Installing a gain control - noob question

[Venusblue]

Hey, If you guys saw my other thread, I'm working on a sketchy design that's real basic. The fuzz circuit was meant to be turned up to 11 at all times and not have any kind of pots. That makes me unhappy D:

So after reading through a plethora of books and websites I get how to do a volume pot, But how do I control the gain? I couldn't find much online and wasn't really looking for it when I was reading through the books. I'm assuming that it would go in front of one of the transistors to cut down on how much juice it was getting, but i'm sure that's probably wrong.

Does anyone know of a web page that explains this, or would anyone mind explaining it? What is the proper name for this kind of pot?

[liquids]

I haven't seen your other thread, but thought I might offer some starter info.

Keeping it simple, you are correct in thinking 'gain pots' often are just a 'volume control' after one stage, that is hitting the next and controlling 'how much juice it is getting.'  Nicely said.     Bit not always...there are dozens of variants, of which this is the most common I dare say.   You can see this kind of gain control in most amps, or more practically, in fuzz circuits like the big muff.  Does this particular circuit you are working on have two stages?  You might wire a 'volume' control between them as a gain pot.  Others...keeping it to the 'fuzz' world, there are some alternatives.

In more than a couple fuzz pedals, there's really only one stage making the fuzz.   Hence, the 'gain' control is actually just a volume control at the 'input' to the circuit, which determines how much signal gets into the circuit, as a way to control gain...functioning not unlike your guitar's volume control. 

In other fuzz pedals like some tonebenders, the gain pot is simply a pot wired as a variable resistor (and this is, generally speaking, my preference with bombastic fuzz pedals, rather than a voltage divider gain control).   What that means you are really only using two of the pot terminals, and there is no connection to ground, so no signal is lost to ground persay.  More so, it is just a varying level of resistance between the two stages (or between the input and the circuit).  This more so just 'dulls' the strength and tonality of the signal going from one stage to another.  It is not that common outside of classic-type fuzzes, but useful to know and use nonetheless.  I think in circuits like the big muff, the fOXX tone machine and the like, it's actually preferable to wire things this way, since shunting some or any of the signal going to ground has mostly a negligible effect and the range of pot control seems to owe more to series resistance than signal to ground.  YMMV.

There's plenty of other variations, but that's for starters. 

[Venusblue]

Thank you very much! The people here are very nice, but maybe i'm just used to asking for advice on 4chan, lol.

This here is the fuzz circuit I made . I put a mid-boosting circuit into the middle of a fuzz circuit, because some one told me that would be the best thing to do, instead of just having it as two separate circuits. I don't know if that's correct, or if I merged them 100% correctly, but I tried. I'm assuming the two circuits would make it a two step pedal, unless i'm not understanding the full idea of the term.

So since I have something interrupting these two transistors, I wouldn't know where to put the "gain pot". I'm assuming that I would want it after the first transistor, but before the mid-controlling circuit, that way it does not dull the mid-boosting signals (Gotta love the midrange).  Feel free to edit my schematic if I've done anything wrong.

See I took the mid boosting circuit off of this schematic and then I put it smack in the middle of this really basic fuzz circuit . Was this a good idea?

Some on a different forum said he knew a little bit about this stuff (But that I should come to the experts here) and he said the line I made on that schematic going from R4 to the 22k resistor was not needed, and that I could just take out that entire section, including the 22k resistor, but he was not sure if that would affect anything. Could I take out that resistor and cut the flow there?

[liquids]

I put a mid-boosting circuit into the middle of a fuzz circuit, because some one told me that would be the best thing to do, instead of just having it as two separate circuits. I don't know if that's correct, or if I merged them 100% correctly, but I tried.

It seems cool enough to try out.  I kind of want to try it myself.  But I am not certain if or how your additions would work...hopefully it works for you.  A little experience and you might also be able to conceive of how to mod the values, etc, to suit your tastes if it works as intended...

So since I have something interrupting these two transistors, I wouldn't know where to put the "gain pot". I'm assuming that I would want it after the first transistor, but before the mid-controlling circuit, that way it does not dull the mid-boosting signals (Gotta love the midrange).  

