"Assassin of Silence" Cascaded EH LPB based fuzz

[frequencycentral]

Yeah yeah another fuzz circuit. Nothing original to see here, move along! This circuit originated over on circuitworkshop.com in a discussion of the best place for a 'fuzz' control on a fuzz. It led me to breadboard two cascaded EH LPB's, with a switchable 10uF bypass cap on the second stage. With the switch disengaged it sounds nicely gritty, with the switch engaged it gets massively crunchy. I tried a bypass cap on the first stage too, but I'm getting undesirable oscillator type whistling at a constant pitch - anyone have any idea why? I'm using two 2n5088's for the transistors. With the 'Sludge Switch' engaged, and with maximum gain and high volume I'm getting the type of squealing people tend to report with BSIAB's - probably because this in on breadboard. I'm sure a proper build with screened wiring would fix this. I'm sure this must have already been done before. It does sound really good though! Will one of you guys breadboard this up and let me know what you think, maybe suggest some improvements?

[svstee]

What about adding clipping diodes in the style of the Electra Distortion? You could make them switchable. Do you think clipping diodes would add too much gain?

[sean k]

The cap on the emitter on the first stage might be creating far too much amplification so a small pf cap from collector to base might quell that. I suppose doing what one does with multi stage tube amps might be advised as well. Amp it as much as possible and tone shape then use voltage dividers to knock it back down again before it hits the next stage. Maybe  resistor after the first stage output cap and use a DPDT switch so when you switch in the cap on the first stage emitter you also put a resistor before or across the first volume pot.

[Renegadrian]

I'm sure this must have already been done before.

I remember THIS ONE and THIS ONE TOO...
Never tried it anyway...Guess my next try on a LPB will be trying 10n caps (to go treblier) cause I always found it to be too dark to my ears...

[frequencycentral]

What about adding clipping diodes in the style of the Electra Distortion? You could make them switchable. Do you think clipping diodes would add too much gain?

Hell, it's already a case of 'oh no not another fuzz' without complicating matters with 'oh no not another diode clipper' !!

The cap on the emitter on the first stage might be creating far too much amplification so a small pf cap from collector to base might quell that.

Tried that with no success. Maybe I should try it with 430k/43k base biasing instead of 1M/100k.

I suppose doing what one does with multi stage tube amps might be advised as well. Amp it as much as possible and tone shape then use voltage dividers to knock it back down again before it hits the next stage. Maybe  resistor after the first stage output cap and use a DPDT switch so when you switch in the cap on the first stage emitter you also put a resistor before or across the first volume pot.

I'll give that a go - thanks!

I'm sure this must have already been done before.

I remember THIS ONE and THIS ONE TOO...
Never tried it anyway...Guess my next try on a LPB will be trying 10n caps (to go treblier) cause I always found it to be too dark to my ears...

That second link in your post is foxfire, I just searched for his thread - thanks for the memory jogger Adriano!

http://www.diystompboxes.com/smfforum/index.php?topic=75310.0 Rylan seems to have had success withe a first stage bypass cap, though didn't use one on the second stage.

[sean k]

Another way is to put a resistor above or below, in series with, the emitter capacitor to ground to control the amount of AC "positive feedback?".

[Gus]

LPB is a textbook circuit and has limitations

Few things to try
Calculate the input resistance of the 2nd stage.  Then read R.G.'s and or other write-ups on how to taper pots.  You can use a lin taper pot for the volume(gain) and adjust the taper by the loading of the 2nd stage.

Bootstrap the input or use the beginner boost as the first stage

[frequencycentral]

Here's IvIark's turret layout, nice:



Here's my PCB layout and PnP:





Here's a super simple vero:



No perf layout?? I've recently moved away from creating perf layouts on DIYLC. I've started creating PCB layouts instead, that way you can colour code the +ve, ground and vref traces etc. The traces can be thicker too, compared to perf layouts. I'm still building onto perf from the PCB layouts I create, I'm just finding the PCB layouts easier to create and easier to translate onto perf.

[Renegadrian]

Rick, my friend, let me tell you that you're not the best when it comes to lay on vero...I shrinked your layout, here it is...
I guess it's ok, still I haven't build it, so class it as unverified for now.

[soggybag]

What about adding clipping diodes in the style of the Electra Distortion? You could make them switchable. Do you think clipping diodes would add too much gain?

Good idea. I think it might eventually evolve into a BMP. I wonder if EH tried this on the way to the BMP?

[frequencycentral]

Rick, my friend, let me tell you that you're not the best when it comes to lay on vero...

