The “Slum Dog Riley” Medium Gain Overdrive

[frets]

Hi Guys😸😸😸

As some of you know, I’ve been expanding into guitar pedals.  I have come up with many but wanted to share with you an easy Overdrive design that has considerable merits.

What I did was take the basic design for the Lovepedal COT50, I swapped out the diodes for BAT46’s that give it a nice boozy flavor, added a saturation control, and added the tone stack from a version of the Big Muff.  What came out was a great overdrive (I think) that I call the “Slum Dog Riley.”

The three tone controls really make the overdrive purr with immense tonal control, the added saturation control gives more nuancing to the crunch and in tandem with the gain, you can have minimal breakup to full breakup.

Its an easy build.  I made the diagram in DIY Layput Creator and you will need to download and enlarge it to read the values.

So for us overdrive addicts, I highly recommend this pedal.  I have it in a 1590BB enclosure.

[stevewf]

I ain't no pedal person but that seems interesting.

If I wanted to build this pedal, I know I'd need a case, all the electronic components including jacks, etc. But how, frets, do you go about the physical wiring? Generic perfboard?

[unreg]

Feb 3, 2023 17:21:57 GMT -5 frets said:

I made the diagram in DIY Layput Creator and you will need to download and enlarge it to read the values.

Or, when using a touch screen, just press two fingers together on your diagram and the spread fingers apart. Then the image gets bigger without downloading your layout creator.

It is also easy to read. I’m sure your image responds exactly the same if you enlarged it with any good graphics program…

Really cool you made your own overdrive frets!

[frets]

Hi Steve😺,

I breadboard the circuits out and then design the pcb board and send them into China to be made for 50 cents a piece plus shipping.  I use PCBWay as I find their services to be consistent and exact.   

Designing the boards is extremely addictive.  I’ve had my shares of board mistakes but am being very consistent now.  I have about 25 pedals developed.  I plan to sell them through my business.

But one thing that takes a lot of time is doing the artwork.  Another arduous task is getting everything measured appropriately for the holes in the enclosure.

But you could do this pedal easily on a Veroboard.  The only semi-difficult part is getting the tone stack right.  I know a lot of guys don’t feel that tone pots are that useful on a pedal.  But on overdrives, I find having three tone pots (a mini EQ) to be essential to dialing in the sound you desire.

If you decide to build it, I can help you out.

[thetragichero]

so it's basically an electra distortion with added tone controls eh

any reason you've got the low pass filter after the volume control? before result in weird interactions? you'll want to add a resistor (volume pot suffices in many circuits) to ground at the output of the circuit to minimize switching pops

[frets]

Hi Trag,
I did that because that’s what the tone stack had. I can easily remove it. I’m confused as to where you are recommending the pot and how would it be configured in terms of wiring. I think the pedal sound outstanding but am always open to your input.

What I have learned is many overdrive pedals have this familiar Electra configuration as transitor/diode based overdrives . Lovepedal in particular uses this formula over and over again. I find it a testament to how good the Electra circuit sounds. I did change out the diodes from the Lovepedal’s.

You mentioned it being the Electra with a tone stack. The saturation control is actually a powerful mitigator in this configuration. The tone pots in conjunction with the gain and saturation give it a high degree of nuancing. To the ear, the interaction of the controls sounds quite diverse.

But I would like clarification on the 22k 470pf circuit conclusion. I’m not really in favor of adding another pot if that’s where you’re suggesting it go. I think eliminating those two components will not adversely affect the circuit.

[thetragichero]

what I'm saying is that if you have that low pass filter where it is, add a resistor to the end (say 1M to ground you can go lower but this will lower output a bit)

[stevewf]

Feb 3, 2023 19:27:25 GMT -5 frets said:

But one thing that takes a lot of time is doing the artwork.  Another arduous task is getting everything measured appropriately for the holes in the enclosure.

