Tried the wing mod for MG Head DT
Apr 8, 2002 at 5:31 AM Thread Starter Post #1 of 12

TimSchirmer

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... I desoldered the green wires, and sealed them with duct tape. I gave it a listen, and was amazed by the new dynamics and soundstage. However, the sound is now a bit more harsh and grainey than before...and there is a buzz that varies depending on the volume. The whole reason I went with tube was to get a silent amp...and now i have buzz during the very quiet parts of songs, go figure. I guess the MG Head is just not the amp for me. I will be selling it soon to save up for an Earmax (or maybe something solid state)
 
Apr 8, 2002 at 6:35 PM Post #3 of 12

MirandaX

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Nick never recommends this, but you should try Chych's "invert the polarity" fix first, since it doesn't require opening up the MG Head and IMHO it makes a much more noticeable difference with sensitive headphones. If you want a completely silent MG Head, you should do both fixes.
 
Apr 8, 2002 at 7:29 PM Post #5 of 12

chych

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Actually you should reverse the polarity last if the twisted pair fix does not work, as the wires leading to the switch should be twisted in the first place.

Wait a sec... hmm if changing the polarity switches the direction of the flux away from the left tube, and the wires are twisted, that must mean that the direction in which the power wires are twisted matter as well... there must be a right way to twist it and a wrong way... Nick, wanna tell me what way your cables are twisted (or take a picture)? Anyways, it means that twisting the pairs only cancells some of the magnetic radiation and a good portion is still being emmitted, though away from the left channel tube so it is neglible.
 
Apr 8, 2002 at 9:31 PM Post #6 of 12

PRR

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> The whole reason I went with tube was to get a silent amp...

It is generally a whole lot easier to make a tranny amp quiet than a tube amp. Especially with ICs.

I will assume your signal source is hum-free.

Noise (hiss): In all situations, a transistor can make less noise than a tube. The fundamental reason is that random noise is proportional to absolute temperature, and a tube's gain part (grid-cathode space) has to run 3 times hotter than a transistor just to work at all.

Hummmmm: In all situations, it is possible to reduce hum as low as you can afford. Just do what it takes. Good basic circuit that doesn't pass B+ ripple to the output (zero feedback plate-load triodes are excellent in many ways, but pass ripple right through). Good power supply filtering. Keep AC lines far away from signal circuits-- this may mean a larger case or even an external supply. Bringing the power switch to the front, past the amplifier and near the audio controls, is a classic problem.

Transistors again have an advantage. They typically use less power so power filtering is less expensive. Tubes work at higher power, higher impedance, and larger dimensions, so are more likely to pick up hum. Tubes can work low-hum with AC on the heaters, but when that isn't good enough (or you get bad tubes) you need a very large and quite clean (thus expensive) DC supply for the heaters.

Many small transistor amps work acceptably on batteries, which avoids all power-source hum. You sure can run tubes on batteries but you need a lot more of them.

-PRR
 
May 2, 2002 at 3:54 AM Post #7 of 12

Wing

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I moved the power switch to the rear and that fixed the left channel buzz. The low level 60hz hum was fixed with power transformer reorientation. Harsh and grainy sound is probably the 12ax7. I fixed mine with the delicious Mullard CV4004. Haven't tried the better 5751s although I didn't like a GE JAN 5751s I have. Man, I've been so busy, I hardly even read headfi anymore.
 
May 2, 2002 at 4:16 AM Post #9 of 12

2 channel

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Quote:

Originally posted by Wing
I moved the power switch to the rear and that fixed the left channel buzz. The low level 60hz hum was fixed with power transformer reorientation. Harsh and grainy sound is probably the 12ax7. I fixed mine with the delicious Mullard CV4004. Haven't tried the better 5751s although I didn't like a GE JAN 5751s I have. Man, I've been so busy, I hardly even read headfi anymore.


Hi Wing,
Do you have pics of your transformer reorientation?
 
May 2, 2002 at 9:57 AM Post #11 of 12

lextek

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Quote:

Originally posted by Audio&Me
I tried the wing mod, sounded like total ass. My 2¢.


So you didn't like the sound of the Mod? Your the first one to say that.
 
May 2, 2002 at 7:03 PM Post #12 of 12

Wing

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2 channel - The transformer was reoriented in the only way possible, by rotating it 180 degrees so that the output wire bundle is further away from the OPT. Any other kind of rotation will not allow it to be remounted on the original holes in the chassis. Sorry no pics.

Like I mentioned in my initial mod post, removing NFB highlight the strengths and weaknesses of the tubes. I tried a Sovtek 12ax7LPS into the MG Head and it did sound "like an ass" - noisy, brittle, yucky.

I would love to be on the THSP list but I'm so busy nowadays I don't even have time to work on my own tube amps. BTW, I built something akin to the Ciufolli SESS amp with various current production tubes Sovtek 6H30, JJ ecc99. It has as much bass and treble as a solid state but unfortunately, did not have the midrange beauty of the MG Head with the Mullard. There are too many interesting possibilities right now. Certain NOS tubes do seem to have something current production tubes lack.
 

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