70 Volt Amplifiers
The 70-Volt diagram on the previous page illustrated an Amplifier powering an “external” 70-Volt Transformer feeding speakers connected to the line. Currently, this configuration is not as widely used anymore as manufacturers have been designing amplifiers with Main 70V Transformers “built into” the amplifier (pictured below). This is a very convenient and efficient way to drive 70-Volt speaker lines.
Many 70-Volt Speakers have Taps for 70V and 4 or 8-ohm speakers (Labeled “Thru” – see image below right). With this in mind, Amplifier Manufacturers have designed their amplifiers with both 70-Volt and 4-ohm / 8-ohm speaker outputs (see Combo Mixer / Amplifier below). 70V speakers are covered in more detail on the following pages.
The Combo Mixer / Amplifier speaker output (below) has both 4-Ohm or 70-Volt (70V) outputs available. A Combo 70V speaker (below right) has several 70V taps, and a “Thru” (which is either 4 or 8-Ohms).
70 Volt Speakers will have multiple wattage taps to choose from (see below). And most will have a “Thru” selection (which bypasses the 70 Volt transformer). This type of speaker works very well with Combo Mixer / Amplifiers (gives you the option of 70 Volt or 4 / 8 ohm outputs).
Note: Amplifiers with built-in 70V transformers are widely used so you may never have to wire or connect external 70-Volt “Main” Transformers to a “standard” Power Amplifier. Since some older 70-Volt Systems still use external 70-Volt Main Transformers powered by an amplifier – both versions have been covered to ensure the reader understands both concepts.
