will this work?

Discussion in 'Shock Brother's DIY Amps' started by Jewellworks, May 6, 2021.

  1. Jewellworks

    Jewellworks Tele-Meister

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    im attempting to do a little tone shaping, so my EQ isnt overwhelmingly low end. i seem to have a sweet spot where it sounds great, and i can cut lows from about the last qrtr turn of my tone pot. but anything below that, as far as rolling off high end (which also boosts the low end somewhat) gets muddy quickly.
    i switched to a linear pot last night, and this is what im getting. it was even worse with an audio taper pot.
    mind you, im not complaining about the taper, so much as the sudden woof of low end. just trying to get more useful tone control from the sweet spot down. there are several ways to do it, and i was thinning the coupling cap, and thinning the bypass cap on the cathode... then i thought of this.

    Image1.jpg

    will this work? where i have it?
    how will it effect the EQ? -or should it?
     
  2. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    If I am looking at it right, ime it would help keep some highs but the pot(s) would still dump it to ground. It may be better to go the more traditional approach with the *bright cap* located on the pot(s). Maybe both bypasses could be implemented or a hybrid (some point in the signal path to the wiper).
     
  3. Jewellworks

    Jewellworks Tele-Meister

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    well, i still want to roll off the highs when turned down, so i have a true tone control, but its like, ive got a ton of lows. i was looking to reduce it to have a more "balanced" control knob. on the one hand, i want to keep the lows because it drives the signal pretty hard and i get a fat distortion. but on the other, its a LOT. just looking to find a middle ground somewhere.

    my biggest concern here was if this was in the right place or not. or maybe after the 250k wiper, but before the gain pot?
     
  4. ThermionicScott

    ThermionicScott Poster Extraordinaire

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    "Muddy/woofy" is what a Big Muff tone control does when you turn it down. Especially if what you're feeding it is already bassy. ;)
     
  5. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    How about working on the low pass filter. The .01uF to ground. Maybe something quite a bit smaller to let some highs pass.
     
  6. Jewellworks

    Jewellworks Tele-Meister

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    ive been messing around with the TLC Big Muff simulator (actually, the XL Spread from this thread) :

    but its all relative to how much low end you have feeding the tone stack to begin with. ive been making my adjustments with this as my guide. it includes the coupling cap, which the TLC version doesnt.
    so again, im thinking if i cut some lows before it hits the tone stack, i should actually have more control over the tone im looking for.
     
  7. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    Perhaps putting in a resistor to ground right after the coupling cap. This would form a high pass RC filter which would not be intertwined with the circuit. A 470K resistor and a .0047uF cap would result in a corner frequency of around 72Hz.
     
  8. mrriggs

    mrriggs Tele-Meister

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    When I get some time, I'll revise the spreadsheet to show your circuit changes.

    In the mean time, may I suggest you look into an "S" taper pot. I have a tilty-type tone control in my amp and it was way too hard to control with a linear pot. I ended up making a 220k-S pot out of a 100k-L pot by narrowing the carbon track between about 3 and 7. Made a HUGE improvement in the knob range.

    [​IMG]

    Just kind of eyeballed it and scraped the carbon off with an Exacto knife. You should be able to see shiny spots where the wiper is contacting the carbon track. Scrape off everything outside the shiny spots, leaving the full width at both ends of the track.
     
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  9. mrriggs

    mrriggs Tele-Meister

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    I'm working on the spreadsheet now. Did you adjust the Zin value to match your 6SF5 and 150k plate load? Should be about 45.8kOhms. When I plug that in with resistors and capacitors shown there is a huge treble cut which leaves a big bass hump. That alone may explain what you are hearing.
     
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  10. mrriggs

    mrriggs Tele-Meister

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  11. mrriggs

    mrriggs Tele-Meister

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    Fiddling around with different values, I think you can get closer to what you want with just the single coupling cap. Plug in these values; Zin = 45.8kOhm, coupling cap = 4.7nF, R1 & R2 & R3 all 1MOhm, C1 = 0.22nF, C2 = 1nF, R4 (your gain control) = 500kOhm.
     
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  12. Jewellworks

    Jewellworks Tele-Meister

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    @mrriggs
    that spreadsheet is amazing. your amazing.
    im going to try all the above. i didnt think about the 6SF5 being THAT far off from a 12AX7! yes, im hearing a big bass hump, and would like to get more of something to play with around the sweet spot. i kinda like the super excessive low end when driven hard. its such a FAT tone! but more often than not, ill stick to the sweet spot. ill adjust all this tonight.
    ill reserve scraping the carbon trace for after i hear what this does.

    cant thank you enough. this spreadsheet is fantastic. it takes into account a high impedance input with the coupling cap, whereas the TLC Web version assumes a Cathode Follower circuit.

    now do one for the Bone Ray... ;)
     
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