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Post by kidmagic on Feb 21, 2008 12:41:52 GMT -7
Just got a Z28 1x12 Combo new about 4 weeks ago. A few days ago I started to noticed a strange almost buzz everytime I hit a D note on 6th string 10th fret, or 5th string 5th fret. It also comes out a bit on Db. Even if I play a cord with a D in it, I can hear that buzz. It's a low buzz, almost like a car idling at twice it's normal speed (call it 2k rpms) - but's very noticable. Doesn't really fade as the note falls off, just stops at a certain level of note decay. The note quality doesn't seem affected.
I'm playing at low volumes too, just practice in the house - running the amp very cleanly. Other than that the amp sounds great.
Any ideas?
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Post by amakitalo on Feb 21, 2008 14:00:41 GMT -7
I am sure others will chime in here as well, but make sure the bolts on top your amp are tight. Also, check the tolex around the amp; I've had amps with loose tolex parts that we re "flapping" in the wind so to speak. Check the front and rear panels of the amp. Sometimes the plastic in the panel becomes loose and rattles when you play. Easy to fix with silicon.
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Post by kidmagic on Feb 21, 2008 23:23:56 GMT -7
Amakitalo - thanks for the response. Checking stuff tonight - that's definitely not it. In fact now that I'm paying really close attention new facts arise. The sound doesn't start right away, but came up after the amp has been played for a bit - so I'm thinking it's got to be something in the wiring /caps etc. anyone?
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Post by benttop (Steve) on Feb 21, 2008 23:30:19 GMT -7
Amakitalo - thanks for the response. Checking stuff tonight - that's definitely not it. In fact now that I'm paying really close attention new facts arise. The sound doesn't start right away, but came up after the amp has been played for a bit - so I'm thinking it's got to be something in the wiring /caps etc. anyone? 99% of all issues like this are a bad tube. You should have a spare set anyway - pick up some tubes and start swapping one by one. You can do some preliminaries though - wait till the amp is good and warmed up, then use a pencil and tap the eraser on each preamp tube very lightly. You may discover a microphonic tube. They will probably make a slight noise when you tap them, but if it is microphonic you'll know right away because it will be very noisy or loud. It's a shame we don't have all the great tubes available that we had in the '50's and '60s, but those days are gone for good.
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Post by kidmagic on Feb 22, 2008 17:55:41 GMT -7
Tried tapping on the pre-amp tubes and there were no problems - dead silent. I have a 6545 down at my studio, so I'll probably pull the ef86 tonight and swap the other 12ax7's, but I'm definitely not convinced it's a tube problem (I've been through that before with other amps). But I really want that to be the problem cause it's an easy fix - so fingers crossed.
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Post by benttop (Steve) on Feb 22, 2008 18:16:55 GMT -7
I'll cross mine too. ;D
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Post by kidmagic on Feb 22, 2008 20:38:19 GMT -7
Well shoot..... not the pre-amp tubes or the rectifier. On a good note I found an old GE 5751 to go into P2 that I thinks sounds better than the Sovtek - also found an current run EF86 and 5ar4 in my tube junk box that I swapped in, but alas the strange noise continues..
Really strange, doesn't happen right when the amp is fired up, but comes on pretty quickly (as I've been swapping tubes in and out). The sound reminds me when your in your apartment and you can hear your neighbor turn on their shower and there's that faint whinning of the water running through pipes.
Crap - I have a feeling it's a bad cap or something. That sucks- the amps maybe 4 weeks old.
Any chance it's a power tube issue??? (I don't have any extra's of those).
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Post by benttop (Steve) on Feb 22, 2008 22:03:35 GMT -7
Odds are it's a tube more than any other thing, but sometimes infant mortality strikes. It would be worth trying the power tubes before you send it in to the Doc and have to be without it for a while....
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Post by DRZ on Feb 23, 2008 5:26:54 GMT -7
What is the serial number ? Were did you buy it ?
Z
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Post by kidmagic on Feb 24, 2008 22:23:42 GMT -7
Hi - thanks for checking in Dr. I purchased it from Willcutt Guitars on January 7th, the serial number is Q45266.
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Post by DRZ on Feb 25, 2008 15:00:08 GMT -7
That's not a correct Z-28 serial number please check again. And the Q designates 2006 build.
Z
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Post by kidmagic on Feb 25, 2008 15:31:57 GMT -7
Oops, serial number is Q 15266. Sounds like it was an '06 that sat at Willcutt for a year, because I just bought it, and was told it was brand new - and I still have the receipt to prove that if necessary.
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Post by DRZ on Feb 26, 2008 5:52:22 GMT -7
No that's cool, of all my dealers Willcutts has the largest in store inventory of Z-Amps and that happens sometimes.
E-Mail Sales@drzamps.com and request a RA form.
Fill out the form and send the amp back we'll fix it up.
Your sure it's not a tube, tube clip, or even your guitar pick-up right ?
Z
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Post by Phil (aka Phil) on Feb 26, 2008 7:58:08 GMT -7
No that's cool, of all my dealers Willcutts has the largest in store inventory of Z-Amps You ain't kiddin, Doc. I'm always amazed when I drive down there. Amy *hates* it when I tell her I'm taking a road trip to Willcutts. I always come back with some Z product. Last time it was a convertible 1X12 cab with a G12H30.
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Post by kidmagic on Feb 26, 2008 10:50:01 GMT -7
Dr. Z. Thanks - much appreciated.
What is a tube clip?
I've changed all the tubes except the power tubes (because I didn't have a spare set). I'll pick a pair up in the next couple of days and give that a try - trust me, I'd much prefer if that were the issue. It's definitely not my guitar, or guitar cable (I have several, as well as several amps).
