The Importance of Storage (14/03/2001)
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High Voltage = High Energy

The relationship of C X V reveals why tube amplifier always sound so much more powerful than transistor amplifier. Look a tube amp like the McIntosh 75 watter, the capacitor storage could be a pair of 415V 4,700 uF caps. For a powerful Japanese transistor amplifier, the capacitor storage could be a pair of 40V 20,000 uF. But after some simple computation, the energy for the tube amp is 3.9J. But the transistor amp is merely 1.6J, less than HALF the energy storage!

In most amplifiers, what really determine the sound could very well be the filter capacitors.

In the diagram on the left, is a typical American amplifier (Adcom). The filter caps are the two huge blue cans. In this amplifier, the capacitance is about 10,000uF at 63V. This powers the whole system. From calculation, we can see that the energy stored is in fact less than the typical energy stored for a 50W monoblock or stereo tube amp.

Replacing the generic capacitors usually would allow for an instant upgrade of the amplifier’s performance. This practice was once very common in the 70s and 80s for DIYers.

Usually, the Black colored and Golden wording Japanese type cpas are used for high end audio. Blue type are used for computer or switched mode applications. Recently there are many excellent capacitors for switched mode power supply. As their performance is so high, these switched mode caps could be better than the traditional ‘For Audio’ type caps. These caps could be wrapped in black or orange plastic sleeves.

If you are replacing the capacitor, not only you have to observe the Capacitance, the Voltage, you also have to look at the Temperature rating. Usually, the 105 degrees type are the first choice. The 85 degrees type are fine, but depending on the working environment, the inside of the amplifier could reach a very high temperature. If the caps get too hot, and they do get hot, their life will be severely shortened.

Dissipating Factor

Dissipating factor is determined by the function (tan delta). All electrolytic caps have a dissipating factor, and this should be as low as possible. Usually, the higher the temperature rating, the lesser the dissipating factor. The DF has an effect on the ‘quickness’ or the transparency of the sound.

Leakage

Unfortunately, all electrolytic caps have leakages. It is defined by I = K X CV. Usually K is about 0.01 to 0.03. Of course, the lower the leakage, the better. If the amplifier sound slow and blur, it could very well be the caps have very high leakages.

Importance of Storage

A man with S$1 Million in the bank, and can use it as he wish, always have more say than a man like me with only $100 in the bank. Likewise, the capacitors in the amplifier is indeed very very important. It should charge up quickly, and release the energy as fast as possible, (even though it is limited by its internal resistance).

If you examine your amplifiers, look at the pair of capacitors in it. Are they big? Are they of a high capacitance (22,000uF at least)? Are they of a high quality (RIFA, SPRAGUE, ELNA, NIPPON CHEMICON or SANGAMO)?

In fact, there is a saying, listening to Hi Fi is listening to the quality of the power supply. The quality of the power supply is very much dependent on the quality of the capacitors.

There is no need to spend a few hundred dollars buying exotic capacitors like ‘Black Gate’ or Elna ‘Cerefine’. The caps could easily cost more the amplifier! Modern switched mode power caps like RIFA are low cost and have very high performance. They can be bought at $40 a piece.

If you plan to upgrade your amplifier, then you really need not go thru the big hassle of selling it away and buy a new one. Very often, replacing the caps could yield a result equivalent to upgrading the amp. Of course, at a fraction of the cost only!

I can list some amplifiers that could be ‘DRASTICALLY IMPROVED’ by just the cap upgrade:

Audiolab, Adcom, Classe, B&K, Yamaha, Pioneer, Marantz, NAD, just to name a few.

Joe and me enjoy our Sherwood 50W amplifiers. The secret weapon was two pairs of Sangamo 22,000uf 50V computer grade capacitors to replace the old, puny caps. It is indeed important to have a good storage!

Happy Listening!

Jon Wong