Swell Fuzz

[seanthomas46]

Just curious if anyone has built a fuzz pedal with the swell effect.  Where it sounds the note after pick attacks?

[Bernardduur]

Doesn't "The Experience" of Prescription Electronics have such an option?? I already saw some schems of that pedal

[seanthomas46]

I think you're right.  I've also seen a Wyllie Moonrock schematic for sale.  But I'm mostly interested in hearing from someone who has built one, or if they had modified a fuzz with a swell effect. 
  Right now, this project is a little ahead of my exp., skill;         
          (Just curious is all, if I can get through my boost first, a fuzz face project, then I'll try it)

[Bernardduur]

Here are the schematics BTW; including the swell circuit.

[seanthomas46]

a single swell effect pedal would be f*n cool to me.

[R.G.]

The swell effect on the Experience Pedal is not really a swell effect, although sometimes that's how it sounds. The swell is a side effect.

The swell section of the Experience Pedal is the entire circuit of an early distortion pedal, one that appeared in Popular Electronics in about 1969, author of Anthony Leo.

What happens on the swell effect is that the output of the swell section is DC coupled to the output jack, not separated by a capacitor to block DC. The pedal normally sits at a DC level that pulls the input of a follow-up amp or effect into a non-conducting condition, so no signal gets through. When signal hits the output, the DC conditions change so the amp gradually starts passing signal. It works better with some amps than others, and the use with following effects is cautionary.  It requires a fresh battery to work well at all. But it does work sometimes.

If you want a swell effect, you want the "Slow Gear". The schemo is available.

[seanthomas46]

So, would it be safe to have a dc powered swell pedal?
I'll check out the slow gear definetily.
thanks again R.G.

[Gus]

this can have a swell effect

http://www.diystompboxes.com/pedals/ousb.gif


It has a bunch of sounds it is all about the gain setting and the guitar vol.  One setting will decrease at first and then the sound comes up.  Lots of Fun.  I wonder why I gave it away. 

It is not a turn the knob to ten effect it is very interactive with the guitar vol setting.

[jmusser]

I didn't know it would do that. I'll have to dig it back out again and play with that aspect of it. To me it's great whether it swells or not. I actually like it better than the Tychobrahe. Your Simple Octave Up is hard to beat also. It's a totally different sound, but a great pedal in it's own right.

[markphaser]

"What happens on the swell effect is that the output of the swell section is DC coupled to the output jack, not separated by a capacitor to block DC. The pedal normally sits at a DC level that pulls the input of a follow-up amp or effect into a non-conducting condition, so no signal gets through. When signal hits the output, the DC conditions change so the amp gradually starts passing signal"

So on the output of the swell effect there is DC offset? so its audio with DC offset?

How can a distortion or fuzz section in series with a swell circuit have audio plus DC offset going into a guitar amp?

The Swell Circuit takes its output from the middle of the 2 stages why?

How does the Sweel circuit work ? it looks like it using feedback path

[soggybag]

The OUSB looks pretty interesting and not too difficult. I may have to try and make it.

I wish I had thought of the name "Swell Fuzz". I may have to use it on a box...

[seanthomas46]

That's the name of my next project.  The Hornet, with a friend of mine helping me with the swell circut. 
  call it: Swell Fuzz
              V      T
                   S
           OJ          IN
                  DC
   With a rainbow shaped box
"It's going to be awesome!" the little birdies are telling me flying above my head holding lightbulbs.
    -sean

[markphaser]

R.G i posted the swell questions here now

[R.G.]

So on the output of the swell effect there is DC offset? so its audio with DC offset?

Yes. More properly, there is no output capacitor to block the DC that's there, so the audio goes through on whatever DC level the effect puts out. In the case of this one circuit, set up as it is, the average DC output level changes as a note plays.

How can a distortion or fuzz section in series with a swell circuit have audio plus DC offset going into a guitar amp?

By leaving off the output capacitor that we put on everything else to block that DC level. Almost every effect has a DC bias level internally, with the audio alternating around it. The input and output capacitors block that internal DC level from affecting whatever is outside the effect circuit.

The Swell Circuit takes its output from the middle of the 2 stages why?

I'm not sure. I believe that someone was messing around with it and just found out that one point had audio plus a DC level, and tried hooking it up to an amp. That's not a very satisfying answer, but I believe it's close to the truth.