The guy who requested the vero layout is new to electronics, so I figured keep it 'wide open' and simple to build, yet still easy to fit in a 1590B. 

I might build this over the weekend. I need another dirt box like I need a hole in the head, but I haven't build a pedal for a couple of months. And the name suggests a cool graphic.............

[philbinator1]

Rick, my friend, let me tell you that you're not the best when it comes to lay on vero...

The guy who requested the vero layout is new to electronics, so I figured keep it 'wide open' and simple to build, yet still easy to fit in a 1590B.  

I might build this over the weekend. I need another dirt box like I need a hole in the head, but I haven't build a pedal for a couple of months. And the name suggests a cool graphic.............

I've almost finished your vero "Assassin.." layout Rick, and its way, WAAAAY easier for me to do than the perf version i tried.  Looks great, if I get
it to work i'll post photos...looks much neater than perf too.  Only thing I'm having trouble with is where wires go from the pots, and figuring out which pot
is which (gain/vol)...?

[EDIT].. i'm installing a 3pdt for true bypass and led using the Tonepad Offboard wiring diagram 5.   i have all of the connections made except the "output"
which is the top right lug on the switch...i can't find which one it is on the vero layout.  little help?   

[arma61]

output is taken from the middle lug (2) of the volume pot, and lug 1 (or 3! I've never understand which is which) goes to ground, look at the PCB picture

Ciao
Armando

[frequencycentral]

^^^

Lug 1 goes to ground!

By the way, I breadboarded this again before I perfed it. I changed the value of R3 on the perf layout to 1K (that's R4 on the vero layout).

Here's my perf build, hoping to get it boxed up over the weekend. I thought I'd try it with some metal can BC107A.

[philbinator1]

Dude that build is amazing!  that must be the tiniest fuzz i've ever seen (snigger).  but anyway i just got mine completely
done and still no luck...perfect bypass signal, as soon as i turn it on nothing, nada, zip as you guys say.  and as a bonus,
while i had a 7 colour changing led in there it made a funny droning noise while the led changed colour (but not between
colours).  the droning noise did sound fuzzy though, partial triumph!  anyways i de-soldered it, no noise at all.

I think i've reached the Zen state of DIY effects acceptance, not even phased by it (well i wouldn't be would i, it's a fuzz...
ba-dum tish).  so yeah.  back to reading for a while methinks!   

btw nice trick with the scrolling pix...how you do dat?

[frequencycentral]

What transistors are you using? Do you have the pinout correct for the transistors? Is your off board wiing correct?

Re the scrolling pics, see the scrolling 'M' button, and the 'inset image' button when you post a reply? Just add some images without any linebreaks, select then and hit the 'M' button. If you quote my post you'll see the coding.

Cool isn't it?  

[philbinator1]

What transistors are you using? Do you have the pinout correct for the transistors? Is your off board wiing correct?

Re the scrolling pics, see the scrolling 'M' button, and the 'inset image' button when you post a reply? Just add some images without any linebreaks, select then and hit the 'M' button. If you quote my post you'll see the coding.

Cool isn't it?  

yeah i triple checked the trannies...the layout is *exactly* per the vero layout.  I'm pretty sure it's the off-board...it looks a complete mess,
i didn't put it in a box, just did it all naked.  oh and i'm using 2N5088's, i even measured the hFE for both, and both are exactly 485 each.

Very cool!   

[frequencycentral]

Are the 5 track cuts on the vero all in the correct places? And are they all 100% cut? Got any solder bridges anywhere?

[philbinator1]

Are the 5 track cuts on the vero all in the correct places? And are they all 100% cut? Got any solder bridges anywhere?

Yip they're all cut sweet as, I counted holes (eg 10 holes from the leftmost hole then 4 up from that 10th hold, cut track
with dremel diamond cutter attachment) for every single component, so they are all matching your vero lay exactly.  I also
did continuity tests for each track cut.  

And after each solder i went over with a magnifying glass to check for bridges, even went so far as to scrape in between
them with a pointy soldering tool anyway, just to be sure.  Hmm...i'll just go get the camera and photo it so you can see...







i'm happy with the vero but the off-board is messy, ah well.  i just got a drill press so i can do the enclosure tonight.  what
do you reckon; jack holes at the top, on the sides?  anyway hopefully you'll see a horribly obvious mistake here somewhere  

[frequencycentral]

^^^

Your stripboard looks sweet, so I'm guessing the issue must be the offboard wiring. Here'e a little offboard help from the superb Beavis: http://www.beavisaudio.com/techpages/StompboxWiring/