Humming noise problem with guitar amp.

[Jered Bolton]

Hi,

My local church recently bought a (stereo) keyboard, a volume foot
pedal volume (stereo) and a (small) two channel guitar amp. This was
so organists would be able to change the volume of the music with the
foot pedal.

The current set up is to take a signal from the headphone socket on
the back of the keyboard, through the pedal where seperate left and
right signals feed into each channel of the amp.

The outcome of this setup is a very noticeable (earth loop like)
hum/buzz. Channel 1 of the amp is a Low-Z input, and channel 2 is a
normal high impedance input. When channel 1 is connected by itself
there is no buzzing. Channel 2 hums less, when the volume pedal is
turned to full on i.e. least resistance to signal.

Any suggestions as to how this hum can be removed will be greatly
appreciated.

Thanks,

Jered.

[Mike Rivers]

In article > writes:

> The current set up is to take a signal from the headphone socket on
> the back of the keyboard, through the pedal where seperate left and
> right signals feed into each channel of the amp.
>
> The outcome of this setup is a very noticeable (earth loop like)
> hum/buzz. Channel 1 of the amp is a Low-Z input, and channel 2 is a
> normal high impedance input.

Does the keyboard have a line output or two, or only the headphone
output? Most stereo keyboards have two outputs, and one is designated
as mono if you don't need stereo patches or effects (which would be
lost in your church setup anyway.

What you want to do is take a mono signal out of the keyboard, into
the volume pedal, and into the input of the amplifier that works best
with it.



--
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[Jered Bolton]

(Mike Rivers) wrote in message news:<znr1068585431k@trad>...
> In article > writes:
>
> > The current set up is to take a signal from the headphone socket on
> > the back of the keyboard, through the pedal where seperate left and
> > right signals feed into each channel of the amp.
> >
> > The outcome of this setup is a very noticeable (earth loop like)
> > hum/buzz. Channel 1 of the amp is a Low-Z input, and channel 2 is a
> > normal high impedance input.
>
> Does the keyboard have a line output or two, or only the headphone
> output?

Just the headphone output (Cheap plasticy keyboard).

> What you want to do is take a mono signal out of the keyboard, into
> the volume pedal, and into the input of the amplifier that works best
> with it.

Any suggestions as to how I can get a mono signal? Cheap mixer or
something? I'm thinking that this will be easier than trying to
impedance match each input of the guitar amp - which even if acheived
may not remove the hum.

If it was up to me I'd get rid of the guitar amp (as the keyboard
(unsurprisingly) sounds horrible through it) and get a nice (2
channel) keyboard amp. However, I wasn't involved in the purchasing of
said equipment - I've just been asked to make it stop humming and
sound nice

[Garthrr]

>In article >
writes:
>>
>> > The current set up is to take a signal from the headphone socket on
>> > the back of the keyboard, through the pedal where seperate left and
>> > right signals feed into each channel of the amp.

I missed the beginning of this thread. If this is a standard guitar amp then it
doesnt want to see a signal as hot as a headphone out. It wants to see an
instrument level signal or a -10dB line level signal at most. I guess thats the
reason for the volume pedal right?
The hum may be caused by the huge amount of gain being applied to the (already
hot) signal or it could be a ground loop between the keyboard and the amp. Any
way you cut it though this is not the way to do this IMO. Square peg, round
hole.
Why is anyone insisting on playing this keyboard through this amp?

Garth~


"I think the fact that music can come up a wire is a miracle."
Ed Cherney

[Mike Rivers]

In article > writes:

> > Does the keyboard have a line output or two, or only the headphone
> > output?
>
> Just the headphone output (Cheap plasticy keyboard).

> Any suggestions as to how I can get a mono signal? Cheap mixer or
> something?

Just parallel the outputs. Radio Shack makes a stereo-to-mono plug-in
adapter that you can just plug into the jack on the keyboard and then
plug a standard "guitar type" cable from the adapter to the amplifier.
The Radio Shack stock number is 274-1520. I trust they still make it.



--
I'm really Mike Rivers - )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo

[Mike Rivers]

In article > writes:

> Why is anyone insisting on playing this keyboard through this amp?

Because it's a church and nobody who know anything was involved in the
purchase.



--
I'm really Mike Rivers - )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo

[Willie K.Yee, M.D.]

On 11 Nov 2003 10:01:40 -0800, (Jered
Bolton) wrote:

>Hi,
>
>My local church recently bought a (stereo) keyboard, a volume foot
>pedal volume (stereo) and a (small) two channel guitar amp. This was
>so organists would be able to change the volume of the music with the
>foot pedal.

How is the volume pedal powered? I get a hum with my Morley when using
wall wart power. I get around it by running it off battery when it
matters.
--

Willie K. Yee, M.D. http://users.bestweb.net/~wkyee
Developer of Problem Knowledge Couplers for Psychiatry http://www.pkc.com
Webmaster and Guitarist for the Big Blue Big Band http://www.bigbluebigband.org