Possibly, but i fear any voltage divider or series resistance 'gain' control before or after the gain circuit would be highly interactive with the 'mid tone' control.
Some options for adding a gain control:
1) well, build it and see if you think it needs one, first and foremost
2) Put a 'volume control' at the input, as mentioned in my previous post.
3)Examine the 'beginner project' / Gus' NPN boost.  This implements a gain control that would be a relatively simple mod to your existing circuit, via controlling the gain of the second transistor.  Look it over thoroughly, and post back if you have questions.
4) you could simple connect the emitter of the first transistor to a 10k or 5k pot wired as a variable resistor to ground.  Right now it got no resistance to ground, but as you add resistance between the emitter and ground, you can control the gain somewhat.

Those are some simple options...more complex variations on these themes can be found, but these are pretty standard and basic...not easy persay, just basic one part mods--adding a pot or replace a resistor with a pot.

If you add a gain control, you'll want a volume control.  Right now the circuit is lacking one...and it seems designed to reach unity via the way the second transistor is biased and tapped...but if you add a gain control, you'll want a way to compensate with a volume control.  Note that you might want to tap the signal going to the capacitor out directly off the 2nd transistors junction with the 4.7k resistor...or, replace the 4.7k and 470R resistor with a 5k pot...connect one side to 9v, the other side to the collector, the wiper out into the capacitor, and voila, you have another cool volume control variant.

Some on a different forum said he knew a little bit about this stuff (But that I should come to the experts here) and he said the line I made on that schematic going from R4 to the 22k resistor was not needed, and that I could just take out that entire section, including the 22k resistor, but he was not sure if that would affect anything. Could I take out that resistor and cut the flow there?

If you mean grounding everything rather than make it a 'feedback loop' of signal all going back to the first transistors base, than, yes, but it will have a dramatically different effect than as pictured.  I can't verify if one, the other, both, or neither will work, but yes, for sure, it will be different (barring the slim change that neither will work, which I doubt).

Sorry, there are experts here, but I'm not one.  Hopefully one will chime in...until them, happy expirimenting!  

[petemoore]

  the 11meg is odd, it is an LPB booster with some kind of tone control.
  the 11meg could or should or shouldn't be a much smaller value, simply lifting it out of the circuit would be the same because it's such a large value.
  I would download Duncans Tonestack Calculator, try out BMP, Marshall Fender knob adjustments and see the actual frequency graphically on the...graphs as you turn the knobs. Note that when the lines are higher at any frequency, this means less attenuation at that frequency, you might want to shop for one that has 'high lines' at the frequencies you think you'll want high, lower lines = more attenuation of frequencies = lower output.
 
 

[petemoore]

  That's an Orange Sunshine ! Pretty cool for fierce fuzz, kinda strange or exotic, responded to guitar volume in frequency active way IIRC, very cool treble boost tone w/...whatever I had set up then.
  You might like something more 'generic'.
  I'd like to say Fuzzface now and in general, but sometimes a distorter is more at home with...well it depends on what else is helping or not so helpful to the type of distortion you're seeking, what they're known for wanting to do may be where to look for the best results.
  Some circuits don't mind tone controls, though controlling tone can be done in more ways than just adding a tonestack. Frequency shaping is all passive, loading the signal...attenuating ''it''...what frequencies are attenuated and how much depends on the settings.
  When you start running low on the output...
  Buffer can be used to supply better current drive into passive losses, especially useful where circuit has high output impedance, driving cables etc.
  Boosted input, start with more, end with more, but the impedances 'should be' matched to some degree, low output impedance is nice to have sometimes, high input impedance is ok, anything less than a 10:1 [or high output imp trying to drive a load such as low input impedance], related signal integrity losses.
  The bipolar transistor LPB type thing, see if that can be working:
  Base above emitter by a small voltage [the base/emitter diode drop], collector near middle of between ''ground = 0.0V'' and 9V+, right around 4.5v or 5v.
   http://www.generalguitargadgets.com/index.php?option=com_content&task=view&id=72&Itemid=26

[Venusblue]

A little experience and you might also be able to conceive of how to mod the values, etc, to suit your tastes if it works as intended...

Yeah, I'd love to be able to know how to do that. It'll be great when I can just look at a schematic and be able to understand the purpose of all the parts. I'm starting to be able to do that a little bit, Learning how to make volume controls, duel gang pots, etc. but I don't understand the theory of why every part is there, or how to construct a circuit myself. I'd love to take some classes on this though.

1) well, build it and see if you think it needs one, first and foremost

Oh, I'll definitely want one. I'd like to be able to roll it back for a muff tone, or all the way back for just deep saturation, or open the pot up for a pure noisebox. Mmm, makes me salivate just thinking of all the insane mids and messy distortion everywhere.

