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Question regarding changing components to be more bass friendly


Jimothey
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I’m about to undertake my first pedal build its based on the DOD 250 Overdrive pedal which I’m making for my 6 string electric and was wondering if I wanted to make a bass friendly version is it just the value of the capacitors that you change or is there more involved than that 

I've tried to learn about sine wave modulation but it went right over my head so I could do with some advice in layman’s term please............👍

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Generally the input and output (first and last in the circuit) caps need doubling in value (47nf to 100nf) and depending on the circuit I’d do the coupling caps too.

 

edit: there’s also a capacitor from pin 2 of the 741 opamp which connects to a 4k7 resistor, then to the ‘gain’ pot. 
the resistor sets the minimum signal level, so that when the gain knob is at zero you’re still allowing some signal to pass, and the capacitor before that helps to form a high pass filter for the drive circuit, I’d increase that too; doubling this cap value will drop the frequency by an octave 

Edited by paul_5
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1 hour ago, paul_5 said:

Generally the input and output (first and last in the circuit) caps need doubling in value (47nf to 100nf) and depending on the circuit I’d do the coupling caps too.

 

edit: there’s also a capacitor from pin 2 of the 741 opamp which connects to a 4k7 resistor, then to the ‘gain’ pot. 
the resistor sets the minimum signal level, so that when the gain knob is at zero you’re still allowing some signal to pass, and the capacitor before that helps to form a high pass filter for the drive circuit, I’d increase that too; doubling this cap value will drop the frequency by an octave 

Thanks for the reply I think I understand but here’s the schematic for reference 

853A9079-A05B-44BF-AA1D-4538513F5030.jpeg.212d1634a5846fa4e382ba120a6a35e4.jpeg

I’ve found the cap that comes off the opamp it's labelled C2 

Sorry (I’m still learning) but which ones would be the first (C6??) and last and the coupling caps........

Edited by Jimothey
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The input cap is C1 - stock value is 0.01uf (10nf), I’d crank it up to 0.1 (100nf); this is the component that determines how much  low end goes into the circuit.

Edit: because you’ve got a high value resistor before the cap (2M2 going to ground)  forming half of the high pass filter (hpf) your ‘corner frequency’ is about 7Hz, try it as it is before changing it out.

C2 is the 0.047uf that goes into the 4k7 resistor, then to the gain control. That might be ok as it is, but if you find that you’re losing too much low end, or that your distortion is a bit ‘fuzzy’ then increase the value of this cap, you can work up and experiment (I think the next value would be something like 0.068, then 0.1)

C3 is a tiny cap, and shaves off all of the extreme, unpleasant noise that we don’t want amplified. You can leave that as is. 
 

The coupling cap is the 4.7uf polarised electrolytic after the opamp stage. That filters the audio signal so that we don’t have DC noise in the audio path. In guitar and bass pedals anything of that size (or bigger) is generally used for DC filtering -C6 and C7 are large values (relatively speaking) and do just that to the power supply input at ‘+9v (T)’.

 

Your output cap is C5 and in this configuration is acting as half of a low pass filter (along with the10k resistor) so should be fine as is.

then you’ve got a final clipping stage (the 3 diodes going to ground) before the master volume control.

Depending on what you want to use it for then you can decrease the value of the gain pot; 500k is a LOT of filth! 

Hope this helps.

Edited by paul_5
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Thanks mate that has helped a lot!!

The gain control is actually a C500k reverse log Which if I understand correctly it will give most of the control in the middle portion of the curve instead at each end, which I think will be fine for guitar but I would lower the value for bass.........👍

Edited by Jimothey
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If you're building from scratch/kit and making your own enclosure, then you can always add switches for various things.
I built a distortion years ago and changed the input cap, to make it more bass friendly, but it didn't sound quite right with a guitar. So fitted a toggle switch for the cap. 

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I’ve bought a PCB to make my life a bit easier for the first build, I’ve sourced all the parts myself and am trying to build a wooden enclosure so it’s a bit different I have started a thread on the Build Diaries Page for it but if it doesn’t work then I’ll just get an Alu one instead 

This pedal is going to be used with a guitar but I’m thinking if building another one maybe a fuzz instead to use on my bass but I really like the idea of a toggle switch to switch between the cap values tho

I was really just wondering what mods do you need to do to optimise pedals for use on bass as there is a lot more pedals for the guitar than bass I do want to try and build a chorus pedal as well..........👍

Edited by Jimothey
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1 hour ago, simon88wilson said:

yep there is some good advice in this thread. I would look into using socket pin connectors for the capacitors that you are looking at changing. that way you can experiment with different values.

Oh yes. I'd forgotten that step.
I feed out to a breadboard, to swap caps about. Once I've decided on values I solder them in to the pcb/switch. means there's no unnecessary sockets in the pedal.

Edited by bartelby
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9 hours ago, Jimothey said:

I was really just wondering what mods do you need to do to optimise pedals for use on bass as there is a lot more pedals for the guitar than bass I do want to try and build a chorus pedal as well..........👍

How about a HPF in front of the pedal and another LPF in parallel for letting the low end through? This is a X-over.

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