A Few Booster Questions

[KerryF]

Heres some questions about boosters.

1. What are the parts that make up a booster?  (Input Filters, Output Filters, Buffers, Boosts?)
2. How is the boost part of a booster circuit made up, or how does it work?
3. How is a regular booster different from a treble, bass, mid booster?  (How to change one to the other?)
4. What would happen if you put more than one transistor in parallel?  (Any sound difference between one transitor, two transistors, five transistors, ten transistors in parallel?)

I may have more, but I will post when I think of them.

Thanks,
Kerry

[Meanderthal]

 1. Yes.
2. Gain stage, buffer, or both.
3. High pass, Low pass, Band pass filters.
4. Piggybacking can result in more headroom. Might be worth a try if you're desperate to stay clean. Ten would be one hell of a stack for no reason.

[zjokka]

4. What would happen if you put more than one transistor in parallel?  (Any sound difference between one transitor, two transistors, five transistors, ten transistors in parallel?)

4. Piggybacking can result in more headroom. Might be worth a try if you're desperate to stay clean. Ten would be one hell of a stack for no reason.

Piggybacking 2 transistors in parallel will bring the gain down to 5 - 15. You can get the gain back up by using a resistor. Check the piggyback threads. It is the real way to go if you really want a certain gain.

zj

[KerryF]

Thanks.  I would like to do a nice headroomy boost so I guess "piggybacking" is the way to go.  What about #3?

3. How is a regular booster different from a treble, bass, mid booster?  (How to change one to the other?)

Besides filters because the input sections of most boosts have high/low filters.

[GibsonGM]

Isn't any boost circuit dependent on filtering for proper frequency transfer?  You can set up a BJT to just boost the signal, and use large in/out caps to keep the results as "true to life" as possible - you'll hear what the transistor is doing.  After which you'll crave some filtering, LOL (sounds like junk usually).  Op amps & trannies have operating ranges, which determines how much a certain frequency gets boosted.  It's those in/out caps & filters that make the sound pleasant.   

So, I'd guess it's those and possibly a feedback filter network that will determine what you hear...you could make it switchable to go from lo to hi to mid, easily.  I'd imagine an op amp would be easiest to get what you want out of...

[petemoore]

1. What are the parts that make up a booster?  (Input Filters, Output Filters, Buffers, Boosts?) DC blocking caps keeping DC contained to circuit can also be used to filter low freqs.
  Unless it is an 'attenuation' circuit hiding under the name 'boost' you'll need active component[s and that also means power supply and resistors to bias the active.
2. How is the boost part of a booster circuit made up, or how does it work?
  If it's using say an NPN Si Transistor as a gain stage... "*Voltage controlled [*ac source voltage applied to base] >Current Source" [>the emitter/collector uses voltage supply to output 'boosted' signal], a small voltage from say a PU 'wiggles' the voltage on the base of the Q, controlling the current flowing through the E/C, producing a 'mimic'-ed version of the input signal, at a higher voltage.
3. How is a regular booster different from a treble, bass, mid booster?  (How to change one to the other?)
  Bass content can be attenuated by reducing the value of the input and/or output capacitors [high pass filtering]...or 'treble booster'..which more exactly state is a booster for all freq's that has HP Filtering.
  Caps attenuate lower frequencies, stop very low frequencies and DC. by adding a cap between signal path and ground you have created a LP filter...caps lets the highs only through and in the case of a LP Filter those freq's get shunted to ground...hence LP Filter!...add Lp and Hp filtering and all that is left is mids...that'd be a midrange boost or 'bandpass'...frequencies 'in the middle of' or between the Lp and Hp filtering are passed...higher and lower freq's are attenuated...increasingly as they move toward where the 'rolloff' begins.
4. What would happen if you put more than one transistor in parallel?  (Any sound difference between one transitor, two transistors, five transistors, ten transistors in parallel?)
  Plenty and most booster schematics require only one transistor, piggybacking to reduce transistor gain...well check out RangePig or Miss Piggy...cool to mess with, but for Si gain stages it may be deeemed unnecessary.

[KerryF]

Thanks alot all of you.  I think I am getting it better now.

Thanks.

[Dragonfly]

Thanks.  I would like to do a nice headroomy boost so I guess "piggybacking" is the way to go. 

if i wanted "headroom", i wouldnt go for a piggybacked boost...id design an 18v mosfet or opamp based boost...but thats just me....

AC

[KerryF]

I am here in school.  Just started my design for the boost in English class .

Well its comming along I guess.  Should be pretty cool  .  Let ya know when I am done or have questions.

[Jay Doyle]

Piggybacking won't increase the headroom. The headroom is determined by the voltage supply and the ratio of the collector/emitter (drain/source) resistors.

[Ben N]

Well its comming along I guess. 

Maybe you should put the design down and concentrate on the English.
Ben

[KerryF]

^-Dude  .  Dont be all like that.  Its a typo...  I was in a hurry typing before lunch ran out.

[KerryF]

Ok another question while im here finishing the schematic.

How do you create a high impedence input? (Like the Zvex Super Hard On says it has a high impedence making it clear up the sound when you switch it on).

[Seljer]

go read the article on impedance on AMZ

basically use a device that has a relatively high input impedance (typically these are usually FETs of all types and opamps, though certain setups with BJTs can also work)

[KerryF]

So a good choice for the input filter section would be:

[343 Salty Beans]

GEO also has an impedance article, too.

[Jay Doyle]

A buffer is more than the resistors at the beginning of the circuit. That would work for a JFET, sort of, but NOT for a MOSFET or a BJT.

And, in my opinion, there IS something as TOO HIGH an input impedence. The higher the impedence gets, the easier it is for higher impedence noise sources to be coupled into the input.

Your sig. says that you "designed" a pedal called 'Vintage Booster', I have to ask how you did that without knowing all of this???

[KerryF]

This was a circuit I did based on another boost.  I did this Vintage Booster with the help of Markm.

I didnt mean input buffer there.  I meant "input filter section".

Sorry to bring this up, but it really seems like you have something against me in the ways you have said things in two of my threads.

[Ben N]

^-Dude  .  Dont be all like that.  Its a typo...  I was in a hurry typing before lunch ran out.

I was kidding--sorry it came off that way.
Ben

[KerryF]

Its ok.  Just came off a little mean to me but its ok  .