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5E3 Mods gone wrong?

Discussion in 'Shock Brother's DIY Amps' started by James Knox, Sep 8, 2020.

  1. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    To stay true to the schematic, wire the switch like the layout.

    The wiring of the *picture of the switch* may sound similar to the schematic but it is different.
    The RC filter would allow more lows through. (The RC filter of the schematic is very low already so I doubt you could hear a difference.)
    Below is how the schematic would appear if wired like the *picture of the switch*.

    Inked5e3p_Cascade_Mod_Schematic_LI.jpg

    Maybe @robrob would like to see this.
     
  2. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    I would try the 470k.
     
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  3. James Knox

    James Knox Tele-Holic Silver Supporter

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    Thank you!

    I have been staring at the two different schematics and see what you are saying, but I have no clue have you figured that out. I guess it is time in My journey to begin learning how to read schematics. I’ll try. I promise.
     
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  4. jmp81sc

    jmp81sc Tele-Meister

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    Hey James,
    I spent a lot of time looking at all of this and my conclusion also was that the layout was the same as the schematic. The photo of the switch does not match the layout.
    It was very confusing to me and I'm glad Lowerleft Coast confirmed this.

    I would also like Rob to comment as this is from his website, and he has way more knowledge than I do.

    I am following this as I am considering this mod also.
    John
     
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  5. jtcnj

    jtcnj Tele-Holic

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    Interested, will follow.
     
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  6. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    If you are not familiar with RC filters, it is a good time to start. The 1M potentiometer and the .1uF capacitor form a High Pass RC Filter. Depending on how the switch is wired, the RC Filter would change.
    To avoid the math calculations, you can look up RC Filter Calculator. There are several available.
    Simply plug in the resistance and the capacitance of the components. The calculator will determine the cutoff frequency of the filter. The same calculation is used to determine high pass filters and low pass filters.
    On a schematic the filters look like this:
    hi pass.gif low pass.gif

    Using the calculator:
    1M pot with a .1uF cap = 1.6Hz cutoff frequency.
    1M pot + 680K resistor = 1.68M with a .1uF cap = 0.9Hz cutoff frequency.

    As you can see there is not much difference in frequency. The cutoff frequency is so low you would not hear a difference.

    On a side note... the Volume pots on a stock 5E3 are not wired as one would expect. The RC filter cutoff frequency varies with the rotation of the pot. This is part of the 5E3 charm.
    When the cascade switch is used the pot is no longer wired like the stock 5E3. The full 1M resistance of the pot is part of the RC filter so the cutoff frequency remains constant.
    Since it remains constant a much smaller capacitor can be used, for instance a .0033uF cap would result in a 48Hz cutoff frequency. That would still pass all guitar frequencies, yet cutoff some subs.
     
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  7. James Knox

    James Knox Tele-Holic Silver Supporter

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    Awesome stuff. Gonna study this.
     
  8. tubegeek

    tubegeek Friend of Leo's

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    The way I like to look at these filters is as a voltage divider.

    1st diagram has C, then R in series between input and ground. Tapped in the middle between the two. Very similar to a volume pot with a wiper tapping the middle, except it's frequency dependent.

    A high frequency passes through a cap with a low impedance, and a low frequency meets with high impedance. So a high frequency is going put the tap point close to the top of the divider and a low frequency closer to the bottom. The tap point will contain more highs and less lows. High pass filter - highs pass through, lows are filtered out relative to that. In the middle range there is a transition between the two behaviors.

    This divider's behavior is reversed for the second diagram; the result is a low pass filter.

    The RC formula just tells you where the "middle" of the frequency range is found: where the divider shows an audible difference between its treatment of highs and lows.

    It is always (in my experience) helpful to consider circuits with caps from 3 perspectives - high, low, and in-between frequencies.

    A power supply filter for example: allows lows to pass and filters out highs including 120hz rectifier ripple. DC is 0 hz - extreme low frequency. At the tap of this divider lows predominate and we want the transition to be well below 120hz for effective filtering. The R's in power supply filters cannot be too large or we will lose too much voltage drop in the R's and waste a lot of power through heat. This requirement means the C's must be relatively large.

