First Post - Project Question

[Mike6158]

I like to work on tube guitar amps. My two favorite projects to date are (1) a Gretsch Model 6151 and (2) Sears Silvertone Model 1484 that I'm still working on. Both amps are mine (which is what makes them my favorite)

Building "vintage" stomp boxes just seemed like a logical thing to add to the to do list and I'm a big fan of Pink Floyd / David Gilmour, so I started checking into 70's vintage stomp boxes. The Big Muff ∏ and ProCoRat came up quite a bit. I found a website with numerous schematics and settled on the V2 the David Gilmour may have used (depending on the source he either absolutely used a Big Muff or just had one plugged in but he never used it). I built the schematic in Eagle and created the board file this evening. Before I send it to my board mill, since I don't know much about audio circuitry from a circuit board perspective, I was wondering if anyone here would be interested in looking at the layout and orientation of the components?

Couple of notes- I did not create the board with the intent if mounting the pots or stomp switch on the board. You'll see terminals labeled Tone 1, Tone 3, and Tone W for tone pot connections, Sus1, Sus3, SusW for the Sustain Pot, and Vol1, Vol3, and VolW for the volume pot connections. When looking at the back of the pot 1 is on the left, W is the wiper, and 3 is on the right.
IJ = Input jack. Both sides of the board are a copper ground plane designated as ground so any connection with no trace is probably a tie point to ground.
OJ = Output jack
SO, SI, SC are all for the stomp switch. SC = Com, SI - Input, SO - Output.
Batt can either be a battery or wired to jack and use a 9V wall wart

Questions:

(1) Is it going to be ok to wire from the pots to the board vs board mounting the pots?
(2) Should I use shielded wire for the input and output jack conections?
(3) Shielded for the stomp box connections?

My process: First I make the board file. Then I print it 1:1 to see if all of the components fit (I have the teeth marks in my a** from not checking the board before I mill it). If the components work I send the file to my Othermill and make a prototype. I build the prototype and if that works and I don't need to change anything I may or may not order from Osh Park. The cost for the board I just made would be a little over $33 for 3 boards. There are cheaper board houses but Osh Park makes very nice boards and I usually don't need 3 much less 5 or 10 that the other houses will make. I'm a little out of my comfort zone with a project like this one (not a tube to be found) so I thought I would ask before I spent a few hours milling the prototype.

Comments are appreciated. Here's a screenshot of the board

[PRR]

Welcome!

I encourage you to browse the forum (even "uninteresting" topics"). I think some of your questions have been asked before.

> ok to wire from the pots to the board

I think you will see many happy builds doing it that way.

I think (with digging) you will find rabid for/against arguments which nobody wants to get into again (or maybe they will?).

I won't even touch the shielding issue because you don't have to carve it in stone. Build with short wires. If it screams supersonics, re-wire so output stays away from input. Still touchy? Rewire with shielded. "I have gotten good at fixing my screwups."

> Big Muff pi and ProCoRat ...., since I don't know much about audio circuitry from a circuit board perspective, I was wondering if anyone here would be interested in looking at the layout and orientation of the components?

Plagiarize, plagiarize, plagiarize ! ! !

Never re-invent known-good layouts. Life is much too short.

I am sure gut-shots of pi and Rat have been posted. I think there are several published build-yer-own plans for pi and Rat. No they are not perfect (and 7 smart designers might present 13 different "better" layouts). Yes, they work (the originals and most recreations).

Cheating? No. First I bet you will persist in drawing your own, only "guided" by plagiarism (which makes it "research"). Next I suspect you will ask "Why they do it that way?" and this may uncover insights into design for audio and also for assembly.

[armdnrdy]

Never re-invent known-good layouts. Life is much too short.

#1 Great info!
You will learn how to route boards correctly by studying what already works...and through mistakes by deviating from that!

[Jdansti]

Welcome!

