Tube matching?

Discussion in 'Amps and Cabs [BG]' started by Edword, Mar 28, 2018.

  1. Edword

    Edword Supporting Member

    Jun 23, 2005
    I'm once again on the hunt for 6KG6As for my Traynor YBA-3A, and as usual can't find a matched set of four.

    Could I get away with getting 2 matched pairs and installing one pair V1 - V4 and the other V2 - V3?

  2. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
  3. Edword

    Edword Supporting Member

    Jun 23, 2005
    Much obliged!
  4. Wasnex


    Dec 25, 2011
    With separate bias for each pair of tubes it should work, but the more dissimilar the tube's operating characteristics are, the worse the results will be.

    Two tube are connected to one side of the output transformer (OT), and two tubes are connected to the other side of the OT. Pairing a weak tube and a strong tube together typically results in the weak tube conducting less and the strong tube conducting more, so you want a reasonably matched pair on each side of the transformer. 15% variance is reasonable; 20% will work. As the mismatch gets worse you loose output power because the tubes are operating further from the ideal bias point.

    Separate bias is required to balance current passing through each side of the output transformer. In others words, the total current passing through each pair of tubes should be equal.
    At some point you may want to convert over to JJ EL509S. These are current production tubes. You'll need different tubes sockets and a bit of rewiring. Here's a thread you may find interesting. Traynor YBA-3A 6KG6 to EL509S
  5. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

    Jun 16, 2021

Share This Page