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  1. D

    Simple Attenuators - Design And Testing

    I had to mess about with the gain on the mic input to get the levels close to each other. I'll do another test with the EL34 valves in it, might be interesting. I got the amp cheap on the local adds here in Edinburgh, £120 I think, it had the foot switch plug (mini 5 pin DIN) snapped off with...
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    Simple Attenuators - Design And Testing

    Some sound clips from todays testing: Strat PU position middle/neck position, middle has magnet poles reversed mod. Clean channel gain maxed then master volume increasing with successive attenuation, ending up with the amp gain and master vol maxed out.
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    Simple Attenuators - Design And Testing

    Big thanks to John for his design. Another plus for the bigger case was I drilled 2.5mm holes in the case then cut a tread with a M3 tap, I used the screws from the switches I bought, dual pole dual throw, each came with 3mm threaded terminals and 6 x 3mm screws, to fix the resistors to the...
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    Simple Attenuators - Design And Testing

    So finally got the M2 8ohm version built and running some tests, sounding sweet :) will upload some samples to Soundcloud next week. I used my 3d printed bobbin to wind L1 and used wire gauge for 50W amps. For the 100W capable coil I’ll print a bigger bobbin. I added an extra heat sink over R1...
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    Simple Attenuators - Design And Testing

    This low cost winder...
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    Simple Attenuators - Design And Testing

    Excellent info, thanks John, just what I needed. I'll measure the 1mm wire I bought with a micrometer, I'm assuming the 1mm spec is for the copper only and doesn't include the insulation layer. I might need to add small amount of space to my bobbin to allow for this. Even if it's only 0.05mm...
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    Simple Attenuators - Design And Testing

    Would be helpfull if you could post the dimensions (in mm) of the copper windings for your coils? The wire gauge, internal diameter (ie 1st coil winding), outside diameter (last coil) and the height/thickness excluding the plastic. I may revise my bobbin, the one I made might be a bit closer to...
  8. D

    Simple Attenuators - Design And Testing

    My main take-away from that reference was the cross sectional shape of the windings to give the most effiicient inductance/weight of copper, if you look at the commercially available coils,the coil cross section is mostly square.
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    Simple Attenuators - Design And Testing

    Deep dive... http://info.ee.surrey.ac.uk/Workshop/advice/coils/air_coils.html
  10. D

    Simple Attenuators - Design And Testing

    Here's a zip of the 3d model I created to make the bobbin, result is better when printed in 2 parts then glued together (with acetone = nail varnish remover).
  11. D

    Simple Attenuators - Design And Testing

    Here are the calculated values for winding the coils for an M2v when using my 3d printed bobbin: For the 16/8/4Ω version: L1 Inductance 0.91 mH DC Resistance 0.36 Ohms Wire Gauge 18 AWG Wire Diameter 40.3 mils (1 mil = .001 in) Coil Length 0.8 in Coil Inner Diameter 0.6 in Coil Outer Diameter...
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    Simple Attenuators - Design And Testing

    Hi John, my meter doesn't do inductance. These are calculated values but audio specific, site I used diyaudioandvideo dot com Calculator/AirCoreInductorDesigner/ Size wize they are similar to the dimentions of the ones for sale. For some future research I was thinking of including an option to...
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    Simple Attenuators - Design And Testing

    The last items I need to build John's attenuator are the inductors, Instead of buying I made my own :) First I 3d printed a bobbin, I used '3d Builder' feee app from Microsoft, the whole thing is made up of a series of cylinders of various sizes, added to and subtracted from each other. I...

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