Amp “Gain” for Dummies ?

sage1 · #1 12-05-2018, 04:59 PM

Have my first acoustic amp, never used one before. It has a few features above my head but Gain shouldn’t he one of them. So I’m hoping someone will take a minute and “learn me something”. When I turn it down the ambient amp
hum goes away, but why I don’t know. I did google it but IMO the explanation was still a little foggy.

Thsnks for the assist.

S1

ljguitar · #2 12-05-2018, 05:27 PM

Quote:

Originally Posted by sage1

Have my first acoustic amp, never used one before. It has a few features above my head but Gain shouldn’t he one of them. So I’m hoping someone will take a minute and “learn me something”. When I turn it down the ambient amp
hum goes away, but why I don’t know. I did google it but IMO the explanation was still a little foggy.

Thsnks for the assist.

S1

Hi S1

A few more facts may help us to be able to help you.

What is the amp? (Company and model)
Is it humming when you have nothing plugged in?
How loud did you turn the gain up to?

Gain is the input volume of a device (amp, mixer, recorder etc), and Master is usually the output volume of the device (amp, mixer, etc).

Gain should be set as loud as possible without distortion from whatever device/instrument/microphone/preamp is plugged into it. Master volume should be set appropriately for the room/stage/player.

If you are plugging several preamplified/amplified things together, the gain for each should be set properly moving from first device in line to the last.

sage1 · #3 12-05-2018, 06:18 PM

It's a Schertler David and I am only plugging one guitar into it at this time. A Taylor with the ES2. Yes there's only a hum with the guitar plugged in Do you mean turn the gain up to where it squawks then back it down. My cable is a Quantum Audio 2100. Just unplugged the cable from the guitar, it's still plugged in the amp and the hum increased, even more so if the plug end touches the floor. You think a better quality cable is needed?

sdelsolray · #4 12-05-2018, 06:49 PM

Quote:

Originally Posted by sage1

It's a Schertler David and I am only plugging one guitar into it at this time. A Taylor with the ES2. Yes there's only a hum with the guitar plugged in Do you mean turn the gain up to where it squawks then back it down. My cable is a Quantum Audio 2100. Just unplugged the cable from the guitar, it's still plugged in the amp and the hum increased, even more so if the plug end touches the floor. You think a better quality cable is needed?

You are conflating gain with hum. Gain deals with increasing voltage of an input signal, such as your guitar's pickup. Hum is a symptom of one or more grounding problems with your power supply to your amp when connected to you mains voltage source (e.g., your 110v source).

Certainly, if you increase the gain you will increase the perceived loudness of any associated hum. Other than that, gain and hum have no connection, correlation or causal effect.

lschwart · #5 12-05-2018, 10:05 PM

I don't know what is causing the hum, but here's a basic, quick and dirty way to set the gain properly on your amp:

Turn the gain and the volume knobs down on the instrument input channel of the amp (make sure the EQ controls are all set flat).

Turn down the master volume on the amp.

Set the volume on your guitar's system for a start at about 2:00.

Plug in the guitar.

Play as hard as you are likely to play while slowly turning up the gain. Stop when you see the clip light next to the gain knob flash on loud strums. Then back down slightly until the flashing stops. Don't worry if the light never flashes. If that's the case, turn it up, as a start, to somewhere a little beyond the 12:00 mark, and you should be fine.

Turn up the channel volume to around 10:00 as a starting point.

Turn up the master volume until you get to a decent volume for your purposes. If you find that the volume is rising too fast with just a little bit of turning of the master knob, dial back the channel volume, and that should give you a little more play on the master, making it easier to adjust things finely. If you find you're maxing out your master and not getting the level you want, turn up the channel volume until you get what you want from the master. If that's still not enough, and you never got the clip light on the gain knob to flash, you can turn the gain knob up as well, but I suspect at that point that if you're not hearing what you want it's because you're either deaf or you simply need a bigger, louder amp or PA system for your purposes!

If at some point you have someone play another instrument through the other channel or if you sing through that channel, follow a similar procedure, but use the channel volumes to get a proper balance between the two channels and the master volume for final overall volume. Both signals should be set just below the clipping point at the input gain stage, but if neither or only one gets the clip light to flash, set the channel volumes at the same point and the master at a point at which it comfortable to listen, and adjust the gains until the two signals are at about the same volume. Then you can use the channel volumes to to set a balance that's proper for actual performance (with again the master volume giving you the final overall level).

Louis

pieterh · #6 12-06-2018, 03:47 AM

Are you plugging into a grounded socket? I have a simple active speaker that I use for rehearsals and stage monitor and it hummed like crazy when I plugged my Taylor with the ES2. Then I plugged the speaker into a grounded kitchen socket and it was hum free. So I rewired my whole flat, grounding everything and making it safer in the process!

By increasing gain you are also amplifying the ground hum. By using the master volume to set the levels you run the risk of amplifying other noises (hiss etc) relative to your desired signal (the guitar).

gfa · #7 12-06-2018, 02:52 PM

Gain adjusts the level of the input, volume adjusts the level of the output.

Br1ck · #8 12-06-2018, 04:38 PM

Do you have a high z switch? Your guitar has a pre so disengage. you don't need this feature. You probably don't need full volume either from your guitar. Try halfway up. Make sure you don't have any mic input switches turned on. You don't need that much gain either. Also don't forget to check the LED that is on the guitar's preamp board. This is a battery check.

Does your amp have an input clipping meter? This can be as simple as an LED or two. Amber is ok, hitting red is not, so back off the guitar volume or input volume. Once you have this sorted bring the master up to taste.

Ground issue hums are another issue. Plug your amp in in another location, first in you house, then somewhere else. This will tell you if your house wiring is the problem. i'm not a fan of lifting grounds, but this will tell you a lot too.

sage1 · #9 12-06-2018, 05:34 PM

It won’t surprise me if it’s from the house electrical system. Nearly every outlet I’ve opened up over the years has had the ground wire disconected. Thx for all the info, I’ll be checking a few things on the amp as well.

Schertler USA · #10 12-07-2018, 07:58 AM

Quote:

Originally Posted by sage1

It won’t surprise me if it’s from the house electrical system. Nearly every outlet I’ve opened up over the years has had the ground wire disconected. Thx for all the info, I’ll be checking a few things on the amp as well.

If you need anymore help, please private message me anytime .
Thanks,
Dave

drive-south · #11 12-07-2018, 11:23 AM

If the cable is plugged into the amp but not plugged into the guitar the cable is acting like a big antenna. If the tip of the 1/4" jack touches the floor it may ground the input. Ouch, dont do that!

I always plug the cable into my guitar first, then the amp, then turn the amp on. I dont unplug the guitar while the amp is on unless I have a device in the loop that can mute the signal.