anyone know a good clean booster circuit?

[dosmun]

I have built and tried many Boosters (SHO, Mini Booster, Mosfet boosters, LPB1 etc etc) and my fav so far is Dragonfly's Sparkle Boost.

[tone_crafter]

Pete let me know how you go with the shakabooster because I don't have the facilities to make up temporary circuits at the moment.

What difference will 220pF cap make? Will it form a low cut? Can I leave it out. Also what difference did it make changing the input and output caps to lower values? Should I stick with 0.1uF.

Also let me know if you try changing the 100K output resistor what difference it makes. Im gonna make it into an AB box so its going to be at the beginning of the chain.

One final thing is for powering the opamp to i connect -Vcc to ground and +Vcc to 9V or do i need to try and form +4.5V and -4.5V from the power source and power the opamp with that.

I might just go out and buy a bread board and some components and try some stuff out.

[aron]

-Vcc is ground. The two 10K resistors bias the op amp input so you are good there. The 250pf can be anything from 50pf to 250pf. It just smooths out the top end a little and can help prevent oscillation.

[tone_crafter]

What is the difference between different opamps, in particular the 1458, 4558 and TL072. I've seen a lot of people using TL072 in circuits. What should I use for this application? :?

[aron]

Use the TL071 or half of a TL072.

[amz-fx]

From an EE stand point it may not be *clean*, but from a practical gigging guitarist's POV it is *perceptually* clean if you have enough headroom ( and don't crank the gain all the way up). I use the Mosfet boost for clean jazz tones all the time and it works well to compensate volumes between humbucker guitars and single-coils.

It is quite clean and linear within the limits of the 9v power supply, which will also be the limiting factor with an opamp design.

Read more about what makes boosters clean in my article: Boosters, Gain and Distortion

regards, Jack

[R.G.]

It is quite clean and linear

It may be clean sounding, but it's not especially clean. It's really, really hard to get under 2% distortion with any single device unless you're using it as a follower, which of course has no boost. MOSFETs are square law devices, which means that there will always be some second order distortion, as well as second order intermodulation products. Whether these are good or bad is up to interpretation, of course, as I noted before.

The oddity of the human ear in hearing few-percentage-points of distortion as a tonal quality rather than distortion is what's going on.

Of course, it's possible that there are now completely linear MOSFETs which don't need feedback to get to linearity. Maybe I just missed that. Time and technology do march on.

... within the limits of the 9v power supply, which will also be the limiting factor with an opamp design.
Read more about what makes boosters clean in my article: Boosters, Gain and Distortion

Craig Anderton also covered just this point in one of his books years ago. The issue is clear - guitar signals have a high, peaky attack, so you can't really amplify them much without exceeding 4.5V peak, the limit of a 9.000V battery. Real batteries and circuits have to do with less, of course.

There are two ways around this. One is to use just-adequate gain to not distort on peaks, the other is to use a bigger power supply so the peaks don't get clipped off when you get the sustaining section boosted up to where you want it.

Using a correct gain rather than attenuating the signal for better noise performance is a touchstone of all standard low noise practice. The phono preamp guys have been all over this for decades.

[gez]

As a practical matter, any input impedance over a few megohms is going to make almost as many problems for you as it solves in terms of noise pickup, sensitivity to dust, and amplifying piezoelectric and triboelectric noise from the insulators that connect to the input

The "sensitivity to dust" bit, how does this work?!  Is this a static thing or something?

[aron]

Run the Shaka Boost at 18V (i.e. 2 batteries) or wallwart.

[R.G.]

The "sensitivity to dust" bit, how does this work?! Is this a static thing or something?

Dust collects, forms a substrate that attracts and holds more dust, and it's hygroscopic  - it attracts and holds humidity. Unless you keep dust off circuit boards with conformal coatings, dust eventually lowers the impedance of *everything* down to a few megs.

[davebungo]

Not to mention spilled beer - really nasty stuff when it gets inside a stompbox especially into switches and stuff.

[ejbasses]

How do i hook up a opamp with a voltage divider bias / bi-polar suply to turn on like a pedal? Ya know... when you insert the jack it should turn on.

im having problems because i tried hooking up the negative side of the battery to the jack but at the same time the ground is connected so all i get is this distorted sound. I hope im making sense here

[tone_crafter]

Should I use a linear pot or a log pot for the feedback pot in the shakaboost?

Also Aron u said that you can vary the output resistor (to ground) and make it less than 10k. What difference will this make? If like I said this pedal will be at the beginning of the effects chain do I leave it as it is or am i better to change it?

[petemoore]

How do i hook up a opamp with a voltage divider bias / bi-polar suply to turn on like a pedal? Voltage divider is the same as a V-/V+ supply as far as a stereo input jack breaking the connection to the power supply [usually the Neg battery or power supply connection] when a mono plug isn't in it.
 >By breaking the PS Circuit. Connect Battery _ to the ring of the the stereo input jack, and circuit _ from the board to the sleeve. This way when a Mono phone Plug is inserted the Ring/Sleeve connetion 'arms' will be connected by the plug, completing the power supply circuit.
 
 im having problems because i tried hooking up the negative side of the battery to the jack but at the same time the ground is connected so all i get is this distorted sound. I hope im making sense here

.
 >Which of the how many connecions on the jack [stereo jack?] did you connect the battery to.

[ejbasses]

pete,

i hooked it up like a stompbox. Negative of the battery to the ring and the ground at the sleeve.

[bwanasonic]

Dust collects, forms a substrate that attracts and holds more dust, and it's hygroscopic  - it attracts and holds humidity. Unless you keep dust off circuit boards with conformal coatings, dust eventually lowers the impedance of *everything* down to a few megs.

In the not-too-distant past, if you wanted to scan an image for printing, you needed a piece of equipment the size of a Yugo (at least) that had a ton of knobs and a couple of dozen circuit boards (at least). These things started to get weird in their old age, but a can of dust-off could make you look like a wizard.

Kerry M