What do you think of the jack orman mosfet booster?

[demonstar]

What do you think of the jack orman mosfet booster? worth the build? it would be a second project? (first was dist+)

[The Tone God]

Use the function as Jack's booster has been discussed at length here.

Andrew

[petemoore]

  Dist + sounds great with just about any active boost component in front or behind it.
  Something with a teeny bit of grit up front sounds good to me.
  Mosfet boost is very nice on the output/input...fet's are well liked.

[demonstar]

Thanks. I did search before I posted but I was just a little unsure about it because although it is praised highly here seemed to be a lot of mods to it and people having difficulties with it and I was just wondering how it sounded without the mods. I'm just gona' go and build it anyway. I've aranged a stripboard layout already. I just need to go and get the parts.

[Mark Hammer]

Thanks. I did search before I posted but I was just a little unsure about it because although it is praised highly here seemed to be a lot of mods to it and people having difficulties with it and I was just wondering how it sounded without the mods. I'm just gona' go and build it anyway. I've aranged a stripboard layout already. I just need to go and get the parts.

1) People report having difficulties because it is regularly recommended as a great beginner project for newbies wanting to make something useful, inexpensive, great sounding, but simple enough for a newbie......at least most of them.  In other words, you hear about difficulties not because it is difficult, but because a lot of the folks attempting it and requesting help are just starting out, therefore likely to have some growing pains because of lack of knowledge or technique.  The circuit itself is not problematic.

2) Circuits that get modded are not necessarily poorer designs.  Indeed, some may consider moddable circuits as better designs because they permit custom tailoring.  In this case, a simple preamp stage is something that many different folks can find a different use for in their particular context, so again you are likely to hear about mods because of how many people have successfully and happily built it (include me there...twice), and because they could think of many ways to merge it with their needs.

3) How does it sound stock?  Fine.  Just fine.  It does everything that good buffering and a bit of gain ought to do.  That's not particularly exotic, but it is always useful and always compatible with ANY style of music or musical purpose.  As noted above, an excellent recommendation for a beginner and something that, if you can build things in a reliable manner (i.e., decent soldering, wiring, etc.), will be useful to you long after you've gotten jaded and bored with this fuzz, that one, or some other more obvious effect.

[Dragonfly]

Its excellent...the main mod i'd recommend is using a REVERSE LOG 5K for the gain pot...i believe www.smallbearelec.com stocks them.

[demonstar]

Mark you've put my mind at rest so thankyou!

I won't be using the 5k rev log pot straight away as I'd have to mail order it and I'm just going to get a 5k lin locally. I'll bear the tip in mind for the future. Maybe replace it at a later date.

[dmk]

the mosfet boost is an amazing circuit. i adore the sound of mine, especially with the gain all the way up. adding a master volume makes it more usable.
i always wanted a bit more gain from it though, so i simply made 2 and cascaded them with a switch to add the 2nd for more gain. also a cap (cant remember what value) to ground to smooth out the top end a bit when both are on.
really opened my eyes what a simple circuit can do.
i made a clip of it but never had the confidence to post it  its direct into my computer with a software preamp and speaker sim. the bad playing is my part of the equation.
http://www.52teenagers.com/dmks%20crap/mosfetboost.mp3
be gentle 

[markm]

I received many favorable build reports about this one here;
http://aronnelson.com/gallery/album76/Modified_MosFET_Booster_LAYOUT
-Or-
To make the biasing of the circuit easier, this;
http://aronnelson.com/gallery/album76/MosfetBooster_LAYOUT

[momo]

I received many favorable build reports about this one here;
http://aronnelson.com/gallery/album76/Modified_MosFET_Booster_LAYOUT
-Or-
To make the biasing of the circuit easier, this;
http://aronnelson.com/gallery/album76/MosfetBooster_LAYOUT

I did Marks MosfetBooster layout, sound great driving my Ruby and was easy to bias....I added a 16mm 100K pot, turned it about halfway,not even checking the voltage!, tried different positions on the bias pot, once the mosfet was "open", it did not make a difference in sound, biasing "more or less on the pot, as long as the mosfet was open, it was great!

[demonstar]

Thanks and especially for the sound clip Dmk. Don't ever be shy to post sound clips. It sounded great and I hope mine sounds that good.

I'm using the tonepad scematic and I've done my own stripboard layout. I've cut and drilled the board. I got all my pars today but the guy at the shop has given me a 4.7uF electrolytic cap instead of the 10uF. Does anyone know what the 10uF cap does? That way I can work out if it'l make much difference. I'm guessing it'll just mean the voltage is a little rougher from the battery but I could be well off the mark.

[MetalGod]

Thanks and especially for the sound clip Dmk. Don't ever be shy to post sound clips. It sounded great and I hope mine sounds that good.

I'm using the tonepad scematic and I've done my own stripboard layout. I've cut and drilled the board. I got all my pars today but the guy at the shop has given me a 4.7uF electrolytic cap instead of the 10uF. Does anyone know what the 10uF cap does? That way I can work out if it'l make much difference. I'm guessing it'll just mean the voltage is a little rougher from the battery but I could be well off the mark.

C2 looks like a smoothing cap for the voltage divider to stabilise the bias voltage.  4.7uF should still work fine.

[Mark Hammer]

The gain is set by both the 100uf cap and the 5k pot.  The cap sets where the boost will be applied to, and the pot sets how much.  If you drop the value of the cap, then the portion of the spectrum where the boost is applied is moved higher up.  So, for instance, you might get a treble-booster if the 100uf cap was changed to, say, 2.2uf or 1uf.   Just make sure to observe proper cap polarity.

When the resistance to ground that the cap sees gets larger, then the gain is reduced.  Lets put both these things to work for us.

Imagine you had two caps instead of just the one.  Let's have our stock 100uf cap and have a 2.2uf cap with its '+' end tied to the same on the 100uf cap.  The negative side of each cap goes to the outside lug of a 25k linear pot, and the wiper of the pot goes to ground.  We'll stick a 22k resistor between the wiper and each outside lug to get a better taper.

What do we have?  Essentially a combination full-range booster and treble booster.  In the middle position, the gain knob selects little or no gain from each type.  Rotate the knob in one direction and that resistance value between cap and ground gets smaller, yielding more gain, while the other cap sees greater resistance, making that path essentially ineffective in terms of setting gain.  Rotate it the other way and you get the other type of boost.  The parallel 22k resistors are there because 10k is probably not big enough while 25k is a little too high a value.  The added resistors also improve the taper a bit.  happily, there is no cap-related "pop" because neither cap ever stops seeing ground at any time.

Whether 2.2uf is the ideal value for attaining a treble boost function, I can't say.  It's just a shot in the dark and you are welcome to experiment with other values, starting with maybe 10uf and working smaller/lower.

See, I told you its a flexible circuit!   Just note that by saying it can be a treble booster, I do not mean it subs for something like the Dallas Arbiter Rangemaster.  What I mean is that it will apply more gain to the upper part of the spectrum than it does to the mids and bass.  No more, no less.  Whether than creates crunch on your end is entirely up to your signal path.

[demonstar]

Thanks Mark. It's not the 100uF cap I altered the value of. Im still using the 100uF one. It's the 10uF one at the start of the circuit thats become 4.7uF.

I've actually built it now and I'm debugging it. I've explained in this thread...

"http://www.diystompboxes.com/smfforum/index.php?topic=58631.0"