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Post by johnnyrocker on Nov 29, 2006 21:21:11 GMT -7
i've been noticing something wierd about my amp. When I strum lets say an open G chord I am getting a harmonic that seems to be coming from the third string open. I found the pitch of the harmonic. I'm pretty sure it is a G note which sounds two octaves higher than a G on the first string 15th fret. If I am strumming pretty hard it comes out as very shrill sounding. At least the harmonic is a G and not an F#, I guess. I would like to know how to get rid of it though, it doesn't sound very musical. Other than that this amp sounds amazing.
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Post by guitargeorge on Nov 30, 2006 4:55:08 GMT -7
welcome to the insane world of the Dr Z. MAZ 18. This amp is one of the coolest sounding amps being made today but it is also one of the quirk-iest little beasts I have ever encountered in ampdom. I've had mine for about 6 years now and for the most part anything that went wrong with the amp could be fixed by swapping out tubes or cleaning connections. I made reference to hot italian sports cars being like the MAZ 18 cause to keep them up to snuff you have to open the hood up regularly and tinker with it. The MAZ 18 is very finnicky about what tubes are in it, the power tubes must be matched or it will get a slight hum and I mainly use JJ's but I have had weird harmonics things occur with brand new JJ's. I used also Groove Tubes but also had some sets that possibly were'nt matched as good as they should have and were noisy in the MAZ. I e-mailed Dr Z about my harmonics problem and he replied that this is normal, which I will attest to that being true, just play a vox or seventies Marshall and you get some harmonics that sound out of tune when you play certain notes or double stops around the 12th fret.Also where you are plugging in has a bit to do with it, I find a clean power source like a line with no other interference inducing demons works best. I found out that most of the weirdness is a result of the power tubes and that should be the first place you should look, next go through the amp with a screwdriver and make sure nothing is loose, especially the 4 bolts that hold the chassis in place, there's a shielding plate on top of the amp cab that must be snug or it will cause problems as happened to some members of this forum, a loose pot will cause problems, don't over-tighten them but make sure they are snug. JJ rectifier tubes have slightly smaller pins than some of the others so you may have to retension the recto tube socket. The reverb cables are another source for trouble, every now and then give em a shot of de-oxit. Your speakers should not be so tight that the speaker frames are in contact with the baffle board but just snug enough that the gasket on the face of the speaker is slightly compressed. If you bought the amp used you may want to check that. Be careful removing the speakers because the gaskets sometimes stick to the baffle board and you can ruin your speaker easily, use a thin putty knife to carefully separate the speaker from the baffle. If you have an older version say from the early 90's you may have a hum in your reverb circuit. This can be fixed by isolating one of the reverb jacks from the chassis and regrounding the jack at a different point. I called M.Z. and he told me how to do it and that problem went away. I have my MAZ operating at pretty much 100%, I still have weird harmonics happening but they are minimal, the cause for mine was the power tubes and I changed them and that solved it. hope this helps.
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Post by johnnyrocker on Nov 30, 2006 10:16:18 GMT -7
I just played a Z-28 head with a two 10 cab at a music store and was getting the exact same harmonics. wierd, it was the same pitch and everything. Different amp different guitar.
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Post by guitargeorge on Nov 30, 2006 12:04:49 GMT -7
I know the guy I bought my Z from and he said the amp made strange noises on some notes when he got it direct from dr z. He also is pretty much an old vox expert and said that the vox amps did this also, to a much greater extent than the z. I had on certain notes what sounded like a background hum behind the note and on the 1st string from the 12th to the 14th fret it was very evident. I swapped out the power tubes and it seemed to clear it up, I have a box of tubes and found 2 or three sets that were quiet and did'nt cause this phemomenon. Dr z and the guy from top hat (I had a club royale that had awful sounding bass tones when I played double stops at the 12th fret) said this was normal so my advice is to find power tubes that lessen this and just live with it. In a gig situation a lot of the extraneous noise will be absorbed by the band and the ambient noise in the room so a normal ear won't even notice it. I however had a bass player who had a set of dog ears who could hear this whenever I played my Z. He's the only one that ever commented on it. These Z's arent Fenders and although they get close they still arent Fenders.
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Post by johnnyrocker on Nov 30, 2006 12:30:37 GMT -7
what do you mean there not fenders, is that good or bad?
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Post by guitargeorge on Nov 30, 2006 12:53:14 GMT -7
I have a Fender amp also, it's a princeton reverb II. It's quiet, notes played out of it are clean, with no overtones, sparkly, this is kind of a general thing with Fender amps, Like a Fender twin, loud n clean, however the Z's are a little like a Vox and they arent as crystal clean as a Fender. Vox's tend to be chimey, heavy on the midrange tones, and break up pretty early and are kind of touch sensitive, meaning the harder you dig in to the guitar the more grit you get. The Z is like a cross between a Fender and a Vox with what I think is more of a slant to the vox side, or should I say more of the vox charachteristics, like weird harmonics and overtones. When I say the Z's not a Fender it's not a bad thing, but the Z as it will get close, It won't ever sound like a Fender.
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Post by (8^D) on Nov 30, 2006 17:32:24 GMT -7
I kept hearing harmonics from my Jr yesterday. Turns out it was a Mandolin on a stand right behind w/sympathy vibrations.
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Post by guitargeorge on Dec 1, 2006 4:50:00 GMT -7
I at one time had 2 of the first (not made in china) vox ac 15 reissues and I had the rattlin amp blues bad, the amps sounded great but there was this annoying rattle happening when I'd play the bass notes. Turned out to be the 2 little rods that are pressed in the reverb tank that are there to keep the spring chassis from flappin around too much were loose and rattling, I put a dab of silicone on the inside around each one and the problem vanished. I also used to keep my amp in top of a road case and the handles on the case would vibrate and cause a weird buzzing sound. The thing I was experiencing was electronically related, I've heard some techs referring to EL84 tubes as "Buzz Pencils" and it seems like pot luck to find a set that works smoothly in a Z. I found that damper rings help also, I use that automotive silicone (Hi Temp) and put 2 or three rings around power tube, and the rectifier. It eliminates that rattling glass sound that happens when the maz 18 is really cranked. I've had good luck with JJ's but had a bad set or 2, I've also had bad luck with Groove Tubes, got a few sets that worked in other amps but not in the Z. I never tried NOS but one tech I know said that a good set of NOS 6BQ5/EL84 would clear up a lot of the weirdness.
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Post by bolanrox on Dec 21, 2006 16:13:14 GMT -7
when i went into the studio two weeks ago we were setting up my Z getting some sounds, and we actually got an harmonic an octave lower than the note i was fretting. as it turns out it sounded really good for that part, enough so that i am thinking of trying to duplicate it with a pedal, because once mic'd you could not hear it.
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