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Why isn't my amp loud enough? Connecting consumer audio devices to Crown amps


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#1 Kevin Heber

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Posted 09 February 2011 - 02:43 PM

When connecting a consumer audio device such as a receiver, iPod/mp3 player, or DVD player directly to a pro audio amp, chances are that the output level on these devices will not be high enough to drive the amp to full power.  All Crown amplifiers require at least 1.4Vrms (also known as +4dBu) at the input in order to reach full power at the output.

For example, the iPod's headphone jack produces a 1.0Vrms output, which will only allow the amp to produce 50% of its rated power.

Typically, an XLR connector will carry pro audio levels.  Most mixing board outputs provide these.  The consumer audio standards, on the other hand, are the RCA connector (usually red and white) or the minijack/miniplug (used for portable audio players).  The XLR format provides a higher voltage signal as well as two copies of the signal, together called a balanced line.  The extra copy of the signal has the added benefit of being used by the amplifier to eliminate noise that gets into the audio link from lights, computers and other nearby equipment.

So the best way to convert an unbalanced, consumer audio output to the Crown's XLR, balanced pro-audio input is with an active converter box -- essentially, a little preamp placed between the unbalanced source and the amp.  A simple XLR-to-RCA adapter cable by itself will not provide any boosted or balanced signal conversion, so this usually won't provide satisfactory results.

Converters come in many varieties, but normally you will only need a simple 2-channel version.  These should cost less than $100 and can be found at any pro audio retailer.  A Google search of "unbalanced to balanced audio converter" will yield several good choices such as the ART CleanBox or Rolls ProMatch.

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#2 Mctwins

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Posted 10 March 2011 - 07:42 AM

Hi
I tested with the ART cleanbox and must say I wasn't happy with it. It was to sensitive to outer interference and static charge. When I touch the unit it send nasty spikes through the system.

I would not recommend it.

I am gonna test another unit. The Sonifex Redbox RB-UL1. I will post some result later on.
Thanks


#3 Mctwins

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Posted 25 March 2011 - 11:48 AM

Hi
I can recommend the Sonifex Redbox. rolleyes.gif  No problem at all with this unit and works great.
Thanks

#4 torres

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Posted 08 February 2012 - 12:23 AM

hello, im having the problem mentioned above with my amp i already checked the specs on the mixer i'm using and apparently i would need an active box the one mentioned here. my question is... if i get a crossover would that provide me the extra boost i need going through the crossover or do i still need the active box in the middle of the crappy mixer and crossover?

#5 pegasuspy

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Posted 28 November 2013 - 12:12 PM

You said "All Crown amplifiers require at least 1.4Vrms (also known as +4dBu)", but 4 dBu is equivalent to 1.228 Vrms, I need a mixer with output equivalent to a 6 dBU (1.546 Vrms) to operate this amplifier?

#6 dakos

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Posted 06 December 2013 - 12:42 AM

Dear pegasuspy,
You're correct about your voltage Vs dBu conversions and yes, to get the full power of an amp that needs 1.4Vrms you'll need a 5-6dBu mixer but the difference between the standard 4dBu and 1.4V is negligible so in real life there is no sonic difference.
Avi

#7 joust

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Posted 06 December 2013 - 03:06 PM

Hello Torres,

Basically, if your equipment has a 'low' (-10dB) output you may want to use a 'preamplifier' (ie. active box) to get the levels to a point where it will drive correctly the amp. And yes, if you used an electronic crossover, such as the dBx 223, you may be able to boost your mixer signal to your preferred listening level. Furthermore, other types of electronic equipment such as eqs, other xovers, may have a selectable -10, +4 dB sensitivity switch for correct input or output voltage conversions.

Alain

#8 joust

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Posted 06 December 2013 - 03:10 PM

Torres,
The answer to the question if you needed the extra active box between mixer and crossover would be yes, if the downstream equipment (crossover) wasn't equipped with a boost drive or conversion switch. You wouldn't need an active box with the dBx crossover (223) mentionned.

Alain