[chych]

Today I was replacing my existing outlet with an ACME Silver plated outlet and found an interesting revelation... First off, I noticed that on this outlet, I never got hiss from the MG Head, and from other outlets, I did. What was wrong? Well, I got an outlet tester today and found out that the outlet that did not make the MG Head hum had the hot and neutral wires reversed! So I put in my new outlet with hot and neutral in the correct way and bam, the amp hums.

So, all we need to do is reverse hot and neutral on the MG Head some how, be it the power cord or the internals and it should not hum. I built a diy powercord so I am going to reverse the hot/neutral and the amp should not hum anymore ([shameless plug]I have some leftover Belden 83802 cord if anyone wants to buy some

[/shameless plug]).

I hope this works for others who are having this problem...

 

[chych]

Well I have just reversed the hot/neutral on the power cord going to the MG Head and it does not hum anymore. I think this may be the final answer to the MG Head hum, I hope other's try this as well.

 

[Wing]

This hum you are talking about is not the left channel buzz right? That's caused by the power lead to the on/off switch. The general low level hum on my MG Head seems to have gone away when I remounted the power transformer 180 degrees around so that the output wires were furthest away from the OPTs. I'd be very careful about reversing the hot and neutral as there may be some safety issues. If I remember correctly, neutral is tied to ground somewhere in the house circuit so that ground faults can be detected. Reversing the power connection may mess with this maybe. Can someone with an electrical background comment?

 

[chych]

No, it is the left channel buzz... and I can reduce it by moving the wires to the power switch, but changing the polarity of the power cord seems to take it out completely...

I never experienced a general low level hum though...

And nothing has happened to my amp yet, I've been running it on reversed polarity for nearly a year and it still works fine

 

[Joe Lau]

Quote:

Originally posted by Wing This hum you are talking about is not the left channel buzz right? That's caused by the power lead to the on/off switch. The general low level hum on my MG Head seems to have gone away when I remounted the power transformer 180 degrees around so that the output wires were furthest away from the OPTs. I'd be very careful about reversing the hot and neutral as there may be some safety issues. If I remember correctly, neutral is tied to ground somewhere in the house circuit so that ground faults can be detected. Reversing the power connection may mess with this maybe. Can someone with an electrical background comment?

Reverse of neutral is no problem - The power transformers is isolated to secondary. It only reverse the polarity of Wiring only.
But it should change by experience electrician not for general user.

 

[Videoshielded]

Wow, cool catch!

I've had a similar experience with a preamp. Results are not necessarily consistent from unit to unit, though.

This is where I found out about it:

http://www.siteswithstyle.com/VoltSe...ay_Preamp.html

 

[is2us]

As the Mg Head hum drives me crazy

and the power switch wires moving doesn't help much I searched the forum and found this thread.

Wouldn't just using a "Cheater plug" (3 pin to 2 pin AC plug adaptor) and then just plug it reversly to the outlet will be enough ? instead of having an experience electrician change them in the outlet or in the amp?

 

[TimSchirmer]

I solved it too! I got a new amp

 

[MirandaX]

Quote:

Originally posted by is2us Wouldn't just using a "Cheater plug" (3 pin to 2 pin AC plug adaptor) and then just plug it reversly to the outlet will be enough?

Yes, this is how I solved the hum. It's easy, and the adapter costs about 70 cents, so it's cheap to try. (The adapter will come with instructions for proper grounding, and to be 100% safe you should follow them; most people just ignore them though.)

 

[2 channel]

I must have just gotten really lucky with my MG-Head DT. I did the wing mod and there was a very slight left channel buzz. I pulled the on/off switch and curved the wires (which are now twisted) towards the left side of the amp, put the on/of switch back in and no buzz!
My amp is totally silent now.

2

 

[chych]

Aye, I just realized it depends on the way the wires are twisted... I think... so you would need to reverse polarity if your wires are twisted the "wrong" way...

 

[ICU]

Is2us, your suggestion is a thumb's up! I got Tim's ole HUMMY head, and the humm was killing me, my other Head is dead quiet.

Putting off internal mods, and reverse wiring of power cord, I found your simple mod the most efficient. (As my physics prof would say, an "elegant" soln.)

The freakin head, now => "MG Head", is quiet as a sleepin babe! Thanks, dude. Wah Hoo!

 

[is2us]

Quote:

Originally posted by ICU Is2us, your suggestion is a thumb's up! The freakin head, now => "MG Head", is quiet as a sleepin babe! Thanks, dude. Wah Hoo!

I'm glad it worked for you. It didn't work for me.
I still have a hum. It's probably not the left channel hum, It's on both channels. It started two weeks ago and it's driving me crazy.
I was going to buy the Er4, but with this hum they will be very annoying to use.

I tried to switch tubes and I got the hum with all combinations.
When I'm switching the amp on, there is quite for a few seconds and then the hum starts.
I still got the hum with nothing connected to the amp (just the power cord). I also moved it around the house to diffrent outlets.
Nothing helps.

Can any one help me here?

 

[ICU]

Yikes! I left the 3-prong plug, with the polarity of the power cord reversed, plugged in for the last couple of days. Now the strange part, I first changed the EL84 for a set of 6BQ5, took off the 3-prong, and switched on: no hum!

Thinking it was the tubes, I put the EL84s back in, still no hum. The hum, which was most annoying, is no longer there!

What gives?

Is2us, to address your issue, is it remotely possible that at the endstage, tubes may start to produce some hum? Have you tried changing the EL84s?

 

[is2us]

Quote:

Originally posted by ICU Is2us, to address your issue, is it remotely possible that at the endstage, tubes may start to produce some hum? Have you tried changing the EL84s?

All I got are the Ei which I usually use, and the stock Sovteks. I tried the Sovteks and they also hum, although a bit less.

BTW I remounted the power transformers today, like Wing suggested. It was a lot of work. It was my first time doing this kind of thing and I didn't have the proper tools. And of course... It didn't help.
Could it be that all my tubes are humming ? The hum level changes when I change tubes.
Should I spend more money on more tubes to check it, or just save it for another amp ?

Also I noticed once that the amp is still humming when I turned it off. than I turned off my NAD CDP and the hum stops. Than I turned on the amp again and the hum is back and strong.

For a few days now I'm just listening to all kinds and levels of hums instead of listening to music