I've built a butt load of pedals by now and I never in my life cared a whole lot for ANY fuzz pedal. In my process of building the openhaus I got a few extra transostors from steve at smallbear that came with specific resistors. I figured what the hell. It there has to be some reason SO many ppl love these. I put it together and I was surprised how much the simple design grew on me. In my experience pedals like these sound very gated and muddy. I HATE gated sounds. This was almost like a glassy overdrive that wasn't quite as smooth. I actually perfer the sound WITH a buffer in front. Don't nail me to hard...
so I started digging threw my transistor drawer and found some ac188 2n1309, ac128 and started learning the process of figuring gain leakage and all this wonderful stuff.
my question is to those who have build SEVERAL FF. When biasing I used the online calculator and I always come up short with the voltages. 2-3v for Q2 collector. Sounds muddy and gated. Grrrrrr. When I start tweaking resistors to get 4.5 it just doesn't sound the same as my finished build. I've been obsessing over this for 2 days and in need of some explaining.
Before anyone goes through the trouble of posting links (as much as I appreciate it) I've read them all. And I can't get a clear cut answer. Even when I use a trimpot it seems to compromise the circuit. The gains are 111 and 86 roughly both with 100 leakage. Am I doing somthing wrong?
This is hardly limited to Fuzz Faces: it's the reality of working with the wild inconsistencies of Germanium.
You will not be able to exactly duplicate the sound of another Fuzz Face being without extraordinary lucky. You would need identical characteristics of two different sets of transistors. Unlikely. Do you know the exact characteristics of the set you used previously? How close are they to the ones you're using now? What were the types of transistors? There can be a big difference between the breakup characteristics of TI vs. AC vs. RCA vs. OC etc etc.
Some things that might help:
Those other resistors from Smallbear are part of an overall biasing network. Are you tweeking those to produce the same voltages on ALL pins of both transistors, or simply trying to hit 4.5v on the collector of Q2? There's a big difference, and there's a set of target voltages for each pin from units known to sound good. Luciferstrip has posted them many times on DIYstompboxes. Some transistors simply won't hit these target numbers. You should at the very least measure the voltages on every transistor pin in your finished model and use those as your targets. That's apparently the sound you like: so you need that exact data as a reference.
Next, use your ears in addition to your multimeter. The simple fact is that some fuzz faces will sound better with 5.5 volts on Q2c. You'll certainly avoid gating in those situations.
I always build FF with bias trim pots or normal pots because I like having the option of being able to adjust it easily so I can get more gated or bigger sounds from it. I'd recommend doing that in the future :)
in my original build I used 2n1306 or 9.. Not positive. They were an NPN set and I didn't take the time to test them honestly bc I was pretty sure I'd hate it lol. And no I'm not using the same resistors but I'm trying to find that magical method to come up with that "biasing network" you speak of. With out it, it's garbage as far as I'm concerned. I figured that I wasn't hitting those pin voltages bc 4.5 collector for q2 sounded like shit. It's like a murder mystery figuring this out for me at this point. If you change one resister you gott change them all it seems like. I havnt messed with the 100K feedback. I'm assuming that one is pretty universal? So do you know what I'm trying to do besides hit the collector voltage? What I might do is break open the first one and get the readings and start trying to match and see if it sounds similar. But this is also a difference between 2n and AC.
Quote from: 9Lives on August 17, 2012, 07:31:54 PM
in my original build I used 2n1306 or 9.. Not positive. They were an NPN set and I didn't take the time to test them honestly bc I was pretty sure I'd hate it lol. And no I'm not using the same resistors but I'm trying to find that magical method to come up with that "biasing network" you speak of. With out it, it's garbage as far as I'm concerned. I figured that I wasn't hitting those pin voltages bc 4.5 collector for q2 sounded like shit. It's like a murder mystery figuring this out for me at this point. If you change one resister you gott change them all it seems like. I havnt messed with the 100K feedback. I'm assuming that one is pretty universal? So do you know what I'm trying to do besides hit the collector voltage? What I might do is break open the first one and get the readings and start trying to match and see if it sounds similar. But this is also a difference between 2n and AC.
Ah.
The feedback resistor should not be altered.
I should tell you that PNP germaniums tend to sound different from NPNs. They will have brighter clean tones, sometimes a little harsher and more scooped, but they tend to sound softer when distorting. I don't know why this is, and I don't have a spectroscope to prove it, but I was very happy to learn I was not the only person that thinks so. :) I also happen to think that the RCA 2N13xx NPNs sound
spectacular despite some consistancy issues, and Smallbear has also said the same thing ... but that no one wants them because they're hung up on getting continental transistors.