Derek
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Post by Bill on Feb 26, 2008 11:23:54 GMT -7
Dr. Z. Thanks - much appreciated. What is a tube clip? I've changed all the tubes except the power tubes (because I didn't have a spare set). I'll pick a pair up in the next couple of days and give that a try - trust me, I'd much prefer if that were the issue. It's definitely not my guitar, or guitar cable (I have several, as well as several amps). Derek Doc's referring to a tube retainer clip...they'll sometimes vibrate against the tube and make a tinny buzzing sound. You can temporarily release it from the tube and then see if you still hear the same buzz.
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Post by kidmagic on Feb 26, 2008 22:52:37 GMT -7
Holly-relief!!!! it was the power tubes. Made the trek to the dreaded Guitar Center and purchased a new set of power tubes tonight and popped them in there; I played for at least a half with no sign of that weird noise! Fantastic - you guys were dead-on. So strange that noise was caused by the power tubes, and with no other decay to the performance of the amp.. Anyway, thanks everyone - happy ending. lesson learned.
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Post by benttop (Steve) on Feb 27, 2008 6:45:15 GMT -7
Hey that's great news! Tubes are weird that way - so many bizarre things that they are capable of doing when they malfunction.
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Post by Phil (aka Phil) on Feb 27, 2008 7:09:41 GMT -7
Hey kidmagic, I've got a Z28 that had a stock power tube (6V6R) go bad a while back. I took that opportunity to try out various NOS 6V6's. I tried out some NOS GEC 6V6's from Mike at KCA NOS and really liked 'em. I also tried the Brimar STC 6V6 GT's, but the latest ones I have in my Z28 are these: www.kcanostubes.com/products/236/NOS-JAN-Philips-6V6GT-Matched-Pair.htmSo far I think the JAN Philips are my favorites. The GEC's have a great midrange that kind of remind me of a "Route 66 Jr." The Brimars are a little darker; they would be great with a Tele. The JAN Philips are a little brighter and have a little more "spank". Either way you go, the NOS ones sound better (IMO) and are more reliable than the 6V6Rs. I biased 'em at 24mA. I also changed the rectifier to a NOS while I was at it. Phil
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Post by DRZ on Feb 27, 2008 7:37:22 GMT -7
Hey Kidmagic, E-Mail me Sales@drzamps.com and request a new set of 6V6's . Your amp is only a few weeks old and I'll send you a back-up set. Just include your address.
Thanks for going the extra mile and finding the problem, I'll cover the tubes.
Z
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Post by kidmagic on Feb 27, 2008 9:53:26 GMT -7
Dr. Z - Wow, thank you, that's very generous. I recognize that tube durability is out of your control, so thank you - that's above and beyond. Really, much appreciated!
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Post by kidmagic on Feb 27, 2008 10:08:47 GMT -7
Hey Phil - I'll definitely have to try out some NOS power tubes one day - but I've never learned how to biase an amp and understand I'll need a meter of some kind (nor do I want to kill myself). So I just do the Groove Tubes power rating thing and don't worry about it.
I do however want a NOS rectifier tube. Thinking Mullard because I've heard they're brighter and have less sag than the mislabeled Jan Philips 5V4GA I got from KCA NOS Tubes which I already have in my 6545. Do you know of a trusted source at a reasonable price?? (KCA is out except for the $200 versions). Also there seems to be a million on ebay, but they are all different - what do you look for?
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Post by fishman on Feb 28, 2008 19:42:33 GMT -7
kidmagic, find a guy on here by the name of nitehawk, email him and ask him if he has any NOS rectifiers for sale. I have bought a couple myself and they really make a difference that you can hear right away. Also, no worries dealing with nitehawk there are several guys that have had dealings with him with no problems.
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Post by Phil (aka Phil) on Feb 29, 2008 5:20:16 GMT -7
kidmagic, I've got a few real Mullards (that I bought years ago) along with some mislabeled Philips, a GE, and a few others. I've been a tube geek for many years- I started restoring/repairing old vacuum tube radios and moved into building/tweaking guitar amps, so I've got a few vacuum tubes in the collection ;D
My opinion is that going from new production to NOS rectifiers is the most important and biggest step; the different brands of NOS rectifiers do have different characteristics but it's not nearly as big a difference. What I mean is that going from "new" Russian or Chinese to NOS is like 80% or 90% of the difference, and the "brand" might be that last 10% of the equation. The Mullards are great but honestly the GE or mislabeled Philips are really close, IMO. You can hear the difference in a quiet room but it's not something you'd ever hear on stage with a band. The biggest thing is that any NOS rectifier will have a *much* longer lifespan.
I personally would not ever buy something like a Mullard from Ebay. There's way too many fakes out there, or it could be a used tube with not much life left on it. Very few people have the test equipment necessary to really test a tube any more, so you're taking a big leap of faith.
If you're not a comfortable working inside a "live" tube amp I'm with you about the biasing. Since you have to bias a Z amp with the chassis out you could get killed really easily by touching the wrong thing. I will say that on a fixed bias class AB amp like the Z28 that I like to check the bias after going from a "new production" rectifier to a NOS. Theoretically you should be okay (it's not like you were going from a tube rectifier to a solid state rectifier; then you would *have* to check the bias) but I've seen some tube recto changes that have changed the bias by a few mA. You should be okay though.
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Post by dongiesen on Feb 29, 2008 18:34:51 GMT -7
Nighthawk is the man ok. I think he even listen tests them in his amps after whatever else.
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