2) Put a 'volume control' at the input, as mentioned in my previous post.

I was going to do this, but I was going to put it at the very end of the circuit, because i've looked up some schematics and this seemed to be where they normally are. I thought putting it in the beginning of the circuit will mess with the levels too much. Is that correct? I'm also putting in a "voltage sag" pot because I like the sound of near dead batteries sputtering out fuzz, and it's a very easy looking mod. Again, Don't know if this will affect my mids too much though.

3)Examine the 'beginner project' / Gus' NPN boost.  This implements a gain control that would be a relatively simple mod to your existing circuit, via controlling the gain of the second transistor.  Look it over thoroughly, and post back if you have questions.

I can't find this anywhere? I used the search function and looked through the first three pages but didn't really see it.

4) you could simple connect the emitter of the first transistor to a 10k or 5k pot wired as a variable resistor to ground.  Right now it got no resistance to ground, but as you add resistance between the emitter and ground, you can control the gain somewhat.

This is sounding like the best idea so far, or one even better that I came up with.

I can just set the mid adjusting circuit first, then the fuzz circuit, that way I can put a gain pot in front of the first transistor and not need to worry about it messing with the mids. Or in front of the second transistor, I don't know which one would be a better idea to do this one. Would that be a good idea? Would the voltage sag pot still be a reasonable mod to put in to this pedal? I'm drawing up a few schematics right now.

[liquids]

Oh, I'll definitely want one. I'd like to be able to roll it back for a muff tone, or all the way back for just deep saturation, or open the pot up for a pure noisebox. Mmm, makes me salivate just thinking of all the insane mids and messy distortion everywhere.

But without breadboarding it, or hearing one, how do you know it's going to sound anything like that? 

2) Put a 'volume control' at the input, as mentioned in my previous post.

I was going to do this, but I was going to put it at the very end of the circuit, because i've looked up some schematics and this seemed to be where they normally are. I thought putting it in the beginning of the circuit will mess with the levels too much. Is that correct?

A volume controls at the end would be for overall volume, or output level, but would not affect 'gain.'    We were talking about a gain pot... controlling how much fuzz/distortion.   I was saying a 'volume control at the input' is actually way to control the gain.  It's used in the jordan bosstone, for example.  .  I also posted an option or two for how to wire up a way to control the volume/output, in my previous post.   But really, you are best getting a small stash of parts if you don't already have them, and a breadboard, and wiring up these ideas and options on the breadboard, so you can audition and  experiment with this and all other possible scenarios, and find for best sound to your ears, all without committing anything in solder until you do...and learning a lot in the process.

I'm also putting in a "voltage sag" pot because I like the sound of near dead batteries sputtering out fuzz, and it's a very easy looking mod. Again, Don't know if this will affect my mids too much though.

Well, it's a fine idea, but who knows if you'll like it in reality.  And what value will you use?  Will you sag the voltage on both transistors, or just one?    Again, you need a breadboard so you can hear it...and get the best result by ear, with your equipment, rather than talking theory and imagining it will sound awesome...and it may, but what kind of awesome do you want? 

3)Examine the 'beginner project' / Gus' NPN boost....

I can't find this anywhere? I used the search function and looked through the first three pages but didn't really see it.

The beginner project is a sub-forum under 'projects,' a bit  below this sub forum 'building your own stomboxes.'   Also, if you click up above on 'schematics,' you'll see an old text page aron linked to, with listing of schematics (and many of the links are now dead).  If you find GCS/Gus Smalley, the NPN boost is listed there as well, and all those links are good.

To the rest of your questions...one word answer for you:  Breadboard!   

[Venusblue]

Hmmm yeah, I'll be taking a trip down to radioshack for some breadboard next time I get paid. I'm ordering some parts through mouser though, mostly the caps.

I initially thought that you could not re-use parts that you used on a breadboard for some stupid reason, which is why I wasn't going to do it. Now, I'm totally all for it though, since I learned you can re-use the parts... mostly. Lol.

As for the voltage sag, I'm going to hook a pot up to the battery itself. I read a guide on how to do it, and I like the sputtery yardbirds kinda tone it gives, so I figured i'd try that on a pedal. This really is going to be one frankenpedal.

My initial thought was "Learn everything and work out every kink before trying this", but now I think part of working out the kinks is actually doing it. Thank you very much This will be a great project, and i've been wanting a really crazy fuzz/noisebox for relatively cheap for a while.