Here are Luciferstrip's voltage suggestions:
e b c
Q1 - 0, .1, .6
Q2 - .45, .6, 4.5
Edit: link http://www.diystompboxes.com/smfforum/index.php?topic=98002.0
The dude knows fuzz, so I'd say these are every bit as important as what RG Keen says ... if you can get to these and you don't like it, it's okay. You might just not be a fuzz face guy. There's no shame in that! I'm not a Tonebender or Muff guy, but I like Fuzz Faces, you know?
One thing I'd definitely do if you're aiming for "perfection" is solder up some pots to use as variable resistors -- full sized, accurate ones -- for those four important resistors. (This of course is if you think it's worth the trouble to get a perfect sounding unit.)
I will note one other thing. It's about the gating, because I'm not sure from your description if what you're hearing is always the transistor's natural transition from saturated to clean or actual gating where the sound goes from VERYLOUDDISTORTED to practicallyoff. I know you use active pickups -- and you prefer a buffer in front. Part of what's going on here is that the fuzz sound is always going to gate on some level between input volume thresholds, especially in the bass frequencies. It might be more noticeable with your setup than with low-output single coils, which are known to sound more natural with a Fuzz Face. It's just the way the distortion in it works. Hit it hard and it breaks up. Back off and it's clean.
What happens if you hit the target voltages and you're still not happy? Well, it's time to start looking at other sections of the fuzz. You can increase the mids and the overall output by messing with the 470Ohm resistor. (You can also just add the '69 mids pot.) You can change the bass going to and from the circuit by changing the input cap. You can add the pregain control (I usually have to change the pregain and back off the fuzz knob some to get the sound I want even when I want full-on fuzz). You can reduce the voltage to the entire circuit and rebias Q2c to 1/2 the total supply voltage -- this will give you a darker sound that will saturate more easily, but may occasionally result in some gating or "transistor sound." You could charge pump the thing. You could try a hybrid. You could build a Cosmo instead. ;D
You can also get a more saturated fuzz face (and less gating of any sort) by going the silicon route. Play with Brian's "smoothing" cap in the Hipster, find a really low gain silicon for Q1 (PM me if you want the one I used in my Hipster demo ... I'll donate it to the cause, or you can be really adventurous and use a FET :P) and you can get it to sound every bit as good as a germanium.
I know, I know, this seems like a lot of work for a circuit that you aren't in love with. It's like a puzzle, though, right? And it's why people who are really into fuzz don't want to trust buying a FF from DIY guys, because it's actually work to turn it into a great sounding unit.
that's why this circuit is so fun to me even tho I'm not big on fuzz. It's so touchy. I perfer the sound of a good overdrivin amp. Like the klon deal. I don't use the active pups that much. I enjoy using pedals more. The npn ff I made sounds more over drivin. I'd say with the rotation of the fuzz pot I have 75% cleaner tones and dimed out I get the fuzz nastiness. I'm not fond of that. The npn is so smooth and perfect. I'm wondering if I just got freakin lucky on this one.
Now. Back to the PNP. I have a 2n1309 for Q2 gain 111 leakage 100 q1 gain 92 (ithink) leakage 101. I actually managed to hit every pin almost perfect. Q1 .7 .09 0 Q2 4.55 .57 .44 that's real close. I still notice a big difference. NPN is so lush sustain dimed out and clean glassy treb on lower settings. This is with the buffer. W/o it, it just sounds a damn mess to me. Both of em lol. Opiniomn are like assholes tho.. The PNP is more fuzzy at all settings. I don't get that cleaner sound out of it. Like it's some what breathing. Hard to describe. That and my son won't shut up and I can't think straight.
does the value of the resisters matter at all as long as you get the voltages? I had to got down to 15k for Q1 collector. Do I have to be closer to 33? Could the breadboard and the transistor itself cause these difference?
Quote from: 9Lives on August 17, 2012, 11:50:17 PM
that's why this circuit is so fun to me even tho I'm not big on fuzz. It's so touchy. I perfer the sound of a good overdrivin amp. Like the klon deal. I don't use the active pups that much. I enjoy using pedals more. The npn ff I made sounds more over drivin. I'd say with the rotation of the fuzz pot I have 75% cleaner tones and dimed out I get the fuzz nastiness. I'm not fond of that. The npn is so smooth and perfect. I'm wondering if I just got freakin lucky on this one.
