MCM Electronics

Balanced / Unbalanced Line Level Converter By MCM Custom Audio (555-8485) MCM Part #555-8485

5 stars 16 ratings and 15 reviews
MSRP: $79.95
You Save: $39.96 (50 %)
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Specifications Top

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.

Anyone that has attempted to use commonly available RCA-to-XLR adapters 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 adapters, 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.

    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 adapter included
  • Dimensions: 1-3/4" (H) x 5-5/8" (W) x 3-5/8" (D)

    Part Numbers
    MCM Part #:555-8485
    MCM Custom Audio Part #:555-8485
    Package Specifications & Dimensions
    Weight:1.75 lbs.
    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
  • Product Reviews Top

    • by kpackard

      on 7/5/2017

      Great solution to classic problem!

      Overall: 5 out of 5

      This box works great. I have used it with various mixers and powered speakers that typically end up remotely located to help make public address/music for crowds gathered for charity fund-raising events. It has never let me down and the volume control makes a simple way to control the volume to the powered speakers; of course the mixer can serve the same purpose, but when using a variety of mixers, this control is a one-stop-shop for controlling the volume. The mixers I have are single-ended outputs and usually have a short distance connection to the input of a power amp, however, with the powered speakers located remotely, this unit fills the void of single-ended (unbalanced) to differential (balanced) for noise-free audio signal transfer.

    • by KBNR_FM88.3

      on 4/10/2017

      Love at First Decibel

      Overall: 5 out of 5

      This little wonder box is a great value for interfacing consumer gear with professional equipment! It is "plug-and-play" right out of the box with great sound quality and so convenient to use. With the ubiquitous use of computers in sound studios, an interface between the computer sound card and the professional console inputs/outputs is often needed. One 555-8485 is needed for each stereo interface and the price makes it an ideal choice.

    • by deewim

      on 8/21/2015

      Miracle for $40

      Overall: 5 out of 5

      Totally brilliant. Removes absolutely all hum, buzz and hiss from a hifi-audio system playing vinyl. The problem of the ground from the turntable is completely resolved by connecting the phono preamp to this magic box using RCA-XLR cables and getting a truly clean signal out of the other side, which is then fed by RCA cables to the amplifier. The TT earth stays with the phono preamp chassis. Having lived with this problem for so long, I could not believe my ears when I heard absolutely nothing after connecting all the bits and pieces together, switching everything on and turning up the amp to full volume. Total silence. In fact I thought it wasn't working. But when I dropped the stylus in the groove, nothing but pure music came out of the speakers. I am so impressed. I cannot recommend this line level connector highly enough.

    • by deejayrickyd

      on 8/18/2015

      Excellent Value

      Overall: 5 out of 5

      This unit is Awesome! Right out of the box I hooked it up between my laptop directly to my new Behringer iNuke NU4-6000. I had used the amp previously and I suspected I wasn't driving it sufficiently. Needless to say, the amp is indeed a beast! This unit will improve any signal that uses an RCA plug from Cell Phones to DJ Controllers! Well worth the money; The only suggestion I could give is to make it Rack-mountable.

    • by dgreath

      on 7/13/2015

      Great signal interface device

      Overall: 5 out of 5

      We had a need to interface PC audio to powered speakers and tried a number of more expensive options that could be made to work. Then I noticed this device in MCM's catalog and thought I'd give it a try. Not only did it work better but at a fraction of the cost. Anyone who has ever needed to convert XLR signals into RCA with level changes will find this a very useful device to have on the shelf or in your kit. One thing I would clarify. It has two level knobs on it--each one is stereo level, one for the XLR to RCA pair and the other for the RCA to XLR pair. They are NOT left and right volume. This makes sense and it's what you would want given what the device is designed to do. I think there may be some confusion on this point and the documentation is not all that clear on this point. I would also suggest that anyone needing to get PC audio into speakers should use one of MCM USB sound devices rather than the built in headphone jacks on the front or back of the PC. It will sound much better and be more controllable.

    • by hooviemoto87

      on 5/19/2015

      Sounds Great, Simple, Rock Solid Reliability

      Overall: 5 out of 5

      I recommend this for any professional needing a powered unbalanced to balanced converter for laptops or other consumer level equipment to professional line level. It sounds very transparent, has a lot of gain if needed, and has been running for a few years now, left on all the time, with no issues. This is a very good find and less expensive than something such as a Radial PC-DI.

    • by mark

      on 1/12/2014

      Balanced/Unbalanced audio match box.

      Overall: 5 out of 5

      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.

    • by yesman6

      on 1/6/2014

      A must have item for audiophiles !

      Overall: 4.5 out of 5

      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.

    • by installpro

      on 6/4/2013

      Rock Solid

      Overall: 5 out of 5
      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.

    • by gbrionjr

      on 4/9/2012

      Line Level Converter

      Overall: 1.5 out of 5

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

    • by spalermo

      on 1/3/2012

      Does the job in radio

      Overall: 5 out of 5

      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.

    • by sthome25

      on 5/16/2011

      I didnt need it

      Overall: 4.5 out of 5

      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.

    • by shaun.ivy

      on 2/10/2010

      Great product

      Overall: 5 out of 5

      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.

    • by NeubaumTurk_DYCA

      on 11/13/2008

      This baby works great

      Overall: 5 out of 5
      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?

    • by jturnerinc

      on 9/14/2007

      Great product!

      Overall: 5 out of 5

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