D*A*M - Meathead [traced]

[beedotman]

Those 4 boards were made from an earlier version of my layout. Can't remember why I changed it, probably because I thought the new way looked cooler! And yes, every original Meathead I've seen has been made on vero.

Not all... there where some original DAM pedals made with pcb, including Meatheads.

[beedotman]

Those 4 boards were made from an earlier version of my layout. Can't remember why I changed it, probably because I thought the new way looked cooler! And yes, every original Meathead I've seen has been made on vero.

Not all... there where some original DAM pedals made with pcb, including Meatheads.

Here is pic of PCB Meathead Deluxe.

[beedotman]

fresh layouts with full wiring

[beedotman]

and one knobber

[beedotman]

And another vero layout

[johnnyg]

Those 4 boards were made from an earlier version of my layout. Can't remember why I changed it, probably because I thought the new way looked cooler! And yes, every original Meathead I've seen has been made on vero.

Not all... there where some original DAM pedals made with pcb, including Meatheads.

Here is pic of PCB Meathead Deluxe.

BYOC Fuzz Face pcb?

[phibes]

Those 4 boards were made from an earlier version of my layout. Can't remember why I changed it, probably because I thought the new way looked cooler! And yes, every original Meathead I've seen has been made on vero.

Not all... there where some original DAM pedals made with pcb, including Meatheads.

Here is pic of PCB Meathead Deluxe.

BYOC Fuzz Face pcb?

Yup. He used BYOC muff boards for some Ram Heads too.

[johnnyg]

They're decent pcbs & would prob speed up production I guess

I noticed people have been adding switches to change between different values of input capacitor? Here's how I'd do that (apologies if it's been mentioned - I've not read the entire thread). I expect I may add this option if I build one of these again (I gave the two or three I built a while back away to mates):

input.jpg (10.29 KiB) Viewed 3743 times

With two 47nf capacitors in series you get 23.5nf (2209/94); with the spst switch on and bypassing one of them you get 47nf. (Which are the two input values used on regular versions of this).

You won't get any obnoxious pops or thumps when you switch from one value to the other using this method.

[astrobass]

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Can anyone confirm if this layout/PCB is correct?

I just tried and I'm getting no sound through the circuit when it's on.

Tested continuity on my traces, they're all good. No bad solder points. Nothing is shorting, and I've tried this with BC184 and 2N3906s, and MPSA18s.

Here's what my layout looks like. The 120K is a 100K plus two 10K in series. The 18K is a 10K in series with a 10K parallelled with a 33K (result is 17.6K). Otherwise I'm using the exact values for everything except the input cap, which is 22n not 10n.

Power is coming from a Dunlop DC Brick, it works fine, and the pedal does get power. Not sure what to test next. I have DMM for testing. Suggestions?

Pics show what I've got.

[astrobass]

I posted that in the wrong place. Feel free to delete, will repost elsewhere!

[Nocentelli]

2N3906 is pnp, so definitely won't work. Also, the BC184 (L?) I used has an unusual pin-out - I only know this because I couldn't get my Meathead to work. I'd advise carefully checking the pinouts, before audio-probing it to see how far the signal gets.

[astrobass]

Okay, so I was testing this with NPN transistors in each socket and trying to solve the riddle as to why it STILL wasn't working, and I noticed that it was acting like it had no power. At which point I realized that I'd wired the power backwards. So uh, I'm an idiot, I guess, is the moral of the story.

Ugh. Just. Ugh.

[Hexjibber]

Hello,

I'm new to pedal building and just found this forum, have been keenly reading this thread as I'm looking at modding a Meathead kit a made a while ago. I'm trying various caps on input and output and just ordered a BC239C to try in place of the 2N3904 I currently have in there, found that info on a D*A*M forum somewhere. Anyone had any experience with using BC239C/BC182L combo, will it be noticeably different? I'm building to 'Dark' specs btw.

Also my main question is that in the original D*A*M boxes he uses these old school looking axial parts which seem hard to come by (on eBay at least!), I'm just using standard radial electrolytic and polyester box caps, is there any difference in sound? Am I right in thinking that the electrolytics he uses are tantalum, is there much of difference with these if so? They seem to go for outrageous prices online!

Cheers!
Graham

[astrobass]

Expensive caps rarely seem to make a difference, generally speaking. The only time I've found a difference was replacing low quality ceramic caps with 5% film caps, and that could just as easily have been due to differences in true capacitance rather than materials. To get really scientific you'd have to set up a test rig with A/B switching between measured and matched caps of different materials and honestly I wouldn't even bother. The caps you're using are very likely just fine.

Different transistors will yield different results, but the difference is primarily observed in the overtones you get. With a fuzz face style circuit like this, you get this electric sounding buzz on top of your tone that decays into the main tone after a few seconds. The intensity of that overtone, how long it takes to decay, how evenly or sputtery the decay is, how bright or dark or tight or open sounding it is, all of these attributes are directly affected by the transistors that you're using. Not just individually but also the combination and which one is Q1 or Q2.

