Modding the Blues Jr "Tone Stack" mods

Discussion in 'Amp Central Station' started by Tele Vince, Dec 2, 2016.

  1. Tele Vince

    Tele Vince TDPRI Member

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    Has anyone experimented with changing the mid tone cap at all?

    I’ve changed my bass cap from 0.022uF to 0.1uF. Happy with that change.

    However, I also changed the mid cap from 0.022uF to 0.015uF, per BillM’s specs. Now, I find the mids to be muddy (too many 150-400Hz, not enough 700-1,000Hz).

    Would it make sense to put the 0.022uF mid cap back in? Or maybe go all the way up to the 0.047uF that many Fender amp’s use?

    Thanks!

    Note: To sit well in the mix, I keep treble around 9, mids around 9 (would go up to 10 for the high mids, except those low mids are too prominent), and bass around 5 or so. My BJr is loaded with an Eminence GA-SC64. (I was going for a speaker that would be like a cross between a Jensen C12N and Emi Texas Heat.)
     
  2. Andy B

    Andy B Friend of Leo's Ad Free Member

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    I use a .022 mid cap & .1 bass cap in the amps I do. I've thought about using a .047 for a bass cap but haven't tried it out yet. Speakers I like are Red White & Blues. MY personal amp has a reconed UL Twin Reverb Pyle speaker in it.
     
  3. Tele Vince

    Tele Vince TDPRI Member

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    Are you pretty happy with the .1 bass and .022 mid combination?

    I was thinking that changing the mid cap to .047 (but leaving the bass at .1) would maybe help create a higher ratio of high-mids to low-mids.

    I hadn't considered yet reducing the bass cap to resolve my issue. Would that be beneficial? I feel like my bass knob isn't affecting the "muddy" frequencies as much as the mid knob does.

    Thanks!
     
  4. Tele Vince

    Tele Vince TDPRI Member

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    Switching to 22nF from 15nF seems to bring those frequencies down about 1dB, but is that enough? 47nF definitely gives the type of curve I'm looking for, but will it take out too many overall mids? That is the question. Any input is appreciated. Thanks!

    15nF - white
    22nF - pink
    47nF - green

    [​IMG]
     
  5. JD0x0

    JD0x0 Poster Extraordinaire

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    700-1000hz can be boosted without the lower mid/bass mud by increasing the 'treble cap' FWIW. This is a common midboost mod, switching a 1n-2n in with the standard ~250pF treble cap.


    Also, you can also try keeping the 15nF midcap and raising the slope resistor to get rid of mud. The Dumbles skyliner stack uses a 10nF mid cap, 100nF bass cap, and a 150K slope. The higher value slope resistor helps tame the low frequencies a bit.
     
  6. Tele Vince

    Tele Vince TDPRI Member

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    I currently have the 250pF treble cap. What value would you recommend replacing it with?
    Do you happen to have more info on changing the slope resistor?

    Thanks!
     
  7. JD0x0

    JD0x0 Poster Extraordinaire

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    It's probably easiest to download this and experiment
    http://www.duncanamps.com/tsc/

    The slope basically controls the 'slope' of the EQ. A smaller value leans the slope towards a more mid/bass heavy sound, while a higher value reduces gain, and slopes the EQ so that lows/low mids are reduced.

    As far as the treble cap, again, experiment. Marshalls typically use 500pF and the Dumble 'mid boost' is usually in the ballpark of 1.2n-2n (up from stock 330p) which gives a much more serious mid boost, that tends to be better when tied to a switch because of how extreme it can sound.
     
  8. Tele Vince

    Tele Vince TDPRI Member

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    Your nuanced approach of changing the slope resistor sounds like a good one.

    Since I already had the part, I tried just putting a 0.022 mid cap back in. Seems to have removed the muddiness. (Yay!) I do understand though why BillM recommends the 0.015. That definitely sounded fuller when clean. So, it's a trade-off between fullness and mud. Since I play more overdriven than clean songs, the less muddiness was a larger priority. (If I was playing mostly cleans, I'd probably leave the 0.015 cap in.)

    Either way, increasing the bass cap was still the way to go. I'm happy with the 0.1 I have in now, but I bet a 0.047 could be a good choice compared to the stock 0.022 too.
     
  9. Andy B

    Andy B Friend of Leo's Ad Free Member

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    Sorry I didn't see this before. I am pleased with using the .022 cap for midrange. Works well with single coils & humbuckers. I want to try the .047 as a bass cap but not enough to tear the amp apart. Next time I have one apart I will experiment more with cap values. Most BF amps used 250p, .047u, .1u for the tone stack. The Super & some Bandmaster Reverbs used 250, .022, .1. You find the 250, .022, .022 in tweed amps. Another choice which I like & use as a normal channel revoice is 330p, .033, .033.
     
  10. Tele Vince

    Tele Vince TDPRI Member

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    Yeah, that 0.015 mid cap was just pure-mud when I'd switch to the ES-335 instead of the Tele. Not a good cap for use with humbuckers. The 0.022 seems to work well.

    I'd be afraid that increasing the mid cap to 0.047 would mid-scoop that amp too much, and I think a bass cap at 0.022 doesn't allow enough low end into such a small cabinet.

    If you try 0.047 as the bass cap, let me know how it goes.

    Using the Tele into the BJr, with 250p, .022u, .1u in place, I'm liking this setting: Treble - 9.25, Mid - 10.25, Bass - 5.5. I need those mins somewhat cranked to cut through my horn section.

    What have you found are the big tonal and control advantages to 330p, .033u, .033u?
     
  11. Andy B

    Andy B Friend of Leo's Ad Free Member

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    The 330p, .033u, .033u tone stack gets you more towards a tweed sound with a little more mids & the lower bass slightly rolled off. I like that on BF/SF amps to compliment the Vibrato channel. I've reworked my amps so I can jumper the 2 channels & then blend in whatever sounds good. I've thought about using that tone stack in a Jr. but lean more to the 250/.022/.047 setup. Next one in for service I'll experiment if time allows.
     
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