Artwork, well, I've never been much of a creator there. Slap some paint and marker pen on there. There are no tolerances to deal with. But for positioning holes in the enclosure, yes tolerances to deal with, and that seems like it might be tricky. A way to collect aluminum carcasses.

If you decide to build it, I can help you out.

Well, that's very kind. Let me see if I can exhaust your generosity, starting with this one: just how do you go about matching the PCB with the holes? I've never designed PCBs, but I've seen an inkling of it via EasyEDA, and I've never drilled a pedal enclosure, though I play one on TV

I have about 25 pedals developed. I plan to sell them through my business.

25 after only recently diving in! What's your favorite? And, would you sell me a Slum Dog Riley? (PM me)

[newey]

But one thing that takes a lot of time is doing the artwork

Given that you're going to be making multiple units for sale, I would think screening the graphics onto the enclosures would be the efficient way to do this. You might need to shoot a coat of clearcoat over the finished graphics to protect the graphics. But once you make the screen for a particular model, you can crank out the enclosures pretty quickly.

We tend to think of screen printing as something just for t-shirts, but lots of stuff around your house is screen-printed- product logos, graphics, labels, lots of things. And, in industry, it can be pretty high-tech- the screens are designed on a graphics program and sent to a digital printer that makes the screen, and then the actual screening process is fully automated. But it's an old technique, and DIY is certainly possible.

This is in no way a product endorsement, as I've never used this product. But this is the kind of thing I'm thinking of for you. I'm sure other options exist, I just grabbed the first one I saw off the web that seemed suitable. You will need to be sure any kit you buy is suitable for printing onto metal. This one says it will do so:

www.ezscreenprint.com/products/diy-screen-printing-ezscreen-mini-starter-kit

[cynical1]

Feb 3, 2023 19:27:25 GMT -5 frets said:

But one thing that takes a lot of time is doing the artwork.  Another arduous task is getting everything measured appropriately for the holes in the enclosure.

There are a lot of ways to do this, but the easiest and least annoying way to do it is die cut vinyl. It works like this:



Your vinyl material, whatever color, is cut while it's on the backing paper.  Then they peel the unwanted vinyl off, apply a masking cover sheet and ship it to you.  You remove the backing from the original vinyl, leaving the graphic stuck to the top masking sheet. (which is typically translucent)  Line up your graphic holding the masking sheet, then card it into place, remove the top masking sheet...and it's done.  Like this:



As long as your artwork is in any Adobe format or .eps format, most print shops should be able to reproduce it.  Depending on how uniform your enclosures are, it's a matter of making a few digital templates, then adding or creating a new one for each pedal.

You can paint the enclosures, then apply, or just leave it bare.  Shoot some poly, or epoxy if you're a masochist, and you're done.

HTC1

[frets]

Thanks guys,

I really appreciate the help on the graphics. The vinyl and the screen kit are great ideas. To date, I’ve been using waterslides and it takes FOREVER. Because you have to wait for each piece to dry.

I had no idea it would have taken this much time from breadboarding to designing the pcb to drilling the enclosure to doing the artwork.

So thank you for the recommendations. I’m going to get some vinyl and look into the screen kit. It just looks so professional.

Steve,
My favorite? It’s a clone of the Jext Telez White Pedal. A British Invasion pedal that sounds like you’re playing a song on “Revolver.” I also really like the “Darkside” clone for a Pink Floyd sound. A Stevie Ray pedal and a number of overdrives.

But I still have a lot of work to do getting them in enclosures and doing the artwork.

Thanks guys😸😸😸

[thetragichero]

waterslide decals are convenient because they can be printed on an inkjet printer but a total pain in the rear, I've had issues with them staying down with a topcoat. I've switched to having a local trophy shop print me thin (1/16”) aluminum panels using dye sublimation. comes out looking professional, not too pricy (i think this one was ten bucks), and supports another local business

[kitwn]

Feb 3, 2023 20:31:04 GMT -5 frets said:

As if you don't have enough to be getting on with!...