    We have much less difficult constraints with audio band filters and so we can use much smaller C ranges and larger Rs. Also because the position of the R is at the bottom of a high pass filter, in this arrangement a large R value won't cause us trouble from voltage drops, so the R*C product can be conveniently made larger (if we want), by raising the R instead of getting big cumbersome Cs.
     
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  9. andrewRneumann

    andrewRneumann Tele-Holic

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    @James Knox the value of that resistor will probably have more of a noticeable effect on signal level (and depth of second stage overdrive) than on tone. A lower value will give you a hotter signal, but you can turn it down with the "gain volume" knob. If it's breaking up too early at a low "gain volume" setting, or if it's just too much scream and "over-distortion" at higher "gain volume" settings, then consider increasing that value. Use this as a chance to "voice" the distortion and make it your own!

    That resistor will also have the effect of cutting the high-end, which is a matter of taste in overdrive. Soldering a bright cap in parallel with that resistor would restore high freqs. Again, another chance for you to make it your own!
     
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  10. James Knox

    James Knox Tele-Holic Silver Supporter

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    I excitedly read through this with my head exploding Realizing I need to read it through *slowly about 10 more times and let the lightbulb start coming on. Thank you for educating...
     
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  11. James Knox

    James Knox Tele-Holic Silver Supporter

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    I want to do just that! You alway have good and practical ideas...
     
  12. D'tar

    D'tar Friend of Leo's

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    A 1M linear pot wired as a variable resistor in place of the 680k and the gain vol maxed will let you dial in the "max" signal you would want. Find your spot, measure the pot at that value and replace with the appropriate fixed value.
     
  13. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    @tubegeek @andrewRneumann @D'tar
    I am sure the OP would be interested in all that we have said. The problem is he does not have the chops to read/comprehend schematics... yet.

    Do any of you know how to school schematic? Get him on the fast track so to speak? He has built a few SE amps and the 5E3. Maybe start with circuit analysis of 5F1/5F2A amps?

    He could benefit from tracking the signal. I know Rob has illustrated that on his site.

    Maybe you gents can give him a nudge in the right direction.
     
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  14. D'tar

    D'tar Friend of Leo's

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  15. D'tar

    D'tar Friend of Leo's

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    I'm lost without a schematic. I dont know how anyone gets anything done without one. Sure once you know whats going on you can do things on the fly. I use schematics constantly and without one, a guess is just a guess on how things are designed. Referring to WAY more than just tube amps.
     
  16. andrewRneumann

    andrewRneumann Tele-Holic

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    I'm no expert in schematic reading. I get better every time I look at a schematic I haven't seen before. It's definitely like learning to read in a new language, or learning to read music on a staff.

    At first, you see three notes and you have to individually think about each note and what it is and where it is on your instrument. Then you start to see patterns emerge... ahhh, those 3 notes stacked on top of each other like that are a triad and my fingers need to go to this shape. Then you start playing Cmaj without even thinking "C", "Maj", or even the individual notes C-E-G. My experience with learning to read schematics is similar... just repeat and repeat until you see the same patterns emerge. The biggest pattern is the potential divider. And like @tubegeek elucidated earlier... filters are a natural extension of potential dividers.

    All that being said, my mind still swims for a while when I see a schematic I've never seen before. Sometimes when I read some annotated schematic that says "x is parallel y" I still have to scratch my head and figure out why that is. And I definitely can't figure out complicated circuits just by looking at a schematic. For instance, I'm currently learning about the long-tail pair phase inverter. Yeah, I can read a schematic, but I NEVER would have been able to figure out how a LTP works just by looking at the schematic.
     
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  17. robrob

    robrob Poster Extraordinaire Ad Free Member

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    The layout of the cascade mod is the preferred way to do it. The switch picture is from an older version of the mod. I meant to delete that picture. I'll do it now.
     
  18. James Knox

    James Knox Tele-Holic Silver Supporter

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    Good idea! I want to try that...

    Ive read through it nice. Was a bit over my head. Been awhile, I go bac in!
     
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  19. James Knox

    James Knox Tele-Holic Silver Supporter

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    Good point! Just like music theory... gotta keep playing and keep learning.
     
  20. James Knox

    James Knox Tele-Holic Silver Supporter

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    Thanks Rob! Yes, I followed the layout... worked out good!
     
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