Now. Back to the PNP. I have a 2n1309 for Q2 gain 111 leakage 100 q1 gain 92 (ithink) leakage 101. I actually managed to hit every pin almost perfect. Q1 .7 .09 0 Q2 4.55 .57 .44 that's real close. I still notice a big difference. NPN is so lush sustain dimed out and clean glassy treb on lower settings. This is with the buffer. W/o it, it just sounds a damn mess to me. Both of em lol. Opiniomn are like assholes tho.. The PNP is more fuzzy at all settings. I don't get that cleaner sound out of it. Like it's some what breathing. Hard to describe. That and my son won't shut up and I can't think straight.
does the value of the resisters matter at all as long as you get the voltages? I had to got down to 15k for Q1 collector. Do I have to be closer to 33? Could the breadboard and the transistor itself cause these difference?
The value of the resistors doesn't matter, though there is a small possibility of very large deviations affecting the serial resistance of the whole pedal, which can change tonal response at the output and occasionally necessitate a different output cap. (Find CJ's recent post on a useful tone calculator ... you could maybe measure the serial resistance of the whole circuit and match the PNP's to the NPN's at the output with a resistor in series with the volume pot.) If you were WAY off, I would say it was indicative of a transistor being inappropriate for the circuit. You aren't that far off. It's not like you had to use a 330K or something.
As far as 75% of the fuzz pot being cleaner tones, use a reverse taper. It's a bias control and you can test where the "fuzz" starts happening by sticking fixed resistors of varying values in there. You'll find it's usually somewhere south of 500Ohms (and really kicks in around 100Ohms), so a 1KC is a better taper in
any circuit like this (e.g., the SHO's 5kC pot), since you'll get the last little bit of resistance for a lot of the pot's travel. You can splurge on the final product and get a 500OhmC, or retaper a 1K. Like I said before, I (and many other people) back off the fuzz control a little.
I can say this about the buffer: The fuzz face I use on my board always falls after a compressor (at unity volume) and I set it up to sound good that way. The Silicon Fuzz Face I actually bothered boxed up (on the Hipster board) is voiced to sound good after another pedal through a bigger smoothing cap and really low gain Q1. So I don't subscribe to the "can't have a buffer" rule. Some just sound better that way to some peoples' ears. That's why MXR puts it on a buffer on it. Heck, Skreddy gets tons of work building Fuzz Faces with good input sections for a reason. Some "rules" are just dumb if the don't get you a pedal that sounds like what you want. If yours sounds better with a buffer, stick a decent buffer in front of it when you get around to soldering.
That said, when this is all done, you might want to just build a Screwdriver if you want this family of sounds in your stable. It's got Fuzz Face character on command but works much better as an overdrive. Everyone should have a real honest-to-god Fuzz Face built and boxed, but that doesn't mean you have to like it and use it. :)
I've had good results recently using this calculator recently to get the correct resistors for a fuzz face. Much better than with trimmers.
I've built 4 or 5 with varying gains, and they all sound great, not gating, decaying nicely to clean. I used RG's method to calculate the real gains of the germanium transistors, never tried it with silicon.
http://www.diystompboxes.com/analogalchemy/emh/emh.html
ok guys, I f*#%d around with this thing until 4am determined to re create the sound of the first one. I just can't accept a pedal on my board on luck. I have to know how it works (is that weird?) what I found is that on my GE NPN version (all american npn) I had the bias WAY up on the trimmer. 7v. I backed off it some just bc I felt like I should.. I put it at 6.5 and left it bc that's where I like it. I also figured out the resistor network and got those pin voltages damn near perfect. That is w the 15K resistor. This is probably due to my transistors being on the higher leakage side. 300uA I think may be giving them to much credit. Never the less I found that the normal bias of a fuzz face just isn't my fav sound although I found this little adventure very fun and will continue experimenting and searching for better transistors. I thought the ac188 was the mackdaddy of the transistor world? Mine are fairly high leakage w gain from about 80-110.. Pretty typical? Is it ok to set the bias this high or am I damaging them? I think that's all ineed to make this a "case closed". Thanks your your help everyone.
Quote from: 9Lives on August 18, 2012, 03:14:02 PM
ok guys, I f*#%d around with this thing until 4am determined to re create the sound of the first one. I just can't accept a pedal on my board on luck. I have to know how it works (is that weird?) what I found is that on my GE NPN version (all american npn) I had the bias WAY up on the trimmer. 7v. I backed off it some just bc I felt like I should.. I put it at 6.5 and left it bc that's where I like it. I also figured out the resistor network and got those pin voltages damn near perfect. That is w the 15K resistor. This is probably due to my transistors being on the higher leakage side. 300uA I think may be giving them to much credit. Never the less I found that the normal bias of a fuzz face just isn't my fav sound although I found this little adventure very fun and will continue experimenting and searching for better transistors. I thought the ac188 was the mackdaddy of the transistor world? Mine are fairly high leakage w gain from about 80-110.. Pretty typical? Is it ok to set the bias this high or am I damaging them? I think that's all ineed to make this a "case closed". Thanks your your help everyone.
