Recent content by dougsta

  1. dougsta

    Can you functionally test a 12AX7 for balanced triodes in an amp?

    From the video description: "Using an oscilloscope, and two probes, you can perform the balance of a phase inverter via this process. It should work with any amp, Connect two inputs to each side of the output of the phase inverter, before it goes into the power amp tubes, on each half."...
  2. dougsta

    HAMMOND branded tubes

    Check the etched codes against this page to find out when and where they were made, the printed logo is marketing (but adds a huge amount to the resell price, if they test ok hifi audiophools pay top dollar) https://mullard.org/blogs/news/mullard-valve-etched-codes-how-to-interpret-them This...
  3. dougsta

    HAMMOND branded tubes

    Let me know if you want more!
  4. dougsta

    HAMMOND branded tubes

    A bunch of vintage EL84's, the tooling mark is a single line, not a cross!
  5. dougsta

    HAMMOND branded tubes

    An EF86 from 1958 with the type and date codes upside down!
  6. dougsta

    HAMMOND branded tubes

    ECC83 from Mullard and Telefunken (has white writing on the top) and a Tungsram 12AU7 made by Mullard Blackburn factory in 1962.
  7. dougsta

    HAMMOND branded tubes

    Close up of the cross mark, the one on the left is the mC1 ECC83 with goal post getter, the one on the right is a 1958 Mullard ECC83 made in Holland.
  8. dougsta

    HAMMOND branded tubes

    Here is a Brimar 12AX7 black long plate from the 1950's, it doesn't have the cross mark on the top. Brimar used their own tooling.
  9. dougsta

    HAMMOND branded tubes

    Here is an mC1 revision ECC83 from 1956 B6B factory and date code (aka long plate square/goal post getter)
  10. dougsta

    HAMMOND branded tubes

    Stand by for some vintage valve pr0n... Here's some pics of my vintage audio Mullards + others. You can tell a Mullard (whether made in UK or Europe) even if the writing etching is gone, they have a tooling cross mark at the top of the glass, Philips (owners of Mullard) used the same tooling...
  11. dougsta

    Bassman Micro EF80 PT: Still another idea

    I cheat and roll my own iron! Always a good idea to have a stock of beefy resistors handy though, try a few dropping options (series or parallel some for options) and work out the theoretical drop and measure against what you get when the valves start pulling load at idle or power chords.
  12. dougsta

    Shock mount tube sockets? Yet another thing I didn't know...

    Just checked my EF80 amp, I used the McMurdo skirted sockets on the 2 preamp EF80 valves and regular McMurdo sockets on the PI and OP valves. The 2 skirted sockets were pulls from old reel to reel recorders that used EF86 valves, I did think about using those EF86's for a preamp but went with...
  13. dougsta

    Shock mount tube sockets? Yet another thing I didn't know...

    I used 5 x EF80 valves in my EF80 pp amp head, 2 for the pre amp, 1 for PI and 2 for the pp output stage. I used McMurdo skirted sockets £4 each from here: https://www.langrex.co.uk/products/b9a-mcmurdo-skirted-anti-vibration-new-valve-base-socket-x1pc-b14/ Didn't notice any microphonic...
  14. dougsta

    Transformers - the how, why, when and where!

    But 1st, working on an update for my OT calc app, add more templates and add inches/metric switch
  15. dougsta

    Transformers - the how, why, when and where!

    Now I'm going to have to try and wind one! Doug




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