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  1. HotBluePlates

    Marshall Bluesbreaker reissue EL34 impedance?

    It doesn't matter. Use whichever impedance setting sounds best to you. You can leave it on the 8Ω position (with your 8Ω speaker load) or switch to the 16Ω setting. The latter changes the effective load the tubes are working into, which may or may not alter the power output when you use...
  2. HotBluePlates

    So... I got a Spark

    Why does it need a "grounded supply"? You didn't list Hum among the Cons... Half of the folks starting threads about the Spark mention hum, the other half say there isn't any. I strongly suspect the issue is "crap outsourced power supply" vs "replacement, better power supply" and that...
  3. HotBluePlates

    Thoughts on adding a “FAT” control to a tweed type amp?

    Most "Fat" switches add a bypass cap across a cathode resistor that isn't already bypassed. Make that added cap large & you get a full-range gain boost. Make that cap small & you get boost for highs only. Have a switch with an Off position, small-cap on one side & large cap on the other and...
  4. HotBluePlates

    5E4 Tweed Super Bias and Red Platting

    Yes, if it were my 50's Fender amp I'd leave the original resistor in place. There should be a wire from the Speaker jack back to a 56kΩ resistor on the eyelet board. Try unsoldering that wire & carefully taping the end to insulate it. This opens the feedback loop. If you play the amp like...
  5. HotBluePlates

    5E4 Tweed Super Bias and Red Platting

    Typo; I've corrected above. My reasoning is while higher resistance is worse than lower resistance (for bias stability in the face of grid current), having a pair of 300kΩ resistors in this bias-feed role shouldn't be unworkable. So then I wonder about how the bias voltages at the grid compare...
  6. HotBluePlates

    5E4 Tweed Super Bias and Red Platting

    If it were my tweed Super, I wouldn't replace that resistor (not simply because it's measuring 239kΩ 293kΩ). Try the voltage measurements I asked about. They're more relevant, and will avoid needless part-replacing.
  7. HotBluePlates

    5E4 Tweed Super Bias and Red Platting

    First off, it's unusual to monitor d.c. plate current when playing the amp. Depending on the metering used, direct current will be confused by the alternating current increase (which is your audio output to the speaker). But seeing a higher reading with-signal is normal. I too was thinking...
  8. HotBluePlates

    Thoughts on adding a “FAT” control to a tweed type amp?

    What is "this amp"? It helps to know the starting point. "Fat" switches usually boost amplification of low frequencies. Or the might be a full-range gain boost. Do you care if the boost is "Lows Only" or "Overall Gain"?
  9. HotBluePlates

    Jensen P12R in Deluxe Reverb?

    Give it a shot. Don't be surprised if reality doesn't align with digital simulation + IRs. Worst-case, the P12R is probably easily re-sold if you don't like it in your amp.
  10. HotBluePlates


  11. HotBluePlates

    Blue glow from 6v6

    Do you have another 6V6 handy? If yes, just pull the right 6V6 (with the blue glow) and plug in the other 6V6. If I'm right, the red plating 6V6 will settle down. If you have the tube, it's a 4 minute test (and most of that time is letting the tubes cool so you can pull it with bare fingers)...
  12. HotBluePlates

    Super reverb got back?

    It won't help the tubes get the airflow they need to cool off. The Super Reverb already gets hot due to the power & rectifier tubes (some feel the panel & worry it's "too hot" even though it's fine). Not a great idea to enclose the tubes in a sealed box unless you're trying to make an...
  13. HotBluePlates

    Putting filter cap on a switch

    Good points! Thanks for the sanity check @VICOwner!
  14. HotBluePlates

    Internal speaker cable; where do you find one?!?!

    Mojotone - 19" speaker cable 1/4" Flat Plug 1/4" Right Angle Plug
  15. HotBluePlates

    Putting filter cap on a switch

    DISCLAIMER: I haven't tried this so I might be overlooking an obvious problem. @VICOwner I understand why you switched the positive terminals, since you were using can capacitors with a common negative terminal. However, if individual caps (with separate negative terminals) are available, why...
  16. HotBluePlates

    Variacs (off Amazon)

    I haven't found that to be an issue in practice. That said, I haven't used smaller than a 40w bulb. I suppose ultimately, you just need an obvious change of bulb-brightness from "Normal" (dim) to "Shorted" (full brightness).
  17. HotBluePlates

    Where Leo got the name "Bandmaster" ( my theory)

    Everything I wrote was just an observation, so my own speculation. It would help if I read or owned any of the reference books on Fender history, but I don't. However, very early on there was a "Dual Professional" amp that apparently became the 2x10 Super. So what about 2x12? "Twin Twelve"...
  18. HotBluePlates

    Amp head as a preamp

    Thanks for the correction! I've deleted my post so others aren't mislead by the error.
  19. HotBluePlates

    Where Leo got the name "Bandmaster" ( my theory)

    The other side of that coin is the tweed 5E7 Bandmaster was one of the rarer models, and among the most-expensive vintage amps in the early 90s. Supposedly, Mark Baier got into amp building because he wanted to hear the 5E7 Bandmaster but couldn't find one to play (and maybe couldn't afford it...
  20. HotBluePlates

    Where Leo got the name "Bandmaster" ( my theory)

    Could be. A "bandmaster" is the person leading the band. In an orchestra or marching band, they're the person "conducting" the band. In jazz/pop music, they're the person that's the shot-caller for arrangements & who does what when. In the American Federation of Musicians (AFM) Union info...
  21. HotBluePlates

    Variacs (off Amazon)

    Just be aware that a lower wattage bulb limits current to a greater degree.
  22. HotBluePlates

    Best replacement output tranny for Tweed Bandmaster?

    Your key statement above is "... badly [modified]." Capacitors generate very little heat, even when they're passing huge amounts of energy. So while an electrolytic capacitor will literally explode if you apply wrong-polarity voltage (cause it turns into a short-circuit), the reference to...
  23. HotBluePlates

    5E4 Tweed Super Bias and Red Platting

    First step is getting your wall voltage down to 115v at least. High wall voltage is pushing your supply/screen voltage high, leading to increased tube current. This is visible to us in the high heater voltage of 6.8v instead of 6.3v.
  24. HotBluePlates

    Different shades of blue: Power tubes

    Probably something with the glass used. Because after Philips acquired Sylvania, all the PhilipsECG 6L6WGB tubes also have blue glow at the glass.
  25. HotBluePlates

    Best replacement output tranny for Tweed Bandmaster?

    28w vs 45w is 62% power, and 10 log (28/45) = ~2dB less volume. But you can make that up & more with sensitive speakers. If you use a Celestion G10 Gold instead of a reissue Jensen P10Q volume rises from 10 log (28w) + 93.8dB = 108.3dB to 10 log (28w) + 98dB = 112.5dB So a Bandmaster with...

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