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I'm just wondering about people's experiences with 9V pedals and unwanted clipping.
I've built a voltage-doubled clean boost with an op amp buffer at the beginning of the signal.... sounds really nice.
I'm thinking of removing the doubler and keeping it at 9V but I've yet to try a variety of guitars through it at 9V.
Has anyone experienced unintended (harsh) clipping from particularly hot pickups in 9V pedals (clean boosts) that don't use voltage doubling, and do you think it's a good idea to stick with 18V or do you think 9V is good enough in the majority of scenarios?

Thanks....

I'm curious, why would you run it at 18v if it's just a boost? I mean, I know more headroom. But it seems like unnecessary parts.

Again, I'm just curious, and not being all judgy


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I guess the idea for this is to have it be a volume pedal most importantly, but with the bonus option of being able to adjust the maximum volume a decent amount above unity gain if need be. Basically, a relatively neutral sounding volume pedal. Maybe the 18V is unnecessary, but I just figured it would eliminate the possibility of nasty clipping with hot pickups.

I reworked the schematic but haven't breadboarded it yet... I'd love another set of eyes first.
I decided to change the two inverting stages to non-inverting and use 5532 instead of TL072 which allows for much smaller resistors, and added the 100r resistors at the +input and output pins to help eliminate stray capacitance issues (from what I've read).
I'm unsure what the best value would be for C4.
Are there any ways to improve this?

For a tuner out, you can modify the design I showed a bit further. Ditch the buffered VB rail and use that op-amp as a separate output. It you tie it the volume pot as shown, you'll still get tuner output even when the volume is all the down. Or, just use the same idea to adapt to your design.

Trying to reduce white noise-like hiss from the boost section, do you think reducing R3, R4, R5, and the Boost pot is an option?
What is considered to be an acceptable minimum value for these resistors?

That's great, I'll try this... thanks again!

Here's how I would approach it:

- On the power section, move the 47R resistor to the 9v input. This acts as a LP filter on the main power supply so the charge pump works from the lowest noise floor.
- The unused op-amp stage can be a buffer for the bias supply. Not necessary, but it's good practice when practical.

- On the audio side, a slight re-arrangement offers up some possible advantages. Make the Volume pot a voltage divider and the trimpot the max boost control instead of the other way around. This way the volume pot behaves more like the one on a guitar. Add a switch for active or passive input. So, in passive mode it reacts directly with the guitar volume, and in active mode it has an input buffer. Might come in handy with using different style of pickups.

KIM: this is just how I might do it. Your design is just as good so I'm only trying to show an alternate approach to the same idea.

Brilliant, thank you. If I were to add a jack for a tuner, I've seen with passive volume pedals that the signal at the circuit input is just split, one for audio and one for the tuner. I imagine I could do that with this circuit but is there a better approach in this situation?

Hi all, I've put together this volume/boost design meant to be used in a volume pedal enclosure.
It sounds good to my ears but I would love to hear any advice about improving the design in any way.
The things I want to keep the same:

The Volume treadle pot is A250k
There is a Max pot that sets the volume ceiling when Volume pot is fully clockwise
There is a decent amount of clean boost available

Thanks

This is a great sounding effect. I've been playing around with the various pots and trimpots and to my *imperfect* ears, in the vibrato mode, the amount the pitch is modulated is, let's say, a semitone. So, the signal warbles up and down a semitone and it seems that the Intensity knob attenuates the amount that the semitone warble is heard, but it doesn't change the amount that the pitch changes, if that makes sense. Adjusting the internal trimpots, to my ears, also don't change the amount that the pitch changes, they just alter how pronounced or audible it is.
So, my question is: am I wrong about this, and if not then what specifically could one adjust to control how 'far' the note is bent? Is there a practical way to have a knob which can expand or contract the amount of pitch bending, so as you turn it clockwise the warble increases/decreases in pitch?
I hope this was clear, thanks in advance....

I have a circuit which, with 9V, draws around 31mA. I've been using this voltage 'doubler' (image attached) with a NE555P chip to bring the voltage to 15.9V and the current to 75.5mA.
It sounds fine, no issues I can detect, but I don't have much experience using doublers so I'm curious if this looks like a good circuit to consistently use with that amount of current.
I'd likely use an SMD version of a 555 chip based upon availability.
Thanks in advance!

I'm wondering if there's anything else that could help reduce crosstalk between channel A and B? There's still a faint signal of channel B when panned to channel A and vice versa, although it can be quite noticeable with loud effects in the chain. I was advised to raise C29 to 220u in order to get the impedance at ground to the optimum level and it did help somewhat but I'm hoping there are other ways to help. I've tried isolating ground/Vref paths where possible.

I'm looking for recommendations for quality SPDT toggle switches. I have a few Taiway on hand... opinions?
Also wondering about opinions on good quality 4PDT stomp switches, preferably with a soft click but not totally necessary.
Thanks

I didn't read the earlier thread, but I'm having a difficult time telling what is going on with your bypass setup. Are you trying to have the option for tails with true-bypass? If that is the case I'm tempted to say you need to add a buffer in there somewhere.

I found a setup for something like that with a delay. Maybe this will help.

http://vulcanofx.blogspot.com/2015/03/analog-fet-switch-daughter-board-for.html

Yes, the circuit is true bypassed when tails isn't engaged.
I temporarily bypassed pole 1 of the 4PDT (connecting R5 directly to R27) to see what would happen and the popping vanished so I've experimented with this in mind.
I moved the bypass connection after R5 to just after C1 instead, and added a buffer before the 4PDT pole 1 and this has reduced the popping (after plugging in power, the popping volume drops to a more reasonable level after 7-10 seconds).
I'd like to experiment with the circuit you've linked. I'm going to try to integrate it into pole 1.
Thanks

I was having issues with a parallel looper design and asked for advice a while back to help eliminate switch popping and circuit noise. The attached file [SCHEMATIC_Version1] shows a pop-free version; the switch popping finally disappeared after removing all pulldown resistors. The guitar signal was too quiet, though, and the circuit had a high noise floor. Although the schematic doesn't show it, I was using a voltage doubler.
The second file [SCHEMATIC_Version2] was a redesign using lower noise op amps and other changes. The switching itself remained the same. This version has switch popping issues.
The pulldown resistors at input/output/4PDT lug 4 were added later to try to eliminate the popping but didn't help. I tried lug 6 to Vref as in Version 1 but it didn't help. The LED being removed doesn't help either. I lowered all capacitors in the audio path to 100n to temporarily hear what that did when switching the 4PDT and SPDT(Tails) on and off. There was still a significant pop when either were turned to the on position.
I should note that I used an audio probe to determine that there is *almost* no pop going through the sends, mostly through the circuit output and output jack. I added a 100n capacitor after lug 2 (not shown) and this reduced the pop when switching the 4PDT to the off position.
If there's anything else worth trying, I'd appreciate any suggestions!

Thanks, I'll look into that.

I'm looking for for a solution to popping that's occurring with a 4PDT and SPDT in a circuit by potentially utilizing a microcontroller. I've read that they can be programmed to briefly mute the signal as they switch, which can eliminate popping. It's something I'd eventually love to learn how to program and implement myself but in the mean time, does anybody know of anyone with this knowledge/experience that could provide this service?