40dB Clean Boost and related questions...

[jishnudg]

Hey, all,

http://www.masterbuiltamplification.com/Tongue-Tied.htm

I just came across this one...does anyone have any schematics? Also, can I mod any of the other boost schematics on this forum (SHO, LPB, AMZ MOSFET boost etc) so I can get around 40-50dB clean boost with 9v? Or maybe even use a voltage doubler to feed 18v for more headroom...in that case,would I have to make any changes to the biasing etc? Sorry if these questions sound really amateurish; I just want to learn the general principles and differences between biasing and setting up a BJT,FET or MOSFET clean boost circuit.
Thanks.

[jishnudg]

Also, what are those cool metal handle things called    ?

[slacker]

40 dB is a gain of 100 ie: you feed 1 Volt in you get 100 Volts out, so you can't easily make a 40dB "clean boost" for a guitar and you wouldn't want to anyway, you'd blow stuff up

[anchovie]

Also, what are those cool metal handle things called    ?

Handles. 

[Mark Hammer]

When a mixer or power amp is expecting to get 1V p-p, and a dynamic voice mic can provide 10mv, 40db of gain makes absolute perfect sense, and is easily attainable.  When the guitar produces 100mv for a full chord strum, and the amp is expecting maybe 2v p-p, 40db gain is what you use to overdrive that amp.  IT is doubtful that the pedal's output will be clean, but even if it were, the amplifier output sure as heck wouldn't be.

This is NOT any sort of finger-wagging against trying to produce 40db gain, or pooh-poohing the claim to be able to produce it (as long as the input signal is low enough).  Just recognize that there are circumstances when its use CAN be clean, and circumstances when it can't.

[psychedelicfish]

IT is doubtful that the pedal's output will be clean, but even if it were, the amplifier output sure as heck wouldn't be.

It does say that the pedal is MOSFET based, perhaps it has some kind of onboard boost converter? I'm sure you could get 40dB of clean gain if you were running the FET/FETs on a high voltage supply.

[Gus]

40 dB is a gain of 100 ie: you feed 1 Volt in you get 100 Volts out, so you can't easily make a 40dB "clean boost" for a guitar and you wouldn't want to anyway, you'd blow stuff up

The above is the best post in this thread.

[R.G.]

I completely agree, Gus. That's the kind of thinking that needs to be more common.

There is an alternative interpretation. Knowing that the OP wants 40-50db of clean boost with 9V (presumably as a power supply) the answer is "Yes, you can. But you can only put an input signal into it that's less than 50db below 9V and stay clean."

That is, less than 9V/316 = 28.5mV. A single coil pickup easily provides 100mV at the start of a note, and humbuckers sometimes much more, so you can only cleanly boost tiny signals if you stay on 9V.

The alternative then is to provide an unlimited power supply, and yep, you run headlong into a 1V signal making an output of between 100V (+40db) and 316V (+50db). Things get a little funny about then, not least of which that a 316V output would have to be covered under some of the more stringent safety standards and mean that the *wires* you use, their placing and securing in place would be governed like AC power wiring.

But I digress. 

[jishnudg]

Wow..thanks, everyone who's replied to this - I've learned a lot about the implications of 'clean boost' just from reading R.G, Gus and Marks views on the matter. Now it's time to sit still for a while and digest it Just one last question - what sort of average voltage would I assume a humbucker pickup to make (as everyone seems to be in agreement that single coils are around 100mV or somewhat more)...I guess I'll have to backtrack from there and see what sort of a power supply I want, wire usage etc
Thanks again,
J.

[psychedelicfish]

I'd guess 300mV from a humbucker at a hard strum. If you want a clean booster with a lot of output, take a look at Merlin's Glass Blower design, it can supposedly do 27dB of gain. I think 40dB is a bit excessive and the Tongue Tied almost certainly won't be able to do that much clean.