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-   -   Quiet Amplifier Output... Balanced Line Problem? (http://www.diyaudio.com/forums/digital-line-level/197143-quiet-amplifier-output-balanced-line-problem.html)

ltjenkem 23rd September 2011 06:58 AM

Quiet Amplifier Output... Balanced Line Problem?
 
I have purchased my first two power amplifiers from ebay recently.

Both have arrived, one a NADY SPA 2400 the other an ASHLY CFT 1800.

I have a similar problem with both, that the output is very quiet. I have used guitar cables from an active crossover into the right left inputs on the amp. It is still quiet output... Max volume on the crossover, max on the amplifiers = barely audible.



BOTH OF THEM!

and then comes the problem solver. Putting a female 3.5 to male 1/4 adapter into an "auxilary cable" (3.5 male to 3.5 male)

Plug that into an output source ( line out on cd player )


And it is dead quiet...


Until I slightly unplug the cd player. Just a slight unplugging results in ear damaging noise at 1/4 volume on both amps. ( what I would expect all the time)




What's going on, what do I do, and do I need " Balanced input"///

adason 23rd September 2011 11:37 AM

defnitely! its wrongly wired
radio shack sells unbalanced to balanced transformer based convertors, they work fine, use those in the input
both amps are most likely just fine and will be plenty loud once hooked up correctly

Ouroboros 23rd September 2011 11:46 AM

It sounds as if you might have the 'hot' and the 'cold' inputs on the balanced feed connected together, so that you only have a common-mode signal going in.

If you are feeding a balanced input from an unbalanced source, then you really need to use a balanced cable (twin core +shield) with the 'cold' line connected to the shield at the source end only. The source then feeds the signal in on the 'hot' line, with the combined shield and 'cold' connection as the return.


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