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Post subject: Just bought a used Blues Deluxe! New Tube Question
Posted: Mon Oct 11, 2010 6:45 pm
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I just got a used blues deluxe for 500 even at guitar center. I'm in love with it. I have some Svetlana Winged C 6L6GCs that I would love to put in there. Do I have to get the amp biased, or would the stock bias work for these tubes? Also, is this amp fixed biased or adjustable? I read somewhere that it does not have an adjustable bias pot.

As for the preamp tubes, I have some ruby tubes 12AX7AC7 HGs, and some GT12AX7Rs. I have the Rubys in V1 and V2, and the GT12AX7R in V3, because it's a bit lower gain and I read that a lower gain tube in the phase inverter gives a bit more clean headroom and tightens up the bottom end.


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Post subject: Re: Just bought a used Blues Deluxe! New Tube Question
Posted: Tue Oct 12, 2010 5:32 am
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dgcobb wrote:
...Do I have to get the amp biased, ... I read somewhere that it does not have an adjustable bias pot....


I think that some of the early models did not have a bias adjustment, the schematic on the Fender site doesn't show a bias adjustment, but I believe that they do have one now. If you take off the back panel, look for a blue round adjustment pot, close to the bottom middle of the circuit board. It is always best to check the bias when putting in new tubes, and adjust if necessary. You'll just have to try different tubes to find the sound that you like. :)

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Posted: Tue Oct 12, 2010 7:02 am
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The Blues Deluxe Reissue (made in Mexico) has an adjustment pot the original Blues Deluxe does not. Depends on which one you have.


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Posted: Tue Oct 12, 2010 11:11 am
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My 09 (Made in Mexico) BDRI has a blue bias pot.
You have to take the panel off to verify it, though just in case Fender did make changes "without notice".


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Posted: Tue Oct 12, 2010 12:30 pm
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Blues Deluxe US can be easilly bias pot modified, there are a lot of DIY or good tech that can do it for you (web) and not really expensive but very usefull.
Winged-C- power valves are OK such as JJs. 8)

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Posted: Tue Oct 12, 2010 7:39 pm
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So, I tried out the Svetlana winged c 6L6GCs without biasing just for kicks. They had clean break up at basically the same volume, and the distortion was much sweeter. Here's my question, because they're both technically 6L6GCs (I read the stock GT6L6B is just a relabled russian 6L6GC), could I just stick those tubes in there? Because they have the same power rating and plate voltage (30 watts and 500 volts).

However, I was told by thetubestore that these tubes are equal to the blue GT6L6s, whereas the stock GT6L6s are white. What does this mean as far as biasing? Would I have to bias colder or hotter?

Thanks!


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Post subject: BDlx tubes
Posted: Tue Oct 12, 2010 8:48 pm
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dgcobb wrote:
...Here's my question, because they're both technically 6L6GCs ...could I just stick those tubes in there? Because they have the same power rating and plate voltage (30 watts and 500 volts).


It really doesn't matter if the tubes are similar or not, the bias could be very different between different brands of the same type of tube. It is always best to check the bias, unless you replace the tubes with the exact same brand and type. You might also be very close on the bias on the new tubes, checking it is the only way to be sure. It probably won't hurt anything to try different tubes in the BDlx, the bias will be close enough to try them. Best practice-always check bias with new tubes. :)

dgcobb wrote:
However, I was told by thetubestore that these tubes are equal to the blue GT6L6s, whereas the stock GT6L6s are white. What does this mean as far as biasing? Would I have to bias colder or hotter?


The GT tubes use the color code to denote when breakup occurs. Blue is for early breakup, White is medium, Red is late breakup (most clean headroom). The bias adjustment will also effect the onset of breakup. You can bias hot for earlier breakup, or colder for more headroom, but the bias should be within a certain range for proper operation and longest life. :)

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Posted: Tue Oct 12, 2010 9:06 pm
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Also, it's not a bad idea to wrap your screwdriver's entire metal shank with electrical tape so as not to risk static electrical booboos.


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Posted: Tue Oct 12, 2010 10:08 pm
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Well, the problem is that I want a lot of clean headroom. So with the 6L6GCs in the blue range, I would have to bias the amp cold to get more clean headroom. Is there a difference in tone or volume between a tube with late breakup biased hot, and a tube with early breakup biased cold? I mean, if it was all up to biasing, why would we care what the breakup rating on the tube was?

