Slambox build

[fair.child]

Yesterday, I've finished to make my first madbean mosfet booster.
I've several question about this booster;

1)About the pot
I put my 5kB backwards to change 5kC. My question is, am I doing right ? because I also have have 500kC and I wanted to try make 5kC from it. So please tell how to make 5kC from 500kC, because I think it will give a big different from 5kB which I soldered backwards.

2)About LED board
I've read slambox pdf again, and quite curious about on board LED. Is it the LED should be lit ?because mine is not, and what's the point of this LED?

3)Result
I've noticed that my slambox didn't fulfill my desire about mosfet boost. I tried to plug into my amp and my slambox has lowered my overdrive, when I switched off and got true bypassed, I've got my original amp overdrive which sound louder than when it switched on. I think my slambox buffered my guitar signal, so is this the purpose of slambox ? Isn't it should be make my amp becomes dirt or louder ? please help me to figure it out

Note: I'm quite curious and frustrated about secret life of pots and several discussion about making reverse pot. Some of them are nearly true, but also false. I don't get the basic idea about make it reversing (especially from linear), so please, lead and give me suggestion about making this reverse pot, include from linear and log pot.

Cheers all and thank you

[madbean]

Welcome to the forum!

If your pot is linear (which is what "B" is here in the States, although I think B is audio in Europe, right?) reversing it won't do any good. But, and audio taper will be reverse audio when hooked up backwards.


You can pull your 500k pot down toward 5k by soldering a 5k1 resistor on the two outside lugs of the pot.

If your LED is not lighting up, check to make sure you have the anode/cathode of the LED going to the right place (anode goes to a current limiting resistor which connects to 9v and cathode connects to the bypass switch).

From Wiki




The last problem---sounds like it's not boosting your signal at all. It could be a faulty BS170, so you might need to replace it on the PCB, assuming you have used the right part and it's in the right orientation.

[mgwhit]

In answer to your questions:

1.) Wiring a 5kB backwards doesn't get you a 5kC -- it gets you a backwards 5kB.  If you read that article "The Secret Life of Pots", you can get the formulas for converting linear taper (B) pots into Audio (A) and Reverse Log (C) pots.  I can't think of any way to use your 500kC pot effectively in this circuit, although you should be able to get some value linear capacitor and convert it to 5kC if you just can't get your hands on one.  I'll look at the numbers if I have some time later today.

2.) The LED on the board is the indicator light for when the circuit is on.  If you use the board-mounted LED you don't need to include a separate switch-mounted LED (a la the standard MadBean wiring diagram), although you do need to connect the switch to the board at point SW so that the LED grounds when the switch is engaged.

3.) When engaged, the Slambox should (a.) increase the impedance seen by your guitar pickups, and (b.) increase your signal dramatically.  In addition to just being louder, the large input impedance typically makes your guitar sound brighter, and the huge output usually slams the preamp tubes of your amp and is capable of generating very crunchy distortion.

If you're getting lower output from your Slambox, you have a problem.  Please let us know what other part substitutions you made, if any, and provide the voltages on your Q1 pins.

If you can upload high-quality, well-lit, in-focus photographs of both sides of your board we can double check it for errors.  Good luck!

[fair.child]

Welcome to the forum!

If your pot is linear (which is what "B" is here in the States, although I think B is audio in Europe, right?) reversing it won't do any good. But, and audio taper will be reverse audio when hooked up backwards.


You can pull your 500k pot down toward 5k by soldering a 5k1 resistor on the two outside lugs of the pot.

If your LED is not lighting up, check to make sure you have the anode/cathode of the LED going to the right place (anode goes to a current limiting resistor which connects to 9v and cathode connects to the bypass switch).

From Wiki




The last problem---sounds like it's not boosting your signal at all. It could be a faulty BS170, so you might need to replace it on the PCB, assuming you have used the right part and it's in the right orientation.

Waow, thank you Brian, your reply was help me a lot, better to discuss this one with you. Lucky me you answer my question for the first post, anyway thank you for your welcoming.

Okay about my slambox, I've just want to make sure where is the lugs of 500kC pot should I solder (3-2 with parallel 5k1 resistor , 1-2 with parallel 5k1 resistor or 1-3 with parallel resistor )?

Here the pic about my 5kB pot with 1k8 resistor paralleled into 1 and 2 pot lugs




Currently, my LED was in the right position, I've read carefully about anode/cathode orientation. The square was for the + and the circle was for the -, Am I doing right ?

Abous BS170, yes, I'm using BS170, I will try to post the d-g-s voltage after this post, and I would try to solder socket to it, just to make sure the BS170 worked out.

In answer to your questions:

1.) Wiring a 5kB backwards doesn't get you a 5kC -- it gets you a backwards 5kB.  If you read that article "The Secret Life of Pots", you can get the formulas for converting linear taper (B) pots into Audio (A) and Reverse Log (C) pots.  I can't think of any way to use your 500kC pot effectively in this circuit, although you should be able to get some value linear capacitor and convert it to 5kC if you just can't get your hands on one.  I'll look at the numbers if I have some time later today.

