bittner XB400 - Heat Dissipation and Air Conditioning; Sound Pressure and Ampliﬁer Power

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4 General Technical Information Page 101

Bittner Audio will therefore provide all data in the accustomed fashion i.e. continuous output power to

demonstrate the capacity and stability of the products. In addition, the output power will also be indicated

using the described testing method of a 33.3/66.6 ms burst signal to allow an easier comparison of different

models and brands.

However, care should be taken while dimensioning fuses and or uninterrupted power supplies (UPS). In this

case we recommend applying the power consumption of 1/8 or in the worst case 1/3 load. This also holds

for determining the cooling capacity of air conditioned technical rooms.

For all the described values, including the damping factor at 4 ohms, refer to the technical data tables

(section 5).

4.4 Heat Dissipation and Air Conditioning

The values of heat dissipation, provided by most ampliﬁer manufacturers are normally being used to answer

the question, how much cooling of a closed rack is necessary. However, whether costly air conditioning is

really necessary cannot be easily answered and may be subject to the following considerations:

• an ampliﬁer is designed to operate normally at about 25

◦

C ambient temperature without additional

cooling

• lid or bottom of the ampliﬁer chassis, as well as the side panels may not be removed to ensure a

constant and effective ﬂow of air

• good ventilation of the rack is normally sufﬁcient

• air conditioning may be necessary to provide cooling, if the hot air is not being vented from the

ampliﬁer rack

• ampliﬁers generate the most excess heat while being driven between 40 and 60 percent - no matter

which ampliﬁer class is being used. Therefore, it is reasonable and sensible to use the heat dissipation

values of approximately 1/3 power.

Please note: 1/3 power is a very high value that may occur only in case of an alarm being set off. Therefore,

in most applications, good ventilation will be more than enough to provide safe operation.

4.5 Sound Pressure and Ampliﬁer Power

The dynamic range of hearing reaches from a low whisper to the discomforting roar of a jet engine. This

range equals a ratio of 1:1024!

Experience shows that large numbers cannot be handled easily. Therefore, a system has been developed

to handle these large ratios in easy decibels. This system of number relations may be used to handle both

electrical and acoustical values. Please note the following deﬁnitions:

Doubling a voltage or a current - for example from 1 to 2 volts - corresponds to an increase of 6 dB. Dividing

the same voltage by two will result in a decrease of 6 dB.

Example: If the output level of an ampliﬁer is raised by 18 dB, the actual output voltage is 8 times higher

than the original one, and will raise from 2 to 16 volts.

Doubling the power (or loudness) follows a different ratio. An increase from 1 watt to 2 watts represents a

raise of 3 dB!

This indicates that an increase of 6 dB represents 4 times the original power (see formulas in section 4.6.5).

 2016 Bittner Audio Int. GmbH