SERIAL TONE KILLER - II Le Retour

Discussion in 'Ampage Area' started by hcsterg, Aug 13, 2019 at 6:47 PM.

  1. hcsterg

    hcsterg Country Gent

    Feb 13, 2012
    France
    Reprise du projet - nearly one year later ! :confused::confused::confused:

    I was somewhat fed up by the too numerous issues, and having other things to do... :oops:

    [​IMG]
    [​IMG]
    [​IMG]

    For those who are still interested in o_O... More adventures and pics tomorrow ! ;)

    A+!
     
  2. loudnlousy

    loudnlousy Friend of Fred

    Age:
    53
    Oct 18, 2015
    Hildesheim, Germany
    It still looks impressive to me.
     
    hcsterg likes this.
  3. Ricochet

    Ricochet I Bleed Orange

    Nov 13, 2009
    Monkey Island
    Looks great, I would love to hear it. Why use the Holy grail housing in there? Noise issues?
     
    hcsterg and Merc like this.
  4. Merc

    Merc Country Gent

    May 6, 2017
    Florida
    I wondered the same thing. One thing cool about it unlike most stock amp reverbs, you can switch between Spring and Hall. Or even the mighty Flerb if that’s your bag. ;)
     
    hcsterg likes this.
  5. hcsterg

    hcsterg Country Gent

    Feb 13, 2012
    France
    Exactly, Ricochet : you got it = noise, or more precisely hum due to magnetic induction. And it's still the issue that I have to cure...

    I used a toroidal transformer because - among its significant lightweight - I read everywhere that they provided much less 50Hz magnetic radiation than the classic EI transformers but I'm experiencing that this is not true at all !

    I will probably have to displace the reverb unit, because with already shortened cable, the improvement is good, but I want silence : I am hum allergic...

    Well, I use the (excellent) Spring preset only, so...

    I made some displacement test to judge the hum attenuation :

    [​IMG]

    I draw the conclusion that it was the wires... So I shortened the IN / OUT connections to the reverb. Neat improvement, indeed... But not perfect !

    [​IMG]

    That's why I think that a displacement may be mandatory... It's not what I would, but... o_O:rolleyes:

    A+!
     
    Merc likes this.
  6. dafreeze

    dafreeze Friend of Fred

    Dang HC, it looks awesome...can't make out most of them yellow words, though. Part of a song, maybe? I see le hum, de hum, du hum...yeah, I get it!
     
  7. Ricochet

    Ricochet I Bleed Orange

    Nov 13, 2009
    Monkey Island
    I have no idea what I'm looking at but, what is the function of those (wirewound) 5w1kj cement resistors?
     
  8. hcsterg

    hcsterg Country Gent

    Feb 13, 2012
    France
    Thanks dafreeze ! ;)

    Well, The Great Hum Song isn't my preference at all - I much prefer That Great Gretsch Sound - without hum ! :rolleyes::D

    Yes, Ricochet : these are the screen serial resistors of the 6L6GC power tubes (1K/5W) - usually 470R on Fenders and 1K on Marshalls. This allow me to install 6L6 or EL34.

    Today I made a power transformer displacement tests - quite conclusive :

    [​IMG]

    An EI type transformer of the same power may finally radiate less hum o_O, or at least an orientated one , moreover I can find one giving 2 plate voltages allowing HI power - FIXED bias / LO power - CATHODE bias. :cool:

    But the drawback is the weight increase : +3kg :eek: ! I tried to design this amp to be lightweight... I'm somewhat puzzled... :oops::(

    Wait and See... ;)

    A+!
     
    new6659 and dafreeze like this.
  9. hcsterg

    hcsterg Country Gent

    Feb 13, 2012
    France
    Latest news for today...

    Thanks to a tech-minded member on another forum, I placed the toroidal transformer with its axe horizontal (90° rotation) :

    [​IMG]

    And It eradicated the hum in the reverb circuit ! :):):) As simple as stupid as that... :rolleyes:

    That said, the toroidal transformer is nonetheless a widespread magnetic hum generator : don't expect to approach the amp at less than 2 meters with a single-coil pickups guitar in overdrive mode, and in a chosen precise position, at moderate overdrive and gentle volume.

    I just imagine playing loud with a hi drive level with a strat :eek::eek::eek:...

    Tentatively, I'll install the transformer on a bracket in order to go further in the building / setting of the amp, and make other tests to see if an EI transformer would be worth to install.

    Despite that, I can say that the short sound test I mad this evening were very promising, both in clean and overdriven mode... It's encouraging, finally ! :cool:

    Wait and See, then.

    A+!
     
    Waxhead and Ricochet like this.
  10. wabash slim

    wabash slim Friend of Fred

    Age:
    69
    Feb 10, 2010
    lafayette in
    Grounded shielding inside the amp section of the cab couldn't hurt---basically a Faraday cage. Cuts down on spurious emissions (Spurious Emissions is a great band name, by the way).
     
    hcsterg and audept like this.
  11. audept

    audept Senior Gretsch-Talker

    Age:
    71
    Dec 1, 2010
    Sydney, Australia
    I knew a guy who named his band "Nocturnal Emissions" ;)
     
    Last edited: Aug 15, 2019 at 8:20 PM
    wabash slim likes this.
  12. hcsterg

    hcsterg Country Gent

    Feb 13, 2012
    France
    Thanks for the suggestion, but this grounded shielding is already in the cab since its construction, making a Faraday cage, you guess it, wabash slim... ;)

    [​IMG]

    But this has no efficiency against magnetic field hum radiations. To be truly efficient, the chassis and the upper shielding would have been made from µ metal, an absolute pain to work and costing an eye ! :confused:

    A+!
     
    Waxhead likes this.
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