Looking for help solving this klon mod issue im having...

[ShadSunsCrash]

I built a klon clone about 4 or 5 years ago and its become one of my most used overdrives. When i built it i tried every mod i could find or think of on my own. Most were useless but one I worked out was raising the gain by lowering the 47k resistor (r16 on the electrosmash schematic) just before the summing opamp. But to take it one step further i used a 10K pot instead of a fixed resistance in place of the 47K and put it on a stomp switch so it works as a boost gain control. I also put a "boost volume" on the stomp switch as well that is just a 25k linear volume pot that piggy backs off of the stock volume pot but is only active when the boost is engaged. So when you have the boost engaged you have control over boost gain and boost volume.

So now its five years later and im going to rebuild the pedal but do it much cleaner since i already know what modifications ill be making (i didnt breadboard back when i first built this klon so i swapped all my mods directly into the pedal making quite a mess of things over the years lol). But the one thing i still havent worked out is the boost being active when the stock gain pot is below about 25% of the way up. Since the boost is in the op amp gain stage it only works if there is sufficient signal going to that stage. So what id like to do is find a way to make the stock gain pot (the side of the dual gang gain pot that is in the distorted path) jump up to a minimum of 25% whenever the boost is engaged. This way you can use the klon in the much loved clean boost mode then hit the boost and have the typical distorted klon tone or a high gain klon tone at the press of a button.

The boosted mode is a wonderful mod and sounds like a really great distortion as long as you keep the stock gain pot at about 25% or higher. So if anyone can take a look at this schematic and offer a suggestion to simulate the gain pot being at 25% without it actually being above 25% id really appreciate it. This will come with some trade offs im sure but overall i think it will be a great useful mod. I can work out all the switching on my own. I just need help working out how to manipulate the circuit to simulate the gain pot being about a quarter of the way up. In the first version that ive been using all these years i used a 4pdt so i can switch in the 10k boost pot in place of the 47k R16 resistor, add the boost volume/attenuation pot just before the stock volume pot, and switch the bypass led from red to blue to signify the boost is engaged. To switch those three parameters i needed 4 poles but this time around im probably going to use relays and/or JFETs to switch all the parameters.

If anyone can help with this it would really mean a lot to me. Ive tried working this out on my own but im just not seeing the solution. Thanks for taking the time to read all that. Below is the Klon Schematic by Electrosmash that is identical to the one my build is based off of minus my mods.

[MrStab]

Hi Shad,

If four poles are required, and one is used for an LED, a CD4053 analogue switch IC should get you where you need. This IC has three SPDT switches inside, but the LED would be lit on the same line as the 4053's control voltage (for which all you need is one electromechanical SPST switch).

You'd need to do some research on using such a chip, particularly ensuring all inputs/outputs are seeing the same DC bias voltage. But besides that, probably the same wiring setup you've been using on a conventional 4PDT.

http://www.geofex.com/article_folders/cd4053/cd4053.htm

(Bear in mind the above link describes bypass switching from a source which is likely to be high-impedance and biased at 0V outwith the coupling caps. You won't need to replicate all these components if you're already dealing with stuff that's low-impedance and already biased at 4.5V DC, nor do you need to use both outputs of each SPDT switch - though you should terminate unused outputs at 4.5V).

[MrStab]

I forget that the Klon gain pot is a serial weirdo, compounded by being revlog. There's a lot more to this mod than conventional gain stages.

At a glance, I still think you could get somewhere by switching fixed resistors in and out of series with each gang.

[ShadSunsCrash]

I forget that the Klon gain pot is a serial weirdo, compounded by being revlog. There's a lot more to this mod than conventional gain stages.

At a glance, I still think you could get somewhere by switching fixed resistors in and out of series with each gang.

This is what I initially thought as well but since it's a voltage divider setup I though that approach wouldn't work here? Thank you for the reply by the way. I know if I get a few of us thinking about this we can come up with a solution.

[ShadSunsCrash]

Hi Shad,

If four poles are required, and one is used for an LED, a CD4053 analogue switch IC should get you where you need. This IC has three SPDT switches inside, but the LED would be lit on the same line as the 4053's control voltage (for which all you need is one electromechanical SPST switch).

You'd need to do some research on using such a chip, particularly ensuring all inputs/outputs are seeing the same DC bias voltage. But besides that, probably the same wiring setup you've been using on a conventional 4PDT.

http://www.geofex.com/article_folders/cd4053/cd4053.htm

(Bear in mind the above link describes bypass switching from a source which is likely to be high-impedance and biased at 0V outwith the coupling caps. You won't need to replicate all these components if you're already dealing with stuff that's low-impedance and already biased at 4.5V DC, nor do you need to use both outputs of each SPDT switch - though you should terminate unused outputs at 4.5V).

Hey Mr.Stab thanks for the idea. Sadly the switching I'm not concerned with as I can think of several ways to accomplish this. It's the gain pot needing to be at a quarter of the way up when boost is engaged issue that I'm most concerned with. But with that said I'm going to look into your switching idea as it's one route I'm not familiar with. Thanks for taking the time to help out!

[ShadSunsCrash]

I figured it out. To set the gain pot for a minimum gain amount it was as simple as inserting a resistor in series with the gain pot after all. Specifically to set minimum gain i inserted a resistor (about 20K in my case) in between the 4.5v bias voltage (which is essentially ground) and pin one on the dual gang gain pot (the gang that controls gain not the gang that controls clean level). So now i just have to decided which switching method to implement to get 5 poles switching all at once. Before i was using a 4pdt but with this new addition that really dials in this mod ill need another double throw pole. I might go with the recommendation to use a switching IC or use JFETs. Anyways i just thought id answer my own question in case someone has a similar question in the future lol (very unlikely but who knows? It could happen!).