Corroder/HAO Rust Driver PTP--Tutorialish

[comradehoser]

Build Rating

5.00 star(s)

Well, I finally got the massive backlog of drilling and boxing of completed circuits over and done with, so now I can turn my attention to what I've been waiting to do for a while, which is Point-to-Point.

I love Point-to-Point. It's a great crossover point between aesthetics and functionality, and it engages my sculptural/3D and problem solving predilections. I think everybody should give it a shot once. So, since I'm already in private convo with one member around a PTP build, I thought I would just publish this build report as a think-along for the curious, and especially for them. Please feel free to move if you feel like it should be in another section.

I'll publish the circuit in stages here with commentary. Please keep in mind, I am by no means even a competent PTPer and many of my decisions may not be optimal--but I'm def. open to dialogue. I posted in another thread what "real" elegant PTP should look like. That's not me. If pcb assembly is color by number, my PTP are crayons in the fist scribbles. I'm just here to serve as a resource/gateway/enabler/lubricator of means for anybody who is at all curious. I'm not a teacher in this, I'm a co-learner who can maybe save you some headache and give you a path and some encouragement into the journey of your first PTP pedal.

Here is where we start.

Circuit selection.
Especially for a first go around and demonstration purposes, we want something with a low parts count, and not a whole lot of controls, as things get crowded very fast in a 125b enclosure.

I was choosing between Corroder (building for a friend) and the Dung Beetle. I didn't have near enough parts for the Dung Beetle, so it's the Corroder minus a 22p cap. As we shall see, it was a good idea, as the Dung Beetle has 5 pots which will make for "creative spatial reasoning" for me later.

I've already built it, I know it's worth the effort, and I know how it should behave--all good things for this demo.

Here's the schematic



And here I am following it and starting to think about how it could actually look, with some ideas about the aesthetics of the thing.



We'll see what ideas we keep.

A big noticing at this point is the oddity of the power section. Usually it's just the led resistor branch, then the 5817 and 100u to ground and into the circuit. In this case, we have to make our way down to the chip before we get busy with the little 47u/resistor loop that will give us vref and vCC and then into the circuit. And where does vCC even go? Well, let's worry about that in a bit.

 

[comradehoser]

The other thing to notice is that this build is promising because almost everything is tied into the IC, which makes a nice tight unit of assembly that can be auditioned, moved around, and situated in many different locations in the enclosure, with the exception of the power section and everything to the right of c6, but there, it's 3 components, a pot, and a switch with 2 caps going to ground. That's not really going to limit us much. So, the circuit is compact and gives us good flexibility for whatever layout we can imagine.

On the caps, I want to make these socketable, so my friend can try different cap values. The stock values are dark and super dark (almost muffly). I tried replacing them on my build, but ended up going back to the stock values, as for me, it gives the pedal it's charm. Also apparently increases compression or sustain somehow, or makes it more obvious at least.

That's one of the reasons I chose the pedal--it is a MIAB, more or less, which apparently I like. The clipping sounds great to my ears, as well as the sustain. You also control mostly everything from the guitar. It has really great progressive clean-up on the volume knob resulting in a lot of different marshall voicings, which I think will appeal to my friend, who is into clarity and simplicity in his guitar rigs. Doesn't like fuzz or futzy stuff (even though he builds modular synths, go figure...). It's maybe not the ne plus ultra of MIAB pedals, but it is REALLY simple to build and fun to play.

 

[comradehoser]

OK! Here we go...

 

[comradehoser]

So, you can allow function to determine your layout, but in this case, I just decided to copy the layout I had done for my Massif PTP as I liked the way that it looked, and I knew this circuit would not be as exacting as others due to component placement. One advantage with PTP is that you can put your box-facing components pretty much where you want (although you may reap the consequences of contending with an overly fussy or painstaking build).

Drilling aluminium is very easy with a step bit (I can elaborate how if anyone want to know), or you can buy a pre-drilled enclosure. Only mild judgement on that decision, I promise.





Here we can see that I have a nice open space in the southeast corner where the circuit can roam. Remember that PTP builders have a secret superpower: verticality. Or maybe spatiality. Whatevs.

