Amp buzz

[djweiss]

I just got my first amplifier, a used Fender Blues Junior NOS (tweed exterior)...

I've been experimenting tonight with my Phoenix Jazz mandolin, and noticed that when either nothing is plugged in, or I plug in the Piezo pickup, the amp is pretty quiet, with just a very slight hum (I assume that's just the tubes???).

But, when I plug in the humbucker, a more noticeable (almost too much) hum/buzz comes and goes depending on which way I'm facing, and even then it sort of cycles on and off every 5-10 seconds or so...

I'm very new to electric instruments...Is it likely the amp or the pickup? Or is this just part of the mojo?


Thanks,
Darren

[mandroid]

If I hold my magnetic pickup equipped mandolin closer to the Neon Beer signs the hum gets louder .

.. They, and Florescent lights have a ballast and transformer too , that is another coil of copper wire .

perhaps that is how coils of wire communicate with each other , by humming harmonies in the 60 cycle frequency?

[stratman62]

You are living life with a fender tube amp. Thats how they are. Try moving away from the amp, this should reduce the hum. You may also want to keep your right hand laid across the strings during quiet moments. While you are playing with others the hum should not be noticeable when playing.

[Ken Olmstead]

What you are describing sounds like a single coil pickup. Is the Armstong for sure a humbucker or a P-90 type? Either way it does not sound like the amp to me. The Blues Junior has a small amount of hiss and how much depends on the amount of interference you are around: the flouresent lights, the poor grounding present in many old drinking establisments, living near a power line, ect. As you turn the amp up you increase the gain and it amplifies that even more. However, you can move the amp around in the same room and it will not usually change the hissing sound too much.

Usually a single coil will radically change the buzzing sound as you move around. The Pheonix web site did not say whether the Armstrong was a HB or a SC. If it is a SC the buzz is normal. If it is a HB then it is not. The fact that the piezo does not bother you but blending in the Armstrong does makes me suspect the Armstrong or how its wired.

The cycling throws a wrench into things. That does sound like a amp problem, possibly a weak tube. Take it to a Fender repair shop and they can pop some different tubes in there and see if that is the problem. The Blues Jr. is a great amp and has a dynomite rep so it is worth working it out. The mando is also killer! Actually take the whole rig to the Fender dealer and see if you can get it to demonstrate the problem for them. It could be that you live near a large amount of interference. Just trobleshoot by trying to isolate one thing at a time and it should lead you to the answer. Good luck and I bet that is a great sounding set-up!

[djweiss]

thanks for the suggestions...you're right in the fact that I don't know if the Kent Armstrong is a SC or humbucker, as I thought they were all humbuckers...now that you mention it, I've seen his humbuckers on Paul Lestock's instruments, and they look noticeably different...so perhaps I can write it off as a pickup issue!

All that being said, I'm *really* enjoying going electric, and has changed the groove of the swing/honky-tonk trio I play in positively. I'm thinking hard about a solid-body e-mando....

Thanks again,
-Darren

[Christian McKee]

You're getting good tips already: Isolate, isolate, isolate. Swap the cable, try different circuits in the house, move around, etc. Can you look to confirm visually that all the soldering connections are strong? Is the cycling of the noise regular? That would be a bit unusual, in my experience. Could it be synched up with something else that draws intermittent power in your house, like a toaster oven or fan? Good luck!

Christian

[mando.player]

Hi Charlie,
It is a single coil custom-made by Kent Armstrong. Thanks for your interest.
Rolfe
Phoenix Mandolins LLC
----- Original Message ----- From: "Charlie Jones" <charlie@jones-crew.com>
To: <contact@phoenixmandolins.com>
Sent: Monday, September 15, 2008 5:08 PM
Subject: Jazz Model...


Is the pickup a humbucker or single coil?

So it's a single coil pickup. Hopefully that will help in isolating the problem.

[250sc]

Now check our the schielding on the instrument.

[Steve Ostrander]

Also check the ground of your house outlet, and on the amp. Some amps have a 3-way switch that reverses the ground, but I'm not sure if the Blues Jr. does.

A friend of mine used one for blowing harp, but I never paid much attention to it (I mean the amp) It sounded good for harp.

[Ken Olmstead]

I don't think there is much to trace now. The SC is making the buzz. Any cyclical interference in the area would be audible thru the amp. The amp could still have a cycling tube but that is easy to check. I thought that Pheonix would have a humbucker. Go figure!

Sounds like all is normal djweiss. For better or for worse!

