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Posted: Mon Jul 05, 2010 8:42 am
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hey we wont always agree 63, you know that.
i just ask questions to get replies. then its my job from there to do some homework on my own ya know. heck for all we know maybe ya both are dead wrong lol. i just know you have been there and done that.
results may very im sure. i respect your opinions thats why i ask for them.
key word there is opinion. i take the knowledge and go do my research
on my own. all i try to get is a little direction sometimes, from there its up to me. both of you have good ideas, but again results may very. :wink:


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Posted: Mon Jul 05, 2010 9:10 am
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My apologies 63supro,

The part of my post might have referred to you was "The most rare, artistic and scientific". I didn't mean to rip on any one in particular, just generally. See, I know the difference. ;)


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Posted: Mon Jul 05, 2010 9:17 am
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Hey WC Jr, ask away. That's all it is...opinion. What's good for one isn't good for everyone. You either try someone's advice or not. I you get some kind of starting point it's great. You can always tweak away and find you own voice. I've always experimented with sound since I was 12 or 13 years old. When I was 14 I played around with two tape decks, one was a Wollensack tube reel to reel and the other was a Lafayette electronics reel to reel. I made a crude echo out of them. I had a blast and my friends thought it was seriously cool too. That was 1969. The point I'm trying to make is ask questions, have fun and try stuff within reason. That's where signature tones come from. Or just read a book and be technical and think that's the only "right" way. How your gear suits you style is important too.

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Posted: Mon Jul 12, 2010 5:35 pm
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The blues jr's are biased high from the factory, all of them. It's a very good idea to have a trim pot installed for the bias, or at the very least, have the 22K bias resistor replaced with a 27K to 33K resistor to knock the bias down a bit. Ever notice how hot those EL84's get?? There's a reason for that. They're biased too high. Knocking the bias down with the above mentioned resistors will put it closer to the normal recommended bias range for EL84's and will not hurt the tone of the amp at all.


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Posted: Mon Jul 12, 2010 9:17 pm
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go look at the jj tube site. see what he says about baising the blues jr.

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Posted: Mon Jul 12, 2010 9:45 pm
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grbullets wrote:
The blues jr's are biased high from the factory, all of them. It's a very good idea to have a trim pot installed for the bias, or at the very least, have the 22K bias resistor replaced with a 27K to 33K resistor to knock the bias down a bit. Ever notice how hot those EL84's get?? There's a reason for that. They're biased too high. Knocking the bias down with the above mentioned resistors will put it closer to the normal recommended bias range for EL84's and will not hurt the tone of the amp at all.


Adding a trim pot or upping the value of the bias resistor may provide some sonically-pleasing effect(s) but the fact of the matter is, EL84s are hot-running bottles and no mods are likely to significantly alter that fact. However, chilling the bias a skosh might extend the life of the glass.

HTH

Arjay

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Posted: Mon Jul 12, 2010 9:45 pm
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There's nothing on the JJ site about biasing a blues jr. You must have seen something somewhere else. I've worked on enough of them to know that they're biased way too high from the factory. No need to have them that high. Reducing the bias on these amp's = better tone and longer lasting tubes.


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Posted: Mon Jul 12, 2010 9:56 pm
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your right it was the eurotubes site. i was looking for jj tubes.

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Posted: Mon Jul 12, 2010 10:28 pm
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OK, I saw it and have to disagree that reducing the bias slightly chokes the life out of the amp. That may be his interpritation of the tone. He's probably a heavy metal head that likes to heat his apartment with his guitar amp's. I've worked on a ton of these amp's and haven't had a single complaint about the tone disappearing. In fact I hear the exact opposite from my customers. The tone becomes musical rather than shredding. And the red glowing plates. I highly doubt that every case was a bad solder joint. The amp's are biased so high that if you put a tube in the amp that draw's higher than normal current, the plates will glow red. Tubes don't all draw the same amount of current, even if they are the same type , brand, and date code. They're all going to draw different amounts of current, and the ones that draw a high amount of current are going to glow if put into a Blues Jr. that hasn't had the bias knocked down some. I don't know what Bill M recommends as far as the bias goes, but using the resistors I mentioned will keep the bias within range for an EL84. Certainly will NOT suck the life out of the amp!


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Posted: Mon Jul 12, 2010 10:34 pm
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grbullets wrote:
He's probably a heavy metal head that likes to heat his apartment with his guitar amp's.


thats to dang funny right there. i use to be a hardcore metal head.
i know location is everything but what should one expect to pay for a
new bias job?
if you were gonna leave it stock for now, which tube kit from eurotubes would you restock your bluesjr with?

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Posted: Mon Jul 12, 2010 10:47 pm
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Well, you got it right. It depends who you take it to. It's only one resistor. Fifty cent part, about $30 labor give or take $15. It can be done without having to remove the PC board from the chassis if you know how to solder well. I usually replace the 22K with a 27K. Just a slight drop.


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Posted: Mon Jul 12, 2010 10:53 pm
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ok. so IF you were to leave the amp as is, which eurotube kit would you get for the jr? for a bluesy tone?
after the bias which kit?

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Posted: Mon Jul 12, 2010 11:41 pm
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Personally, I wouldn't buy a kit from anyone. I have my own stash of hand picked US made NOS tubes for my preamp sections. However, I do use the JJ EL84's, average matched pairs. (I have 3 Blues Jr's, so I need a good stash of tubes) If I had to choose for an unmodded bias amp, I'd go for a set of the cooler running power tubes. For a modded amp, I would likely go for a standard matched set of power tubes. Preamp tubes are another subject. They all will act differently, even tubes of the same type, brand and production run. The best thing to do is experiment with different types and brands. If you're looking for a nice bluesy tone with good crunch with a guitar, look at the high quality 12AX7 types that have good balance for V1 and V2, but more importantly, you'll want a tube in V1 thats dead quiet. These amp's are very touchy when it comes to microphonic preamp tubes. I use only US made preamp tubes and always have. I never used JJ preamp tubes so I can't elaborate on those. Even slightly noisy tubes in V1 will cause excessive noise in the amp, therefore it's very important that the first preamp tube be dead quiet. Ultimately you'd want quiet tubes in both V1 and V2, but you can get away with a slightly noisy tube in V2 as long as it's only slightly noisy. If you want very clean tone, try a 12AT7 in V2 or even V3. If you want a crunchy tone, a 5751 in V2 or V3 will help. Best thing to do is experiment if possible to find out what types work best for you. I'm not a fan of kit's as far as tubes go. My biggest personal beef with the BJ's is the speaker. I do not like the stock Fender (Eminence) speaker. Something like the Jensen C12N or Celestion Vintage 30 is a far better choice. I think the speaker is the first mod to be done in a stock BJ amp. Then choose your tubes......................Dave


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Posted: Mon Jul 12, 2010 11:45 pm
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my jr is the NOS.

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Posted: Mon Jul 12, 2010 11:54 pm
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Thats a good thing, then you don't need a speaker upgrade. I have a 96 tweed with a 1956 Jensen P12R Professional series speaker, a 60'th anniversary tweed with the C12N, and a relic tweed with a current production Jensen P12R.


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