DSL50 tube selection

Discussion in 'The Workbench' started by wichita, May 10, 2009.

  1. wichita

    wichita New Member

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    I could not find 4 matching 12ax7 tubes yesterday. Here is what i came up with. 2 groove tubes 12ax7M and 2 groove tubes 12ax7R tubes. The russian tubes are the new ones with the sticker instead of the GT logo painted on. would they be a 12ax7R1,2,or3 version,or none of the above? So, if this was your amp (DSL50)what tubes would you use where? New set of GT E34LS with a 7 rating also. I've heard a lot of debate about marshalls 45ma bias recomendation, some say that's too hot. Any one have any experience with these tubes?
     
  2. MartyStrat54

    MartyStrat54 Well-Known Member

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    Well all I am going to say is that Groove Tubes buy all of their tubes and then they relabel them. So you are probably getting Sovtek tubes. Also, you do not need to match the preamp tubes. I would use the two highest gain tubes in V1 and V2 and then some decent tubes in V3 and V4. The phase inverter (V4) does not have to be perfectly matched as many believe. Just a good tube that is somewhat matched will do the trick. The power tubes need to be somewhat matched, within 8 per cent of the highest to the lowest. This benefits the biasing of the power tubes and the distribution of current and voltage on the plate and grids. That's why it is just common practice to buy a matched set and these are usually within 3 per cent of the highest to the lowest.

    A lot of the guys like the E34L tubes. However, JJ makes this tube and it is cheaper to buy them as JJ's instead of Groove Tubes.

    Marty
     
  3. wichita

    wichita New Member

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    yeah,i understand that GT just relabels other brands of tubes. i guess what im getting at is out of these 2 versions of 12ax7(the 12ax7R,and the 12ax7M)what tube has the higher gain? the russian,or the mullard reissue? is the 45ma bias ok for the e34ls? what kind of current do they like to see?:hmm:
     
  4. solarburnDSL50

    solarburnDSL50 Well-Known Member

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    Go for the Mullard. 12AX7R: Groove Tubes select Russian type, slightly brighter and lower gain, excellent for most Fenders.

    Its cheaper if you don't buy GT. They relabel and increase the price.
     
  5. mystic fred

    mystic fred New Member

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    you don't have to have matching 12ax7's - it is only important to have matching EL34's and re-bias the amp when fitting. :)
    btw go for British made Mullards (not reissues) or Brimars if you can, they have a well earned reputation, and can be picked up on Ebay for only around £15-20 each.
     
  6. Leo27

    Leo27 New Member

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    Tungsol re-issues and Shuguang ninth generation are fine current production 12AX7 preamp tubes.
     
  7. HAMPAMP TUBE AMP SERVICES

    HAMPAMP TUBE AMP SERVICES Member

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    What you set your bias to depends on your plate voltage and at what % of dissipation you are shooting for. The common formula used is: ( max dissipation x preferred dissipation [no more than 70%]) divided by plate voltage. If your plate voltage were at 375vdc then 46ma would be correct for 70% dissipation. There are a lot of variables and difference of opinions when it comes to bias. I personally don't like to bias at 70% but most seem to want to run it at max.
    When you change the bias setting the plate voltage will change as well so you need to set it and then check your plate voltage then set it then check your voltage again, and again until it's right, especially if you want to run at maximum.
    There is a safe zone that your bias can be set too which falls between being biased to the point of cutoff to biased to the point of destruction (above 70% max dissipation which is 25 watts for an EL34). Any setting within that safe zone that gives YOU the best tone is the correct bias setting. So an amp with 450vdc on the plates could be set somewhere between 27-38ma and any setting in that range that gives you the sound you want is the correct setting.
    AND THAT IS MY UN-BIAS OPINION.
     
  8. kharvelan

    kharvelan New Member

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    I'm using tung sols bought from dougs tubes. they rock, I have seen lots of times people mixing up different 12ax7s I'd suggest maybe getting a few different ones and experimenting until you get a sound you like.
     
  9. MartyStrat54

    MartyStrat54 Well-Known Member

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    You go Mystic! I love the NOS tubes and have a large selection of USA tubes, as well as Telefunken, Amperex and "real" Mullards. If you wheel and deal the right way, some of these tubes can be picked up for $10 (US) on up to about $28 US dollars. I will take the sound of an NOS tube in my amp any day over a current production 12AX7.

    Marty
     

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