I want a lot of clean headroom, and I'm basically trying to decide if I should buy a pair of tubes with later breakup, or if I should just bias the amp cold with my current early breakup tubes.

Thanks


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Posted: Wed Oct 13, 2010 8:00 pm
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You would be best off to leave the bias alone. There is seldom a good reason to mess with a bias pot. There is a proper range for bias adjustment and it should be in that range for most tube swaps. I'm not saying not to have it checked, but if it's in the proper range leave it alone. You can get tubes that are number rated but every company has their own system and I think it's just Sales Hype. If for some reason it needs to be adjusted such as after doing some internal electrical work such as on the power supply section of the amp it may need a tweak. In all the Fender amps I've ever worked on, 100's of them over the last 50 years only a few had bias issues, and I think most of them it was because some fool just had to mess with it. Think of it this way, many amps don't even have a bias pot and swapping tubes is common with no problem.


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Posted: Wed Oct 13, 2010 9:46 pm
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thanks, I asked the guy at thetubestore, and he said it would be fine to put those tubes in without rebiasing. The Fender bias is set cold from the factory, so the only reason to rebias would be if you want to run the tubes hotter, which I don't. So, because I would have to set the bias cold anyways to get more headroom with these early breakup tubes, the amp is already biased where I want it to be.

For the record, those tubes sound awesome in the blues deluxe RI, and I'm still getting about the same clean headroom. My next move is to put a JAN 5751 in V1.


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Post subject: BDlx bias
Posted: Thu Oct 14, 2010 7:41 am
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Hi dgcobb,

And what exactly is your bias setting? You said it is biased cold from the factory, but you really have no idea, right? Are your new tubes balanced? If you were "in love" with the new amp with the existing tubes, why change tubes? If someone says "don't adjust the bias with new tubes", then they don't have a clue about properly biasing an amp. You seem determined not to even check the bias, despite those in the know telling you to check it. :?

Quote from thetubestore website:
"The bias of tubes is critical (learn more about bias) to the sound of an amplifier and the life of its tubes." (This quote from their bias probe ad). :idea:

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Posted: Thu Oct 14, 2010 10:59 pm
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Well the guy from thetubestore told me in an email that I shouldn't have to bias the amp when i put these particulary 6L6GC tubes in, because they have a cool rating and the fender is biased cold.

"As I said earlier, the rating you received is a cooler rating. Adding the fact that Fender's are always set cold at the factory it's only logical to think the bias will remain cold. Perhaps not exact 61mA, but who cares, that's not the point at all. Just install and listen to determine if they sound "right" to you."

"Yes, the SED's should be fine if you just plug them in. If you end up not digging the tone/headroom, have the bias tweaked and you may find a sweet spot for your style."

These tubes are a matched quad. What I gather is that basically this set just happens to be a good match and the stock bias of the amp will stay pretty cold b/c the tubes have a cooler rating. Because I want the bias to be cold anyways to get more headroom, this is ok.


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Posted: Fri Oct 15, 2010 6:35 am
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I think what the Tubestore guy ment is it's biased a bit on the high side (cold), which means it will run cooler and the tubes should last longer, which IMHO is good. My old Twin Reverb was easy in tubes and so were my Deluxe R and Princeton R. Tubes lasted for years, original RCA Power tube that is. Import tubes I doubt will last as long. You should hang on to your old tubes and try to find a Tube tester and compair them to the replacements, you might be suprised what you learn about your tubes. Most Fender amps are biased a tad cold, some exceptions like the Blues jr and some high powered 2 and 4 tube 6L6 amps pushing 60 watts or more, where they push the Plate voltage near 500V and bias it low for more output. Yep the tubes fry in the sockets, won't last as long, kind of like taking a Stock Chevy small block and pushing 600 Hp out of it, it's great for the short run but needs more maintenance.

What ever you do remember the bias control is not a tone or gain control. In most cases I recommend people leave it alone.


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Post subject:
Posted: Fri Oct 15, 2010 8:44 am
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actually I think the tubes are hot, not cold. They are supposed to have an early breakup. He said they were similar to a blue rating on the GT scale.


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