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Post by jacklawtey on Mar 2, 2008 7:52:02 GMT -7
You've probably all heard this before, as I've searched and found a few threads but none that match my problem completely. So I recently bought a used Maz 38 head, and it sounds brilliant, until I turn the reverb up. When I do, I get alot more background noise, and even, sometimes, a microphonic high pitched 'buzz'. This gets worse as I turn the reverb up more, but goes completely when the Reverb knob is all the way down. Would you think one of the pre's is going microphonic?
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Post by benttop (Steve) on Mar 2, 2008 8:31:13 GMT -7
That'd be where I'd start. Turn the reverb up and use a pencil to tap each preamp tube - if you have one going microphonic it will stand out from the others. They'll all make some sound, but the microphonic one will make a lot of sound.
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Post by jacklawtey on Mar 2, 2008 8:47:16 GMT -7
See I did that, but the reverb was only on half.. And I didn't tap them very hard. But none made any noise whatsoever, really.
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Post by benttop (Steve) on Mar 2, 2008 10:18:16 GMT -7
Plan B then - make sure the reverb cables are good and snug. If the ground on one of the connections isn't making good contact you can get this same issue. Pull them off, check them over, then push them on good and snug.
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Post by jacklawtey on Mar 2, 2008 10:28:10 GMT -7
Should I unplug it and let it stand for a few hours? I don't fancy poking around the innards of amp with no knowledge of what could potentially shock me and not! Haha. Thank you for your help
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Post by benttop (Steve) on Mar 2, 2008 10:55:33 GMT -7
No, you don't need to pull the chassis out. So you can not get a shock as long as you leave the chassis mounted in the cabinet. But there are two cables plugged in to the chassis that snake down to the Reverb tank. These are the cables I'm talking about. You might have to loosen the bag that the reverb pan is mounted in, but the idea is to unplug each of these cables, at each end, check to see if it looks ok, then plug it back in and make sure it's on there tight.
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Post by jacklawtey on Mar 2, 2008 11:32:30 GMT -7
I'm starting to think I'm just knit picking. As the difference in background noise isn't massive, it's quite noisy however. I replugged the cables in and it hasn't changed anything. Youtube is just processing a video I made of the noise, shouldn't be long.
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Post by bluzman on Mar 2, 2008 12:41:05 GMT -7
I'm pretty sure it's a V3 and/or V4 Tube. You may or may not hear it by tapping, but the symptoms described are all too familiar where a change with high quality tubes will probably fix it.
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Post by jacklawtey on Mar 2, 2008 12:46:26 GMT -7
The shop I bought it from, even though it was used, said they'd replace any faulty tubes. What tubes are V3 and V4 in the amp? I'm a bit of a tube noob! Thanks.
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Post by benttop (Steve) on Mar 2, 2008 12:55:05 GMT -7
Should be a chart pasted inside the cabinet that shows the locations of each tube.
I agree with bluzman, even if the tubes aren't microphonic they are usually the first suspect if there are problems. The only reason I suggested checking the cables is that I see that occasionally here as well. Amps that get hauled around sometimes have things come loose.
If I were you, I'd invest in some replacement tubes - they are good to have on hand "just in case" anyway. And they are not real expensive for the generic variety such as JJs or Groove Tubes such as might be available at Guitar Center. You can get much better tubes if you are willing to pay a lot more, but if the problem you're having is tube related, you'll find out fast by replacing them. It's a fairly inexpensive shotgun approach to troubleshooting, and if you discover that's not the trouble, you still have a set of backup tubes that you will surely eventually use.
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Post by jacklawtey on Mar 2, 2008 13:10:40 GMT -7
So I need one 12AT7 and one 12AX7 Okay. I've actually never replaced a tube before. Is it as easy as popping the case off, applying light pressure and just pulling the tube out, then pushing the new one in, making sure pins are matched up?
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Post by cheycaster on Mar 2, 2008 13:47:20 GMT -7
your a veteran already!!
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Post by benttop (Steve) on Mar 2, 2008 14:05:06 GMT -7
Yep!
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Post by bluzman on Mar 2, 2008 14:28:37 GMT -7
Get a good 12AT7. I bought a few cheaper ones and only 1 in four or so were good enough. I spend a couple more dollars for JAN Phillips and they seem to do the trick nicely.
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Post by jacklawtey on Mar 2, 2008 14:45:16 GMT -7
I love you guys! Thank you for being so helpful.
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Post by Don on Mar 2, 2008 20:57:36 GMT -7
Those are our boys, and we're proud of them!!!
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Post by jacklawtey on Mar 3, 2008 4:57:51 GMT -7
And I couldn't be more appreciative. The shop has mailed me one 12AT7 and one 12AX7 today! How good is that
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Post by Deleted on Mar 3, 2008 12:00:19 GMT -7
Geez. When I was evaluating a Maz 38 head with reverb I was told by Dr Z that it is an issue with reverb in the heads that can't be helped, which is one reason I went with the combo. This is the reply I got:
Reverb heads have more noise in general. It has to do with the proximity of the reverb tub to the transformers...somewhat unavoidable in the close quarters of the head cabinet. Combos do not have this problem because the tub is far enough away from the chassis. There is a compromise between eliminating the hum and squashing the tone of the amp. Ever wonder why Fender never made reverb heads in the 60s? A tube change in V3 or 4 could diminish some of the hum.
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Post by benttop (Steve) on Mar 3, 2008 12:26:10 GMT -7
Hmmm... it does say "head" in the OP....
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Post by Deleted on Mar 3, 2008 12:37:53 GMT -7
Hmmm... it does say "head" in the OP.... Yup. I had a problem with the head version of the Maz 38 and not the combo. The combo was quiet as could be. Thats why I chose the combo over the head, even though I would have preferred the head. I thought maybe there was something wrong with the head but according to the reply from Dr Z its just an issue regarding heads. I've ordered the Stangray head but won't have to worry as there is no reverb.
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Post by bluzman on Mar 3, 2008 12:53:01 GMT -7
The high pitched buzz made me think "tube" as that has happened with my Maz 18 Jr. combo a few times.
PT
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Post by benttop (Steve) on Mar 3, 2008 13:43:30 GMT -7
Well it's worth a try replacing tubes. It could be just the way it goes, but some tubes will probably be quieter than others.
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