Big Muff - first project

[tjdracz]

Hello there! My first post here Trying to get into pedal building and decide to try and build a Big Muff on a stripboard. I drawn the layout below with DIYLC, using this diagram - http://www.pisotones.com/BigMuffPi/psst/schm-civilwar.jpeg
Layout:
http://i47.tinypic.com/zn4k1l.jpg (posting a link because it's a quite big picture)

Unfortunately, it does not seem to work, while I get the volume pot on guitar to 10, I get noisy feedbacky hum, same (but different kind of feedback), while I kill the signal with a kill switch. Did I mess up the layout or the wiring? Checked for the bridges at the stripboard with continuity tester but none are found. Everything is wired similarly to this - http://www.beavisaudio.com/techpages/StompboxWiring/StompboxWiring96.gif, just no LED or 3PDT so the sleeve from the input goes to ground on the board, tip goes to input, tip of the output jack is connected to the middle lug of volume  and sleeve goes to the ground on the board.

Any help would be appreciated!

Thanks, Tom

[smallbearelec]

Hi--

With all good wishes, I think you bit off a little more than you could chew for a first build; the BMP has too many stages and too many parts. You may have made a mistake in translating the schem to a board layout, or there may be an error in the wiring. Multiple mistakes in this process are almost guaranteed given the number of land mines. You could:

--Fight your way through the debug, If you can get enough help, OR (what I would do):

--Put this aside and build something on per with One active device from a vetted layout. Many people here will have suggestions for this. Good luck, and stick with it!.

Regards
SD

[tjdracz]

Thanks for reply, you might be right, but given the fact it's already on the board, I'd rather try to find where did I go wrong, rather than leaving it. Learning through mistakes. Will check the cable connections tomorrow but they seem to be alright and measuring continuity, it's where it should be and nowhere else.

Tom

[gcme93]

For your first project, there's a bit of a mine field that you learn how to cross.

I suggest you try and upload a clear picture of both sides of the board? The guys around here (and myself) will do our best to check any transistors in the wrong way around, off value components and other mistakes which are very easy to make.

As a starting point, I often mess up with the track cuts - either forgetting to do one or putting it in the wrong place :s Check over those first?

George

[tjdracz]

Will try and upload pictures tomorrow but so far, I can only tell you it's exactly like in the layout I linked in my first post. Checked four times, tracks cuts are also were they should be, at least where they should be on my layout. I've compared it to the other veroboard layout of big muff and while mine is not as clean and small, it seems to be quite similar if not the same in what connects with what, what goes to the +9V, what goes to the ground etc

Many thanks for the help. Pedal building is something I've been meaning to do for a long time and it's really great to have a place like this forum to get much needed support and information!

[tjdracz]

Actually, looking at my layout, I can see that the ground from the input is going to the wrong place, it should be on the other side of the board I guess. Sustain pot connects to the resistor which connects to all the other ground and in my layout, sustain ground and ground froum input are on the same side of the resistor. That's not right, right?

Also, while testing continuity, I've noticed that in the two suspicious points, there is no continuity beep but the meter display quite high value, around 900, does that mean it's acutally a bridged connection?

[tjdracz]

Well, guess nobody really looked at the schematic and the layout. I've followed it again and found that the blue cable going to the first transistor has been mistakenly put in one line with the transistor's collector, not the base. After moving the cable into the correct position now I get followning behaviour:

Tone      Sustain       Effect
Max       Max             High wistling noise
Min        Max             Low humming noise
Min        Min              High wistling noise
Max       Max             Low humming noise

Of course the high and low ones don't sound the same with different pot dials. However, all the noise, high or low, depending on the position of the pot disappears when I turn down the volume on my guitar slightly, yet, it comes back at the very end of the pot counter-clockwise turn.

With sustain at max and tone dialed down slightly, I can hear the distorted signal coming through, being quite heavy on the lower end also the high note I played sustained pretty much indefinitely.

Any thoughts?

