Solid State Drop-in Tremolo

Discussion in 'Shock Brother's DIY Amps' started by Bitsleftover, Feb 4, 2020.

  1. Bitsleftover

    Bitsleftover Tele-Meister

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    I recently added a tube tremolo to my 5f2ish based build.
    It turned out great and gets a lot of use.
    During the early stages of planning my next build I started looking at other ways of adding tremolo without adding another tube.
    Brother PAUL-T drew my attention to the “Sluckey tremolo” over on the EL34 forum, and that concept was developed into an LND150 MOSFET driven version of the same by 2deaf
    There was no real documentation of anyone implementing it into an amp so I thought I’d have a play with it and report back.
    I ordered the VTL5C1 optocoupler from Tube-Town along with all the other components and mounted them onto a breadboard.
    I’ve put them all into a plastic enclosure to avoid any zaps and left my B+, Ground and signal hook-ups sticking out the back with crocodile clips to allow me to test different positions within the amp.

    [​IMG]


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  2. Bitsleftover

    Bitsleftover Tele-Meister

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    [​IMG]


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  3. Bitsleftover

    Bitsleftover Tele-Meister

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    I took the B+ at the highest smoothest point I have which gave me 315VDC
    I tried tapping into the signal at the volume pot wiper, and my master volume wiper just before the power tube.
    First obvious observation was that the 50k depth pot draws the signal level down significantly. Like turning the volume pot down about half way.
    I experimented with different value pots to find that 250k gives the least level drop while still functioning. Anything above 250k turns into an on-off switch at about 9 on the scale.
    The best place to insert turned out to be the Volume or Gain pot.
    This gave the deepest and most controllable sweep on the pot with the least amount of signal reduction.
    With it connected to the Master Volume, the volume drop seemed much more intrusive and the tremolo didn’t seem to be as deep or controllable. In fact the depth pot did virtually nothing for the first half a turn of the dial.
    Overall, I will use this on my next build but put a switch to totally remove the circuit when not in use.
    The circuit is quiet with not added noise and no Trem ticking or thumping.
    I’ll try and work out a way of hooking a mic up to my iPad and post a clip next





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  4. Wally

    Wally Telefied Ad Free Member

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    Here is how Mark Bartel did it in the Tone King Imperial MKII....very nice bias vary trem.
    B3CDFD62-EFEB-477F-8A9A-52572084D4DC.png
     
  5. Wally

    Wally Telefied Ad Free Member

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    Here is how Mark Bartel did it in the Tone King Imperial MKII....very nice bias vary trem.
    View attachment 680386
     
  6. Paul-T

    Paul-T Tele-Meister

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    really interesting. thanks for pioneering this!

    Does it have much of an effect on the signal when turned off?
     
  7. Bitsleftover

    Bitsleftover Tele-Meister

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  8. Ten Over

    Ten Over Tele-Meister

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    Have you tried connecting it like this? I'm guessing your Master Volume is installed as shown.

    MOSFET Trem for 5F2.png
     
  9. Bitsleftover

    Bitsleftover Tele-Meister

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    Yes, the reduction in signal level I was referring to is with the effect selected off. That’s the problem with it. The total resistance of the depth pot (250k in this case) is always always there as a path to ground.

    In a champ or Princeton, I’d remove the 220k resistor to ground just before the power tube and I think it would be perfect. (Ie no loss).


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  10. Bitsleftover

    Bitsleftover Tele-Meister

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    My master volume is a 250k pot in place of the 220k resistor to ground.



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  11. Ten Over

    Ten Over Tele-Meister

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    A 1M pot would be better if you construct the circuit as I showed.
     
  12. schmee

    schmee Poster Extraordinaire Silver Supporter

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    I have recently went over to a tremelo pedal. I really like it.
    -It's cleaner sounding and cuts through better in the band mix.
    -A "pedal pedal" isn't any worse, maybe better, than a cord and pedal from the amp for tremelo.
     
  13. Bitsleftover

    Bitsleftover Tele-Meister

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    Where do you place your pedal Shmee?Upfront or in the loop?



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    Last edited: Feb 4, 2020
  14. Bitsleftover

    Bitsleftover Tele-Meister

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    Yes. I’ll confess. I had a 1 meg master volume pot straight after the 220k resistor at the start of this experiment.

    I can’t remember the maths, but I think a 1 meg in parallel with a 220 is about 200k

    I think the takeaway fact, is that...if there is anything at around 220k to ground in your circuit that you can swap out for a 250k pot... it’ll be seemless


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  15. separateness

    separateness TDPRI Member

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    Just to add another option into the mix, I put one like this in my Twin rebuild, which I found over on ax84. I like it and it blinks in time with the oscillation. I intend on modifying it to vary the cathode bias of a preamp tube, but that little mod is well down my to do list.
     

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  16. Bitsleftover

    Bitsleftover Tele-Meister

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    Oh yeah! I hear ya!
    I’m getting married in 4 1/2 weeks! My workshop time has become a very clandestine affair!


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  17. Bitsleftover

    Bitsleftover Tele-Meister

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    Nice Trem by the way.
    After a little more testing, I think I find bias wiggle slightly softer than just shunting signal to ground.
    I’d be interested to hear your results.


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  18. Bitsleftover

    Bitsleftover Tele-Meister

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    So I tried to record a clip of the Trem tonight.
    Plugged in the Line 6 Sonic Port XV I bought a few months back.
    No ticket no laundry!
    Line 6 say my Audio Interface does not work with iOS 13 so it’s just a big red paperweight.
    Thanks a lot! No plans to fix it so there’s £150 I’ll never get back!
    I’ll maybe try and capture something off my phone tomorrow.


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  19. separateness

    separateness TDPRI Member

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    I will see if I can make a recording and find a way to share it on here but it will probably have to wait until Monday. I like the way it sounds a lot, although I dislike that I have to set the output tube bias a little cold in order for the effect to come through strongly. This is in part why I want to move the point of action to a preamp tube cathode.
     
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