Just to add to what PRR said about shielding, most stompboxes use the metal enclosure as the shield. Make sure all of the grounds are all connected together and connected to the enclosure. Some super high gain circuits might need shielding inside the enclosure, but it is rare. As PRR said, keep internal wire lengths as short as reasonably possible.

Something to watch for is your power jack. Most (but not all) stompboxes and stompbox power supplies use negative center polarity. Since your enclosure will be connected to ground, if you use negative center polarity, be sure to either use a plastic power jack or use isolation if you install a metal one. Otherwise, you'll short your power supply.

Good luck! Let us know how it turns out!

[Mike6158]

Great replies everyone. Thank you.

Just for clarification: The board mill doesn't remove all copper except the traces, it cuts away copper around the traces but leaves most of the copper on the board. I'll try to remember to post an image that shows what I mean when I finish the milling process. In this "test" I used a double sided board made what's called a "copper pour" o both sides and designated each as ground. The entire board, with the exception of the traces, is a ground plane. I can isolate it from the box with plastic standoffs or I can tie it to the box with metal (brass) standoffs). The original ∏ was built on perf board. No traces, just hard wiring. By the time they got to V2 there had ben many, many versions of V1 made but they had switched to circuit board. 

Layout - I "sort of " followed the V2 layout with one exception (the one that may be a problem). I compressed everything as tightly as I could to save board cost (which, of course, isn't a savings if it doesn't work. But that's why I have a prototype mill. Ok the real reason is that I just wanted one).

Step two would be to switch to surface mounts components. Ironically, I could have better spacing with the same board size if I had used SMD's but (1) things like carbon comp resistors aren't available in SMD components and (2) I hate working with SMD's.

At this point, just for fun, I think I'm going to mill it and build it, and see what happens. The good news is that once the schematic is done in Eagle I can make different versions of the the board.

I'll post results when I get them. At the moment I'm waiting for parts. I want to compare what I bought with the footprint. Especially the .1µF caps. I selected a modern Kemet cap and it looks like a little cube. If this board doesn't work I may try a different package.

It sounds like I have a lot of forum posts to read... best get to it...

[duck_arse]

it's a nice looking thing. one minor point - you might want to add thermal reliefs around/instead of the pads on the parts that connect to the ground planes. easier to solder, then.

[PRR]

> what I bought with the footprint. Especially the .1µF caps. I selected a modern Kemet cap and it looks like a little cube.

If you are building a million, your PCB layout guy and your part-buyer guy must coordinate to be sure all parts will fit.

In DIY work, it is wise to allow for "different parts". 1/4W resistors are fairly predictable. Transistor pin-out DOES vary. Caps are the worst offenders. I would always allow more space, then layout a *lot* of holes so caps of 0.1" 0.2" 0.3" 0.4" 0.5" leg-spacing will fit.

This stuff is mind-numbing. Neat consistency may help the workers. Also some day somone may peek inside. I see some caps E-W and some caps N-S for no apparent reason. This may be getting too fussy, but I hacked a sketch (extra holes, rotated bodies) anyway.

https://s9.postimg.org/7tximtrzz/Mike6158.gif

Oh... me myself, "123" on a transistor does nothing to understand the function. I would love to find "EBC" on the PCB. Then when I get one of those dratted alternate pinouts, one less step in the translation.

[Mike6158]

If you are building a million, your PCB layout guy and your part-buyer guy must coordinate to be sure all parts will fit.

It's a one off. Technically a 3 off since Osh Park sells them in 3's

In DIY work, it is wise to allow for "different parts". 1/4W resistors are fairly predictable. Transistor pin-out DOES vary. Caps are the worst offenders. I would always allow more space, then layout a *lot* of holes so caps of 0.1" 0.2" 0.3" 0.4" 0.5" leg-spacing will fit.

I've seen that with production kits. I'm not going to sell kits. The parts list is small for a Big Muff. I just matched the board with the parts that I have on order. In a couple of cases I had to make my own package but it's pretty easy to do.

