[LAU] General Audio question - soft recording and bad SNR?

Oon-Ee Ng ngoonee.talk at gmail.com
Mon Jul 28 09:30:08 UTC 2014


On Fri, Jul 18, 2014 at 6:22 PM, Fons Adriaensen <fons at linuxaudio.org> wrote:
> On Fri, Jul 18, 2014 at 10:14:36AM +0000, Fons Adriaensen wrote:
>> On Fri, Jul 18, 2014 at 09:17:39AM +0800, Oon-Ee Ng wrote:
>>
>> > The maximum volume I get from my Shure SM75 seems very low. The result
>> > of this is when I normalize I get fairly significant background hum.
>>
>> If this is really hum - a constant low frequency drone like sound -
>> then the first thing to check is the cable.
>>
>> Or is it noise - a hissy sound with no particular frequency ?
>> The UA25 is not really low noise, but for speaking close to the
>> mic it should be perfectly OK.
>>
>> Could you make a short (30 second or so) example available
>> somewhere ?
>
> In a later post I see you have an XLR to TRS cable. This will not
> work well as the TRS input on the UA25 is attenuated before is goes
> into the preamp. You really need an XLR to XLR cable.
>


To conclude, once I got the time to do another spot of recording, the
noise is a hissy sound. After taking Lens' advise on the high-Z
(that's input 2 of the UA-25EX, as he mentioned), the volume is much
improved, enough so that I don't have to amplify the signal to get
usable output (and hence almost no audible noise). Using an XLR to XLR
cable.

Looks like a 'simple' impedance matching issue. Probably blindingly
obvious to most here (at least to Fons, Lens, and the other regulars),
but something my googling did not show up. Will file that away in
memory as something else to check in future.

Thanks all!


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