You won't damage the transistors. 7v is Rangemaster/treblebooster voltage ... so you've basically created a Rangemaster with a feedback stage. That's why it sounds like an overdrive instead of a fuzz. :)
hellz ya. So I'm going to put that bias trimmer as a pot. That will be a good mod for me. Thanks
Quote from: marauder on August 18, 2012, 08:17:57 AM
I've had good results recently using this calculator recently to get the correct resistors for a fuzz face. Much better than with trimmers.
I've built 4 or 5 with varying gains, and they all sound great, not gating, decaying nicely to clean. I used RG's method to calculate the real gains of the germanium transistors, never tried it with silicon.
http://www.diystompboxes.com/analogalchemy/emh/emh.html
A little bump on this thread.
I havent bothered much so far, for getting into the universe of Fuzz Faces, but i guess now is the time, as a friend actually asked me to build him one. So, as i type, I'm browsing around the web for do's n dont's etc... The only suitable transistors i have at hand is 2N3904, so i guess i will start my breadboard work from there.
Question: The EMH calculator in the quote ^^ refers to a "Beta" value, that could be measured with a DMM. What exactly is that Beta value and how do i measure it? Leakage?
Cheers!
Edit: I guess i found the answer myself... sometimes wikipedia is helpful: Beta=Ic/Ib, correct?
Beta is hfe, no leakage on silicons. I've never used that calculator with silicon, only germanium, so it will be interesting to know your results.
Quote from: marauder on September 01, 2012, 11:16:49 AM
Beta is hfe,
Yea, of course its hfe... sometimes the answer makes the question almost too obvious :) Thanx for clearifying.
***
Another "moron of the day" is that i just spent an hour measuring that hfe getting ... strange results ... til i found that i used 100k base resistors instead of 1M... hell well... I even made a Spice model to see wtf was happening, before i happened to put my eye on those ... color rings.
***
Anyway; with those hfe/beta measured on a few 2N3904, i build a circuit with:
hfe(Q1)=187,
hfe(Q2)=213,
... (and R4=100k, gain pot 1k), gives me
R1=15k
R2=4,7k
R3=220
... thats the calculated results. I guess u were more curious about the sound results though. Ill be back!
Some voltages after breadboarding the calculated resistor values (prev post):
Battery: 8.48
Q1:
C 1.58
B 0.65
E 0
Q2:
C 3.38
B 1.58
E 0.90
When i change to components as in the Hipster schematic (including trimpot, and go for Q2c==4.5V ), i get:
Q1:
C 1.42
B 0.63
E 0
Q2:
C 4.57
B 1.42
E 0.75
...and i am not really sure how to "translate" those numbers to the reality of good fuzz faces. In the first place, its pretty far from (actually VERY far from):
Quote
Here are Luciferstrip's voltage suggestions:
e b c
Q1 - 0, .1, .6
Q2 - .45, .6, 4.5
Edit: link http://www.diystompboxes.com/smfforum/index.php?topic=98002.0
...but those values are for GE transistors. Is it relevant to compare them to a silicon based circuit?
Also, i play with pretty high hfe values on my transistors. If i understood things right, hfe for Q1 is recommended to keep low.
If my circuit sound "good" so far? Nah, not really. But if i shall compare the two setups (as above), i prefer the first one, with 3.3V on Q2c.
Now; bedtime in sweden...
Cheers
Quote from: Vallhagen on September 02, 2012, 09:18:58 PM
When i change to components as in the Hipster schematic (including trimpot, and go for Q2c==4.5V ), i get:
Q1:
C 1.42
B 0.63
E 0
Q2:
C 4.57
B 1.42
E 0.75
Sorry if im almost flooding this thread and even quote myself... But i browsed around and found some reference voltages for SI NPN at GGG (as a comparison for the GE values earlier in this thread). Maybe its old news for you guys, but someone hopefully finds it useful. Fairly close to my measurements above.
Supply: 9V
Q1:
C 1.4V
B 0.6V
E 0.0V
Q2:
C 4.5V
B 1.4V
E 0.8V
***
I just orderred a few different transistors to play around with. Hopefully ill come up with one of those
nice boxes when im done.