This stuff is mind-numbing. Neat consistency may help the workers. Also some day somone may peek inside. I see some caps E-W and some caps N-S for no apparent reason. This may be getting too fussy, but I hacked a sketch (extra holes, rotated bodies) anyway.

https://s9.postimg.org/7tximtrzz/Mike6158.gif

Yes it is (mind numbing). Hence the caps laid out with no consistency. A numb mind will do that. I spent a day making the board layout and about 1/2 again as much time tweaking it. Extra holes = extra space and my intent was to cut way down on space (which very well may bite me in the a**). The board is only 1.85" x 3.65" in size.

Oh... me myself, "123" on a transistor does nothing to understand the function. I would love to find "EBC" on the PCB. Then when I get one of those dratted alternate pinouts, one less step in the translation.

I'll have to see what Eagle allows with that. I agree that EBC is much better than 1, 2, 3. The transistor that I'm going to use was one of the transistors in the Eagle Library, 2N8059, and the data sheet shows the pinouts. I just checked, the package came with 1, 2, 3 and I can't change it unless I make a package with EBC. I deleted 3 of the 4 transistor part numbers because there wasn't room for them but left T1 as a reminder. I know they are all 4 the same so having one part number listed works for what I'm doing.

When I started OtherPlan, the mill software, it asked me if I wanted to update the software first rule of computers- if you need to use your computer and it wants to update, Don't do that. So I did... and now the mill is dead. As in the software won't talk to it. The Mac sees the microcontroller connected to the USB port but they aren't speaking to each other. I've got a ticket in with tech support but they don't work in the weekends. They are on the west coast so it'll be a while before they get to it in the morning. I went ahead and ordered the board(s) since I don't know how long it will take to fix the mill. It's times like these that I miss etching boards (not really). I want to see just what kind if oddball noises this thing makes. Who knows... it may actually work but I'm concerned that I went to far with "scrunching" everything together. We'll see...

This is what is ordered:

[Mike6158]

The boards and parts finally arrived. I stuffed the board this evening. I'm not going to get too excited about a box until I hear this thing. I need to round up some jacks and some place to put the pots. The two big caps are very high voltage. It's all I could find but probably not all Mouser had. Not the size of the white 0.1µF caps vs the silkscreen :/ Apparently the dimensions were for the cap laying down and the leads bent 90°. I might have been able to scrunch the design a little more. But, before i get too excited about that, I think I'll see if it even works first

I put a small ruler in for scale

[vigilante397]

Where do I get one of those rulers? I'm trying to overcome my fear of SMD.

[bluebunny]

I'm sure I saw something like that on Tindie. But I'll let Mike give you the correct answer.

Sent from my E2303 using Tapatalk

[Mike6158]

Where do I get one of those rulers? I'm trying to overcome my fear of SMD.

Adafruit

It looks like they are out of stock but there's a "Notify" button so maybe they plan to make more

https://www.adafruit.com/products/1554

I've built some things with SMD's. I can't say that I like to build with them. 0805 parts are as small as I like to use but I have used 0603 resistors, diodes, and LED's  before. SOT223 is my preferred size for transistors but I've used SOT23. I may have actually run out of bad language when I used the SOT23 part. IMHO, solder paste and a cheap Chinese reflow oven is by far the easiest way to to assemble boards that use SMD's.