[Mike Burgundy]

Things don't always get solved within a day, so don't worry. Wanting to go through with this, even when it's your first project, is commendable. Just be prepared for frustration and be very, very patient and dilligent. Since you are a self-proclaimed novice, debugging this thing through the internet might prove difficult, but kudos for wanting to give it a go and refusing to give up (although I am aware that Steve wasn't talking about giving up at all, just a little side-step to get some experience and then return to it). remember, this takes time and effort, comparing a vero layout to a schem isn't done in 10s (at least not by me) ;P
The best thing to do is start from the top - look up the debugging sticky, and follow it. Include detailed pictures, and everything else stated.
That said: what is the pinout of your transistors? I suspect it's EBC (legs down, looking at the flat face) which does not correlate to your layout on Q1. Haven't looked any further. Oh, and there are lots of tracecuts missing (C12,13,7,3,4, might be more)

The trick to checking a layout is simply tracing a new schematic from it. Don't cheat and have the original schem in sight: do it from scratch.

Edit: I'm not too happy with the input layout either. There's obviously one or several problems which prevent this thing from working anyway, but in a high gain pedal like a Muff I can't help but feel you set yourself up for trouble if you make the input path to the first transistor that long and run basically through the entire rest of the circuit. All lines would preferably be nice and short, keeping input *away* from outputs.  I would like to advise you to build this after a verified vero - there are lots around. I know, it's annoying and you want this thing to work, but it will probably save you a lot of headaches and time. Oh, and Steve is Steve Daniels aka Smallbearelec ;P

[tjdracz]

Thanks for the outputs tip, will keep it in mind next time And it's fixed now! Still didn't work after resolving the problem with jumper wire to transistor but I've noticed that the voltage is.only around 5V but after bypassing the DC Jack and wiring the battery straight to the board it works! Still there's some buzz hum and that's something to fix. Thanks for support!  

[LucifersTrip]

but given the fact it's already on the board, I'd rather try to find where did I go wrong
Tom

then the first step is following the debug thread:
http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

the most important part is posting your voltages and comparing to working ones.

In the meantime, one suggestion. Tho the BMP has a a good amount of parts and 4 stages, those stages are linear with nothing fancy...and 2 stages are nearly identical.

You can check the sound at the output after each stage to see what you have. For instance, first check the sound after the .1 before the sustain pot....then move to right (on the schematic) one stage at a time.

btw, did you breadboard this first to see if it worked?

[tjdracz]

but given the fact it's already on the board, I'd rather try to find where did I go wrong
Tom

then the first step is following the debug thread:
http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

the most important part is posting your voltages and comparing to working ones.

In the meantime, one suggestion. Tho the BMP has a a good amount of parts and 4 stages, those stages are linear with nothing fancy...and 2 stages are nearly identical.

You can check the sound at the output after each stage to see what you have. For instance, first check the sound after the .1 before the sustain pot....then move to right (on the schematic) one stage at a time.

btw, did you breadboard this first to see if it worked?

All good advice, good shout about breadboarding it first in the future but as I posted above, got it working and it's a pretty great sounding pedal. Guess the problem was with battery connection or jack wiring because both cables fell of the clip and after wiring it again with another one, it all works as it should, both with battery and with power supply through DC jack. However, while battery sound gets some background hum, nothing special, the pedal with power supply plugged in gets audible rattling hum, mostly audible when there are no strings played or if I killswitch the signal. Guess the cheap power supply from far east is not the best one here but is there anything to remedy that?

[DekkerFuzz]

yea check out "the humminator" from beavis audio, also he' got some great starter projects, well done on the big muff

[tjdracz]

Thanks! Humminator looks like an interesting and useful little project. Don't have any spare jacks DC plugs to make it now though. However, if I understand correctly, I cold just wire two caps (100uF electrolytic, 47nF ceramic) like in humminator between power supply and the ground on the board and it would achieve the same effect,  is that right? http://www.generalguitargadgets.com/pdf/ggg_bmp_grus_sc.pdf - I assume that's the role of additional C14 cap in this GGG schematic so only 47nF one would have to be addes.
Also, out of sheer curiosity, what's the role of additional C15 cap on GGG diagram, non-polarised 100pF going from input to the ground and additional R26 1M5 resistor between the input and the ground? R26 was in my diagram but with 1M value but apparently it's not always there in the stock BMP