Monday, 21 September 2020

BAJA EVH 5150 Overdrive w. MTKs gain mods

 MTK have done some great work on the BAJA 5150 OD circuit to squeeze more gain out of it.

 


 



 
 

And a short video clip. stock settings in the first 20 seconds, after that, the modded settings.



 


19 comments:

  1. I swear there are only 58 cuts on that picture... I've counted it like 5 times. Am I going crazy or is there a cut under one of those caps?

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    1. Counted it once more and it is indeed 58 cuts. Added and image with transparent components to make it a bit easier find those cuts under the components.

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    2. And still 57 on the original layout ;-)
      I started with the original and will switch on this one, apart from adding a cut at w24 and changing some values I guess both are identical ? (you moved the switch 2 wire by placing the 1µf horizontally but that shouldn't change anything)

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    3. :-) Changed it to 57 cuts in the original layout.

      Yes I moved the 1uF cap at the bottom right to make room for the optional pF cap which I accidentially forgot to add but is now added.
      The connecions and the signal flow remains the same.

      Whef, I've said it before but I say it again, this layout was a PITA, luckily it is a good sounding circuit......but I don't want to count all the cuts once again.o.O

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    4. 😅 Thanks for your time and the great work !

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  2. So I built it with MKT's mods. Lots of gain, not as much as the powerball (mighty nut) or tight metal but enough IMO.
    The bass aren't tight enough for my taste, a bit too loose/flubby, and with full gain it gets fuzzy.
    Also, there is a significant level drop when the tonestack is bypassed, maybe there could be something to tweak around IC4. With full volume it's barely above unity.
    MKT is it the same for you ?

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    1. Oh, and the circuit is totally noiseless, that's great

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    2. Shit! I forgot about that volume drop when it's bypassed. I'll fix that and get back to you.

      I agree the bass isn't super tight but throw an OD in front of it and it's gold. Are you running it in the FX loop as a preamp or in your clean channel? I think it sounds badass as a preamp. I changed the Tone Stack on mine to this.

      https://i.imgur.com/kLD2YsG.png

      The Green is the version Bajaman used, and I switched a couple things out. I like the TS from the Model T but added a larger bass cap. It's the Red line.

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    3. I run it in front of my tweed set clean, no fx loop.
      Does it sound tighter with these red TS mods ?

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    4. Sorry for leaving you hanging, man. The reason the EQ bypass has a volume drop is from that 360K resistor(bottom right) that's limiting the signal that hits the EQ/IC4 section. Basically, you'll have to move the switch in front of the coupling cap, directly connected to the output buffer. Each section, bypass and EQ, will then need its own coupling cap, the EQ section will have the added 360K resistor.

      It's less confusing on paper - https://i.imgur.com/tlvNs8I.jpg

      I'm not sure if they'll be exactly the same output because I removed the toggle from my build, I wasn't planning on using that function anyway. You can play with the gain of IC4 to get the volumes to match.

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  3. Build this beast, play some machine head em very satisfy with it, some hiss had come when some setting, add 47p for C20 did help, thank to MTK awesome mod, and dirtbox's layout, will combine with choru in a box.
    here a test clips :
    https://www.instagram.com/p/CYdjm9uhhcb/?utm_source=ig_web_copy_link

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  4. I built this into an amp with the stock tone stack values on a toggle and the mod MTK pictured above for the volume drop issue, sent it to the baja res&pres circuit on a bypass toggle and then to an 80w mono class d amp board...this stands its ground against my buddy's 5150III 15w very well :)

    Noiseless. Wonderful layout and mods gentlemen.

    Fwiw; with whatever res&pres settings on the baja circuit, the MTK tone stack values sounded a lot like the blue channel on the 5150III

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  6. Could you help me? I'm not sure about the pinout of the toggle dpdt on. My tone stack is not working in any position.
    Thanks guys!

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  7. Hi guys,

    I'm brand new at this, but really enjoyed building it. Sadly its not working. Probably a bit too complex a project for my first go at something like this. Could someone help me understand the switch wiring? I have a DPDT switch with 6 connectors (I googled which connector is which), when I apply power, the led glows for a second then shuts off and the switch does nothing. What's confusing me is that MKT has two 9 connector DPDT switches on his....

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    1. Hello .. because I was new in this field, I made many mistakes and still make some of them.. you have to understand how a signal passes through the circuit to find what you did wrong or where the circuit is shorted. I would tell you to make an audio probe, it like an oscilloscope but works with sound (less less expensive). you need - 2 wires - 1 cap 100nf /400 v - 1 alligator clip - 1/4 male Jack and a mini screwdriver….. connect the cables on the Jack ( ground to ground and signal to tip of Jack ). And on the other side of cables connect the signal to the 100nf cap and the cap twisted on a side of screwdriver ,, and the other side of ground cable connect the alligator clip ,, now you have an audio probe ..so now you can give on your board sound ( connect the board input some like pc or phone , and play music , and plug the audio probe into an amplifier , and now you can trace the signal , when you hear the sound , the signal pass .

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  9. Works perfect ! But I disable the tonestack switch. Big difference between volumes .. so for disable tonestack switch , just connect the switch 6 cable from board to level 3 ( instead switch 5 cable ) ..and connect together the switch 2 and switch 3 .

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