How to add gain to a condenser mic successfully?

[Jedaks]

Hello, I've got a question about to boost the signal coming from my condenser mic so that my amplifier is louder.

I'm not sure where to start so I'll start with my rig. I have a JTS NX9 condenser instrument microphone, a Behrigner Xenyx 502 mixer-preamp, and a Kustom Sienna 16w acoustic amp. The microphone as an on-board AA battery for power, or it accepts phantom power.

When I plug the microphone directly into the amp, I get a lovely clear sound, but its not very loud. When I run the mic into the little mixer, the volume is increased substantially but I get lots of hiss and problems with feed back.

The acoustic guitar amplifier, when I plug my steel string guitar into it (that has a pickup), can get loud and clear, so I know the amplifier itself has the loudness and clarity I require.

Is there some way I can do the same with the microphone but without the hiss and feedback? ( P.S. I have the amp facing the audience and I sit behind it, so the amplifier does not project into the microphone.)

[riffmeister]

It is the job of the preamp to amplify the signal coming from the microphone. You can also move the microphone closer to the source (guitar) to obtain a stronger signal. You can reduce feedback problems by properly positioning the microphone relative to the speaker.

[gilles T]

Hello,

You may consider adding a graphic equalizer in the loop. This way, you can isolate and lower the precise frequencies that trigger feedback. It won't add more gain, but since the feedback problem is solved, you'll be able to raise the overall volume on your amp.
Regards,
GT

[robert e]

Is the hiss the same no matter which mixer channel you use? Is it the same whether phantom power is on or off? Is it the same no matter which input on the amp is being used?

[robin loops]

I have never had good results with Behringer equipment. I can't say about your mixer but something that has a good clean preamp with a good signal to noise ratio and a lot of headroom will make a big difference. When you go directly into the amp you are just hearing the mic (albeit without enough gain) but when you go through the preamp, you are limited to the quality of it's circuitry. A chain is only as strong as its weakest link really applies with audio... From the strings on the guitar all the way to the speakers on the playback device and every pass along the way make up the audio chain. In this case I am going to put my money on the preamp/mixer being the issue.

Anytime you use gain, it is a balancing act between volume and feedback. Especially with microphones. There are many parts to the equation but there are some things you can look out for.

A poor signal to noise ratio can result in more feedback issues because at a certain volume for the actual music you will have an overall higher volume (when factoring in the added noise). And extreme example of how this works is, imagine if the noise were twice as loud as the actual sound from the guitar. In this case you would only be able to go up about half as loud (as you would when there was no noise) before getting feedback. That's a bit of an oversimplification though. More headroom will have a similar effect in that if there is less distortion of the source. Distortion 'fills' the sound wave out (squashes and compresses the sound wave) so also plays a role in feedback problems.

Mic position also plays a major role in controlling feedback (especially with classical guitar). Two major things to watch for. First the proximity effect causes the sound to get boomier (bassier and muddier) as the mic gets closer to the source and can cause more feedback. But get too far back and you need too more gain and pickup more from the speaker. So you have to find the sweet spot, close enough for lower gain far enough to avoid boominess.

You also want to be aware of the polar pattern of the mic you are using (from where it hears sounds). And locate the amplifier relative to the mic's 'dead spots' so it doesn't pick up the speaker. Reflections off walls can come from anywhere so they can be harder to eliminate with mic placement/polar pattern considerations. Wall deadening materials (a blanket, pillows, acoustic absorbing panels, etc) can help a lot there.

[Jedaks]

Thanks, everyone, for your advice. It is appreciated.

Regarding the Behringer mixer, yes, it is the same hiss on any input, so perhaps it is the mixer itself. I can attest that the microphone and amplifier itself are top performers (for their price range). I feel pretty certain that if I put a pickup in the guitar then I would get the volume without the hassles, but I've not yet heard a pickup that sounds as nice as a microphone.

[robin loops]

One option to get the gain you need would be to Burbank simple mic preamp and use it instead of a mixer. Not only can you get a good Mic preamp cheaper than a good mixer with decent preamps, but it will only be running through the preamp and not extra mixer circuitry.

[Paul Janssen]

Forgive me asking the obvious question, but have you tried setting the gain appropriately on the Xenyx 502?

Here is a simple method to use as a starting point to setting the gain on the X502.

1. Unplug all inputs and outputs from the X502 except for the power cord.

2. Turn down the level control all the way to the left (minus infinity) on inputs 2/3 & 4/5

3. On input 1 (your microphone input) set the level control to zero (12 O'Clock position), and the EQ High, EQ Low and Pan controls also to their mid point (12 O'Clock) positions

4. Set the gain control (the top nob) on input 1 all the way to the left.

5. Set the Main Mix Output nob (bottom right nob) to 0 (12 O'Clock) position

6. Plug in the Microphone only into the XLR input (the 3 pin input) on channel 1. Important point: you need to use the 3 Pin input rather than the LINE IN plug for proper results.

