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Groove Tubes

10/20/2000 1:16 AM
Groove Tubes
I attempted to order a set of replacement tubes (Groove Tubes 6L6B)for my Hot Rod Deluxe. In the process of ordering, I was asked what the "hardness" was of these tubes. How do I find this info? There's nothing on the tube. Nothing in the owners manual. Nothing on the Fender site as far as I can see. The original tubes have white lettering if that matters. I noticed at another site there were the same tubes but with 3 different color printing. I'll assume the color-coding indicates the hardness. Any help would be greatly appreciated as I am a novice at this. All this talk about re-biasing,etc. has got me a little nervous. I just want to replace the tubes with the exact same thing that Fender had in there when I bought the amp. It's my understanding if I do this I won't have to worry about any re-bias.
10/20/2000 2:29 AM
Steve A.

    The original GT power tubes will have a number stamped on them, from 1 to 10. At least in the newer Fenders, the GT's are now color-coded with one of 3 colors. If your tubes have the GT logo but not the Fender logo check for a number stamped on them.  
Steve Ahola
10/20/2000 9:06 AM

Thanks Steve.....the tubes do have the Fender logo on them. And other than GT6L6B there's no number. All the lettering, GT logo, Fender logo is white. Can you provide anymore info. I'm really trying to avoid having the amp re-biased.
10/20/2000 11:17 AM
Naked Clarke

My newest Fender Tube Amp is a 1971 model so I do not speak from experience here but I have read that the newer Fenders are biased very cold from the factory in order to make the tubes last longer. I do not know if the GT color coded plug in tubes will perpetuate that situation or not, but you should consider having a tech check the bias out anyway. You may discover some welcome new tones from that amp.  
10/20/2000 6:03 PM

I must agree with Naked Clarke.  
The sooner you get away from F****r and Gr**** T****  
Chinese output tubes at ballpark bias settings, and get a good set of Tesla, Phillips or Svetlanas in there and biased properly, the quicker you will start to reap the sonic harvest that your amp is capable of producing. You might even save yourself some money.
10/20/2000 6:14 PM

They're RUSSIAN you say... Well, I still stand by the rest of my statement.
10/20/2000 7:26 PM

Hey Custom,  
In agreement with the preceeding fellows of distinction (being naked in public is pretty distinctive) I'd like to note that having your amp biased isn't like having the engine in your car replaced, more like just adjusting the idle. That is, a simple basic adjustment that any experienced tech should be able to perform in 15 minutes (assuming no repairs lined up ahead, no interruption, and the presence of a bias pot and come sort of cathode current bias probe - I can usually do it in that time while still having to jerk the chassis). If your tech really makes a big deal of it and wants large bucks - dump him!  
In any case, components age and the unadjusted bias current may not be appropriate for any set of new tubes. And since you're used to hearing the sound of aged tubes any tonal differences between the sets will probably mask any audible effect of the bias adjustement (assuming that you wish to re-adjust to factory settings - to "warm" up the amp will be different in a positive way)  
Lastly, it's easy to return the bias Voltage to the existing level on each tube's control grid if you don't like the sound.  
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