Anyone that has attempted to use commonly available RCA-to-XLR adaptors to send an RCA line level output from a tape deck, CD or DVD player, into an XLR input of a pro-sound amplifier or mixer, knows the problem of levels being too low.
This occurs for two reasons:
•“Line-level” signal level for consumer audio equipment is nominally -10dBV (0.32V RMS). However, “line-level” signal level for pro-sound equipment is +4dBV (1.23V RMS). Simply put, pro audio gear is looking for a 14dB higher signal level.
•XLR inputs are “balanced”, in that the positive and negative components of the signal are carried on two separate conductors (hence the use of 3-pin XLR connectors). When using standard RCA to XLR adaptors, the line level signal is supplied only to the positive pin. The negative pin is either tied to ground or left open. This absence of half of the component creates a -6dB signal deficit.
Conversely, when coming from the record output of a mixing console, or similar equipment, to send to a consumer tape deck, computer sound card or VCR, the line level is often far to hot to be usable.
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