Newbie amp/guitar questions

[Alden_Sloe]

So, I'm very new to recording. I'm not a musician but I'm having fun helping my son record some of his work. He sings and plays piano. Those I've been able to record with mics. I've also recorded acoustic guitar from mics. Now he's got an electric guitar and an amp which only serves to further reinforce the feeling that the more I learn the more I begin to understand how little I know

He bought a cheap amp. A Brand X which is a badge Fender puts on a line they have made in China. I know you tend to get what you pay for but since this is supposed to be a learning experience for $40 on Craigslist I figured it would be worth it for experience if nothing else. I'm of the opinion that if your first car is a beater you'll end up knowing a lot more and have a much better appreciation of a fine automobile later on in life

Back to the amp. The first experience was that of problems with excessive noise. I think the proper term is hum as buzz seems to refer to resonances from the guitar. But I started doing some experiments and it seems the hum isn't there when nothing is plugged into the input. Plug in a standard instrument cable and buzz. Mmm, the cable seems to be acting like an antenna It's not a balanced cable and I'm not sure what shielding a "standard" instrument cable should have. I tried two mid priced different brand of cable and same thing. I didn't have a balanced (TRS ?) cable to try but I did have a set of stereo headphones. I know, you're saying what?? this fool plugged a set of headphones into the input of a guitar amp Well, yes I did. Guess what? No hum. And if you turn the volume way up you start to get feedback; nice "clean" feedback with no hum.

Next experiment was to plug in a microphone cable. 1/4" unbalanced jack on one end and XLR at the other. Without a mic same hum as the instrument cable. But connect a cheap dynamic mic and no hum with the mic in either the ON or OFF switch position. With the mic on the sound out the amp is pretty good. In fact clean is very clean and seems better than through the preamps of either my Roland MMP-2 or Fostex MR16HD! So I think we've at least got a decent little amp

If you're reading this saga so far you're likely wondering, "What about plugging a Guitar into the Guitar amp?". Well, we did try that. Hum, buzz, just about all manner of bad noise. How good is the guitar? Well, refer to the comment above about owning your first car It's an old Harmony solid body (not vintage, just old like me ). Hey I'm sure we'll get our $20 worth of experience out of this investment. Like did you know there's a fundamental difference in the way humbucker and single coil pickups are wired Here's another thing I discovered, if I touch my finger to the metal of the 1/4" jack on the guitar the noise almost dissappears. The nut which secures it to the guitar was a little loose and I've only finger tightened it at this point but I think there's a grounding issue at work here I also noticed that there's some play in the volume knob (pot, see I'm learning) which may improve with cleaning or simply need to be replaced. The great thing about a $20 guitar is I'm not afraid to open it up and experiment.

So, any tips, tricks or advise on where to go from here in minimizing the noise would be greatly appreciated. Failing that I guess there's always the Lynard Skynard approach.... "turn it up"

 

[pikingrin]

I think you got close with the grounding issue. Could also be poorly shielded. If you got a little bit more specific with the guitar people would most likely be able to give you some things to try to resolve the issue with the noise.

 

[stoneyblues]

Sounds like grounding noise to me too. Maybe picking up some 60 cycle hum if you've got single coil pickups. Don't be surprised if its not your guitar cable. You probably don't have a high dollar cable there I would guess based on the cost of the guitar and amp. I would check out the guitars wiring before I went much farther.

 

[Roguetitan]

if you have a Stratocaster copy or something similar that has single coil P-ups it is more than likeley that the Pickup pockets need to be shielded you can use aluminum foil and spray adhesive to line the pockets and the back of the pick guard or if you preferr you can line the pockets with copper shielding tape but Aluminum foil will work just as good.

pre fit the aluminum foil with the shiny side out then spray the adhesive to the back of the foil then install into the pockets and the wiring channell the pockets and channel need to be completley covered with the foil so that no wood is exposed.

then remove the pickups from the pickguard and pre fit the foil, then apply the adhesive and carefully install foil to the pick guard not to get a lot of wrinkles in the foil, then replace the p-ups on the pickguard and reinstall the pickguard on the guitar body.

you will also want to make sure that you have a ground fastened to your bridge from one of your control pots.

 

[Dani Pace]

The "good old hum" annoyance problem.... First off, rest assured you are not the first to have this problem. Hum as you described is usually a grounding problem someplace. A weak connection anywhere can cause it. It could be something as simple as the nut on the input jack (on the guitar) being loose to the pickup(s) needing replaced. Anything loose or wobbly would be a good place to start as well as cleaning the pins of the jack. Cleaing the pots may help, if they are loose they should be replaced. Weak solder joints (cold joints) will cause hum, if any solder is dull looking this indicates a bad connection. There should be a wire, probably grounded to one of the pots which goes to the bridge or tailpiece, often the end of this wire is just stripped and placed under the bridge, corrosion on the end of this wire will cause hum. One more thing to consider is how close to the amp the guitar is. Being very close (especially with single coil pickups) will greatly increase hum as will bieng close to computer monitors, TV sets and some other appliances. Hopefully this will give you some idea of things to check, hum is very annoying so I hope you can find the cause. BTW welcome to the forum.

