By Al Keltz • July 2, 2012 Election cycles are getting longer and longer and more campaigns are on the road for extended periods of time while cable and Internet news outlets hunger for content to fill their 24-hour news formats. This has resulted in an increased demand to sound companies and AV rental houses for providing press conference feeds. If you do not have at least one press mult in your inventory, you may be missing out on increased revenue opportunities. At a minimum, you need a passive multiple channel distribution box or panel. Because you never know where, or when, you will need to set up a press conference, one important design concern is its ability to keep RF and other hums and buzzes from getting into the feeds. It’s not unusual to be asked to provide feeds at an airport, government facility, arena, banquet hall, school, etc. and in many cases, your gear may be subjected to increased levels of radio traffic from police, security, and other general event radio communications. Immunity to RF is improved by utilizing high-quality transformers between the input and each output. Transformers, by design, increase the Common Mode Rejection (CMR) of your feeds and although they don’t come cheap, a well-designed mult will have them. Another consideration is, “How many channels?” Off the shelf commercially produced passive press boxes are available in configurations of six channels and up. But the most important issue for a press mult is that it be designed to have a high degree of isolation between outputs. You never know ‘WHO is going to plug WHAT into your press mult and you’ll want to avoid someone killing your feed at the last minute or worse, DURING the press conference. Even if someone dead shorts one of the outputs, it must have a negligible effect on all of the others. A 12-output passive press mult. (click to enlarge) PASSIVE PRESS UNITS, LINE GETS YOU MIC Most passive press mults utilize transformer coupling and resistive pad circuits to attain improved CMR and isolation. This usually results in at least a 40 dB drop in level from input to output and requires that you feed a strong line level signal into the press mult to get a usable mic level signal out. Most members of TV and radio crews and media reporters are experienced with this situation and are equipped to accept mic level signal into their gear. FYI – it’s not uncommon for someone to see an XLR input on a press mult and stick a mic in it expecting it to work. This results in extremely low or no output level. Remember, with passive press mults, you need to provide a line level signal from a mixer or other separate mic preamplifier to get mic level out. Read the rest of this post 1 2 Comments Leave a Reply Cancel reply Your email address will not be published. Required fields are marked *Comment Name * Email * Website Tagged with: Al Keltz Audio Basics Interconnect · all topics Subscribe to Live Sound International Subscribe to Live Sound International magazine. Stay up-to-date, get the latest pro audio news, products and resources each month with Live Sound.