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SM58 / Pre Amp - input requested

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SM58 / Pre Amp - input requested

Postby Madman_Greg » Wed Feb 06, 2013 5:08 pm

I am going to try out the options I have. But wanted get some input as to what to consider.

Problem, my interface (Mackie Satellite) does not have sufficient gain to work effectively with my Shure SM58. I end up virtually winding the gain all the way up.

Now I know I need a pre amp to raise the level of the gain, then to feed into the Mackie at line level. All I need is to increase the gain. I am not interested in adding colour to the sound etc….

So I am looking at low cost options to resolve this.

I have a Yamaha FX500, which I dusted of and tried and it works OK, but have not tried critically yet. The A2D and D2A are 16 bit, so assume I would potentially suffer with increased noise floor.

I also have a Tascam 424 Portastudio, which I am going to try for this. Unsure on the quality of the electronics and the likely hood of noise. But will give it a go. Its quite old !!

There are a number of low cost microphone pre amps on the market. Are these worth considering.

Thanks in advance for any help / input.
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Re: SM58 / Pre Amp - input requested

Postby Sam Inglis » Wed Feb 06, 2013 5:14 pm

Madman_Greg wrote:I am going to try out the options I have. But wanted get some input as to what to consider.

Problem, my interface (Mackie Satellite) does not have sufficient gain to work effectively with my Shure SM58. I end up virtually winding the gain all the way up.
.

But do you get sufficient gain when you do this? If you do and the signal is not noisy, then surely there is no problem -- the reason the preamp has the range it does is to cope with mics of varying sensitivities. Also, many budget preamps have much of their gain range bunched up in the last few degrees of travel, so it's quite normal to need to turn the knob pretty much right up with dynamic mics.
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Re: SM58 / Pre Amp - input requested

Postby Madman_Greg » Wed Feb 06, 2013 5:27 pm

Sam Inglis wrote:
Madman_Greg wrote:I am going to try out the options I have. But wanted get some input as to what to consider.

Problem, my interface (Mackie Satellite) does not have sufficient gain to work effectively with my Shure SM58. I end up virtually winding the gain all the way up.
.


But do you get sufficient gain when you do this? If you do and the signal is not noisy, then surely there is no problem -- the reason the preamp has the range it does is to cope with mics of varying sensitivities. Also, many budget preamps have much of their gain range bunched up in the last few degrees of travel, so it's quite normal to need to turn the knob pretty much right up with dynamic mics.


The mic gets microphonic if that the right term and there is little precise control at that end of the gain knob
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Re: SM58 / Pre Amp - input requested

Postby Sam Inglis » Wed Feb 06, 2013 5:34 pm

The mic is supposed to be microphonic! I'm not quite sure what you mean -- do you get hiss or other noise on top of the signal?

Unfortunately you are unlikely to get more precise gain control with any other budget preamp. You could perhaps use a fixed-gain inline preamp like the Cloudlifter.
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Re: SM58 / Pre Amp - input requested

Postby Madman_Greg » Wed Feb 06, 2013 5:53 pm



Thanks, reading the clloudlifter blurb it talks about cable length

Is is worth trying a shorter cable, not sure on the actual length I have, but its one I used to use on stage, so is a reasonable length.
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Re: SM58 / Pre Amp - input requested

Postby Sam Inglis » Wed Feb 06, 2013 6:29 pm

Cable length is unlikely to be an issue unless you are trying to send the mic signal a hundred yards, or something. I'm still not exactly clear on what the problem is here -- in what way do your recordings not sound good?
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Re: SM58 / Pre Amp - input requested

Postby shufflebeat » Wed Feb 06, 2013 7:11 pm

When you say microphonic do you mean there's a sound of interference? If there was a dodgy earth that might account for noise and a low output. Can you try another XLR cable?
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Re: SM58 / Pre Amp - input requested

Postby James Perrett » Thu Feb 07, 2013 2:01 pm

Looks like you have a problem somewhere as the Mackie preamps should be perfectly capable of working with an SM58. Yes, you may have to turn the gain control 3/4 of the way up to get a sensible level but that will be the same with any cheap preamp.