 

[Milnoque]

Try taking the guitar and cable to a music store and plugging it into an amp there. If it makes noise there, try a different cable. If you still have noise you know for sure the source is the guitar. If you don't have noise at the music store, the source is the amp.

Either way, hit Radio shack and get a can of contact cleaner. Read the directions and use it on both the guitar and amp, Working the pots and switches as you do. While you have the instrument and amp opened up, carefully inspect for any visual signs of bad connections. Pay special attention to the guitar jack where the ground wire is attached. Avoid touching the electrical parts inside the amp. It's probably solid state and the risk is very low, but the capacitors can still hold a charge. If it's a tube amp the caps can be dangerous.

Button it all back up and try it out. Report back if you still have a problem.

Even cheap amps and guitars should be able to work quietly enough to move you forward with your recording.

 

[lpdeluxe]

Take it to a tech.

When I'm confronted by a problem like that, I take my amp to the local tech. Even though this is a small town in Texas, there's always someone around who knows what to do-- right now the local Fender dealer has a retired Navy electronics tech working for him.

A lot of times he'll find something remarkably simple like a wire that's come adrift and it's actually rare that I pay more than the $50 bench fee (which to me is better than electrocuting myself). I should point out that I have had a stable of old-to-elderly tube amps, including a Sears Silvertone and an Ampeg B15N.

 

[ggunn]

I'm of the opinion that if your first car is a beater you'll end up knowing a lot more and have a much better appreciation of a fine automobile later on in life

Or just maybe you'll come to realize that an old VW will serve your needs just as well as that $200K Ferrari and you don't need to spend all that money... ;^)

Plugging a TRS cable into the amp doesn't accomplish anything; the input jack on the amp doesn't have a ring terminal. The reason the amp doesn't hum with nothing plugged in is probably because it has a grounding jack which shorts the input when there's nothing plugged in. The reason that it hums with just the cable plugged in is that you have the input unshorted but unterminated. All this is normal.

That's not to say that you don't have a grounding/shielding problem with the guitar and/or the cable, but into every electric guitar player's life, some hum will fall.

 

[toobalicious]

take it to the local tech!?!?!?

no, this is the correct answer:

you will also want to make sure that you have a ground fastened to your bridge from one of your control pots.

as evidenced by this:

I discovered, if I touch my finger to the metal of the 1/4" jack on the guitar the noise almost dissappears.

to OP, the wire that grounds the bridge has been compromised or isnt there. this allows you to "touch" ground all of the time by virtue of touching the strings during playing. it basically has to be there if you are getting interference like that. if it isnt there, you will want to solder a wire from the back of the volume pot to the bridge. how it attaches at the bridge end depends on the type of bridge you have.

a

 

[killthepixelnow]

I think you got close with the grounding issue. Could also be poorly shielded. If you got a little bit more specific with the guitar people would most likely be able to give you some things to try to resolve the issue with the noise.

I think so. I worked with EL Cheapo bass last year to do some cheap recordings (you see... cheap bass, cheap recording, ha!) To avoid the buzzing I stringed a wire from the bridge to my pinky finger... DONT DO THAT... now that I think about it, it was kinda dangerous ... but it stopped all hums...

Another thing to consider is that inexpensive unshielded cables tend to pick up annoying noises... maybe changing the cable you'll solve the issue.

 

[seansdadj]

Most likely a grounding problem. I would take it to my tech as well... they usually fix it up for me and it sounds like new again.

 

[Alden_Sloe]

Thanks everyone that replied. It really helps clarify what I'd been able to come up with by researching for myself on the net. I'm pretty sure the amp is working about as well as you could expect from an entry level practice amp. There is noise introduced when you use the "overdrive" channel and turn up the gain but I think this is normal. There's also some noise introduced by the reverb (they call it a spring reverb but it may be a solid state imitation). Again from what I can tell this is to be expected and it's not horrible. Interestingly I wasn't sure the gain/distortion or the reverb were working at all when we tried out the amp with just the guitar. But when I used the dynamic mic the effects were very obvious.

if you have a Stratocaster copy or something similar that has single coil P-ups it is more than likeley that the Pickup pockets need to be shielded you can use aluminum foil and spray adhesive to line the pockets and the back of the pick guard or if you preferr you can line the pockets with copper shielding tape but Aluminum foil will work just as good.

I'd read on line about shielding and wondered if anybody had tried aluminum foil. The only downside I see is that it's near impossible to solder to but if there's some overlap around the screw holes I'd expect it to suffice as a ground to backing on the guard that covers the pocket. It would certainly be a cheap experiment to try and probably worth it for the experience before attempting to do it "for real" with adhesive backed copper foil which is kind of spendy and a lot harder to remove if you screw up.

you will also want to make sure that you have a ground fastened to your bridge from one of your control pots.