2.) The LED on the board is the indicator light for when the circuit is on.  If you use the board-mounted LED you don't need to include a separate switch-mounted LED (a la the standard MadBean wiring diagram), although you do need to connect the switch to the board at point SW so that the LED grounds when the switch is engaged.

3.) When engaged, the Slambox should (a.) increase the impedance seen by your guitar pickups, and (b.) increase your signal dramatically.  In addition to just being louder, the large input impedance typically makes your guitar sound brighter, and the huge output usually slams the preamp tubes of your amp and is capable of generating very crunchy distortion.

If you're getting lower output from your Slambox, you have a problem.  Please let us know what other part substitutions you made, if any, and provide the voltages on your Q1 pins.

If you can upload high-quality, well-lit, in-focus photographs of both sides of your board we can double check it for errors.  Good luck!

Here some hi-quality photographs -slambox







Hope you'll help me out again mgwhit

1) So that means, it will be a lot of easier if I can find 5k log audio taper then solder it in backwards, am I correct ? 500kC is over big value, it is 100 times larger than listed value so, you're correct it won't be effectively in this circuit

2) Yes, I've used switched mounted LED, so is it correct if the board-mounted LED doesn't lit on ?

3) Yes, I will post the voltage of Q1 in d-g-s pins, soon

thank you for your suggestion, it is really helping me to figure it out

[mgwhit]

Bean's right about using the 5k1 resistor in terms of parallel resistance, but I'm not sure what the taper would be like using the 500kC since (a.) there's a 100x difference and you're already working with a reverse log pot.  I could be wrong, but I would think the taper would be ridiculously bunched up (and that the 5kB you have wouldn't be any worse).

I haven't had much time to review the board, but check your solder joint for R4 (at the bottom).  It's not effectively connecting that resistor to ground.

[fair.child]

Bean's right about using the 5k1 resistor in terms of parallel resistance, but I'm not sure what the taper would be like using the 500kC since (a.) there's a 100x difference and you're already working with a reverse log pot.  I could be wrong, but I would think the taper would be ridiculously bunched up (and that the 5kB you have wouldn't be any worse).

I haven't had much time to review the board, but check your solder joint for R4 (at the bottom).  It's not effectively connecting that resistor to ground.

Hey mgwhit, looks like I've got my slambox working, finally, thanks for your help. this time I tried to change 500k B with A10k and I would said it works perfectly great, I tried to reverse 1 and 3, then the pedal started to scream,  this is good,

The problem is BS transistor (MOSFET) is bad, I tried as your previous post to change my BS, and I've made the LED switch on too. The problem about LED that I faced before is I forgot to wired up the switch cable to 3PDT, so it means there will be not 9V power to switch it up, but the 3PDT LED is working now.

I also make 47k mod for me (I add 50k Linear pot to make the volume control) with lug 1 and 2 to R4 replacement, and I realized the other pin of 47K should be grounded. I've checked with the schematic, then it's okay.

Glad to know this MOSFET booster work. I've got to drill my box tomorrow and do some waterslide decal. I'll post for the final work.

Thanks for your biggest help, Bean and mgwhit, I'm very happy now

[DutchMF]

I think B is audio in Europe, right?

You're right about that Brian, we do pot-tapers backwards over here. But since most of the stuff we buy here comes from overseas anyway (some British&German manufacturers are the exception) it's far more useful to use the American standard. I think I spied an Alpha pot in fair.child's pic, so it should be linear.

Things would be so much easier if we could just all agree on simple things like this, don't you think?

Paul

[fair.child]

I think B is audio in Europe, right?

You're right about that Brian, we do pot-tapers backwards over here. But since most of the stuff we buy here comes from overseas anyway (some British&German manufacturers are the exception) it's far more useful to use the American standard. I think I spied an Alpha pot in fair.child's pic, so it should be linear.

Things would be so much easier if we could just all agree on simple things like this, don't you think?

Paul

In my build, I tried several trial and error with pot tapers backward. I followed the EMH calculator, but the result was not exactly like I wanted with the taper. I got frustrated a bit, then I tried to contact my friend. He handed C500k and C1K, so I bought 50pots from him and tried several trial error. I've found if we do the backward pot, then it will be a little bit differences between normal reverse pot. We will face it in some gain knob or booster pedal (like mine too). In backward pots (mine), It will scream fiercely when I pulled up on 3- 4 o'clock, but it will come to normal when I tried to pulled down on 9 until 12 o'clock, but it will normally pulled up the gain when I tried not to use backward pots. I decide let it normal pot wiring then use backward, maybe it's kind a weird but I like it..

All of this my opinion, just my subjective perspective, please correct me if I'm wrong.

Cheers all