Cheers
I just finished a buzzaround (by far my fav) and what I'm noticing is, that the leakage matters more than the gain. I'm not stating anything universal here but to MY ears the lower leakage transistors sound better. The fuzz face being picky-er than buzzaround (by a landslide). I've played with 20 or so transistors pluging them in and switching and matching and the best results are lower leakage. I have a few 2n1309 which I find are badass Q2's. Super low leakage >100 <25 and Q1's I've used ac188. Looks cool and sounds good to me. Gains 80-120 leakage 100 on all mine. If you keep in the gain ranges everyone post they'll be ok. Just find the low leakers and use them in the right places. Don't use them for the helluvit. And I haven't built these circuits with si but I would think the voltages would be way diff since the hfe so high. But I'm not sure
Yes, the voltage on Q1 in a silicon will almost always be above 1, mostly due to the gain of the transistors coupled with the extremely low (almost nonexistent) leakage. Leakage is a pretty big factor in fuzzes, like Grant says. (Though a lot of experts on the Buzzaround say that a leaky tranny is a little better better in Q3, same deal in a lot of 3-transistor fuzzes like the Screwdriver.)
This is part of the reason a silicon fuzz doesn't react to the guitar volume the same way. Normally, you distort the first stage when your guitar's input signal exceeds the headroom of the first stage. Since there's only half a volt, this can start happening fairly early on the dial and then reach saturation even with low-output single coils.
There are ways to build the bias network will be a little closer on Q1 with silicons. Another easy way to get it to react more like a Ge is to use a very low-gain transistor. hfe of 60-70 is good. Something around 40-60 is even better (my favorite Q1 for the Hipster was a weird metal can with an hfe of about 55). The reason to use the lower gain transistors rather than changing the bias network is that you'll get less "transistor sound."
Hey J, on my buzzaround I accidentally used a 500K pot for the sustain control. It's a lil non-responsive. Kinda seems like it's wide open all the way down to nothing.. The nothing. Is it worth changing the pot back to 100K you think?
Quote from: 9Lives on September 04, 2012, 03:51:36 AM
Hey J, on my buzzaround I accidentally used a 500K pot for the sustain control. It's a lil non-responsive. Kinda seems like it's wide open all the way down to nothing. The nothing. Is it worth changing the pot back to 100K you think?
The Sustain pot is essentially a volume control between the two-transistor input stage and the "zomg fuzz" stage. It works a lot like a pre-gain control on a fuzz face, except in that case, the signal you're reducing is coming from the guitar, which is the right call there given that so much distortion is created on the first transistor. In the Buzzaround, a lot of the distortion is created at the third stage. Reducing it will certainly help some with what you're experiencing -- it will also probably brighten up the effect considerably. Q1 and Q2 actually have a fair bit of voltage to play with (so I don't think it's something like hot pickups affecting it much), and they pass on a fairly clean and very LOUD signal to the third transistor. Slamming that first transistor, creates a lot of the distortion.
The Buzzaround also has a hard clipping diode, and this is the reason it doesn't clean up quite as linearly with the guitar volume as a Fuzz Face design. Normally turning down our guitar volume would result in less signal slamming the third stage, but with diode distortion it's notoriously hard to reduce the input volume enough to change it. On my build, even with three Russian trannies below 80hfe, I get quite a bit of fuzz anywhere past 10:00 with the 100K pot, and there aren't really any completely clean settings to be found in the pedal. You could try lifting the diode if you want more clean and more volume, but it can be a real trap to tune every fuzz in your arsenal to sound similar ... I fell into that and figured out that there was no reason to reach for fuzz numbers 2 and 3 if I kept making them sound like fuzz #1. That diode is part of what gives the Buzzaround its overall sound (more compressed but still punchy), in addition to the Balance and Timbre controls.
I used 2 ac188 for darlington setup and a hi gain 2n1309 SUPER LOW leakage for q3. Somthing above 25 less than 100. Also reduced input cap to 10n. The input cap really affects the total fuzz imo bc the low freq give it that messy sound. I was going for a Ge OD sound and I got pretty close.
Some great info here. Thanx guys. I just received a bunch of different transistors (as recommended above and on other places), and i am about to re-start my breadboard experiments as i type.
Further questions; the positive/negative ground dilemma; IF i choose to go the PNP way, but still want to feed my FF with the "common" negative ground supply, do i really need to do an internal conversion to -9VDC with a 1044 circuit (or similar)?
The tonepad version of FF; http://tonepad.com/getFile.asp?id=82 (http://tonepad.com/getFile.asp?id=82) have the option of keeping the negative ground. Is there any disadvantage in that solution? At least i am pretty happy to run across it, it looks clever.
Cheers
Bengt
Quote from: Vallhagen on September 16, 2012, 10:52:49 AMFurther questions; the positive/negative ground dilemma; IF i choose to go the PNP way, but still want to feed my FF with the "common" negative ground supply, do i really need to do an internal conversion to -9VDC with a 1044 circuit (or similar)?
