Which 5881/6L6 for my Bluesbreaker RI?

Discussion in 'Amps and Cabs' started by Dashface, Apr 26, 2016.

  1. Dashface

    Dashface Member

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    So... I bought a Bluesbreaker (as some of you may know) last week. Played a couple of shows with it, and I liked it but it wasn't my favorite thing ever. It was awfully harsh and bright no matter what way I set things.

    Now, it's not my first BBQ, so I don't think it's really user error... But I noticed it definitely has the original Sovtek power tubes in there. I swapped out the V1 and V2 preamp tubes for some nice Brimar ones, which helped, but... I think those power tubes need to go.

    So my question is which 6l6 or 5881 should I get? I want something warmer and broader. I wouldn't hate it if it broke up a bit earlier. Right now the amp is very spiky, which doesn't work for me. The obvious choice would be KT-66, but as my Bluesbreaker is from 1992 it apparently won't fit them (due to the narrow cab).

    Ideas, gents?
     
  2. Stormin

    Stormin Staff Member Gold Supporting Member

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    I have a BBRI and a JTM45RI.

    My BB came with NOS Tung Sol 5881s which do sound really nice, but I know they're expensive these days. I had a pair of Winged C 6L6s laying around and I put them in the JTM. They sound great. I also have several pairs of TAD 6L6WGC short bottles. That'd be my recommendation for great, affordable current tubes. They'll kick the pants off the Sovteks.

    You could also ask @Blue Strat if he has any Phillips 6L6WGB pairs left. That'd be another affordable NOS choice. I shoulda got a pair but I don't see them on his site anymore.

    One thing to keep in mind is that when stock, the BBRI is more like a 1987 with a tube rectifier and 6L6s. It's not very close to an original BB. To get those Beano KT66 tones requires a lot of work changing out the filtering, speakers, OT and other components.

    I should also ask, how are you running the BB? Are you using it clean and with pedals? That's how I run mine. If so, what really warms it up for me is to plug into input 1 on the bright channel and don't jumper them. I set the bright volume to what I need and then turn the normal volume up to 6 or 8 (even though I'm not plugged into it). That works really well to thicken the tone because of the way the channels interact. Give it a try.
     
    Last edited: Apr 26, 2016
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  3. Dashface

    Dashface Member

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    Thanks for that excellent advice. I have been using it clean with pedals and just need it to be way less harsh - so I'll try what you said!
     
  4. dmentzer

    dmentzer Supporting Member

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  5. HandOfTheHost

    HandOfTheHost Member

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    JJ has 5881's available. I have not heard them but I like their 6L6's
     
  6. Mark Kane

    Mark Kane Silver Supporting Member

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    I would check to see if the tubes you have in it now are properly biased.
     
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  7. crazyneddie

    crazyneddie Member

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    Congrats on such a killer amp. I love mine, just wish I had more muscles! Seems strange to find these amps harsh. I would also wonder if the tubes are biased correctly. I have a set of NOS tubes all round, Mullards mostly and they break up early and sound great. But, I was very surprised how good the amp sounded right out of the box brand new. These amps are hard to get bad tones out of, so I would get a little TLC on that amp. Also, a bias adjustment pot is dirt cheap to install and I get one put in every amp I am going to keep. Also, maybe someone has modded it and f'd it up. What kind of guitar are you playing? Where on the volumes does it start to break up with no boosts, Pedals, etc? You may also try plugging in to the normal channel. Like another poster stated, both volumes effect the fullness of the tone even if you are only plugged into one channel. So you could plug into the normal channel, don't jump the channels, but crank up the bright volume. You'll hear it fatten up as you turn it up.
    But most likely they are tired old tubes and a new set and a bias should solve your problems.
     
  8. Stormin

    Stormin Staff Member Gold Supporting Member

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  9. Dashface

    Dashface Member

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    Yeah
    Yeah, I'm thinking it must be badly biased and crap old tubes... I mean, it's not my first BBQ and I know my way around an amp - but I just couldn't get a tone out of this thing that I liked to save my life.

    To answer your question, I played it in two shows two nights in a row - three sets per night. So, it got a good little workout. Used my usual pedalboard (which is all very nice things), and used a 99 LP Standard with Wizz pickups, a Historic SG, and an AVRI Tele Custom with Bareknuckles. So... Decent things.

    Too bad it doesn't already have a bias knob - I'll have to take it to a tech I guess. It was really hard and unforgiving, and really crisp in the highs. Broke up a bit around 3 on the knob. But not in a nice way. Tried both channels.
     
  10. Stormin

    Stormin Staff Member Gold Supporting Member

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    There is a bias pot inside the amp. It's the blue one labelled VR1. VR2 is the hum balance pot.

    The gotcha is that there are no external test points. That means you either poke around inside the amp with a multimeter, or you buy a bias probe (I got a Compubias and it's fantastic).

    At the end of the day, you need to know 2 things: the DC plate voltage and then the bias current. The BBRI and JTM45RI run in the neighborhood of 400 VDC, give or take how strong or weak the GZ34/5AR4 rectifier is. If you're way off from this, you may need to try another recto tube. Once you know you have good voltage to the plates, then you can set the bias current (which will vary depending on the exact tubes your using). Somewhere between 55% to 70% of max, depending on what you like to hear.
     
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  11. Dashface

    Dashface Member

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    Well, I talked to a couple of techs, and then I figured what the heck... Opened it up, and found that the V1 bias knob was absolutely all the way on full.

    ...So, I backed it off about a quarter turn and buttoned the amp up again :D Very scientific, I know.

    The result is that the amp sounds about 1/3 less loud, but waayyyyy warmer and smoother. Much more to my liking. Before it was harsh and cold, now it sounds wooly and wonderful. Much improved! :)
     

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