MINIMIZING NOISE IN THE SYSTEM
Your choice of separate components is the right way to secure the best performance from a music system, but the wide-band characteristics and complexity of the best sys- tems may also not conceal the introduction of ground loops and noise pickup-especially RFI (radio frequency interference). With exceedingly high quality equipment we may become conscious of distractions that would be ig- nored on a lesser level. Careful interwiring practice will greatly reduce the likelihood of such problems.
The DH-110 is a very quiet preformer. There can be oc- casions where even the finest equipment exhibits hum or noise due to irregularities in its interconnection. The sim- ple expedient of reversing line cord plugs will often reduce hum. Listen to the hum level after each change, reversing only one cord at a time.
CAUTION: Do not indiscriminately disconnect and reconnect a power amplifier when other components are turned ON. Use the DH-110 muting circuit for protection against loud noises. With the power amp connected to a switched convenience outlet on the DH-110, turn the preamp OFF, reverse the amplifier line cord, and then turn the preamp ON.
Use connecting cables of high quality, and treat them with care. Unplug cables by grasping the connector-not the cord-to maintain good connections. We have no evi- dence that special connector platings are required, but the surfaces should be free from grease, fingerprints, or any contaminate that may prevent a firm and complete connec- tion. Some audiophiles are convinced that a good contact cleaner is an important adjunct to a high quality music sys- tem.
It does not usually reduce noise to connect each compo- nent to an ‘earth’ ground. This may even aggravate a ground loop problem, for good ‘earth’ grounds are hard to find, and unsatisfactory grounds are likely carriers of RFI.
The previous suggestions may also help reduce RFI. In difficult cases, RFI filters can be purchased for insertion between the line cord plug and the wall outlet, or a device called a ferrite bead may be installed in the phono stage by a competent technician. If you use a pre-preamplifier and find that it is RF1 sensitive, increasing the cartridge com- pensation capacitor may help (moving coil cartridges do not require a specific value), or try connecting a 0.01 mfd capacitor across the phono input jack that feeds the pre- preamplifier. Even for experienced engineers, RFI pre- sents problems which often demand that they simply ‘try and try again’.
