1964 Mercury M-12a noise

[Jdsimms]

Hello everyone,

New to the forum; I am hoping someone can help me determine the cause of this noise. I have had this amp to 2 different techs in my local area and neither were able to satisfactorily resolve this issue.





I love this amp; just don't love the noise!

Any help would be greatly appreciated.

Thanks!

[Hangman]

Hi JDSimms,

not sure if you tried to post an audio file, if so can you try again?

-hangman

[Jdsimms]

Hi JDSimms,

not sure if you tried to post an audio file,  if so can you try again?

-hangman

Hi hangman,

Thanks for the reply; the video clip embeds in my post above shows the exact amp and issue.

[journeyman]

The early Ampegs did not use a grounding plug, so with nothing plugged in, they have that ground hum. Does it dissappear when you plug your guitar in? My M-12 is the same. I recently got a 1958 Jet and had the amp tech install modern Switchcraft input jacks and there is no ground hum when I unplug the guitar. Let us know, because if it does this with the guitar plugged in, there are other issues that can be addressed.

[Jdsimms]

The early Ampegs did not use a grounding plug, so with nothing plugged in, they have that ground hum. Does it dissappear when you plug your guitar in? My M-12 is the same. I recently got a 1958 Jet and had the amp tech install modern Switchcraft input jacks and there is no ground hum when I unplug the guitar. Let us know, because if it does this with the guitar plugged in, there are other issues that can be addressed.

Thanks for the reply Journeyman,

A three prong cord was attached. The noise occurs with when nothing is plugged into the amp and when the guitar was plugged in.

I did notice today that after playing through the amp for about 30 mins, the noise was better, not great but better.

[journeyman]

My amp tech did a couple of things to get my old Jet running quietly. Of course we replaced the filter cap can, but then he reconfigured the daisychained grounding so that there are now two separate points of contact. That helped a little bit, but then he added a tiny bit of filtering. To counter any potential stiffness caused by the additional filtering, he reduced the amount of negative feedback. I'm very happy with the amp now; it runs very quietly and is very responsive.

I used my M-12 on the weekend with a stereo jack and it sounded amazing. Good luck with yours; it'll be worth the effort to get it running the way you want.

[Jdsimms]

My amp tech did a couple of things to get my old Jet running quietly. Of course we replaced the filter cap can, but then he reconfigured the daisychained grounding so that there are now two separate points of contact. That helped a little bit, but then he added a tiny bit of filtering. To counter any potential stiffness caused by the additional filtering, he reduced the amount of negative feedback. I'm very happy with the amp now; it runs very quietly and is very responsive.

I used my M-12 on the weekend with a stereo jack and it sounded amazing. Good luck with yours; it'll be worth the effort to get it running the way you want.

Thanks for the info journeyman! Some day I hope to be where you are with this amp!