• Skip to primary navigation
  • Skip to main content
  • Skip to primary sidebar
  • Skip to footer
Contact | 360-778-1266

Center for Hearing Loss Help

Help for your hearing loss, tinnitus and other ear conditions

  • Home
  • About Us
  • Contact
  • Reference
    • Glossary of Ear Terms
    • Drug Pronunciation Guide
    • Looping Information
    • “Learn About Hearing”
    • Useful Links
  • Museum
  • Blog
  • Shop
    • Alerting Devices
    • Assistive Listening Devices
    • Books
    • Loop Systems
    • Speechreading CDs
    • Telephones, amplified
    • Visor Cards

Two Basic Kinds of Loop Amplifiers and Why the Current Amplifier is Better for Loop Systems

There are two basic kinds of amplifiers-voltage amplifiers and current amplifiers. Amplifiers designed specifically to work with loop systems (like the Contacta HLD3) are current amplifiers. Amplifiers that drive normal loudspeaker systems are voltage amplifiers.

Current Amplifiers

If you are setting up a loop system, using a current amplifier is much easier than using a voltage amplifier because you don’t have to worry about things like matching the impedance of the amplifier to the loop like you have to do with voltage amplifiers. With current amplifiers the length of the loop is not important. Using too long a wire (too big a loop) will just result in a weaker signal. Therefore, for best results, match the size of the loop to the manufacturer’s recommendations for proper signal strength. Likewise, using a particularly small loop won’t damage or burn out your current amplifier like you can do with a voltage amplifier. Furthermore, you can use a single wire loop without any problems. This is simpler to install than a double wire loop. Order one of the best little current amplifiers, the Contacta HLD3.

Voltage Amplifiers

With voltage amplifiers, loop length, thickness of the wire and the amplifier output impedance are all important. If you do not do things right, you can burn out your amplifier. With a voltage amplifier, using too short a wire will result in too low a resistance and you can quickly burn out the amplifier unless you add a resistor of the proper value into the loop circuit. Doing this wastes power. Likewise, if you use too long a wire or too thin a wire, you may increase the resistance in your loop. Again, you are wasting power rather than putting the full power of your amplifier into the loop. In order to roughly match the resistance and impedance, it is advisable to use a double wire loop, rather than the single wire loop you can use with a current amplifier.

Making a Voltage Amplifier Loop System

If you still want to make your own loop system using a voltage amplifier and are not afraid of some technical discussion, here is how you can do it. Note: you do this at your own risk. Use the following information as a guide only. A relatively good, yet cheap voltage amplifier suitable for a home loop system is the Radio Shack 40 watt P A Amplifier (Catalog No. 32-2054) for $99.99 in the USA. This amplifier requires a total impedance of between 4 and 16 ohms. Thus, you need to design the impedance of your loop system to fall between these two values. Impedance is the sum of both the reactance of an AC circuit and its DC resistance. Both resistance and reactance are measured in ohms. Impedance is difficult to measure unless you have the right equipment and are knowledgeable in electronics. The DC resistance of the loop varies according to the following two principles. The larger the wire the less the resistance. The smaller the wire, the higher the resistance. Wire size is measured as wire “gauge.” The bigger the number, the smaller the wire. The smaller the wire gauge number, the bigger the wire. Thus 0 gauge wire is a big wire with a small resistance as compared to 18 gauge wire which is much smaller wire with a higher resistance. (As a matter of interest, 14 gauge wire is used in standard house wiring circuits.) Using an ohmmeter, you will discover that the resistance of a 200 foot loop (100 feet of speaker wire in a double loop configuration) of 18 gauge wire is about 1.4 to 1.5 ohms. The impedance of this loop will be about 5 ohms. Thus using a 200 foot 18 gauge double-wire loop should be safe for this amplifier and should produce a good signal. Learn how to make a double wire loop system.

Reader Interactions

Comments

  1. jerry says

    May 8, 2019 at 11:45 PM

    Some new good quality digital power amps are actually current amplifiers. they drive less than .5 ohms. The power supply adapts for the current draw. Plus the quality is much better.

    Reply
    • Barry E. Sharrow says

      March 18, 2020 at 12:27 PM

      Jerry,

      Having severe hearing loss, I am personally interested in experimenting with loop design. Please name and source the amplifiers of which you speak, so that I may investigate and possibly acquire a suitable amplifier for my DIY designs.

      Thanks for your help,
      Barry

      Reply

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

Primary Sidebar

Hearing Loss Research & Resources

Free Visor Cards

Download your free Visor Cards for hard of hearing or deaf people here.

Loop Systems

Loop your home or meeting room. Discover how you can hear wonderfully clear sound again when listening to the TV/radio, etc, or when listening to a speaker at a meeting.

Loop systems are one of the best-kept secrets in town. To learn more about Loop Systems and what they can do for you, click here.

Take Control of Your Tinnitus—Here’s How

If your ears ring, buzz, chirp, hiss, click or roar, you know just how annoying tinnitus can be. You do not have to put up with this racket for the rest of your life. This book teaches you many things you can do to help bring your tinnitus under your control so it no longer bothers you.

Learn More | Add to Cart—Printed | Add to Cart—eBook

Sounds Now Too Loud for You?

Hypersensitive to Sound front coverIf some (or all) normal sounds seem so loud they “blow the top of your head off”, or make you wince or jump, or cause you headaches or ear pain, or affect your balance, or result in fear or annoyance of sounds so you feel you have to avoid these sounds, this book is for you!

Learn More | Add to Cart—Printed | Add to Cart—eBook

Hearing Phantom Sounds?

When hard of hearing people begin hearing phantom voices or music, they immediately worry they are going crazy. It never crosses their minds that they are sane and are just experiencing Musical Ear syndrome.

To learn more about the strange phantom sounds of Musical Ear syndrome and what you can do about them, click here to read a comprehensive article about Musical Ear Syndrome.

Or get the book—Learn More | Add to Cart—Printed | Add to Cart—eBook

Glossary Navigation

  • Full List of Glossary Terms
  • A to Z Index

Footer

Center for Hearing Loss Help

Neil G. Bauman, Ph.D.

1013 Ridgeway Drive, Lynden,
WA 98264-1057 USA

Email: neil@hearinglosshelp.com

Phone: 360-778-1266 (M-F 9:00 AM-5:00 PM PST)

© 2025 Center for Hearing Loss Help – Help for your hearing loss, tinnitus and other ear conditions

"The wages of sin is death, but the gift of God is eternal life [which also includes perfect hearing] through Jesus Christ our Lord." [Romans 6:23]

"But know this, in the last days perilous times will come" [2 Timothy 3:1]. "For there will be famines, pestilences, and [severe] earthquakes in various places" [Matthew 24:7], "distress of nations, the sea and the waves roaring"—tsunamis, hurricanes—Luke 21:25, but this is good news if you have put your trust in the Lord Jesus Christ, for "when these things begin to happen, lift up your heads [and rejoice] because your redemption draws near" [Luke 21:28].