FOIL SIGNAL CAPACITORS

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Why did we move to oil filled Mylar from oil impregnated paper?

When truth be told we have been experiencing increasing problems with the failure rate of our paper in oil capacitors over the past 3 to 4 years, and despite a major research program into the causes of this increasing break down rate we have really come up with a blank. We suspect that the cause has to do with subtle changes in the chemistry of the paper, the oil or some other key part of the caps, possibly due to new environmental requirements imposed on the production of the paper, but who knows? Anyway, when it became obvious that we were unable to fully establish and rectify the cause, we decided to try Mylar. The initial experiments with oil impregnated Mylar were not sonically satisfactory, so we experimented with changing the construction to oil filled, the materials sealing the capacitor and the way we connect the foil ends to the lead out wires and voila! After some running in, the new Mylar/oil filled capacitors actually sound better in most respects than the previous generation of paper signal caps, the only real drawback is that they take nearly twice as long to run in and sound quite a bit worse than the old paper/oil type when they are new. So there you are, you don't get something for nothing!

Directionality

As you can see from the above pictures, each of our signal capacitors is marked with a line on the right; this marks the start of the foil. It is our experience that the Audio Note (UK)™ capacitors perform best when the start of the foil is "facing" the incoming signal.

Matching

We are getting an increasing number of requests for the delivery of matched pairs of both copper and silver foil capacitors, which in combination with increased use of matched pairs in the production of M6 Phono and M8 Phono pre-amplifiers has made it necessary to invest in a calibrated instrument for testing large numbers of capacitors. So, we are now able to offer a matching service at £2.00 per capacitor, order code: CAP-MATCH.

We have to make the following clear; when we match the copper foil/Mylar in oil capacitors, this is done at room temperature. Since the temperature co-efficient of these caps is fairly high, the value can change by several percent if the capacitor is close to a heat source, such as a valve or a dropper resistor. This will result in a variance in the capacitance and especially if the capacitor is in a RIAA network, will effect some minor change in the frequency response.

Component Warranty

All Audio Note (UK) capacitors are guaranteed for 3 months, with the following conditions: -

1.)    They must be returned to the factory here in the UK within 7 days of failure and no later than 3 months after purchase.

2.)    They must be accompanied with a receipt of purchase, which clearly shows a purchase date.

3.)    A note giving us a brief description of how and where the capacitor was used, how long it lasted and what the failure was.

No capacitor will be replaced without the above being complied with and there will not be exceptions made to that rule.

Photography by Jess Thomas

TIN FOIL SIGNAL CAPACITORS

In all our Level One amplifiers, such as the OTO Phono Push Pull, we use the green ERO MKP metalized polyester capacitors, these cheap and cheerful industrial capacitors have been chosen through extensive listening tests against practically every commonly available polypropylene, polycarbonate, polystyrene and polyester capacitor on the market. They are far from perfect, but from a sonic standpoint they are purely detractive, meaning that they lose information rather than add it (which every polypropylene, Teflon etc. capacitor we have ever heard does to excess).

We used to use the Jensen made aluminium foil signal caps in our Level 2 and Level 3 products, and although we were never 100% happy with the sound of these, they were less flawed and thus far better than any of the available alternatives at the time.

When we stopped using Tobias Jensen in Denmark to make our branded custom paper in oil capacitors and started our own production of copper foil paper in oil (now mylar in oil), and silver/mylar signal capacitors, we decided against reinstating the aluminium foil type for reasons of sound and instead started exploring other materials, such as tin foil and various composite foils.

The resulting dry tin foil signal caps have now been on the market for a few years, and the move away from the copper paper in oil prompted us to introduce an oil filling in the tin foil caps as well, since this then makes the processes the same across the board for the tin and the copper foil signal caps, the oil filled tin caps do offer slightly improved sound compared to the dry versions.

We are still developing the high capacitance values and they will become available at some point in the near future.

Sizes may vary, depending of can stock

COPPER FOIL SIGNAL CAPACITORS

Our own production audio signal capacitor range is now complete with the addition of the 0.39uf/630 volt capacitor. This is without question the best and most competitive range of audio signal capacitors available by some considerable margin.

The new copper and silver foil signal capacitors are available in a range that is specifically targeted at the single-ended triode amplifier market, although most values will also be excellent for other types of audio application.

Apart from the considerable improvement in price, the fact that the new copper foil capacitors are considerably better sounding than anything else - including the previous Jensen-made copper signal caps - makes them even better sonic value. The improvement is due to the use of greatly improved materials, better production methods and tighter production tolerances, plus the fact that the new caps are encased in copper instead of aluminium, glass or plastic.

Sizes may vary, depending of can stock

SILVER FOIL SIGNAL CAPACITORS

Our silver foil capacitors use a fine Mylar film instead of a paper in oil dielectric, which we have found to be the best compromise between sound and reliability. Those of you who have tried these copper encased silver foil signal capacitors can confirm the fact that the new Audio Note (UK)™ silver caps are better than anything else available, no mean feat when you also look at the prices. The only possible improvement over the Audio Note (UK)™ silver signal capacitor is an interstage transformer, which removes the need for a coupling cap altogether!

Our specially made Mylar/oil caps have an immediacy, life, colour, lack of harshness and evenness of dynamic behaviour across the frequency range (or as we prefer to call it, the harmonic envelope), which is guaranteed to brighten up your day! Recommended as replacements in old and new valve amplifiers alike (and even in the odd transistor amplifier), and the finest possible choice for DIY projects.

In line with the best environmental standards, all Audio Note™ oil filled Mylar  capacitors contain only non-toxic, biodegradable vegetable oil. The Mylar dielectric enhances longevity and sound quality, to ensure optimum performance in all areas.

These capacitors are very heavy and should be mounted with suitable care to prevent the lead out wires breaking in transport.

Sizes may vary, depending of can stock

 
 
 
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