loud left channel buzz in MG Head DT
Apr 3, 2002 at 11:39 PM Thread Starter Post #1 of 9

zzz

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For about half a year now I've been a proud owner (yes, proud indeed; the look on some people's faces when they see you on the street wearing those *huge* headphones is alone totally worth it
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) of a portable system consisting of some walkman, hd600 and a total airhead. For the first four months I considered it to be quite smashing, but recently an idea of upgrading or at least getting something more appropriate for home listening started bugging me a lot...

So this Monday I got myself an SD-9200 (mostly because all the reviews I read were raving about its sound quality. unfortunately I had no way of auditioning it before ordering, but oh well) and started looking for a new amplifier. Being temporarily broke after getting the player but still interested in getting into the tube sound, I decided to go for the MG Head [another reason would be that Soundstage Fine Audio (DivTech retailer) is about 30 minutes walk from where I live, so it's probably the cheapest and the fastest option for me as well
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].

But I digress. The thing is that when I went to the shop, they had one brand new MG Head in stock. So it was unpacked, plugged in, and there it is, at zero volume level, fairly loud buzz coming from the left ear of my HD600. Disconnected it from the player -- nothing changed. If volume is turned to the max, buzz becomes just a tad louder, so my guess is that input circuitry is probably not responsible for the noise. If the knob is touched at virtually any volume level, pretty loud noise of somewhat different nature enters the phones. Store owner tried using a different power cord (I don't really know how different, at that time I was mostly looking around at all the things I'm not going to own any time soon
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. I know it was plugged into some large Lightspeed surge protector though), tried cleaning tube contacts, all to no avail. In the end we agreed that it is not supposed to be like that, and that he's going to go to Divergent today and get another amp, which would hopefully work as intended.

So my question is, has anyone experienced such problems before? Maybe there is a trivial widely known remedy that I, being uninitiated, and the owner, having too much good stuff around to pay much attention to the lower spectrum of audio electronics
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, simply have no idea about? On the way back home I thought that maybe it has something to do with polarity, as I've heard some audio electronics is pretty picky about that, but I was already more than halfway back, and it was cold and nasty, so I decided to let him get the new amp anyway.

I have to say that modulo the buzz I really liked what I heard in those few minutes of auditioning the amp. Hopefully either this problem is easy to fix or new amp wouldn't have it.
 
Apr 4, 2002 at 12:06 AM Post #2 of 9

Nick Dangerous

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Yup. This is a known issue.

Fixing the left channel buzz:

1) Unplug MG Head
2) Unscrew the bottom chassis plate and remove.
3) Pop out the power switch
4) Rotate power switch until red wires are snugly intertwined (not too tight!)
5) Re-install power switch
6) Route the twisted red wires as far away from the green circuit board as possible
7) Re-attach the chassis plate, turning the screws very gently because the holes are soft and strip easily

Tah da. No more buzz.

Volume switch noise:

This is probably due to a highly microphonic tube. I had a Svetlana 12ax7 that was so microphonic I could tap the desk and hear it. Try changing the tubes. Things get even better. Amazingly so.

I'm glad you liked the way it sounds. The MG Head OTL is the price/performance king of tubed headphone amps.
 
Apr 4, 2002 at 1:23 AM Post #3 of 9

chych

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Or, if you reverse the polarity of the power cord (hot and neutral) you change the direction of the uncancelled (by twisted pair) flux in the power wires going to the switch to the left, outside the amplifier, so it does not interfere with the left channel... at least, thats what I have to do to get rid of the hum (my wires are twisted but I guess it isn't perfect)...
 
Apr 5, 2002 at 4:41 AM Post #4 of 9

zzz

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Thanks!

Fortunately, I didn't have to do any of that for now, as Divergent had one more MG Head in stock (OTL this time, not DT) which worked perfectly from the start.

However, it's a good tip for the future. Maybe it's worth creating some sort of MG Head FAQ if such issue is that common?
 
Apr 7, 2002 at 3:15 AM Post #5 of 9

MirandaX

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Quote:

Originally posted by chych
Or, if you reverse the polarity of the power cord (hot and neutral) you change the direction of the uncancelled (by twisted pair) flux in the power wires going to the switch to the left, outside the amplifier, so it does not interfere with the left channel... at least, thats what I have to do to get rid of the hum (my wires are twisted but I guess it isn't perfect)...


Chych, thanks so much for sharing this! I too couldn't get rid of the hum by twisting and moving the wires. I went to the local hardware store today and bought a 65 cent adapter that lets me reverse the polarity of the power cord. Wow! The unit is completely silent now, even with the very sensitive Etymotics. Very nice.
 
Aug 16, 2003 at 10:20 PM Post #6 of 9

sephka

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I have this buzz in the left ear also. I was wondering, when removing the plate, where do you stand the head? Upside down, on the interconnect outputs (doubt that...) or what? This is a good sounding amp, but i'm having a lot of problems with it.
 
Aug 16, 2003 at 11:13 PM Post #7 of 9

Sean H

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Man, those first run DT models were quite plagued. Didn't the dealer have any of the new OTL MKII models with the outboard power supply? These new ones are not supposed to have any of the problems the old DT and first run OTL models had. The outboard power supply has a polarity switch too.
 
Aug 17, 2003 at 1:29 AM Post #8 of 9

joelongwood

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Quote:

Originally posted by sephka
I have this buzz in the left ear also. I was wondering, when removing the plate, where do you stand the head? Upside down, on the interconnect outputs (doubt that...) or what? This is a good sounding amp, but i'm having a lot of problems with it.


Upside down, resting on the transformers.
 
Aug 17, 2003 at 5:52 AM Post #9 of 9

sephka

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Gah...I hate to be a pesk, but i'm being real careful-like with this head, and i was wondering just how i'm supposed to pop out the power switch.

Edit: Well, all i had to do was move the red cables. They were adequately intertwined. However, they were resting rather close to the circuit board, and that appeared to be the problem. No more buzz for the time being.
 

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