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Hi Everyone,

I just finished the Lazy Sprocket build last night (stock build, no mods). If I have the trimpot fully counterclockwise, then it seems to work as expected; the volume loss starts to kick in at Attack settings above 3:00, but from what I understand, this is par for the course. However, if I move the trimpot, I start to lose all volume pretty quickly.

I'll double-check to make sure I have all the right component values in the right places, but I'm curious as to whether anyone else has encountered this, or whether the tolerances of the components are such that this could happen.

Thanks,
j_p_312

The conventional wisdom on this effect is that it is 1) subtle 2) has a fairly small range of variation within the workable settings and 3) is highly dependent on the guitar signal it's getting. So what you're describing might be "normal" depending on your setup. We're happy to be extra sets of eyes on your build if you'd like—just post up those photos!

_________________
Scott

My band, Austin Hollow

This certainly doesn't sound like normal behavior to me. It's almost never normal when you have to run a trimpot at one extreme or the other of its sweep to get it to work correctly. Somewhere in the range of +/- 25% from the midpoint is pretty typical for an optimal setting.

As Scott mentioned, the nature of the Lazy Sprocket/Slow Gear circuit is such that the incoming signal can drastically affect how the Attack and Swell pots need to be set to get a good swell effect. Different guitars will require significantly different pot settings. The initial setting of the trimpot should be done exactly as described on page 9 of the instructions.


Component tolerance shouldn't stack up nearly enough to cause what you describe. A misplaced component or a bad solder joint would be much more likely. A good set of photos would be very helpful to us in providing you with guidance on what to do next. They need to be LARGE, well-lit and well-focused shots of BOTH sides of the PCB and all of the switch and jack wiring.

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2

Thanks, Scott and duhvoodooman. I checked the part population and it appears to be correct. I'll probably try reflowing the solder joints next and see what happens.

For what it's worth, I was playing a Strat through it. I experimented with a compressor in front of it to boost the signal, which seems to help for overall playability, but maybe not for the trimpot issue.

I reflowed the solder joints, but it did not seem to help. There is noticeable volume drop as the attack/swell time increases. Pictures to come in the next post.

Pics below

I can't see your pot values. Any chance you have the two mixed up? The swell time increases as the resistance of the attack pot increases. 25k is about as much resistance as you can apply before it starts fading, so a 100k pot there would explain why the pedal works till about 3:00 on the dial.

_________________
*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com

I verified that the pots are installed in the correct locations per the PCB silkscreen.

Please take voltage readings of the 741 chip and the S and G of the JFET.

_________________
*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com

With a DMM, I measure 4.773V at the output of the op amp. The gate of the JFET is at about 4.818V, and the source is at about 4.815V.

The op amp output voltage looks good and so does the JFET gate, but the source should be up around 5.3V, about a half volt higher than the gate. At least that's what I see on my Sprocket.

Your gate and source voltages are essentially identical. I would be checking carefully for a possible solder bridge between the G and S eyelets. I don't see anything on the solder side of the board, but I obviously can't see the solder joints on the component side. You can also check for continuity between them with your multimeter.

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2

Whoops, my mistake. I was still measuring gate instead of source. I measure 5.32V at the source pin.

Well, that's right on the money.

Could you also measure the voltages on pins 2, 3, 4 and 7 of the 741? Probably OK but we should just confirm.

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2

Pin 2 = 4.729V
Pin 3 = 4.625V
Pin 4 = 0V (as it should since it's ground)
Pin 7 = 9.186V (as measured while using a 9V battery)

All good on those.

Now don't take this the wrong way, but I'm starting to wonder if there's nothing wrong with the pedal but it's just not behaving as you expected that it would. I say this because we've had this come up a few times in the past on the Lazy Sprocket. The swell effect is more subtle than many people expect (it's not like riding your guitar's volume knob) and it really only works on single notes. You also have to play around with the Attack and Sensitivity pots to get the swell optimized for a given guitar. For my Strats, I find that a setting of about 3 o'clock on the Attack and 1 o'clock on the Sensitivity is about optimal. My internal trimpot is set a little less far than yours in your photos--the flat spot on mine is pointing right about at the corner of the square silkscreened outline at the bottom right of the trimpot adjacent to the 3904 transistor.

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2

If I keep the pot all the way counterclockwise, it seems to work more or less as I expected, if maybe not optimized. It's just strange that the trimpot has to be fully CCW to get any sound and doesn't seem to have room for much adjustment from there. Maybe that's not unusual given component tolerances and the inherent nature of the circuit design. But I do appreciate your help in making sure that the circuit is otherwise behaving as expected.

Another thing to check:

Electromechanical devices, like trimpots, are almost always more prone to failure than purely electronic ones. Will only take you a few minutes to check that it's working. Measure the resistance between the bottom leg and the center leg of the trimpot at three different settings: full CCW, halfway, and full CW. On my LS, the those values (in order) are 8.8K, 4.4K and 0.

While you're at it, you may want to check the two control pots as well. Do that similarly, measuring between the center lug (wiper) and one of the outside lugs. They are both linear taper pots, so you should see ~0 resistance at one extreme of the pot sweep, the full rated value of the pot (or close to it) at the other extreme, and ~50% of the rated value at the midpoint.

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2

The pots seem to be working as expected, as measured at the solder joints on the PCB. However, the Sensitivity pot was definitely not linear, but I believe that's what it's supposed to be (audio taper?).

Yes, that's so, according to the parts list. I think I must have a linear pot in mine.

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2

So after spending a late night with the pedal and trying to dial things in, here are my observations.

1) Up until about 3:00 on the Attack, the pedal seems like it's operating perfectly fine. I get a decent amount of the signal, the swell is definitely working, and the Sensitivity control also appears to have some effect, though I find that the optimum setting for it may be dependent on the Attack knob setting to some degree. The pedal does seem to respond better if I have some boost in front of it, particularly for single-coil passive pickups. I was pleasantly surprised when I tried it with humbuckers - I got a nice fat swell. Adding some reverb to the output makes it sound pretty sweet.

2) Above 3:00 on the Attack knob is where I start to notice a drop in volume, which gets worse the higher I go on the Attack knob, to the point where the weak sound also starts to get crackly. This is where not having much usable range on the trimpot may be preventing me from optimizing this range of the control, unless that's just the nature of the design. I literally go only go a small bit away from full CCW on that pot, and it only further weakens the sound before killing it completely.

I'm wondering if there's an issue with the signal from the emitters of Q5/Q6. It would seem that if I'm getting a suitable signal to drive the Attack pot, then at least that part of the chain should be okay.

Sounds like there may be a problem with your JFET. Please contact sales@buildyourownclone.com and we'll send you a replacement.

_________________
*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com

Will do. Thanks, Keith.

I received the replacement JFET today, and it seems to have done the trick. Now I have the trimpot somewhere closer to the middle, but slightly toward the full CCW position, with room to adjust in either direction as I see fit.

Glad to hear it! Nice finish on that pedal, too. Well done.

_________________
Scott

My band, Austin Hollow

Thanks!