Now there's something I'd missed in trying to research this on the net. I'd say it's very likely this is broken, corroded or was never there in the first place. If it was functioning properly I'd expect touching the bridge or the strings to have the same effect as touching the output jack but in fact it has no effect what so ever. I'd say that's a pretty clear indication

If the ground wire to the output jack is completely broken would you get any sound at all from the guitar? My reading of the schematics is that would leave the pickup coils as an open. On the other hand the unattached cable is in effect an open and it's capable of generating hum from all the background EMI and the strings would still be creating a change in the magnetic field of the pickup coils.

Plugging a TRS cable into the amp doesn't accomplish anything; the input jack on the amp doesn't have a ring terminal. The reason the amp doesn't hum with nothing plugged in is probably because it has a grounding jack which shorts the input when there's nothing plugged in. The reason that it hums with just the cable plugged in is that you have the input unshorted but unterminated. All this is normal.

Thanks! That makes perfect sense and wasn't something I'd learn from browsing the net. I've pretty much zero'd in on the main source of the problem being with the guitar. There may be some things I can do to improve the performance of the amp later on but for now it's not the weakest link. In fact I'd give the Brand-X amp two thumbs up as a beginner practice amp.

With the guitar, cord, and amp connected and buzz present, try turning down the volume pot of the guitar. This would usually quiet things up as the wipe part of the pot should short the guitar end of the cable to ground.

Turning down the volume does decrease the amount of noise but it's still a far cry from being silent. It's sort of a no win deal as the ratio of the noise to the sound from the strings gets worse. And there's definitely that loose/dirty crackle sound when you play with the knob which seems to be particularly bad in one spot. I'll try contact cleaner just to see what effect that has but it's more than likely in need of replacement. I work as an electromechanical engineer and soldering in a new pot is some thing that's easily in my comfort zone. Taking apart a guitar is something I'm not famiiliar with but that's the beauty of it only costing $20. I'm really a believer in hands on experience. Even if you take all your work to a professional it's nice to know what you're talking about so you can feed them the important information and develop an effective BS filter to the self proclaimed "experts".

I'll try and post some pictures of the guitar. Maybe a mini how to (or how not ) type sequence as I disassemble, clean and repair.

Or just maybe you'll come to realize that an old VW will serve your needs just as well as that $200K Ferrari and you don't need to spend all that money... ;^)

My first car was a '68 Bug. I really appreciate anything now where you don't have to crawl under the car to adjust valves. No prancing horse in my stable yet but I did put 330,000 miles on an '85 Rustang! My '86 Crown Vic is barely broken it at 260,000

 

[Roguetitan]

Nah... It don't need to be soldered just overlap the foil.

you seem to know a little bit about electronics so this should not be much of a task for you to eleminate the problem.

what you said about distortion leads me to believe that shielding the guitar should eleminate the humming noise problems.

 

[MatchBookNotes]

if you have a Stratocaster copy or something similar that has single coil P-ups it is more than likeley that the Pickup pockets need to be shielded you can use aluminum foil and spray adhesive to line the pockets and the back of the pick guard or if you preferr you can line the pockets with copper shielding tape but Aluminum foil will work just as good.

pre fit the aluminum foil with the shiny side out then spray the adhesive to the back of the foil then install into the pockets and the wiring channell the pockets and channel need to be completley covered with the foil so that no wood is exposed.

then remove the pickups from the pickguard and pre fit the foil, then apply the adhesive and carefully install foil to the pick guard not to get a lot of wrinkles in the foil, then replace the p-ups on the pickguard and reinstall the pickguard on the guitar body.

you will also want to make sure that you have a ground fastened to your bridge from one of your control pots.

sorry to jump in, but i have a cheap squier with a single coil in it, and it has terrible noise, but has a ground to my temelo in the back of guitar.
so if i do what you suggest the buzz will stop?

 

[ggunn]

sorry to jump in, but i have a cheap squier with a single coil in it, and it has terrible noise, but has a ground to my temelo in the back of guitar.
so if i do what you suggest the buzz will stop?

Shielding might help, but there are no guarantees. Single coils will always buzz/hum somewhat in the presence of 60 Hz fields, and there's no way to shield them completely.

 

[MatchBookNotes]

hmm, then maybe its time for some electronics upgrade and hotrail.

 

[Roguetitan]

sorry to jump in, but i have a cheap squier with a single coil in it, and it has terrible noise, but has a ground to my temelo in the back of guitar.
so if i do what you suggest the buzz will stop?

if the guitar is properly grounded the shielding will help significantly to reduce most of the hum.
But I also agree G gunn statement... "Single coils will always buzz/hum somewhat in the presence of 60 Hz fields, and there's no way to shield them completely".

that is even to be said for high end guitars with single coil p-ups.

 

[legionserial]

I used to find sometimes that I got a hum which would go away when I touched any of the metalwork on the guitar. Getting a piece of wire and taping one end to the metalwork and tucking the other end into the waist of whatever I was wearing at the time helped.