pre-amp for UA-25 w/ SM58

Y

ykikuchi

New member
Hi Guys.

I just purchased UA-25 and connected Shure SM58. UA-25 comes with a built-in preamp however, I have to set the input voume max in order to monitor the sound. As a result, I hear so much noise. I heard that SM58 has low output and maybe UA-25's built-in preamp is not good enough...

I just want to know if there's anybody with similar problems and if preamp is the solution....

Any help would be appreciated.

Thanks


-Y
 
Hi there -

I use an Edirol UA-25 too, but I haven't had the low gain problem that you have experienced, although I'm using a condenser mic (powered with phantom voltage from the UA-25). If you have your SM-58 plugged into channel 2, be certain that the high impedance switch is disengaged. Another thing to check would be the gain settings in your PC (if you're recording to a PC or Mac) or the input trim controls on your mixer (if your UA-25 is connected to a mixer).
 
Thank you for the reply.

My mic is plugged into Channel1, and I am monitoring the input with a headphone connected to the monitor output on the right side of the front panel. To light up the limiter(green light), I have to set the channel 1 volume dial at least to 7/8 of the maximum volume and sing loud with the mic close to my mouse.

Could you tell me how you are setting the chennel 1 volume? Is it near maximum??

Thank you!

-Y
 
ykikuchi said:
Thank you for the reply.

My mic is plugged into Channel1, and I am monitoring the input with a headphone connected to the monitor output on the right side of the front panel. To light up the limiter(green light), I have to set the channel 1 volume dial at least to 7/8 of the maximum volume and sing loud with the mic close to my mouth.

Could you tell me how you are setting the channel 1 volume? Is it near maximum??

Thank you!

-Y
Click to expand...

Ahhhhhhhhhhh.....

You have to give this preamp a BIG signal to light up the limiter, which is what you are doing when you sing loudly, with your mouth close to the mic. The limiter should only "blink" on occasionally, since it is used to limit large signal peaks and "spikes, which you want to do to avoid digital clipping (distortion).

The output voltage of most dynamic mics (like the SM-58) is much lower than most condenser mics. So, I don't need to turn the SENS (input volume control) as high with a condenser mic (only around half way).

But even with the SENS control turned up near maximum, I am surprised that you hear so much noise.

What does the noise sound like? Is it a hissing sound (sssssssss)? This could be EMI noise from a poorly shielded computor, or self-noise from a defective mic, or self-noise from a defective mic preamp, or from the headphone amp in the UA-25.

Is it a humming sound (hummmmmm)? This could be caused by bad grounding from a defective mic, defective mic cable, defective USB cable, or defective headphone cable. Also, are there any light dimmers or room fans in the room or building where your equipment is connected? They can cause terrible humming noises in audio equipment.

The type of noise can help determine where the noise is coming from.

Is your UA-25 connected to a PC or Mac? If it is, is it very close to the CPU? If the CPU is not well shielded, it could be causing EMI noise.

I have not experienced any noise with my UA-25... it is very quiet. My UA-25 is connected to my Toshiba laptop with a 3 meter long USB cable, so it is 3 meters away from my laptop, and it does not pick up any noise from the CPU in the laptop. Also, I monitor the sound with high quality headphones (AKG-170M) and a high quality stereo power amp and monitors.
 
Sorry for the late response, but finally I found a reason...

It was because I was using a phone type plug. According to the spec,

UA-25
XLR type: -60 to -20 dBu
1/4 inch TRS phone type: -36 to +4 dBu

So I changed the cable to an XLR type, and I could get enough gain, even though SM58's output is -71dBu, which is a bit lower than the nomial input level. This probably is a very basic thing to check for an expert like you but this was the first time for me to set up a mic so plz forgive me.. :)

The noice was probably a hissing noice. I only hear it when I set the master and monitor volume and mic volume very high, and I believe this is okay because there are not supposed to be set that high anyways.


THanks for great advice!

-Y
 
Glad you got it all resolved. Yes - an XLR to XLR cable on the mic will allow the mic to run in balanced, low impedance mode, which will allow you to have a much longer cable length without high frequency loss or RF noise... plus the signal from the mic will be stronger. Enjoy!
 
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