7. DO NOT PLUG THE MIXER INTO THE AMP AT THIS STAGE!!

8. Position the Microphone as you would when you are playing and then play the guitar at the loudest level that you intend to play (e.g. strumming rather than gentle finger picking if appropriate). Check the output level LED's. At this stage they may not even show anything. Slowly increase the gain control and play the guitar again. Check the LED's again. Play again, increase gain, check again (repeat).

9. Continue to play, check LED's and slowly increase the gain nob until the LED's are lighting up the 0 LED. You may notice that 6 LED only just lights up. This is what you are looking to achieve. If the 6 LED (or worse the CLIP LED) lights up constantly then you have the gain too high and you need to reduce it. The idea is that you want to light up the 0 LED only. This is known as unity gain and is considered the optimum point to run the mixer and microphone whilst reducing/eliminating feedback and unwanted hiss.

10. Once you have the gain set appropriately, reduce the main Mix output nob all the way down to left (minus infinity). Plug the Mixer into your amp and then slowly turn up the main mix output whilst playing. The optimum point should still be the 0 (12 O'Clock) mark, so you will almost certainly need to adjust the input level on your amp as well (most likely turn it down) to reduce hiss and prevent feedback.

Give this a go and see how you land. I'd be interested. Behringer gear often gets a bad wrap, but in my experience the noise levels are not usually as bad as you describe so this suggests a setup issue rather than an issue with the mixer itself.

One last thought. I'm not sure whether the X502 has phantom power. If not, make sure your battery in the Microphone is fresh. They don't draw much current but still best to be sure!!

Good luck,
Paul

[Jedaks]

Paul, you should write technical manuals!

[ronjazz]

A Kremona pickup gets a nice sound, and needs no holes drilled or any modifications to the instrument. While the right mic is ideal, there are rarely ideal circumstances if you're a gigging player, the Kremona is great for outdoors, for Instance: no wind noise. It's also great in small spaces, mics and their stands can use up your space quickly.

It's $70. I have it on my best guitar, and it sounds really good. I've recorded with it, it sounds quite good. It's $70.

Did I mention the price?

[rojarosguitar]

In case you don't succeed to get a noise free signal from the Behringer: I have good experiences with using ART Tube MP in a comparable setting. It has also an unbalanced output that can be fed directly into an amp. It costs around 50$ in the US. It certainly has enough gain that is reasonably noise-free.

[Andrew Pohlman]

Like other posters have said, and very well I might add, get a solid to spectacular preamp. Set the initial gain as much as the conditions allow.

If I understand your question, all the gain should be at the beginning of the signal path. The big rookie mistake is to set up max gain at the preamp, reduce the gain via digital or other signal processing, mess with EQ changing gain at select frequencies, then bump gain again at the end of the signal path or amplifier input. So a plus-minus-plus situation. That only leads to high noise that becomes an inherent part of the signal and very difficult to eradicate in post processing, i.e., the amp amplifies all that the noise.

If you max your signal cleanly, and it's not loud enough, you may just need a more powerful amp, and deal with feedback issues via mic/speaker placement and proximity. Giving the amp a signal made noisy due to excessive gain in the input stage(s) is the wrong approach. You can only go so loud before feedback for any given space, outdoors being a highly forgiving environment in that regard.

Remember, Spinal Tap's amps go to 11. It' hard to go wrong with amps that go to 11!

[rojarosguitar]

PS also usually condensers do not need that excessive gain. If yours needs, it might be a sign that it is defective, or the cable you use is defective. Is it phantom powered or battery powered? If the latter is the case, the battery could be also law. Or the phantom power of the mixer could be insufficient. There are many reasons why a mic can make problems...

[2handband]

1) your amp doesn't have a mic preamp. Your mixing console does which is why it's louder. You need the console BUT:

2) throw the behringer out a window. If it still functions after that light it on fire. Get a decent board. That's probably where the hiss is coming from.

3) another possible cause of your hiss is that your amp may not be (probably isn't) designed to work with the line level signal coming out of that board. A PA amp and a pair of speakers on sticks will serve you better.

4) your mic will sound better with phantom power than batteries.

5) you're getting the feedback because of the increased gain. First things first set the gain properly on your board... it should come just short of red on your loudest playing. It should never ever actually go red. After that the answer to feedback is eq. Get a 31 band graphic and notch out the frequencies that are feeding back. Learn to identify them by ear because every room will be different... it's not set and forget.

[PeteJ]

Great set of instructions from Paul. If this process is not done right then nothing will work properly.