If you want to daisy chain it with other negative ground pedals, yes. If you want to go battery only there's no issue. And if you will be using an isolated power supply for this one pedal, you can just swap the negative and positive wires at the DC jack. However, I really recommend going the road rage route if you're going to be using a power supply. That way you'll never forget, and if it goes to someone else THEY won't forget.
Quote from: midwayfair on September 16, 2012, 05:00:19 PM
Quote from: Vallhagen on September 16, 2012, 10:52:49 AMFurther questions; the positive/negative ground dilemma; IF i choose to go the PNP way, but still want to feed my FF with the "common" negative ground supply, do i really need to do an internal conversion to -9VDC with a 1044 circuit (or similar)?
If you want to daisy chain it with other negative ground pedals, yes. If you want to go battery only there's no issue. And if you will be using an isolated power supply for this one pedal, you can just swap the negative and positive wires at the DC jack. However, I really recommend going the road rage route if you're going to be using a power supply. That way you'll never forget, and if it goes to someone else THEY won't forget.
Thanx for replying:) And to make it clear: Yes i fully understand what you are telling me. And i have actually a few 1044s here, ordered specifically for this task, if needed :)
But...: I was more asking for a different approach. I think it should be possible to - from a DC point of view - isolate in-and outputs from the rest of the circuit. Basically keep the negative ground (enclosure etc), but let the PNP-s "think" that they have positive ground. A workaround without the need of a 1044.
Words oh words... im not sure if i make myself understandable; but did you check the Tonepad document in my previous post? It looks like they have solved it, and it looks... just fine to me.
***
...besides that, i have a wellworking sweetsounding circuit right here. I ended up with two AC128 transistors, and with some tweaking i am pretty much exactly on the recommended voltages.
***
Cheers!
Quote from: Vallhagen on September 16, 2012, 06:01:31 PM
Words oh words... im not sure if i make myself understandable; but did you check the Tonepad document in my previous post? It looks like they have solved it, and it looks... just fine to me.
... and here i am again, quoting myself :-\ ...
I mean - something like this, should work just fine. If i havent missed something obvious?:
(https://dl.dropbox.com/u/10190945/Fuzz%20Faze/ff-neggnd-pnp.png)
...ill give it a try.
Cheers
looks great to me :), how did it come out?
Quote from: 9Lives on September 17, 2012, 01:15:06 PM
looks great to me :), how did it come out?
Hey. Thanx. Yes it looks fine but...
WARNING WARNING WARNING ...
I breadboarded it. Really some easy changes from the usual FF schematic. Result: It oscillates in many settings and it sounds... a little different, in a bad way. Hard to explain how, but i should say more "broken" and thrashy sound. Maybe the word "harsh" is correct. I guess the bad sound is caused by added oscillations too.
And why this happens is beyond my knowledge. i think - as you say - that it looks just fine.
Maybe it is a cause of "happens now and then"; if you try it with slightly different components it may work? Or maybe, if i put it on a pcb and box it, it will be better? I havent done further investigations at that point. As i found "my" transistors and "my" resistor network, i like to go on with them for this FF.
so... i will box it with a 1044 for voltage conversion. This time:)
***
Cheers!
I know from my own experiments that sometimes on a breadboard the Ge transistors a prone to picking up radio freq and amplifing them if not shielded properly. I usually use the remains of a wire after I strip it. Just slip it over the leads and ground your pedal well. Also try a different transistor.. I'm sure you did that, same results?
Quote from: 9Lives on September 17, 2012, 02:45:16 PM
I know from my own experiments that sometimes on a breadboard the Ge transistors a prone to picking up radio freq and amplifing them if not shielded properly. I usually use the remains of a wire after I strip it. Just slip it over the leads and ground your pedal well. Also try a different transistor.. I'm sure you did that, same results?
Thanx for your time.
This time, i dont think it is radio freq. Rather self-oscillating. The circuit also react to the pot-setting on the guitar. when i adjust the guitar volume pot it goes wooiiiwwoooowiiiwoo. Which might be fun ... but not in this project ;D
And no, i really didnt spend much time faultfinding or investigation. I just doublechecked my couplings, and I swapped the transistors to another pair of same model, but that made no - as suspected - difference. And, when i go back to positive ground everything is just fine again.
