Tech: amp buzz

Subject: Tech: amp buzz
From: bet
Date: 23 Jul 13 - 11:08 PM

Here I am in Tucson still and needing information from those of you who know. My Grandson's quitar amp has developed a terrible buzz, just found out about it. We need to get it fixed quickly. One of his bands is playing in Phenoix the 5th of Aug. I searched the yellow pages and have a few leads but thought I'd ask those of you who know this area better than I do if you have any suggestions. We have not tried the music stores but will start there if I need to.
By the way, he loves his banjo that he got for Christmas. We ended up at The Folk Shop, neat place.
Thanks for any help or suggestions you can give!

Subject: RE: Tech: amp buzz
From: GUEST
Date: 23 Jul 13 - 11:48 PM

You are experiencing the infamous "60 cycle hmmmm"

The solution and the problem are in a grounding loop.

Check out this thread from the famous U. C. party school in Santa Cruz California.


http://artsites.ucsc.edu/EMS/music/tech_background/te-15/ground/Grounding.html

Subject: RE: Tech: amp buzz
From: bet
Date: 24 Jul 13 - 12:48 AM

Thanks, I'll have Kage check it out as soon as he gets home.

Subject: RE: Tech: amp buzz
From: JohnInKansas
Date: 24 Jul 13 - 01:11 AM

The link http://artsites.ucsc.edu/EMS/music/tech_background/te-15/ground/Grounding.html is a good one if you have the skills necessary to use the information and the tools to do it, but even the best DIY information doesn't assure a quick repair.

Problems of this kind can be in the guitar (pickup, switches, or any "effects" controls), or in the connector (bad contact), or in the cables (broken shield or internal wires, or the connector on the other end of the cable, or in the amp.

A good music store (preferably one that does repairs) should have what is needed to swap out each component with known good ones to isolate where the problem is, and some would do that without charge, or for a very nominal fee.

Once you are sure which component is the problem, the fix may be very simple, but if it's actually "inside the amp" things might be more complicated. One store in my area offered "loaners" to replace components under repair in his shop (but I'm not sure he's still in business - he was older than me or GOD last time I was in there) and some places may have "rentals" that can be used while the offending component is in the shop, sometimes at discounted rates if it's in their shop. Someone among friends may know someone who knows someone who can loan something too.

If you have the time to do it, learning how to maintain your own stuff is highly recommended; but if you have a limited time and having "something" available soon is important, making sure there's a work-around should probably be taken care of before you start digging too deep into the innards of anything you think you might be able to fix but can't be sure of fixing without having to look for help.

John

Subject: RE: Tech: amp buzz
From: bet
Date: 24 Jul 13 - 09:49 AM

John, Thanks for your info.   I'll share this with Kage when he gets up ( he's a teen and not an early riser).

Subject: RE: Tech: amp buzz
From: pdq
Date: 24 Jul 13 - 10:49 AM

First, make up a "grounding plug". That can be a standard "telephone plug" with wire soldered (wrapped, in a pinch) from the outer to inner conductors. Also, an old "guitar cable" can be cut down and the conductors expoosed and tied together (but soldering is better). The goal is an complete "short" of the input

Insert plug and turn on amp. A hum will now have to come from "inside the amp", not from a grounding problem or a damaged cable.

Subject: RE: Tech: amp buzz
From: GUEST,leeneia
Date: 24 Jul 13 - 11:25 AM

Is the band a folk band or a rock band? ie does it have lots of equipment, or just a little? Because if there's lots of equipment, any item of it could be causing the hum

Do we really know that the hum is coming from the amp itself? Has any checking been done?

Speaking as a practical female, I would do the following:

1. Read this, then follow the steps with the grandson

http://www.ehow.com/about_6600364_guitar-amp-buzzing_.html

There are other articles on the Net with cheap, practical suggestions, which you can find by Googling 'what makes amplifier buzz.' You could find out that the problem is merely a hinky electical outlet.

2. Other practical tips from my husband - don't let cables cross one another. Don't pile excess cable in loops. Don't let speakers get too close to a microphone. Don't let a microphone get in the path of a speaker.

3. If this self-help doesn't do it, I'd e-mail the people who made the amp and ask for a recommendation on where to take it.

FYI, I looked at the article linked in the second post. It was Greek to me, and on the bottom of the page it was dated 1998.

Subject: RE: Tech: amp buzz
From: Richard Bridge
Date: 24 Jul 13 - 11:33 AM

Step 1 - turn on amp but plug nothing into the input. If it does not buzz it is not the amp. Expect a litle buzz from an unloaded input like that.

If it did buzz - do as PDQ said.

The other very possible source of such a buzz - in the amp but not expensive or troublesome to fix (usually) may be the input socket. If the earth wire from that inside the amp that goes to the preamp section has come off a loud buzz is likely. And even a short of the input will not silence it.

Turn the amp off and unplug it and wait for 15 minutes or so for all capacitors to discharge. Have a look for any loose wires. Do not reconnect unless you know what to reconnect to! With a good digital meter measure resistance from the earth side of the input socket to the chassis. If that is not zero, you have a wire off between the socket and the chassis.

If it is a REALLY REALLY LOUD Buzz, suspect something to do with the power supply, possibly a rectifier or a capacitor. If you do not know what you are doing, do not play with it, you might kill yourself.

If PDQ's manoeuvre did silence it, try (a) a different guitar lead and (b) a different guitar.

Subject: RE: Tech: amp buzz
From: GUEST,highlandman at work
Date: 24 Jul 13 - 03:26 PM

If Richard's and PDQ's tests exonerate the cables and input sockets, and it's a really loud "I can't play with this thing making this racket" harsh buzz, I'd bet on a power supply capacitor. Especially if it's an older, fairly high-powered amp; heat and age conk the things out with some regularity.
The good news is that is generally quite cheap to repair (if not done on an emergency basis). But also not something to mess with if you don't have some knowledge and/or good guidance.
-Glenn

Subject: RE: Tech: amp buzz
From: Richard Bridge
Date: 24 Jul 13 - 03:51 PM

If it's an old valve amp it could also be a transformer (probably unobtainable except for pattern ones for Marshall and Vox) - oh and the 700 volt capacitors that some need are WHOLLY unobtainable on mortals' budgets.

Subject: RE: Tech: amp buzz
From: pdq
Date: 24 Jul 13 - 04:02 PM

Failure of the main capacitor in the power supply will result in a hum that is twice the frequency of the power from the wall socket. It will be 120 cycles, not 60. Listen closely to a neon light balast and you can hear the 60 cycle hum.

In Britain, that is called "mains" power and is a different frequency than the US. Japan, I believe, is 50 cycles.

Subject: RE: Tech: amp buzz
From: Richard Bridge
Date: 24 Jul 13 - 04:16 PM

Yes, our mains is 50 Hz 220(ish) volts. And I agree.