Increase Pedal output gain

[MaxDB54]

I have my 1st successful Pedal PCB of the Arachnid pedal circuit. Thanks to all here who answered my questions to build a working pedal!

However I do think the output gain needs increased slightly. It looks like right now it's unity gain. Rf/Rin = Gain

I double verified all component values and they are all correct.

I'm going to bump R10 up to a 22k or possibly 33k to increase the overall output...I'll experiment to find desired level.

Anybody else here feel like the total output volume needs increased slightly?

Everything works fine but I have to turn the volume knob maxed and I would like to be able to have the option to boost the level louder on some FX when the pedal is engaged.

Thx!

 

[MaxDB54]

Anybody have any thoughts on this?

 

[zgrav]

Go ahead and try it. Try doubling the resistor value and see if that is enough to let you dial back the volume knob when you want unity.

 

[GenoBluzGtr]

try using single-pin sockets for that resistor so you can easily and quickly swap resistors.

 

[BurntFingers]

You'll also need to increase the 470p proportionately to keep the filtering in check.

 

[MaxDB54]

You'll also need to increase the 470p proportionately to keep the filtering in check.

OK can you point me in the right direction? Did not think about that!

 

[BurntFingers]

OK can you point me in the right direction? Did not think about that!

Actually I wouldn't worry about it. It's currently filtering off 22.6khz which is way above our hearing and what speakers can reproduce. If you double the resistor to a 30k, you'd need to half the cap value to keep things the same, which would be a 235pf, which you can't get. A 220pf gets you to 24khz which does the same job of being inaudible. A 47k/150pf seems like a good combo, getting you a gain of around 4 and keeping filters as they were.

Use any online filter calculator to check your figures.

 

[Chas Grant]

IC1.4 of the TL074 is the output buffer of the pedal, since its an output buffer it should have a unity gain, The volume gain of the pedal is from the previous op amp stage !C1.1, Check the resistor values associated with this stage. Although reading the build docs, this circuit is designed to have a low gain slightly above unity. if you don't want to mess with the buffer you cold lower both R20 and R21 which should increase the gain and leave the buffer intact. An easy way to test this would be to jumper the same value resistors across R20 and R21 and see how it sounds. If you like the results then just solder the resistors on the back side of the PCB across 20 and 21. Just make sure the resistors are below the 15K of the exsisting resistors to lower the overall value,

 

[MaxDB54]

IC1.4 of the TL074 is the output buffer of the pedal, since its an output buffer it should have a unity gain, The volume gain of the pedal is from the previous op amp stage !C1.1, Check the resistor values associated with this stage. Although reading the build docs, this circuit is designed to have a low gain slightly above unity. if you don't want to mess with the buffer you cold lower both R20 and R21 which should increase the gain and leave the buffer intact. An easy way to test this would be to jumper the same value resistors across R20 and R21 and see how it sounds. If you like the results then just solder the resistors on the back side of the PCB across 20 and 21. Just make sure the resistors are below the 15K of the exsisting resistors to lower the overall value,

So parallel 15k's across R20 and R21 would approximately double the gain? If so that sounds like a good place to start! Thx!

 

[Chas Grant]

So parallel 15k's across R20 and R21 would approximately double the gain? If so that sounds like a good place to start! Thx!

Theoretically it should double the gain. Let me know how it sounds.

 

[jeffhess74]

I have the same issue and I tried parallel resistors on R20 & R21 but it didn't seem to do anything. I connected a 33k resistor in parallel to the R21 resistor and another 33k resistor to the R21 resistor. This should have reduced the 15k resistors to 10K resistors resulting in more signal coming through into the buffer…correct?

UPDATE: I removed those parallel resistors and swapped R10 to a 22k and still no difference. Am I misunderstanding something here?