Again, maybe it will make a difference when really proper boxed/grounded, but ... nope i didnt go all the way to find out:)
Cheers
I'm willing to bet my bottom dollar that it's a biasing issue. The gain of both transistors DOES matter. Bc one transistor is "humping" the other transistor it might be effecting your over all current/voltage. I'm not very scientificly knowledgeable with this tho . I just pick and poke around w these circuits ;D
Quote from: 9Lives on September 17, 2012, 05:21:16 PM
I'm willing to bet my bottom dollar that it's a biasing issue.
No, what he's describing is the type of oscillation that you only get by connecting the input to the output. I suspect it has something to do with the ground, pulldown resistor, and output cap all being essentially in series, but I'm having a hard time wrapping my head around the grounding to be sure. Biasing issues do not typically cause any sort of oscillation.
I am happy to read your post guys:)
In a short hopeful moment after i read your post, midwayfair, i thought it could be solved by removing the input pulldown resistor. So i went back to the breadboard to try it. Result: No luck at all ::) ... same sound.
Anyway... i will finnish this FF with the 1044... but if someone feels like going deeper into this, i will be a more than happy reader.
...cant say it enough times: This forum - you guys - are just great. So much knowhow and sharing:)
Cheers!
Quote from: Vallhagen on September 18, 2012, 06:24:49 PM
In a short hopeful moment after i read your post, midwayfair, i thought it could be solved by removing the input pulldown resistor. So i went back to the breadboard to try it. Result: No luck at all ::) ... same sound.
Oh, bugger. Oh well. Like I said, the isolated multiple grounds is not something my brain will process without some hands-on with a multimeter in tow.
Quote from: Vallhagen on September 17, 2012, 02:01:21 PM
Result: It oscillates in many settings and it sounds... a little different, in a bad way. Hard to explain how, but i should say more "broken" and thrashy sound. Maybe the word "harsh" is correct. I guess the bad sound is caused by added oscillations too.
And why this happens is beyond my knowledge. i think - as you say - that it looks just fine.
Hi, it's my first post here (I just got my first order of a couple of madbeans boards and then registered here).
About the oscillations, I'm wondering if you ended up wiring this as positive ground PNP. I'm working on my first fuzz face type circuit, and I experienced Horrible oscillations (they happened at different settings, and they also happened when I turnied the tone control on the pickup all the way down, and the whole thing sounded harsh). After reading this http://www.muzique.com/lab/fuzzface.htm (http://www.muzique.com/lab/fuzzface.htm) I added a 220uF power filter cap from V+ to ground and the osciallations went away! A similar problem crept in once more after that (loud squre wave synth like sound when I turned my pickup volume all the way down), but this time I tightened some connections on the breadboard and it went away.
Quote from: Yonatan on October 02, 2012, 09:13:53 PM
Hi, it's my first post here (I just got my first order of a couple of madbeans boards and then registered here).
About the oscillations, I'm wondering if you ended up wiring this as positive ground PNP.
Hi Yonatan.
Thanx for your link and hints. I havent read that link before. But the schematic in the link looks very much the same as the one i tried (a few posts up^^). No surprise, i "borrowed" the idea from Tonepad, which in turn borrowed it from Jack Orman, i guess:)
No, i gave up the "upside down" idea for PNP-s, i finnished it with a voltage converter for the negative ground. You can find my finnished build under the "Build Reports" board :) .. In my circuit i have 47uF as 9V filter cap, which didnt help me with the oscillations. Maybe a larger one would have solved it, but i didnt go all that way:)
...and your description; oscillating and harsh; also dependent of your tone (and volume) guitar pot, sounds pretty much exact like my experience.
Cheers
Hi there folks,
I'm into a new fuzz face fx and I was wondering why anybody has never concerned about the voltages in Q1 and then I read this topic.
What i'm really doing is trying to improve the sound of a JHF1 Fuzz Face, what I guess It won't be difficult cause it really sounds like crap. This version mounts a pair or BC108 with hfe of 228 (Q1) and 238 (Q2), and I really ignore the leakage even though it won't be high just because they are silicon trannies...
I have used this applicattion http://www.diystompboxes.com/analogalchemy/emh/emh.html proposed by Marauder, however I still don't get the voltages required in Q1 that are a must have...
According to geofex schematics, I'm using a 100k resistor as R4(feedback resistor) and the calculator says I ought to use:
R1 = 12.3k
R2 = 4.7k
R3 = 220ohms (Actually I have soldered a 820ohm resistor to have more output)
Tweaking the values a bit I get (with a 8.98v battery)
Q1:
e = 8.93v
c = 7.35v
b = 8.33v
Q2:
e = 7.98v
c = 4.58v
b = 7.36v
You will notice that the only voltage value that it is considered acceptable is the colector at Q2. What should i tweak and mod to get acceptable voltages?
