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  1. miallen

    The way you play is about to change...

    Digital signal processing (DSP) does not work well with subtle non-linear processing. By non-linear I basically mean wave shaping and in the most general case clipping. There is a page on the softube website describing how they model harmonics and such. But consider that the page also states...
  2. miallen

    Help! 1959SLP HW PTP Clone - Making Noises/Microphonic

    That sounds like parasitic oscillation. Specifically, if some of the output signal is being injected back into the input, such as because a high current output wire like a power tube lead is dressed too close to a high impedance input wire that is greatly amplified, you can get squealing and...
  3. miallen

    yet another dumb question

    If you're using the 120VAC tap and the transformer has another winding for 240VAC that you're not using, then yes, it's pretty much dead weight. But reducing the weight of the PT by even half (not realistic) would probably not equate to that much compared to everything else in the amp. You...
  4. miallen

    Intermittent Buzzing

    This is an important clue. If you turn the volume down ON THE GUITAR and the noise goes away, that means the noise is definitely not the amp. It would have to be something connected directly to the volume control. So if you think about it systematically and trace it back, it could be: The...
  5. miallen

    Weber 6M45P Head Kit Build

    The bias resistors are 2W. They are exceptionally small but I bought them from Mouser myself. Weber kits are definitely not "ideal". But they are cheap. And the amp rocks. I have been noodling on if for 2 days now and there are multiple sweet tones that can be dialed up. The threshold between...
  6. miallen

    Weber 6M45P Head Kit Build

    I find it difficult to believe that holding the suppressor screen at ground as opposed to through a 1R to ground is going to make a shred of difference. The voltages generated across it are going to be really small in the scope of things. In a cathode biased amp it might be important but not...
  7. miallen

    Weber 6M45P Head Kit Build

    Here are some pics. Seems to work fine so far but I've only been playing for a few hours so I'm not absolutely certain that it's functioning exactly as intended. I am getting some strange frequency responses under the analyzer (notches at 200Hz in some settings - not sure if that sort of thing...
  8. miallen

    Why "Improved" Master Volume?

    No, that can't happen because of grid current limiting as described above. Unlike transistors, tubes cannot saturate because the grid current limits how "on" a tube can be.
  9. miallen

    Why "Improved" Master Volume?

    That is not consistent with my understanding. See page 46 of Blencowe Designing Valve Preamps regarding blocking distortion. In short, when a tube (pre or power) is overdriven, as the grid voltage approaches the cathode voltage, electrons are attracted to the *grid* instead of the plate. This...
  10. miallen

    Why "Improved" Master Volume?

    I'm building a kit and I want to add a post PI master volume. I was thinking of just replacing the pull-down resistors with a dual 250K pot. But it seems there is an "Improved" method that adds a dual 1M pot and 1u caps in front of the pull-down resistors. However it is not obvious to me why...
  11. miallen

    Why Bus Wire Back of Pots?

    It's not a ground loop if the circuit ground and chassis are only connected in one spot. But a ground loop is a potential issue with using the pot ground for signals and not just as a shield. If there is any other place where ground connects to the chassis, that *will* make a ground loop...
  12. miallen

    Why Bus Wire Back of Pots?

    Yes, there are separate grounds. But they all run to a central "star ground". So using a multimeter there should be no resistance measured between any of the "separate" grounds because they're all connected together. But the trick is that they all have to be connected together back at *ONE*...
  13. miallen

    Why Bus Wire Back of Pots?

    I'm not sure I understand this. The major current sources / sinks would be primary members of the star. This would include the center tap of the PT. Actually that might be the most important connection to the star. So in order of importance (meaning they should be large thick short wires), the...
  14. miallen

    Why Bus Wire Back of Pots?

    Now this makes sense. So then pot housings should have a soldered wire connecting them to ground. But I would still argue that it should only be on the shield ground.
  15. miallen

    Why Bus Wire Back of Pots?

    I just don't think the pot housings or even the chassis should be used for any other than a shield. So if the pots are like some Alpha pots that I have that have continuity through the bushing, they should not be used as a ground. Some grounding methods I've been looking at violate some basic...
  16. miallen

    Why Bus Wire Back of Pots?

    Ok, so if the pot housings are already grounded through their bushings and I'm not worried about them spontaneously coming loose, then it's not necessary.
  17. miallen

    Why Bus Wire Back of Pots?

    The housing of a pot is clamped around the front onto the bushing and the bushing is bolted onto the chassis and the chassis is grounded. So why is there bus wire soldered to the backs of pots?
  18. miallen

    Weber 6M45P Head Kit Build

    Where is a good place to post build questions? I just bought (ordered) a weber 6M45P head kit which is a JMP 50 clone. Schematic and layout here: https://taweber.powweb.com/store/kits_60b.htm#6M45PH I have a lot of experience designing and building circuits. Not so much guitar amps but I...

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