MCM Electronics

Balanced / Unbalanced Line Level ConverterMCM Part #: 555-8485  |  MCM Custom Audio Part #: 555-8485

Balanced / Unbalanced Line Level Converter 4.5 stars from 9 reviews.
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Balanced/Unbalanced Line Level Converter

The MCM Custom Audio Model 555-8485 Line Level Converter is an essential interface in sound systems that utilize a combination of professional audio gear, with consumer home theater equipment, PCs, laptops and portable MP3 players.

Product Description

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 -10BV (or -7.78dBU). However, “line-level” signal level for pro-sound equipment is +4dBU (or +1.78dBV). Simply put, pro audio gear is looking for a 11.78dB 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.


  • The 555-8454 Line Level Converter incorporates four independent low noise audio amplifier circuits, to provide two stereo audio channels.

    Channel 1 Accepts L/R RCA type unbalanced consumer line level inputs, electronically balances the signal, amplifies it to pro-sound line level, and supplies it to two male XLR output connections.

    Channel 2 Accepts L/R XLR balanced inputs, electronically converts them to two unbalanced channels, and provides attenuated signal to L/R RCA outputs. Both channel 1 and 2 include level controls for fine adjustment of each pair.

    Note: The advantage of higher gain, balanced audio signals with pro-sound gear is its immunity to induced noise and interference. Since the signal is balanced on two lines, any interference that is introduced on the line is cancelled out at the destination. Additionally, the higher signal level insures better signal-to-noise ratio on the line.

    Therefore, if this device is to be used on consumer equipment that is a great distance from the amplifier or mixer input, it should be located as close to the source as possible. That will allow the distance of signal to be sent at the higher, balanced level.

    Specifications
    Maximum Gain
  • Balanced-to-unbalanced: -8dB
  • Unbalanced-to-balanced: +20dB

    Maximum Output:
  • +18dB balanced
  • +12dB unbalanced

    Maximum Input:
  • +22dB balanced and unbalanced

  • Frequency response: 20Hz~20KHz
  • S/N ratio: >90dB
  • Noise Floor: -88dB
  • THD: <0.003%
  • Power requirements: 12VDC, AC adaptor included
  • Dimensions: 1-3/4" (H) x 5-5/8" (W) x 3-5/8" (D)

  • Product Reviews

    • "Balanced/Unbalanced audio match box." by mark on 1/12/2014
      Overall: 5 out of 5
      Value:
      Quality:

      I am in the AM FM broadcast business and I use these boxes by the car load.
      Best price anywhere for this or any audio level converter. Great for taking a balanced high level signal from an audio console or processor and feeding it to a streaming computer.
      I also use them to feed CD players and computers to On Air consoles at radio stations.
      Need to feed a Barix box to a commercial FM processor, just pop one of these in and the match is perfect.
      Not much to go wrong in it either. A couple of op amps in a box but no one could build one cheaper.
      I have never had a complaint about audio quality when using these in the broadcast industry.

    • "A must have item for audiophiles !" by yesman6 on 1/6/2014
      Overall: 4.5 out of 5
      Value:
      Quality:

      I bought this item because my Behringer A 500 amp had an AC hum when using
      the rca inputs . It solved that problem by allowing me to use the XLR inputs
      plus the added gain lets me get the most out of my amp
      Another use for this product is as a ground loop isolator simply patch the XLR output
      to the XLR input then use the rca jacks as your input and output.
      this worked great for me it took away all the noise and gave me gain control.
      Can't wait till I have some money to buy a second one.
      Only downside is no power switch .Not really a problem for me though
      because my audio system is on a power strip with a switch.

    • "Rock Solid" by installpro on 6/4/2013
      Overall: 5 out of 5
      Value:
      Quality:
      Top 10 Contributor

      I've used several of these, just bought two more. My situations have included connecting a PC's sound card, laptop's headphone out, iPod's headphone jack, stereo receiver's record out, television's headphone jack, tape deck's "play-out" jacks or a low cost FM tuners's line output, to a rack mounted pa amplifier's balanced inputs. In many cases, the signal had to be sent through cable runs of more than 300' (placing this converter close to the source). This thing works absolutely great in every situation. Well made, good performance, very low (undetectable) noise, with very good gain. Connecting an unbalanced RCA line source to a balanced input? This is the baby to use.

    • "Line Level Converter" by gbrionjr on 4/9/2012
      Overall: 1.5 out of 5
      Value:
      Quality:

      Instructions that come with product is incomplete. Input/Output directions is bit misleading & incorrect.

    • "Does the job in radio" by spalermo on 1/3/2012
      Overall: 5 out of 5
      Value:
      Quality:

      I have used these units in Radio where I have engineered for at least three stations. I have yet to hear of any complaints related to this product. They don't cost a lot of money like the Henry units do and they do the same thing to deliver the correct signal level that is needed.

    • "I didnt need it" by sthome25 on 5/16/2011
      Overall: 4.5 out of 5
      Value:
      Quality:

      It does exactly what it claims it does and is much cheaper than similar models however when i tried to use it I kept having level issues with my sound board or amp clipping out. I am sure i will find a use for this yet.

    • "Great product" by shaun.ivy on 2/10/2010
      Overall: 5 out of 5
      Value:
      Quality:

      Used to connect Mackie 1501 to Onkyo 600 series reciever. Before I had the Sub at max, the reciever at +12bD and the mains in the negative range to get any good bass levels. Now the sub is at mid, line level converter at mid, and the reciever at +2, my other speaker levels are in the + side now also. Shake the house base with great sound quality. Running Klipsch RF-3's, RC-3, and RS-2's for the rest of the sound. Finally a balanced sound. No hum, clean bass, good price.

    • "This baby works great" by NeubaumTurk_DYCA on 11/13/2008
      Overall: 5 out of 5
      Value:
      Quality:
      Top 10 Contributor

      I used to simply use an adapter to convert RCA to XLR, and always wondered why it didn't work right. The converter solves all of that. The impedance is correct, the level is correct, and the signal is balanced. Having a local level control can be convenient too. I use this to run from the output on my sound card, directly into the XLR inputs on a QSC amplifier. This device works perfectly, without hiss or noise, has a good rugged, well made feel, and is priced lower than comparable models from Rolls, Samson and ART. What more can you ask for?

    • "Great product!" by jturnerinc on 9/14/2007
      Overall: 5 out of 5
      Value:
      Quality:

      This little jewel works as advertised! Best price for similar devices. 5 and 5!

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    Package Specifications & Dimensions
    Weight:1.84 lbs.
    Hazardous:No
    Warranty:365 days
    Need to Return?
    Length:9 in.
    Width:5.25 in.
    Height:3.25 in.
    Shipping Information
    Extra Shipping Charge:No
    Drop Ship:No
    Catalog Pages
    Catalog/Page:

    MCM Cat 57, Page 047

    MCM Cat 56, Page 206

    PDF Reference

    Requires Adobe Acrobat Reader.

    Mfr. Info

    MCM Custom Audio Logo
    Mfr. Name:MCM Custom Audio
    Mfr. Part Number:555-8485