By acceptable voltages in a silicon FF I mean:
Q1:
C 1.4V
B 0.6V
E 0.0V
Q2:
C 4.5V
B 1.4V
E 0.8V
HELP!
I think you should ignore the calculator for now. Try the original values. R1: 33 K r2 :330 r r3: 8 K 2 r4: 100k
First I would try a 10k trim pot for r3 and get your collector voltage down. It diode suppose to be 4.5 I think. I had
A Hard time using that calculator too. Give out ashot
Silicon fuzz face. Q1 c: Q1.23. B: .5(ish) e: 0. Q2 c: 4.7 -4.5. B: 1.23. E: .6.
See, your voltages are to high. I only use he ge transistors for these but Iimagine
A lower hfe transistor for q1 would help, but some somewhere you have something wrong.
Quote from: Jimihendrix1987 on October 03, 2012, 08:26:55 PM
Tweaking the values a bit I get (with a 8.98v battery)
Q1:
e = 8.93v
c = 7.35v
b = 8.33v
Q2:
e = 7.98v
c = 4.58v
b = 7.36v
[...]
Q1:
C 1.4V
B 0.6V
E 0.0V
Q2:
C 4.5V
B 1.4V
E 0.8V
I think you have measuered your voltage with the wrong reference point. Take a look at this numbers, makes sense:)
Q1:
e = 8.98-8.93=0.05V
c = 8.98-7.35=1.63V
b = 8.98-8.33=0.65V
Q2:
e = 8.98-7.98=1.00V
c = 8.98-4.58=4.40V
b = 8.98-7.36=1.62V
Cheers
Yeah Vallhagen !
Swedish people are smart :) What a brain, discovering arithmetical operations in a glance ! It makes all the sense and the fx sounds awesome !
How do you usually measure voltages in the Fuzz Face? (I've done between +9v and straight to every part of the transistor I wanted to know)
Cheers,
Vallhagen: I just had some oscillations again after switching transistors, and it was solved by biasing Q1 (I put a 100k pot in place of the 33k and tuned it until the oscillations stopped), so you might also want to check that.
Quote from: Jimihendrix1987 on October 04, 2012, 06:51:00 AM
Yeah Vallhagen !
Swedish people are smart :) What a brain, discovering arithmetical operations in a glance !
Hey! I have to keep that as a quote for my signature ;D ;)
To put it simple; your zero-reference is always (one of) your ground point(s). Most common, when gnd is negative, your black battery wire is gnd.
**************
Yonatan. I have actually thought of that in general; why is there (almost) always a trimmer for Q2, but not for Q1, in the FF designs out there...
Anyway, good hint to know that you succeded to trim away the oscillations.
Cheers
Quote from: Vallhagen on October 04, 2012, 02:29:30 PMYonatan. I have actually thought of that in general; why is there (almost) always a trimmer for Q2, but not for Q1, in the FF designs out there...
Because for the most part the voltage of Q1 will not vary by that much, and you get very little sound change by fiddling with them. Really, all you need to care about is whether the guitar input can saturate it, which can happen with anything less than a volt on the collector. You're not going to see anything outside the .5-.7v range on the collector of Q1 with the stock values with any transistor you're likely to use, and anything in this range or within probably a volt or two upward will be sufficient to produce fuzz. Remember, the 100K feedback resistor prevents Q1 from hard clipping (basically, it prevents it from turning off all the way), and the bias on the second transistor therefore affects the gain of the first circuit.
The purpose of biasing Q2 is to balance between actually having it distort and having it hard clip, which produces the "transistor sound" we all know and hate (well, many of us hate it at any rate). Q1 doesn't typically have this problem.
There's a catch, however. The total gain of Q1 does affect Q2 because it overdrives the second transistor. So even though biasing Q1 is largely worthless, the gain rating of Q1 *is* very important. Too much gain and it slams Q2 so hard that the circuit starts oscillating, which is the problem everyone's having with the silicon circuits.
There are two common and easy solutions to this: cut some high frequencies to prevent them from hitting the base of Q2 as hard (that's what that little cap is doing in the Hipster), or use a lower gain transistor* in Q1. There are a few other things you can do ... you can block more of the signal from Q1 by replacing the collector > base jumper with a small resistor, like 1K, or change the feedback resistor value. But any additional changes you make are going to have basically the same effect as lowering the gain of Q1 or using the treble cut cap: darker tone. In other words, you might as well stick to the easy solutions if you want it to behave like a Fuzz Face.
*Edit: You'd be shocked at how much lower the gain needs to be when it's silicon to get it to behave like a germanium in the 60-90 range. Go for something more like 25-60.
Thanx Jon. Now i know a bit more, again:)