Cloud Electronics LM-1 - Manual (Page 8)

LM-1: Installation & User Guide 7
04-11-02 V4.0
9 Solving Problems: Ground Loops & Hum
Trouble free performance can be expected if both the music and microphone sources are
derived from a double insulated mains powered unit (a unit with a two-core power cable that
has no connection to mains earth). This will ensure that the main sound system does not
have an additional power ground (earth) connection. Having more than one connection to
the ‘mains power earth’ can give rise to problems known as ‘earth loops’, which cause a
constant system ‘hum’. The ‘hum’ is usually independent of any system control settings and
will degrade system performance. If a signal source connected to the LM-1 has a three-core
connection to the mains supply, and also has a safety earth connected to the metal housing,
steps should be taken to isolate the this earth termination from the sound system. The best
way to isolate the earth termination is to use a high grade, line level audio transformer with
no link between the primary and secondary windings. Diagrams can be seen on the following
page.
10
Solving Problems: EMC Considerations
When fitted to the Cloud host unit, the LM-1 fully conforms to the relevant electromagnetic
compatibility (EMC) standards and is technically well behaved; you should experience no
operational problems under normal circumstances and no special precautions need to be
taken. If the unit is to be used within close proximity to potential sources of HF disturbance
such as high power communications transmitters and radar stations, the performance of the
mixer may be reduced. We suggest that in these circumstances the lead screens be
connected to the plate of the remote panel via suitable means and the line input leads be
kept as short as possible.
In the interest of continuing improvements Cloud Electronics Limited reserves the right to
alter specifications without prior notice.
Cloud Electronics Limited 140 Staniforth Road Sheffield S9 3HF England
Telephone +44 (0) 114 244 7051 Fax +44 (0) 114 242 5462 E-mail: [email protected]