[Christian McKee]

Djweiss, a good way to test the amp's tubes is to tap them with the eraser end of a pencil after the amp has warmed up for several minutes. If you tap one and hear howling, screeching, or dramatic pinging sounds, you've got a candidate for replacement. In my experience, the pre-amp tubes on this little guy are more likely to go bad - those are the shorter, wider ones, and they can be replaced with a variety of compatible models and brands.

Christian

[djweiss]

Thanks for the great replies, everyone.

I played my regular gig last night at the local watering hole, and if the noise was there, it was unheard...Problem solved

My house is old, ~1930's, and I'm sure it's not grounded, so that can be part of it.

Thanks again,
Darren

[Doug Hoople]

Sounds like a shielding problem to me, typical (from what I've read) of single-coil.

If that's the case, the problem will come and go, depending on the noise nearby. It might return at inopportune moments.

It's probably hard to solve with an acoustic mandolin, but if you do spring for the solid-body electric, make sure you specify really bulletproof shielding. I didn't on mine (granted, I got mine on a whim from a mostly acoustic builder and didn't pay much for it), and it's got grounding problems and shielding problems and is a lot of trouble. I'm planning on retrofitting it myself when I get a bit of spare time.

A really well-shielded, grounded solidbody should be close to silent.

[Ken Olmstead]

I have done extensive shielding projects on electric guitars and its helps a bit but a single coil makes noise. Period. The good news that Darren discovered is that in the context of the gig, it really is not an issue. The old house explains a lot too Darren. It should be good to know that your rig is fine and you can get back to making music!!

[djweiss]

As an addendum, what would be the tonal differences if the Armstrong were a humbucker instead of SC?

-DJW

[Ken Olmstead]

It would be a thicker more powerful tone. With the tone rolled back you could get that thick, juicy jazz tone. However, it would distort earlier and generally they don't "cut" as nice as a SC. Also, I would guess that the SC gives a more acoustic like sound. I have to have noiseless gear. I am insane on the subject! So I always go for a humbucking rig if available. My KM300E is a couple weeks away from being converted to a HB rig for that very reason! But loads of folks would not give up their SC for anything so it is a preference thing.

[EdSherry]

There are a number of makers who make "noiseless" pickups with the "single coil" sound: Kinman, Fender "Vintage" Noiseless, Fender SCN Noiseless, and possibly others.

I used to use active EMG pickups in my Strats and Teles because of noise issues, and I still have them in some of my guitars because they have a very "clean" sound, but I love the sound of the Kinmans (a local guitar repair tech I've used for years turned me on to them and swears by them).

[Ken Olmstead]

There are a number of makers who make "noiseless" pickups with the "single coil" sound: Kinman, Fender "Vintage" Noiseless, Fender SCN Noiseless, and possibly others.

I used to use active EMG pickups in my Strats and Teles because of noise issues, and I still have them in some of my guitars because they have a very "clean" sound, but I love the sound of the Kinmans (a local guitar repair tech I've used for years turned me on to them and swears by them).

This is true. I use them in my strat. However, they are still humbuckers in design. They generally "stack" the voice coil on top of an isolated dummy coil. They work very well at creating a noise free, single coil sound. On my emando, I am looking for a touch more "beef" in the tone so I will be going with a Protrack from Dimarzio. It's goal is to give an accurate humbucker sound in the space of a single coil. That's the beauty of the electric stuff, if you want to take you sound a different direction, there is often a way to do it!!

[mando.player]

I've got a ProTrack in my Mann EM-5. The builder configured it with a push/pull tone pot that takes it from Humbucker to a more hot/single coil sound. It's subtle, but noticeable. Both modes are dead quiet. My amp will hum just a bit, but I'm fairly certain that's normal.

[mandroid]

FWIW, somewhat off topic , but...

I resolved an ungrounded outlet in an apartment I rented, by a kludge of buying a grounded outlet
and then running a ground wire along the baseboard, drilling thru one, and its wall,
and clamping the other end onto the bathroom sink.

.. with it being your own house, [not withstanding any pending foreclosure] , it would be tidier,
of course, prying off the baseboard and running the ground wire behind it.

[Martin Jonas]

There may be some unavoidable background buzz, but much electrical interference and amp hiss can be eliminated by properly shielding your mando, even with single coils. There are some very good instructions on shielding here. I've used those instructions when I fitted a new humbucker to my Amazing solid-body, and there is no hiss, regardless of whether I use it in humbucker configuration or tap the single coils.

Martin