One interesting experiment for a future pedal design would be to put a bass-cut control ahead of the diodes. Altering the audio spectrum going in to the distortion stage will affect the range of new frequencies created, which is different than simply doing an EQ job on what comes out. Since the low frequencies tend to be the high amplitude components that therefore dominate the distortion this may help keep the sound tight and controlled, especially on the lower strings. It's why a bass-cut control is useful in a guitar since the tone controls in almost every amp (bar some Mesa-Boogie models) are after the distorting pre-amp.

Kit

[unreg]

Feb 4, 2023 12:03:19 GMT -5 frets said:

But I still have a lot of work to do getting them in enclosures and doing the artwork.

Thanks guys😸😸😸

Miss frets,

From my single GhostDrive assembly, I feel you should do the artwork first and THEN get your pedal electronics in enclosures. It’s tons easier to decorate just an enclosure.

Though, maybe you need to get the electronics into an enclosure first to know if the enclosure is appropriate. But, after that, please decorate first. (I bet you know this and so this is a waste of text.)

[stevewf]

Also, please help me learn, folks.

I see a "9V+" for the battery, but I don't see a "9V-". There's probably a standard, like maybe the battery's negative terminal is assumed to be connected to to the signal ground.

But I'm green, so I need it spelled out.
1) Where does the battery minus go?
2) What gets switched in those three-terminal jacks? I mean what circuit in relation to the battery is closed when a plug is inserted, pos or neg, and why?
Thanks!

[kitwn]

Feb 5, 2023 0:41:36 GMT -5 stevewf said:

Also, please help me learn, folks.

I see a "9V+" for the battery, but I don't see a "9V-". There's probably a standard, like maybe the battery's negative terminal is assumed to be connected to to the signal ground.

But I'm green, so I need it spelled out.
1) Where does the battery minus go?
2) What gets switched in those three-terminal jacks? I mean what circuit in relation to the battery is closed when a plug is inserted, pos or neg, and why?
Thanks!

Most circuits connect the -ve of the battery to ground/earth/chassis and treat +ve as the 'supply' connection. This is just a convention, the electricity doesn't really care.

Some circuits, especially those using operational amplifier chips, have a dual supply with +9V and -9V as well as ground. In this case there are two batteries, one has -ve to ground and provides the +9V supply rail, the other +ve to ground and provides the -9V supply.

The three terminal jack socket has the tip connected to the signal input/output and the other two terminals are the battery -ve and ground. The shaft of the jack, which is it's ground connection, connects battery -ve to ground to act as an ON/OFF switch simply by plugging in/out.

Kit

PS  I've just noticed that the forum describes me as a "Rookie Solder Flinger". That's a bit rich for someone who's been a professional electronics engineer for nearly 40 years 🤪

[newey]

Feb 5, 2023 3:17:53 GMT -5 kitwn said:

PS  I've just noticed that the forum describes me as a "Rookie Solder Flinger". That's a bit rich for someone who's been a professional electronics engineer for nearly 40 years 🤪

Keep bringing your knowledge to bear here and your stock will rise quickly!
Besides, engineers design, they don't necessarily solder things.

stevewf-

The shaft of the jack, which is it's ground connection, connects battery -ve to ground to act as an ON/OFF switch simply by plugging in/out.

More on this, just FYI-

A regular (mono) guitar cable has a "tip" and a "sleeve" connection (the sleeve is sometimes called a "barrel"), and the corresponding jack has those same two connections; it's called a "TS" jack for "tip-sleeve". The type of jack used in this pedal (and most others) is a "TRS" jack, where the "R" stands for "ring", which is the third connection. TRS jacks are also called "stereo jacks" because these are mostly used for stereo headphones or other (unbalanced) 2-channel connections, where the tip connection is the signal connection for one channel and the ring for the other, with the sleeve as the common ground for both channels. To enable the stereo connection, a corresponding stereo cable/plug must be used. If you examine the plug on a pair of stereo headphones, you'll see the tip, ring, and sleeve contacts, each separated by an insulator.