Basically, you can twist, spiral, stack, fold, or otherwise sculpturalize 2D schematics/circuits and locate them in layers or various designations in space as long as you respect connections and the limits of the enclosure for signal-side stuff. Ground-side, though, don't worry. Some PTP builders build directly off a literal copper ground plane. It may seem flimsy at first floating around, but once we tie in the connections and the ground, the connections add up to make a very solid and stable network.

The challenge for me isn't a functional circuit, it's making it look good.

Finally, I solder anything that will live in the bottom layer or be hard to access before beginning on main circuit or higher layer installations. The spdt on-off-on is prepared with the socketed caps, intended to be tied into the closest grounds on the pot or the TS jacks. The 3PDT has the bypass loop and grounding link installed. This is a 3pdt pcb pin legs instead of solder lugs (it was cheaper at stompbox parts), so for this and the spdt, I follow the soldering technique for PTP, which is really one of the biggest differences with pcb assembly, and I will detail it in a bit.

Next steps: remove the TS jacks and solder in the power sub-unit (have to make some decisions on how to configure the tie-in with the IC) and then I'll lay in my jack ins and outs.

 

[comradehoser]

Finally found some time!!!

I decided to start with the IC, and then locate it and decide how to run the power section.

I had the idea of doing loops for the sections from pins 1-2 and 6-7. However, I'm missing the 22p cap for the pin 1-2 loop. I still decided to stick the resistor in. Usually, I follow the schematic religiously--where there's a T-juncture, I do a T-juncture. We'll see if my ideas here work or not.

Basically, to keep the layout straight, I think what does the signal have to see first.

Here's the pin 6-7 loop. First diode has the kathode facing 7, second, kathode facing 6. Let's align everything.






You can use a flux pen or whatever, I use a wee screwdriver to place flux when needed, or I just dip components when possible. Put in on where you want the solder to go.




I have a video, but the forum doesn't like it uploading, so here is a pic. The flux is glomming the components together, I load a bead of solder on my iron, and then I touch the fluxed components for like one mississippi, if that. Maybe just a Miss. Just the time for it to sizzle.

 

[comradehoser]

First leg installed! Lets make the bends using the wee screwdriver as a bending jig and connect the other side.



OK, I decided that this looked better and I pulled up the loops gradually. Looks kind of like an oyster shell or sound waves. It is messy compared to pro PTP, but I'm just going with "organic". Alright, pin 6-7 loop almost done, I'm going to start 1-2 and the in to 2. I'll add the 22p in a loop like the 6-7 array later. But I also forgot about the 1-6 cap-resistor connection and 7-out cap-resistor, so let's put those on too.




Oh to the no. Broke the pin leg moving stuff into position.

Like I said, ICs and transistor legs, really, really don't like to be bent more than like twice, if that, and especially not back-and-forth, so make sure you hold the pin leg still when positioning things. Unlike me.

Luckily, there's still the big part of the IC pin leg to solder onto. Transistors break off at the body, so forget about that.



That's more like it.



Here is the completed IC assembly and how it might sit in the box. The white cap is the ins, the assembly off the 100nf WIMA red cap on the left is the outs to pin 3 of the pot.

The next pic shows the IC assembly above the power unit mockup. Pin 8 has to connect to the top power rail off the diode; pin 4 on the bottom ground rail off the s-shaped resistor and/or to ground.

I'm think of just laying it as a lower level frame for the IC assembly. It might look a little too rat's nesty/messy. But hey, I'm embracing the "organic" shapes.

We'll see....

 

[comradehoser]

Power section. I decided to try for the "organic" thing.

Power section installed. Please note the importance of consistent bend ratio for clean lines and such. I tried bending by hand, and it's... Okay. I think I'd want to have something more uniform to create consistent arc lines.

I think also it would look much cleaner if I were to redo it. A lot of the decisions emerged from other (suboptimal?) decisions

I also changed the order I usually do things. I put a ground in the lower layers and usually I save it for the top. Also used insulated wire for Jack ins/outs just because I wanted to try it and they were going to be pretty tight to other bare wires.

