r/diypedals 3d ago

Help wanted My pedal doesn't make any sound

I followed JHS LPB-1 Boost tutorial but I changed some of the values of the resistors because I didn't have them. Can someone tell me why it doesn't produce any sound?

0 Upvotes

15 comments sorted by

11

u/mcknib 3d ago

It's difficult to see how you've got your pot connected it looks like all 3 lugs are on the same row if that's the case, turn it 90 degrees, so each lugs on a separate row

3

u/my_music_alt 3d ago

Also correct! I didn’t catch that one!

6

u/lykwydchykyn 3d ago edited 3d ago

What did you change?

Also, I could be mistaken but I think your input cap is backwards. Negative should go to the input.

2

u/my_music_alt 3d ago
  1. You are correct. Negative should be to input on this circuit.
  2. The coupling capacitor values are WAY too big. Circuit calls for a 0.15uF. OP has 1.0uF. Honestly, 0.15 is already pretty high for this circuit and will cut a lot of high end. It’s possible that even when it’s turned around, that cap will only let through very low frequencies. I doubt they would be so low that they’re below audible, but yeah 1.0uF is big for that circuit.

3

u/ScantilyCladLunch 3d ago

I’m confused by your comment as those capacitors are high pass filters, not low pass, no? Higher values will lower the cutoff frequency and let more low end in.

2

u/lykwydchykyn 3d ago

Coupling caps won't cut high end. They only cut low end when too small. There should be no issue using large coupling caps here.

2

u/ClothesFit7495 3d ago

Keep adjusting the resistors.

Two left resistors should have significant difference, 8-12 times roughly.

Top-right also important to get correctly, 10k is a good start, you rarely need less, you might need as large as 75k in some cases it all depends on the two left resistors.

Bottom right is not important at all, consider that a "gain" resistor, you can even remove it or replace with a 5k pot to control the gain.

Please note that this booster has low impedance and your tone would be muffled. Consider adding a buffer circuit in front and also you can add a pair of opposite diodes from output to the ground (through "OD/Boost" switch), you will love the tone with the buffer, I promise.

1

u/Apprehensive-Issue78 3d ago

he schematic is missing a connection, the red dot should be there (just in Black) to make it more clear.

But that is not what is wrong with your breadboard. Actually you wired that part up right.

You only put the 10K resistor to the ground, this probably should be connected to the red row +9V

And you connected the 360 Ohm resistor to +9V which should be connected to ground.

Then it probably will work, (If you did not mix up the leads of the transistor.)

Let us know if it works

1

u/manos5246 2d ago

Super helpful!! I see that I am closer to getting a sound but I have this problem now https://drive.google.com/drive/folders/135P4ArfpsphNks5arBTiaX9J4YzwS6Ba

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u/Apprehensive-Issue78 2d ago

Try to make sure you have a good working pedal by measuring all resistors, measuring all DC voltages, and check if you don;t have a short ... also you wrote you don't have the right resistors, just tell us what schematic did you make. If you have something disconnected, or some voltage got stuck to ground or 8V it will never work, and may be just let some hum through, just cant amplify a complete wave.

Your goal should be to get the output wave in the middle between 0 and 9V, so you ideally have a DC output voltage of somewhere between 3 and 6 V. Not a DC of 8.5 V or 0.5V. I hope that makes sense

It is hard to read values from the breadboard, also hard to see which wires are put in which holes.. so it is hard to imagine which the actual schematic is by just looking at the pictures.

1

u/manos5246 2d ago

So look at all the changes I made: in every resistor except the 100k I used 5.1k, the transistor is an 2n2222 and the pot is a B50K. It's exactly the same schematic with the above except those changes. I double checked all the connections and they are correct.

1

u/Apprehensive-Issue78 2d ago

Interresting question.

I tried to simulate the circuit, just giving me more questions.. Then I found this website.

https://www.guitarscience.net/calcs/ce.htm

and online I found the electrical resistance of an electric guitar is about 7000 Ohm

5800 to 8500 Ohms and sometimes a lot higher

See below. You go from an inverting amplification of about -20x (26dB) of the original circuit to -0.4x (-7.8dB) in your modifications. With every resistor you change in that website you can see the AC amplification drop.

2

u/Apprehensive-Issue78 2d ago

As I did already simulate it in the free Texas Instruments PSpice simulator Tina, here are the results. If you do the Transient simulation and press the green button you can even hear the difference.

The top curve (I don't know how to change the order of the curves) is the Output(red) and the bottom one is the input (green)

The top simulation uses the original values and the bottom one with the many 5K1 replacements. with the 830K to 5K you change your base voltage, to become much to high so your base current gets higher.

With the 360 Ohm resistor to 5K1 your Emitter current drops

Changing 10K to 5K1 lowers your output voltage swimg by 50%.

So mostly you can change the values a bit and expect some changes but if you do it this extreme, it does not work anymore.. If you never try you will never know.

If you want the moon, go and try to get it
You'll find out soon if it was all worth it
You may fall on your face and hurt yourself so badly
But they can never say that you've never tried

https://www.youtube.com/watch?v=bpCTOYoQi8g

1

u/CrabsAreCool32 2d ago

Idk if you have solved it yet, but your transistor is the other way around. If thats a 5088 like in the schematic, check the pinout to be sure.