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Post subject: Plugging into power amp in is noisy
Posted: Wed Mar 13, 2013 5:57 pm
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Joined: Wed Mar 13, 2013 5:51 pm
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Hello- just bought a MF, have a standard cable plugged in Unbalanced L Out and into the Power Amp In on my Hot Rod Deluxe. When I turn on the MF and amp, there is a very loud hum, like I've got the amp turned up all the way to 11.

I know I'm bypassing the HRD preamp but even so I have everything on the amp turned to 0. I can't turn the level knob on the HF even a quarter of the way, otherwise it is way too loud.

I updated the firmware, same issue.

I moved from the Power Amp In to the main Input 1, and the noise goes away until I turn the volume up and then it is the hum again.

Thanks in advance for any input.
gtd

UPDATE- the hum is still there even if I turn the MF off, so maybe it is an issue with my HRD and not the MF?


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Post subject: Re: Plugging into power amp in is noisy
Posted: Thu Mar 14, 2013 1:45 am
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Joined: Sun Jun 17, 2012 11:37 am
Posts: 1315
Location: England
Quote:
the hum is still there even if I turn the MF off

Depends what you mean by 'off' - if you just turn off the switch on the M-Floor itself, that probably doesn't completely isolate the mains supply. Try pulling out the plug to turn it off, does that change anything?

Sounds like a classic case of ground-loop hum. The M-Floor does have a ground-lift switch, have you tried that? Or you could use the balanced XLR out on your M-Floor, connected to the unbalanced input on your amp. You can get cables correctly made-up for this, with a ground connection only at the unbalanced end. That may help too.


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Post subject: Re: Plugging into power amp in is noisy
Posted: Thu Mar 14, 2013 7:27 am
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Joined: Wed Mar 13, 2013 5:51 pm
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Unplugging does make a difference (stops the hum), but adjusting the ground lift has no effect. Unplugging the usb cable makes it worse.

May have to try the other unballanced cable deal, thank you.
gtd


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Post subject: Re: Plugging into power amp in is noisy
Posted: Thu Mar 21, 2013 8:35 am
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Joined: Thu Jan 21, 2010 1:12 pm
Posts: 4396
Hi gtd,

We will be happy to assist. Seems like scott-uk has offered some great advise to this issue (thanks scott-uk) :D . Please let us know if the issue doesn't get resolved and if we can assist further.

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Fender Technology Support Lab
Fender Musical Instruments Corporation
TSL@Fender.com
(800) 856-9801


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