But with a pedal, we can use a TRS jack to disconnect the 9V battery by using a standard TS guitar cable/plug. As kitwn notes, the battery - connection is made to either the ring or the sleeve lug of the TRS jack, the signal ground to the other. By plugging in a regular, non-TRS guitar cable, both the ring and sleeve are connected together when the cable is plugged in, thereby grounding the battery as well as the signal.

There are also jacks and plugs which are "TRRS", with an added ring connection; these are often used to provide a "balanced" stereo connection such that each channel has its own ground connection. If you examine an iphone plug, you'll see a "TRRRS" jack with a total of 5 contacts; this is how your phone can have sound, a microphone, and video/data connections all with a single plug.

So, using a TRS jack to disconnect the 9V battery, as is commonly done in pedals, is a sort of hack, using a stereo jack and a mono cable to switch the battery negative.

[frets]

Trag,
Thank you for the wonderful idea of the aluminum already screen printed. I would like to try that out.

I find the Enamel Clearcoat does very well with the waterslides. I haven’t had any problems. But the waterslides are a huge pain.

I still want to explore Newey’s recommended system.

Unreg😸,

Thank you for the recommendation. I am doing the artwork before I drill the enclosure out. However, it is a challenge to figure how the artwork will fit in relation to the knobs and switches.

[kitwn]

Feb 5, 2023 9:21:11 GMT -5 newey said:

Feb 5, 2023 3:17:53 GMT -5 kitwn said:

PS  I've just noticed that the forum describes me as a "Rookie Solder Flinger". That's a bit rich for someone who's been a professional electronics engineer for nearly 40 years 🤪

Keep bringing your knowledge to bear here and your stock will rise quickly!
Besides, engineers design, they don't necessarily solder things.

stevewf-

Good point Steve! Though the BBC called me an Engineer (complete with capital 'E') after I'd completed all their training in the UK, most of my working life was hands-on. In fact, after emigrating to Australia, I worked as a 'Technician', mainly because the shift work meant being paid more than the Engineers and partly because there was less crap from the management. They don't work nights or weekends.
I've always enjoyed tinkering with electronics at home and, having retired, I'm now learning more about the intimate details of guitar pickups and electronics as well as starting building the guitars themselves. I really like this forum, it's full of real technical knowledge rather than hearsay and voodoo, but everyone seems to have fun at the same time. Hopefully I can contribute something useful and eventually earn my Soldering Proficiency badge.

Kit

[unreg]

Feb 5, 2023 14:19:34 GMT -5 frets said:

I am doing the artwork before I drill the enclosure out. However, it is a challenge to figure how the artwork will fit in relation to the knobs and switches.

I feel your pain… yes that would require drawing a rough sketch of your artwork on a page; and having a transparent sheet with knobs and switches outlined. Then you could either overlay the transparent sheet to check your artwork for errors OR you could instead print a few tiny dots, that mark the edges of each knob’s circumference. Printing the tiny dots may be helpful if you’d rather not remove and replace that transparent sheet during your artistry.

My GhostDrive came with translucent stickers that required me to roughly measure the knob’s radius and then place a tiny dot, on my painted pedal enclosure, at the knob bottom. That dot was placed just inside the knob’s circumference so that the actual knob would cover over the dot. (To do that I believe I just reduced the radius by a 16th of an inch… then measured that smaller radius from each pot shaft hole’s center… and lightly marked my dot. Then, I just had to place each sticker an 8th of an inch below the dot. 1/16” + 1/16” == 1/8”. Perhaps you may want more blank space between your artwork and the knob, so then you might try placing your artwork 3/16”, or any other measurement > 1/8” , below the mark.)

With the dot below each pot haft hole, it was relatively simple to apply the stickers marking “gain”, “treble”, and “output”.

—-

kitwn, look at this thread (especially read newey’s diagram):

guitarnuts2.proboards.com/thread/9352/colors-words-unreg