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Re: SM58 / Pre Amp - input requested

Postby Hugh Robjohns » Thu Feb 07, 2013 2:40 pm

Madman_Greg wrote:Problem, my interface (Mackie Satellite) does not have sufficient gain to work effectively with my Shure SM58. I end up virtually winding the gain all the way up.

There's nothing fundamentally wrong with having the gain all the way up.

So what is that actual problem?

What are you trying to achieve?

What is the source and whreer have you placed the microphone relative to it?

If you are recording, what peak level are you achieving and why do you think it is inadequate?

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Re: SM58 / Pre Amp - input requested

Postby Hugh Robjohns » Thu Feb 07, 2013 2:43 pm

Madman_Greg wrote: The mic gets microphonic if that the right term

Probably not the right term -- Do you mean the mic becomes very sensitive to external mechanical vibration -- handling noise etc? Do you mean it becomes very hissy? Do you mean it picks up a lot of ambient room sound?

and there is little precise control at that end of the gain knob

This is quite normal with the vast majority of budget and mid-price preamps, as others have said. Most of the gain appears in the last 10 of 15 degres of control rotation, so precise control will always be difficult.

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Re: SM58 / Pre Amp - input requested

Postby Madman_Greg » Fri Feb 08, 2013 12:09 am

First let me say thank you to those that replied, or read and considered replying. And let me apologies if I have wasted your time.

As I do not have a problem

Not used a lot of my gear since late 2010, due to being a bit ‘Moby Dick’ and taking a while to get to the point where I can confidently make music again.

Basically unplugging and replugging everything improved the situation, but I still need to wind the gain up a long way, but this is expected. But not all the way now !

And to reply to some of the comments

Do you mean the mic becomes very sensitive to external mechanical vibration Do you mean it becomes very hissy? No
Do you mean it picks up a lot of ambient room sound? Yes
This is quite normal with the vast majority of budget and mid-price preamps, as others have said. Most of the gain appears in the last 10 of 15 degrees of control rotation, so precise control will always be difficult. – Yes this is the case
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Re: SM58 / Pre Amp - input requested

Postby ef37a » Fri Feb 08, 2013 6:49 am

A few numbers OTTOMH Greg,

If I try to record acoustic guitar with my NI KA6 I need the gain knob on the end stop using an SM57 at about a foot. For picked notes this puts the level just about perfectly at -20, -18dBFS.

If I be quiet(and my "playing" demands that!) the basic noise floor is around -75dBFS. If I replace the mic with a 150R load in an XLR plug noise is -80dBfs. Conclusion? My "system" is 5 dB or so quieter than I can ever get my room!

Re 16bits. I always run 24bits but a really good 16 bit device such as my A&H ZED10 is still way better than neg 75. I have not tried it (will if you like) but I doubt the same recording setup via the Z and a 57 would result in a worse noise floor. Also, for ac'git the pre amp gain on the mixer has to be pretty well advanced tha' knows.

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Re: SM58 / Pre Amp - input requested

Postby Hugh Robjohns » Fri Feb 08, 2013 10:07 am

Madman_Greg wrote:And let me apologies if I have wasted your time.

never a waste of time -- I'm sure others reading this thread will have picked up some useful pointers too...

As I do not have a problem

Pleased to hear it!

Do you mean it picks up a lot of ambient room sound? Yes

The SM58 is a relatively insensitive mic, and is designed to be placed very close to the source. So if it's picking up a lot of ambient room sound you are probably placing it too far from the source and thus having to use too much gain.

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Re: SM58 / Pre Amp - input requested

Postby Jim Lockhart » Fri Feb 08, 2013 6:31 pm

Another thing you could try in order to reduce pickup of room ambience would be the use of a portable acoustic screen (e.g. SE Reflexion or Realtraps Portable Vocal Booth), perhaps along with hanging some duvets. See Sound on Sound October 2012 in the Q & A section.
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