[Harp-L] Re: Harp-L -- Amp buzz

[Pat Powers <patpowers@xxxxxxxxxxx>]

Hi Ken,

1) Check the tubes.  Make sure they're seated properly.  Blues Jr re-issues should be transported in an upright position only.  If you lay them down and hit a good bump you could knock the tubes out, or worse yet damage the plates inside the tubes resulting in a short, and the fusable (flame-proof) resistors on the circuit board burning out (yes, it;s ugly).  There's not a lot of wiggle room inside the glass of EL84 power tubes.  I usually strap mine into the passenger seat with the seatbelt like a child.. I would also recommend a Tube Tamer if you don't already have one.  The re-issues should come with one, some older models may not.  It's bascially an aluminum bar with a couple of springs and some grommets that goes across the tips of power tubes and is designed to reduced microphonic pickup (Woof) from speaker vibrations, but it also does a nice job of holding the tubes in place during transport. 

2) Check your mic cord.  If the amp only hums when the mic cord is plugged in, then it's your mic cord, or the mic.  Try another cord and/or mic.

3) Check the AC power.  if your amp buzzes/hums whether the mic cord is plugged in or not, try reversing your AC polarity.  I have a Blues Jr, and it only hummed when I play at one specific club, and found it was because it was an older building and they had the polarity in the updated polarized outlets wired backwards.  When I play there now, I simply use a 2-3 prong adapter and plug it in upside down.  Also, check to make sure your outlet is grounded properly.

4) Check for outside interference. Computers usually don't interfere with un-connected audio amps.  Florescent lights, neons lights,and even incandescents on a dimmer can wreak havoc with amplifiers though, especially if you don't have a good ground.  I originally had a dimmer switch on the recessed light ing in my studio, and had to remove it because of the switching noise it created on the circuit.

Happy Hunting!


Best Regards,

Pat Powers
Allentown, PA


Date: Sat, 30 Apr 2011 10:25:05 -1000
From: Ken Banks 
Subject: [Harp-L] Heartbreak and Trouble: Amp Buzz
To: harp-l@xxxxxxxxxx
Message-ID:
<20110430202505.E94873870ABF@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
Content-Type: text/plain; charset="us-ascii"; format=flowed

I brought home a used Blues Jr. a few days ago. Sounded great where I 
bought it, but at home it has a mean buzz. I'd appreciate some 
suggestions for troubleshooting this problem. I suspect that the 
source might be electronics somewhere in the apartment or the 
neighboring apartment. Could also be the cord, because the seller 
used his own cord when demonstrating the amp at his place. Could it 
be the compact fluorescent lights? We have computers all over our 
pad, too. I'm new to amplification, so I don't know how to 
troubleshoot. Thanks in advance.

Aloha,
Ken


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