Chinese oven: http://www.ebay.com/itm/T962-Reflow-Oven-Infrared-IC-Heater-Visual-Operation-Micro-Computer-New-Setup-/111458775965?hash=item19f375f39d:g:0kMAAOSwvzRX14q9

Of course the price has dropped a little since I bought mine



Here's a linear charge controller for solar panels that I built last year. I made a prototype on the mill and then bought boards from Osh Park once I knew I wouldn't go batty trying to solder the parts on. I used a toothpick to apply solder paste and SMD tweezers to set the part on <--- sounds easy when I type it. The paste I have has to be refrigerated. Adafruit sells some paste that doesn't have to be refrigerated. I haven't received my tube yet but I plan to try it out when I do. Basically you just dab paste on the pads, set the parts down, put it in the oven, select a reflow profile (I used a process known as guessing to select the profile), tell it to go. When it's done the parts are cooked onto the board. Every now and then you have to fix a part or two. That's where a fine tipped iron comes in. 

The one on the left is the thru hole design and the one of the right is mostly SMD's. Same schematic.

[Mike6158]

Well... it works but the output is low. Real low. Like lower than the output from the guitar low.

Sustain, Tone, and Volume all have an effect on the output. I put the output from the board into a Gretsch 6151 tube amp and I had to crank the volume all the way up to get mediocre volume out of it. Plugging the guitar in directly proved that the amp was still in fine shape.

Now for the troubleshooting fun

[GGBB]

Where do I get one of those rulers? I'm trying to overcome my fear of SMD.

Seeed sent me a free one when I placed my first order with them. Just a simple 10 x 5cmx5cm order.

[Mike6158]

I don't know if I should start a new troubleshooting thread or just continue on here.

Well... I've got a 50mV, 261.63Hz (middle C) sine wave going into the muff board and the output connected to one of my Marshall MG15MSII baby stack heads and everything seems to work but the output is low. I can just barely hear it unless I crank it up. Even then it doesn't get loud until I punch the overdrive button.

I don't normally work on things like this so I'm a little out of my element. For instance, I don't know how much output voltage a guitar has. I assume that it's AC and  that it's pretty low. 50mV is as low as my signal generator goes. Actually it's an HP 33120A Function / Waveform generator if that matters. I can turn up the output of the signal generator and it doesn't really affect the output of the pedal that much which tells me that "She's giving me all she's got Captain".

I took some DC readings with it disconnected from everything. I'll list them below. I haven't pulled out the low range AC meter yet so no AC readings. I did put a scope on it and I didn't see anything particularly wrong but, like I said, this isn't my home territory.

I don't know if I mentioned that I'm using 2N5089 transistors and IN914 clipping diodes (until now)

VCC- 9.1V DC

Again, the following DC readings were taken with no input or output

T4 Input amp
C: 5.723 VDC
B: 1.526 VDC
E: 0.952 VDC

T3 and T2 Clipping section
T3
C: 4.084 VDC
B: 0.64 VDC
E: 0.048 VDC

T2
C: 4.095 VDC
B: 0.644 VDC
E: 0.058 VDC

Wiper on the tone control: 1.772 VDC

T1
C: 4.055 VDC
B: 0.647 VDC
E: 0.0514 VDC

[PRR]

> I've got a 50mV, .... I don't know how much output voltage a guitar has.

Many heavy distorters will clip for 20mV in.

A good middle nominal value for straight guitar is 200mV. (Which means a 20mV distorter will be in heavy distortion on nominal strums.)

There's evidence that older guitars could be 500mV strong strum power chord, and modern hot guitars plus pedalboards may be over 1V.

Still it can be 50mV input overload but the output section may not be up to the job. Is there a schematic in this thread? Any DC voltages?

[ElectricDruid]

Building "vintage" stomp boxes just seemed like a logical thing to add to the to do list and I'm a big fan of Pink Floyd / David Gilmour, so I started checking into 70's vintage stomp boxes. The Big Muff ∏ and ProCoRat came up quite a bit.

My own experiments lead me to conclude that a Big Muff or clone followed by a static flanger gets you very close to some classic Gilmour tones. I think he's supposed to have used an Electric Mistress, but I was using my own flanger design (Flangelicious) and that works fine too.

I was wondering if anyone here would be interested in looking at the layout and orientation of the components?

