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  1. JohnH

    Work Bathroom Etiquette

    Fundamental rule if there's two guys there: No talking until you both reach the hand basins. Two women? A man and a woman? - I have no data on those cases!
  2. JohnH

    Simple Attenuators - Design And Testing

    Following on from above, here's a diagram for those who love diagrams: This the calculated response of a basic 8 Ohm M2, driven from an 8 ohm amp tap (based on my VM), stepping through all the attenuation steps from full volume down to nominally -31 db. 'db inc' is the difference from the...
  3. JohnH

    Simple Attenuators - Design And Testing

    Hi Gene, I looked at that before, to try to work out a set of values to buy from typical Chinese sellers - see the first diagram. I went for 5 Ohm at R8 and the diagram shows R7 staying at 33 Ohm. Theres no tonal consequence (less than 0.1db at any frequency) but it shifts the attenuation down...
  4. M2 8 ohm response.jpg

    M2 8 ohm response.jpg

  5. JohnH

    SV20c questions

    Hi Gene, Id like to see those! are you still able to point a link to those comments? J
  6. JohnH

    Simple Attenuators - Design And Testing

    Aluminium is all good, whether its die-cast or extruded. Its about 5x as conductive as steel, and probably 2x as thick in a given application, so 10x better. So between those two AL cases, it all comes down to the thickness of the material and the surface area. My belief is that the...
  7. JohnH

    Simple Attenuators - Design And Testing

    That's a shame! I would have looked very nice Im happy with the Hammond styles for mine, and the box 'lid' is the base which looks a bit better i think due to the slight taper of the sides. These boxes also give you continuous Aluminium for what is then the top and sides, to get max conduction...
  8. JohnH

    Simple Attenuators - Design And Testing

    Hi @Gert-Jan van der Heiden . That looks like a really nice build, clean and simple and I like the 3d coil-mount gadget. Just on the order of stages, yes you can reorder them and it makes no significant difference. A little history.... At the start of the thread, you can see the previous...
  9. JohnH

    I need a way to boost the VOLUME of an already od boosted JCM800

    Just throwing out some thoughts: So if im following this right, there's plenty of volume available, but a pure volume change is wanted for solo/rythym transitions without changing tone? or maybe both are already driving the amp so more front end push doesn't add volume? Also, noted: the desire...
  10. JohnH

    New Harley Benton PA-250 Attenuator

    Yes you should do it! (but keep the day job!). You'll see how easy it is to build the perfect attenuator. BTW, if you do, a voice coil is not the right thing to use in our design. A simple air-coil of the right value and low resistance is the go.
  11. JohnH

    Simple Attenuators - Design And Testing

    ok, I can have a go at working that out. Another reason not to go down to 20ga is to control resistance, which we don't really want in the coils.
  12. JohnH

    DSL401 dead - no sound

    Yep! that's the key question! The classic issue with these amps is the rectifier that supplies the heaters that make these glow. Note V1 is inside a metal screen.
  13. JohnH

    Simple Attenuators - Design And Testing

    Hi @Gene Ballzz , I think the case looks good for the basic versions, given some planning . Would it need some components on the top and on the bottom in order to fit? It's not huge in surface real-estate. On the coils, I think both those values are within range of the sweet spot sych that...
  14. JohnH

    Simple Attenuators - Design And Testing

    Hi @lwgramith , Im very happy that you got it going! My hunch from the various readings is it was some kind of short to ground, maybe between stages 1 and 2.
  15. JohnH

    Simple Attenuators - Design And Testing

    hi @lwgramith , you're in good hands with Gene. If a problem does not quickly become apparent, I'd suggest to do a little temporary rewiring and one more set of tests. Test 3 check that everything that should be 'grounded' (ie connected to the sleeve lugs of the jacks, though it's not a real...
  16. JohnH

    Your first Marshall was...

    All cool tone monsters so far. Mine was just a little Mg10-cd. A rude noisy little b¥gger. I still have it and use it as a desktop speaker.
  17. JohnH

    Simple Attenuators - Design And Testing

    hi @Gert-Jan van der Heiden , thanks for joining in. Yes It would be safe to plug in headphones at max attenuation. But it may sound bad since there's no treble roll off or other tone shaping due to a guitar speaker. It really needs at least a cab-sim circuit, or better, an IR device, before...
  18. JohnH

    Simple Attenuators - Design And Testing

    Hi @gbarker7815 , welcome to our thread. 5% tolerance is fine for any of the resistors. For the base set of values, I selected from the most common ranges of resistors that have steps of about 20%, eg 10, 12, 15 etc. That shows how 5% is accurate enough if that is what you can get. The most...
  19. JohnH

    Simple Attenuators - Design And Testing

    I can't figure out how if might occur, but those two additional tests which are both giving 6.5 or 6.6, that's as if your R1 and R2 are being connected in parallel somehow. eg, a short to ground at the right side of R2, hence meeting the lower side of R1.
  20. JohnH

    Simple Attenuators - Design And Testing

    hi @lwgramith , further on these tests: .....these would be with no amp or speaker, but with leads plugged in and measuring to the far end of leads. All switches to max volume = min attenuation Test 1 If you measure tip to tip from input to output, with M-lite, you should read just L1 (in...


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