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Post by robertlucas on Jun 9, 2014 8:02:08 GMT -7
Hi all, just had the powertubes of my EZG replaced with new groovetubes 6l6GE's and also installed a new Tung Sol 12AX7 V1 tube. But now it seems that the amp produces a much more compressed sound than before. Especially when I use overdrive or distortion. Did I buy bad tubes or can it be something else? Thanks in advance for your comments.
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Post by Eddie on Jun 9, 2014 9:55:03 GMT -7
Did you have a tech replace the power tubes, and was the bias adjusted? I suppose it could be tubes or a change to the bias that is making the tone more compressed.
Also, if you still have the preamp tube that used to be in V1, put that back and re-test.
Keep with it - you have changed a couple of things and just need to back-track a little. You'll get it.
Eddie
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Post by headshrinker (Marc) on Jun 9, 2014 10:14:38 GMT -7
My guess would be that the amp is biased hotter than it was before. I would swap the V1 as Eddie suggested first. It's an easy test. Changes in preamp tubes, especially if you changed brands, can have a big effect.
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Post by wubberdubber on Jun 9, 2014 10:35:19 GMT -7
Some power tubes break up or compress more than others....that's why Groove Tubes used to test and rate (don't know if they still do) their tubes with numbers 1-10, the higher numbers being the "harder" or more headroom tubes. As mentioned, could be a bias issue also, if it wasn't adjusted with the tube change.
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Post by Maddog on Jun 9, 2014 12:36:55 GMT -7
Agree with all above!
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Post by robertlucas on Jun 9, 2014 14:58:52 GMT -7
The bias was adjusted by an amptech. The new powertubes have the same rating as the ones that came with the amp (4) so I guess they should break up and sound the same as the originals. Only newer....:-) I'll try the old V1 tube again. Couldn't it be a problem with one of the other preamp tubes? Thanks!
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Post by jlc on Jul 11, 2014 23:19:21 GMT -7
I am not a tech and i am going throw a number out and more tech savy members may comment.
I think i read or was told that the EZG should be biasd 35 to 37, not gospel, may be wrong, do you know what your tech did?
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Post by dalegreen on Jul 16, 2014 6:39:47 GMT -7
I just did a complete retube of my EZG head (2008 anniversary) and went with the factory spec JJ power tubes with a "5" rating I believe (same as the originals, then no need for a rebias). I also replaced the rectifier and all preamp tubes. I put in a 5751 in the V1 position, really like that tube, brings the initial gain stage down slightly, so I can push it a little harder and drive the front end pedals a little more. I only use a kingsley tube boost fro extra gain, just gives it that slight edge when needed. Also put in a couple of NOS tubes in the reverb circuit (RCA). The amp is the warmest rig I have ever played, use it mostly in a jazz / blues setting, never too much volume .
Your V1 preamp can really make or break the tone you want to get, seems to be the only preamp tube I do alter form factory specs.
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Post by robertlucas on Sept 14, 2014 4:25:27 GMT -7
Thanks for all your answers. My tech set the bias to 37 and I replaced the V1 tube again. It seems to work now!
Cheers!
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Post by Jaguarguy (Mike) on Sept 14, 2014 6:35:39 GMT -7
I just did a complete retube of my EZG head (2008 anniversary) and went with the factory spec JJ power tubes with a "5" rating I believe (same as the originals, then no need for a rebias). I also replaced the rectifier and all preamp tubes. I put in a 5751 in the V1 position, really like that tube, brings the initial gain stage down slightly, so I can push it a little harder and drive the front end pedals a little more. I only use a kingsley tube boost fro extra gain, just gives it that slight edge when needed. Also put in a couple of NOS tubes in the reverb circuit (RCA). The amp is the warmest rig I have ever played, use it mostly in a jazz / blues setting, never too much volume . Your V1 preamp can really make or break the tone you want to get, seems to be the only preamp tube I do alter form factory specs. Just because the tubes have the same "rating" as the tubes you took out doesn't mean they don't need to be rebiased.
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