 

[comradehoser]

And now... the exciting conclusion to this episode....


So, I am doing 22 builds. FINALLY got organized and ordered everything including the very last piece of this jigsaw, the 22p capacitor. You can tell I'm out of practice, because I didn't even listen to my own advice! This phase of the build was littered with annoying disassemblies like the one pictured above where the input resistor/cap/resistor to pin 2 melted off when I put the 22p and resistor loop in-- YOU CAN'T LEAVE THE IRON ON TOO LONG!!! Just lots of flux, touch and go. Fingers were also very shaky. So annoying.



Here is the JRC4558 assembly tied in to the "board in" lug of the 3pdt (made several mistakes there, like locating it to the input jack lug, duh), and the outs to pin 3 of the volume pot.

I still have to tie in to the power subunit: pin 4 to ground; pins 3 and 5 of the 4558 to VREF off of the 47u cap, and pin 8 to the juice line between the 100u cap and the dual 100k resistors. Still no idea why we have VCC. Usually, I try to only use component legs as the lines, but it's not possible given the spatial traits of this build, so I'm going to run copper line jumpers. It looks nice and gives a lot of structural stability, but you could run coated wire if you wanted to. Or whatever. Solder a chain of component legs if that's your thing (would be very annoying).

In the pics below, I decide to essentially run a looping line from pin 8 to the power section exactly where it says to locate it between the 100u and the 100k/47u cap assembly. It's looking a bit bird's nesty, so I tied pin 4 to the nearest ground line instead of its location in the schematic. Ground's a ground, right, folks? At this point, aesthetics was done, it was a tricky solder, so I just went with an ugly x joint. And (large leap of faith for me given my utter ignorance of actual electronics), I jumpered pins 3 and 5 and tied the VREF in a big looping line to the jumper. I melt-disassemblied/collapsed that one several times, so that's why the solder is blobby. Should work, right? Right? WE'LL SEE...









Well, the LED works, at least. Looks "OK". Bends and joints could have been neater, and I need to clean some of the flux up. Too late now! Hahaha....

Overall, though, it looks alright. I do like the loops. It's a different look than the usual linear approach, but I would make it much tighter and alter my assembly to facilitate that if I would make it again.

At this point, I double check to ensure that there are gaps where there need to be gaps, nothing is in danger of moving and shorting (i.e. the VREF loop on the right next to the wall, there) and the bends look as decent as I can get them at the mo. I will ***gently*** adjust anything prior to boxing.



Let's hit some chords.....

Hm.

Hope you can join me for the next episode, TROUBLESHOOTING.









Just kidding! It works great. I worried a bit about maintaining the order of component junctures with so many tying in close to the same locations, but either I was lucky, it doesn't matter so much, or the way I assembled things maintained the order of what the circuit needs to see first, second, etc.. I did try to keep the schematic order of components in the assemblies.

I think if you do that, unless you make a direct mistake (backwards cap, for example), or install a bad component, troubleshooting needs are minimal in PTP since you can literally see and touch every connection.

I A/B'ed it with the original pedal, and it sounds slightly brighter and less grainy in the middle/0 cap switch position and the volume pot needs to travel more to get to the same volume, but otherwise it is identical. I suspect that is due to variances in tolerance of the components. I will most likely do drawing in pencil or other medium, or lately been pasting loteria cards, seal it with clearcoat, and call it a day.

I HIGHLY recommend this build. It is just a really fun pedal and dynamic pedal to muck about with, and a cinch to build. I am going to give myself... 5 stars for the build rating, hahahaha.

I hope this little series was helpful and can inspire you to try your own PTP builds. Please don't hesitate to DM me or post wherever with questions. Like I told @GizzWizzKing, I am nothing but a colearner/encourager with you all, but I'm very happy to share what I can and see what you all can come up with.

Next up: The Dung Beetle (I have wacky layout ideas for that one), the LoFran, and **maybe** the Kilimanjaro?--I think I suffer from Germanium fatigue what with the extra finickyness of Ge transistor parts selection. I think I am nearing the end of my pedal-building career and/or it's time to sell and cull, but anything with a lower parts count, I am just PTPing.