Get a little more boost from this?

[Ben Lyman]

I guess sometimes the simplest circuit can be the most useful, I threw this together on the bb and it sounds great. By having the variable caps tone control in front, it's kinda like an adjustable Rangemaster with a dirt control.  I was inspired by the Colorsound Booster but I wanted to make something very simple. Does it look familiar in some ways? I pulled it out of my brain but I know the variable cap idea is almost exactly like a Bazz Fuss Deluxe. Other than that, I think it's close to an LPB-1 with a dirt knobby or something. This marks the first time I ever slapped something together on the BB (without looking at any schematics at all) and got a winner.

R4 started as 10K but I think I noticed a little more volume with 18K. Going up to 47K R4 made it too dirty no matter what.
Unity is about 12:00 on the boost knob so it's actually very useable as is but I thought it would be nice to have a little more.
The trick here is to find a way to get a little more volume without adding any components! What would you do?

[nocentelli]

Smaller boost pot?

[Plexi]

As I can see, it's full throtle.
What you did is deal with the headroom of the transistor.

[Ben Lyman]

Smaller boost pot?

Or DIRT pot? Maybe I can throw a 1K across the pot to make it 500 ohms? Of course, that means adding a component! Oh well, I'll give it a try, thanks!

As I can see, it's full throtle.
What you did is deal with the headroom of the transistor.

Not sure what you mean. Is it already at max output? Maybe if I change the transistor to a 2n5088, would that be louder with the same components pictured here?

[GibsonGM]

I'd just add another stage...

[Ben Lyman]

I'd just add another stage...

I know, that's the obvious answer but I just want to see if I can do this with a ridiculously low number of parts.

I tried the 500r dirt pot but no difference. Next I will throw a 2n5088 in there asap and see what happens.

[Plexi]

I don't you'll get more output, but for sure more gain.
Sorry to avoid your principal request; but add an LPB/Escobedo Duende and you'll be happy.

[Plexi]

Simple as f*ck... and loud has Motörhead live. 

[Ben Lyman]

Simple as f*ck... and loud has Motörhead live. 

Awesome, thanks! I'm gonna try this with my vari-cap tone control in front of it and an A100K volume pot after.
It's clean sounding loud boost when you want it to be, yes? Not just dirty? I'll find out, thanks again!

[Plexi]

Simple as f*ck... and loud has Motörhead live. 

Awesome, thanks! I'm gonna try this with my vari-cap tone control in front of it and an A100K volume pot after.
It's clean sounding loud boost when you want it to be, yes? Not just dirty? I'll find out, thanks again!

You're welcome!
Yes, is clean: there's a Mosfet version too (but I didn't tried yet)
The 1M pot funcion as master, and remember to bias the 25K trimer to get 4.5/5v at Jfet drain.
That way you'll get max headroom without distortion.

A copy of this design is the JHS Minibomb booster

BTW: I have a LPB inside my tester box, with on/off switch to test about add another recovery/boost section to circuits that are low on output.

[Ben Lyman]

Well Plexi, it does sound great in it's stock form... unfortunately I can't get the variable input caps to have any effect on the tone 
I don't think I did anything wrong but I'll have another go at it later. it's so weird, the tone caps were like magic in the first creation but do nothing at all in the Escobedo thing

[GGBB]

Smaller boost pot?

Or DIRT pot? Maybe I can throw a 1K across the pot to make it 500 ohms? Of course, that means adding a component! Oh well, I'll give it a try, thanks!

BIGGER dirt pot - try C10k.

[samhay]

If you want more volume, you want to get as much swing out of the signal as you can.
What is the collector voltage with R4 = 10k, 18k and 47k? You want this to be at half supply.

[antonis]

What Sam said.. 
(if you intend to feed it from its own power supply, try something around 12 - 15 Volts..)


P.S.
Personal taste: I dislike BJT biasing with a single resistor (feedback or straight) - for some reason it makes me feel awkwardly..

[samhay]

>Personal taste: I dislike BJT biasing with a single resistor (feedback or straight) - for some reason it makes me feel awkwardly..

You and me both. And, for reference is not how it's done in the Rangemaster

[Plexi]

Well Plexi, it does sound great in it's stock form... unfortunately I can't get the variable input caps to have any effect on the tone 
I don't think I did anything wrong but I'll have another go at it later. it's so weird, the tone caps were like magic in the first creation but do nothing at all in the Escobedo thing

You mean in the Duende?
In that case, I suggest to place a ~100nf at the input (after 1M pot and before Jfet Gate).
Play with that value.
The out cap it's more like an impedance filter (If that exist  ): I tried to place there a 100nf and 47uF caps with the same result. You sould send that cap to ground to filter some highs, or use a 100k in series with it (Rat tonestack).

[anotherjim]

Your input tone control is working with the BJT input impedance & that's much lower than the FET.
To put it another way, the frequency dependant impedance of those tone caps is negligible compared to a 1M  input so the tone pot isn't changing the filter in a meaningful way.

You might get closer with the FET if you lower the input impedance either with a smaller pot than 1M or put a lower fixed resistor across the pot ends. You ought to be able to rescale the tone control values (caps down, resistors up), but that means more resistance in series with input and more noise.

A BJT with higher Hfe will raise the input impedance according to whatever the emitter path is worth & probably change your tone control again.

[duck_arse]

lucky lucky jim posted sensible about the jfet impedance, otherwise it'd be me rabbiting on about 1M//100nF filter cutoffs. so wot he sed.

did you [ben] once tell us you were going to buy a cro? did you?

[Ben Lyman]

BIGGER dirt pot - try C10k.

Excellent, I like that idea. thanks!

If you want more volume, you want to get as much swing out of the signal as you can.
What is the collector voltage with R4 = 10k, 18k and 47k? You want this to be at half supply.

Awesome, thanks! I didn't measure it but when you put it that way it starts to make sense to me. thanks!

P.S.
Personal taste: I dislike BJT biasing with a single resistor (feedback or straight) - for some reason it makes me feel awkwardly..

Oh, ok. I was trying to keep the parts down to a minimum but I'm not opposed to adding a resistor or two if it's better. So maybe a couple resistors from the Qbase to + and ground is a better way to do it. Is there a particular voltage to aim for when deciding the values? Like maybe +1.0v or something?

You mean in the Duende?

Yes, the Duende, it's still on the BB so I will mess around with it some more, thanks!

Your input tone control is working with the BJT input impedance & that's much lower than the FET.
To put it another way, the frequency dependant impedance of those tone caps is negligible compared to a 1M  input so the tone pot isn't changing the filter in a meaningful way.

AHA, I knew it! Thanks Jim, I guess having such a low input impedance is not so good, eh? Maybe I should try creating something with higher input impedance and then try to adjust the tone control accordingly. There is some pretty cool magic happening with the sound. I really like the way it is cutting the bass, especially when I'm on a neck pickup or humbucker.

lucky lucky jim posted sensible about the jfet impedance, otherwise it'd be me rabbiting on about 1M//100nF filter cutoffs. so wot he sed.

did you [ben] once tell us you were going to buy a cro? did you?

Yes! Lucky indeed. I actually kinda knew it in the back of my mind but I couldn't form the thought.
What's a cro? I don't think I ever bought one

[Tubebass]

Cathode ray oscilloscope.