I found that a BC108 (Q1) and a 2N4124 (Q2) work really nicely. They're both very close to the transistors D*A*M uses in Hfe, which seems to be the really critical rating to consider for this purpose.

It's a lot of fun to use sockets instead of soldering in the transistors, or a breadboard, and swap different combinations of transistors to see what you get. Generally speaking most people like two transistors that are similar but not identical, and in the 100 to 300 Hfe range. However, if you see them cheap, pick up some MPSA14s and try those. They're 10,000 Hfe. Two of those in combination gives this incredibly squished, buzzy sounding fuzz. It's very different. It's not for everyone, but I'm making a second one using those for the rare occasion it comes in handy. It'd be good for lead guitar riffs in the right type of song.

Edit: one other thing: install a switch to flip between the Dark input cap and a 0.022 uF input cap (the original), and use a 0.1 uF output cap. A toggle costs like $2, and you'll greatly improve the versatility of the pedal by adding it. I found very little difference between a 0.022 and 0.047 input cap, so anything in that range for the bright/normal mode input cap should actually be fine.

[astrobass]

I've done some playing with this over the last few days and can strongly advise the following:

1) In place of the input cap, use a SPDT On-Off-On toggle. Not On-On, you want one with a middle position. Take the input lead up to the middle lug (the "off" position), and connect a 0.022 uF cap to the middle lug, a 0.082 uF cap to one of the "On" lugs, and a 1 uF cap to the other "On" lug. Wire all three caps to the point where the input cap would normally connect to. Now you have a switch whose center position is the standard guitar mode ("bright"), one position is the standard dark mode (well, 0.104 uF, which is too close to 0.1 uF for you to hear a difference), and the third position is bass guitar mode. This adds maybe $2-$3 to your materials costs but adds a huge amount of versatility. I can't justify not doing it unless you really want to build one and you have everything else that you need on hand except for the switch.

2) Add the 1M pull down resistor that D*A*M added in later revisions.

3) The key to transistor selection for Fuzz Face based designs really seems to hinge on using two different transistors whose Hfe ratings are highly similar.
* Lower Hfe gives you more open sounding, looser fuzz, higher Hfe gives more squeezed, tighter fuzz. Lower Hfe is what everyone is used to hearing and will often prefer but really, really high Hfe does create an interesting effect and might be a really great touch to make a guitar solo really stand out.
* Transistors with significantly mismatched Hfe (ratios broader than 2:3) tend to result in an overtone that's too obviously separate from the primary tone and whose fizzle out tends to be pronounced and premature.
* Using the same type of transistor for both Q1 and Q2 makes the overtone sound too consistent and somehow less natural/organic/insert buzz word here.

[Hexjibber]

^

Thanks for both your replies guys, that's all very useful info and really furthered my understanding of what's going on, really appreciate it! I feel like I can approach the transistor side of things without as much guess work now!

I was thinking about adding a switch for the normal/dark modes although generally I prefer the tone to be on the more low-end side of things but as you mention would be useful to have the option.

I've also been trying to source some info on how I could mod my current PCB to include the Meathead Deluxe controls for a bit more versatility. This is the first time I've stepped outside the guidelines of the kit so a bit unsure what I'm doing! Is there a schematic for the Deluxe? I can only find vero layouts so not really sure how to apply them to the PCB I have? This is the kit I've used - http://pedalparts.co.uk/wp-content/uplo ... 0/Thug.pdf

Not quite got to the stage of etching my own PCBs or using vero just yet, working towards it though!

[Hexjibber]

^

Thanks for both your replies guys

Sorry! Didn't realise both replies were from the same person, duh! That's what reading forums on a mobile will do!

[astrobass]

No problem. I've never worked with vero. Not yet anyhow. I also haven't built the deluxe, but I do know that one of the three knobs is the same one that's already there, and one of the others is a replacement for the input cap. The pot is acting as a blend between two caps, I think I read them as 4.7 and 0.01 uF, but that could be wrong, I'd read the thread if I were you.

I don't recall off hand what the third knob controls. Probably just a 1K VR in series with a small resistor in place of the 1K resistor to ground on the second transistor, but that's just a guess based on how popular it is to do that (this would be the "gain" control you see in a lot of Fuzz Face based designs).

[Nocentelli]

Here's a schematic - I couldn't find one on the internet:

Meathead deluxe schem.bmp

Modding your current board is possible, you could add the attack pot by cutting the trace from Q2 emitter to C6, removing R4, and replacing C6, but the extra blend pot will be tricky as there is nowhere on the pcb to mount the extra 1uF cap. I suspect it would be much simpler to use this as an opportunity to dive into the exciting world of veroboard construction using the layout at tagboardfx: It's really quite straightforward, and IvIark and mirosol provide lots of wonderful support.

[onebuzz]

Great thread. Thought I'd post my build. Q1-2N3904, Q2-BC337. Input 22nf and a 47nf output cap. Added a 1K pot for fuzz control.