How obsessive do you want to be about it? Personally, I get pretty obsessive and like everything lined up neatly, although I see plenty of people with boards with parts scattered all over. Both work.

(1) Is it going to be ok to wire from the pots to the board vs board mounting the pots?

Yes. People wire the pots all the time. I would say that perhaps you should think about how to mount the board, if it's not held in by the pots. You've got no mounting holes of any kind, so you're going to be gluing or taping or tying it down to stop it rattling about.

Advantages of wired pots: Flexibility in pot arrangement and enclosure choice.
Advantages of board-mounted pots: Simplicity, speed of assembly, one fewer source of errors.

(2) Should I use shielded wire for the input and output jack connections?

In generel, it isn't required, since the enclosure should be shielded. A high gain fuzz pedal might be one situation where you might see further benefit from shielded In/Out wiring.

(3) Shielded for the stomp box connections?

No, overkill. Keep it short and tidy is enough.

Comments are appreciated. Here's a screenshot of the board

Looks good to me. Like you said, you could tighten it up if you wanted to reduce the board area. 0.4" resistors can sit next to each other on a 0.1" grid easily enough. But that'd need a Mk2 board, and if you've done one that works, why would you bother?!

Enjoy it!

Tom

[Mike6158]

> I've got a 50mV, .... I don't know how much output voltage a guitar has.

Many heavy distorters will clip for 20mV in.

A good middle nominal value for straight guitar is 200mV. (Which means a 20mV distorter will be in heavy distortion on nominal strums.)

There's evidence that older guitars could be 500mV strong strum power chord, and modern hot guitars plus pedalboards may be over 1V.

Still it can be 50mV input overload but the output section may not be up to the job. Is there a schematic in this thread? Any DC voltages?

My guitar is a late 80's vintage Ibanez. My guess is that the picks are fairly hot but not to modern specs. But I'm no guitar expert either though.
DC voltages are in the thread above yours. I have notes all over my "taped together" large schematic so I made one from the Eagle software but I don't see a way to attach it. I'll link a photo instead

To make things simpler to follow I'll include the section from the post above yours that has the voltage readings

I took some DC readings with it disconnected from everything. I'll list them below. I haven't pulled out the low range AC meter yet so no AC readings. I did put a scope on it and I didn't see anything particularly wrong but, like I said, this isn't my home territory.

I don't know if I mentioned that I'm using 2N5089 transistors and IN914 clipping diodes (until now)

VCC- 9.1V DC

Again, the following DC readings were taken with no input or output

T4 Input amp
C: 5.723 VDC
B: 1.526 VDC
E: 0.952 VDC

T3 and T2 Clipping section
T3
C: 4.084 VDC
B: 0.64 VDC
E: 0.048 VDC

T2
C: 4.095 VDC
B: 0.644 VDC
E: 0.058 VDC

Wiper on the tone control: 1.772 VDC

T1
C: 4.055 VDC
B: 0.647 VDC
E: 0.0514 VDC

Schematic:

[Mike6158]

You've got no mounting holes of any kind, so you're going to be gluing or taping or tying it down to stop it rattling about.

Thanks for your replies. Much appreciated. I agree, if what I built works then there's no reason to make it anymore compact. It seems to do what it's supposed to do as far as sustain and tone control goes but the output seems weak to me.

I put a mounting hole in each corner and made it part of the ground pour on both sides. I made them a bit small but they are there

[balkanizeyou]

T4 Input amp
C: 5.723 VDC
B: 1.526 VDC
E: 0.952 VDC

(...)

T1
C: 4.055 VDC
B: 0.647 VDC
E: 0.0514 VDC

That's a little weird. With a 100R emitter resistor and 10k collector resistor for T4 it's unlikely that you would be getting 0.9V at it's emitter. In fact, those voltages look like perfectly reasonable measurements for T1 (and vice versa - the T1 measurements look like they belong to T4). Are you sure you didn't mislabel the measurements?