Gain Issue With Fuzz Pedal

[TheJuke]

Hey guys,

I'm new at this so I'm most likely making an obvious mistake but I am attempting to build this muffer circuit: http://www.muzique.com/schem/muff.gif

The issue is that I lose volume(compared to the bypass signal) and have next to no fuzz until I put my guitar volume knob up to 9 or 10 when the volume and fuzz both go through the roof. Has anyone experienced issues like this?

Its super simple so I'm fairly sure I haven't made a mistake connecting everything together. I have the exact values of every part except the transistor but have tried a 2N2222, BC337 and 2N3904 and I get the same result with all 3.

Thanks.

[aron]

Maybe it's something simple like the 150R resistor is something higher???

[GibsonGM]

Maybe it's something simple like the 150R resistor is something higher???

+1, try a higher value for the emitter resistor; I might even try putting a 10k pot in there as a variable resistor and try dialing around to see if your gain becomes manageable.  And double (triple) check that everything is wired correctly and that your tranny pinout is correct!   

Can you post voltage readings on the C,B, E of the transistor with the circuit powered on, no input?  Do that before changing the resistor, and try to stick with one transistor if you can.    BTW, 5088's are so commonly used, you might think of just getting some if you can!  You'll use them....

[rousejeremy]

Any pics of the board? Both sides and not blurry?

[phaeton]

The issue is that I lose volume(compared to the bypass signal) and have next to no fuzz until I put my guitar volume knob up to 9 or 10 when the volume and fuzz both go through the roof. Has anyone experienced issues like this?

A dumb question on my part, but are you sure you're using an Audio Taper pot for the volume, and not a linear or something weird?  Also, maybe it wouldn't hurt to double check the pot and make sure it's working correctly- remove it from the circuit, put an ohmmeter on it (without any power across it) and turn it slowly, ensuring that the resistance does what it's supposed to.  I once roasted a pot by connecting it wrong (ran all the current an 18V supply could push through it from rail to rail).  It's now all screwed up and has some loud spots, some dead spots and some in between spots.  Whoops...

Otherwise (as others have said) double check components, probe the transistor leads and post voltages.  I've built a copy of this pedal myself from the same schematic and it's a good performer.

[pinkjimiphoton]

sounds to me like the transistor's bias is not adjusted well...
you may want to add a trimmer to it in place of r10, and adjust until your guitar sweeps from off to full smoothly.
if you want to be able to get some gain out of it, change the 150r resistor to a 1k pot. the lower the resistance from e to ground, the more balls you'll get. try 10r or 47 r if you want a fixed resistor.
a 1k pot will let you sweep in the volume range pretty well. a reverse taper pot may work best.

just thinkin' off the top of my pointed little head.

[Gus]

Have you read this?
http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

The biasing used in that circuit should work well with many transistors without changing any resistor values.

[pinkjimiphoton]

hey bro,
i can see it working for a lot of transistors, i mean they'll work/function/fuzz, but not all will sound/feel/interact great.
i prefer sockets, and don't commit to anything until i really dig it.

but sometimes, i think it sounds better to tune the circuit to the transistor if you don't have a lot of stock on hand say.

fuzzes definitely react to your guitar differentely depending on the biasing of the transistor imo. you can change the crossover point between clean and fuzz from the guitar if it's dialed in right.

to me, if the guitar is less than unity until it's cranked, either the biasing needs to be adjusted or there's a cold solder joint somewhere.

[Gus]

Jimi

I am thinking there is a wiring issue with TheJuke build of this circuit.   

[pinkjimiphoton]

gotcha, gus.

hey the juke, can you hit the debugging page and give us some more info?

[smallbearelec]

Hi--

I will keep posting versions of this reply here until I finish the "FAQ For Beginners" that I am working on for my site:

First I'll suggest how to get from where you are to something that works. Then I'll talk a little about how not to get stuck on future builds.

That schem is known to work; your bug(s) is/are almost surely errors in translating schem to layout. So:

--Remove the stomp switch if you are using one; it confuses matters.
--Make clean copies of schem and layout. Pick a point on the schem and use the continuity scale of your meter to make sure that every point that you think should be connected Really Is. Mark off connections with a highlighter as you test. You will find problems.
--When you think you have found all the bugs, wire the input and output jacks directly and connect a battery. If the effect works, then add the stomper.

In the future:
--Work from vetted layouts until you are sure of your skills.
--For doing layouts, learn to use a program like DIY Layout Creator (free) that is optimized for editing boards.

Have patience, and don't give up. IMO, you bit off a little too much of the learning curve at once, but you'll feel better once you "digest" your first build.

[TheJuke]

I had a go with the probe and got this:

c: 7V
b: 0.7V
e: 40mV

After that I changed the 150 resistor and it made no difference. Also, twisting the pot makes no noticeable difference to output.

Photos:
https://www.dropbox.com/s/x8rbnntff9zps4u/2013-07-13%2012.48.02.jpg
https://www.dropbox.com/s/x8rbnntff9zps4u/2013-07-13%2012.48.02.jpg

The orange lead is input, yellow goes to output via the pot. (Ignore the diodes going to ground at the output, I was just seeing if it would clip more)

Thanks for the help guys, I really appreciate it.

[TheJuke]

Meant to link this...

https://www.dropbox.com/s/8agn65jpnie9lxs/2013-07-13%2012.47.35.jpg

[LucifersTrip]

a quick look at the schematic and your bread: a couple quick questions....what are the 4 diodes (2 extra for clipping?), are the yellow caps multilayer monolithic ceramic, and where are the 3 (yellow?) leads from the pot going ? 

[Keppy]

Check the C-B bias resistor again. It should be 470k (yellow, purple, black, orange). It's hard to tell in the photos, but I don't see any orange on that one. It might just be the lighting, but it's worth a check.

EDIT: Also, what's your battery/PS voltage?

[TheJuke]

They are 1N914s which is what is specified on the schematic. The caps are tantalum.

My PS is rated at 9V but seems to be outputting 12V. That might be my issue there, it works fine with my boss pedals but they might have some sort of regulation built in?

[LucifersTrip]

They are 1N914s which is what is specified on the schematic.

there are 2 diodes in the schematic...it looks like you have 2 more going to ground. where exactly are the 3 leads going from the pot? they are partially off screen, so just wanted to be sure.

[smallbearelec]

The photo you added just made me add another "Don't" to my planned beginner FAQ:

"When you learn to breadboard, don't create a "rat's nest." Take the time and trouble to set it up carefully, square off corners and establish clean lines. This makes your work much easier to document later, and makes it easier for you (or other people) to find mistakes." For some examples, take a look at any of the Breadboarding... articles in my How-Tos section.

[rousejeremy]

Re-reading your original post, lost of pedals clean up that quick with the volume pot. Germanium fuzzes can almost get completely clean at 8 on the guitar volume.

[mistahead]

Hey guys,

I'm new at this so I'm most likely making an obvious mistake but I am attempting to build this muffer circuit: http://www.muzique.com/schem/muff.gif

The issue is that I lose volume(compared to the bypass signal) and have next to no fuzz until I put my guitar volume knob up to 9 or 10 when the volume and fuzz both go through the roof. Has anyone experienced issues like this?

Its super simple so I'm fairly sure I haven't made a mistake connecting everything together. I have the exact values of every part except the transistor but have tried a 2N2222, BC337 and 2N3904 and I get the same result with all 3.

Thanks.

I understand this is expected behaviour more or less - as you roll back volume into the FF it cleans up and at a certain point (with some pickups) will hit a "deadish" zone...

Guru's please confirm/shatter my belief!