the CD transport. Having made a dozen products with a capacity from 3000 pF to 0.01 μF, I raised the level of my CD transport to an unattainable height.