How does the Sweel circuit work ? it looks like it using feedback path

The swell circuit is itself a fuzz circuit, from an old Popular Electronics article by Anthony Leo. That one used an output cap. Whomever found the DC offset inside the thing noticed that when that point was hooked up to a tube amp, it made it have a swell effect. I believe that it was no more and no less complicated than that.

At a higher level: Almost all tube amps are DC coupled on their input because triodes can work just fine with their grid tied to DC ground by a 1M resistor. That saved the makers the cost of an input cap. But it leaves the amp open to being manipulated by a DC level at its input. That's what's happening here. If the input signal has DC on it, it moves the grid toward saturation (for +DC) and toward cutoff (for - DC). That changes whether the tube can amplifiy and what its gain is by changing its bias.

[markphaser]

Thanks R.G

How can DC offset create a swell effect?

if the DC offset is like 3 volts positive DC offset with audio riding on top how can that create a swell effect i don't get it sorry?

[R.G.]

The swell effect does not happen in the swell circuit. It happens in the input stage of the tube amp.

The swell circuit does nothing except put out an audio signal that rides on a varying DC level. When there is no note playing, the DC level holds the tube nonconducting. When a note is played, it makes the DC level shift in th swell circuit. It shifts in the direction that lets the tube start conducting and lets signal through.

It takes both the swell circuit and the amplifier to do the overals swell effect. It's confusing because it is entirely a side effect. It does not work well on all amps, or if the battery for the swell effect is not brand new.

[markphaser]

Thanks R.G alot

Which Tube amp does it work best with?

But it leaves the amp open to being manipulated by a DC level at its input. If the input signal has DC on it, it moves the grid toward saturation (for +DC) and toward cutoff (for - DC). That changes whether the tube can amplifiy and what its gain is by changing its bias.

Whats the DC offset doing to the inside of the tube amp? is it shifting the Bais? or changing the reference voltages?

If the tube amp have a DC input coupling cap woudn't it just block the DC offset input coming from the swell pedal?

i thought the DC input coupling cap in a tude amp was support to block DC offset or it just blocks DC only not DC offset?

[R.G.]

Which Tube amp does it work best with?

There isn't any best or worst. It's just different from amp to amp.

Whats the DC offset doing to the inside of the tube amp? is it shifting the Bais?

It is changing the bias of the first tube stage. The first stage is normally biased only by its own conduction through its cathode resistor. Any DC from any source placed on it grid changes the relative grid to cathode bias voltage.

or changing the reference voltages?

Tube amps don't have reference voltages. Each stage is self biased separately, and isolated from each other by capacitors to block the DC levels.

Before you ask the next question, you'll need to go read about triode self bias on the web before I can help you with it. Come back with that question when you understand what triode self bias is, not before. Then we can talk about it.

If the tube amp have a DC input coupling cap woudn't it just block the DC offset input coming from the swell pedal?

Yes, it would.

i thought the DC input coupling cap in a tude amp was support to block DC offset or it just blocks DC only not DC offset?

(a) Tube amps historically do not use input DC blocking caps. Why was that?
(b) There is no difference between an external DC level and a DC offset. The amp only sees external DC. Input caps (if they are used) are intended to block any incoming DC level at all.

This is going to be necessary for you to understand the answers to the next few questions you ask: As you research and study about tube self biasing, figure out why one cannot simply connect two triode amplifiers in cascade without a blocking capacitor between the two stages and still have them provide signal gain. Once you can do this, come back.

[Doug_H]

FWIW, the Roger Mayer Axis Fuzz can swell too. With a hot pickup and the fuzz gain turned up, it will swell on the wound strings. Fun for Jimi-like effects were the note swells into octave blooms and etc. Like Gus's OUSB, which is excellent BTW, it is very interactive with the guitar volume. Not a "turn it up to 10" effect either, you have to play with the knobs and it is very expressive.

Doug

[markphaser]

Thanks R.G alot

Change the bias of a tube makes it swell?

Putting DC offset changes the bias of the tube? The bias should stay the same because the "biasing resistors" are fixed but i guess the input changes the biasing also or having DC voltages on the input of the tube would change the biasing resistor voltages

So DC offset voltages changes the triode self bias? does the DC offset change the voltage drops from the biasing resistors and how the tube will produce gain?

*it seems to me that the DC offset sweeps the gain of the tube which will give that swell sounds because the swell is the gain of the tube going up and down producing a gain curve or slope causing us to hear a volume swell*