fal treble booster from 67

[LucifersTrip]

thanx for doin all the work!  ...a cool Rangemaster variant. Did you make a note of the voltages?

so you have this:

[pinkjimiphoton]

yep, that's it. all she wrote bro!!

i'll write the voltages down tomorrow, and check the hfe of the ac128

seems like the hotter the transistor, the better it sounded. not harsh at all!!

[LucifersTrip]

yep, that's it. all she wrote bro!!

i'll write the voltages down tomorrow, and check the hfe of the ac128

beautiful...I'll breadboard shortly and compare

seems like the hotter the transistor, the better it sounded. not harsh at all!!

yep...the input (especially) and output caps are larger than the Rangemaster

funny thing about this is that not enough people own it (like the Rangemaster) to know if it sounds "right"

[lion]

Jimi - I'm a bit confused.

What is the circuit we are hearing in your "stupid pedal tricks" demo?

You say it's a best guess, but would like to make it EXACT. As far as I can see the demo is posted before Gus's layout. So what exactly is the circuit in the demo - just curious?

lion

[Gus]

So the"final" built circuit does not have a .005uf(.0047uf) input cap?   Two .01uf/10nf in series like Synthi wrote as the input caps would be .005uf.  The only part in Synthi writeup that does not match is the 6.8k or 68k, the third band looks orange in the picture. 

[mac]

Note that the frequency transition of transistors will show up, moving the peak in Gus' graph to one side or the other, and/or narrowing the peak.
For example, a Matsushita 2sd352 will be more like a mid-high booster because of its very low Ft, an ACxxx will be more on the treble side but not so trebly, a Matsuhita 2sb175 will reveal more highs, and a silicon will be very bright.
Salt and pepper to taste

mac

[pinkjimiphoton]

hi guys,

all will be revealed...

i DID make a mistake on the vero, i'm late for a gig, so will have to fix it tomorrow...the output cap should be. 047u, not p...my bad.

the input cap i used.1, it's probably why it has such a nice fuzzy goodness...when i saw the 2 caps at the beginning of gus's sim, i thought that was supposed to show the capacitance of the guitar on the circuit...i'm still fairly new at this despite doing a lot of builds. monkey can see, monkey can do, but monkey can't articulate what he sees and does, ya know?

the existing video demo is for all intents a hornsby skewes treble booster, which works out to be really close to what gus figured out...so that's what's in the box right now. i'll be taking it out and replacing it with the circuit gus helped me with when i get a chance, and stick the other booster (which is silicon/npn and nowhere even close tonally) in it's own box.

i thought the .1 cap seemed kinda big for a treble booster...probably why it has such a nice sounding fuzz. i'll change it to .oo47 when i get the chance that should be close enough to the original circuit i guess.

that said, it IS a nice circuit and works great as gus envisioned...fix the one mistake in value on the output cap, and you should be good to go.

more later...i gotta all-day show outside...and am recovering from seeing the wall last nite.

[LucifersTrip]

i thought the .1 cap seemed kinda big for a treble booster...probably why it has such a nice sounding fuzz. i'll change it to .oo47 when i get the chance that should be close enough to the original circuit i guess.

I changed the schematic to .0047

[pinkjimiphoton]

thanks lu!

here's the corrected verified vero layout for the FAL treble booster as close as i figure we can get at this point.



i used this layout, for a transistor i used an ac128, hfe of 217. tried mp16b, 2n404, several 2scxxx's, 2n3906. to my ear, the ac128 won the shootout for tonefulness..
i socketed the power supply points, transistors, and electros so i could try it as pnp or npn...the pnp ge was so nice, there was no looking back.
i DID build mine with the input cap being .1u...very warm, lively fuzz. i'll make it a standalone box, and build the correct version of this circuit and house it in the FAL box.

voltages i got with a ps of 9.44vdc

e 8.44
b 4.75
c 4.73

so...do you think we can call this one done? lu, have you breadboarded this thing too?

really nice little circuit...i'm kinda a newb, was the hornsby skewes as close as i thought it was?

[pinkjimiphoton]

i went back and looked at this some more, and came to a realization.
mine does not HAVE the "small connector"...all there is is an input jack and an output cable. and the battery door, the battery was originally an "m" size...3.2v, obviously this one is set up to run for 9v...so no, i guess we still don't have the original circuit.

but...if it's out there...it'll turn up eventually!

[pinkjimiphoton]

fwiw, some pics of mine:



see? no third connector...input, output wire, that's it...



and the ciruit board i vero'd up:



i DID change the input cap to .0047, didn't really make as big a difference as i thought it would...more treble significantly, but still a real nice warm fuzzy distortion when the guitar is cranked,
very clear and bright when rolled back.

sounds GREAT in front of my dod250 clone.

i compared it to the hornsby skewes tb i had originally put in there...it's really close to the same circuit. that was using a 2n3906, this one sounds much warmer/better to my ear.

[LucifersTrip]

i went back and looked at this some more, and came to a realization.
mine does not HAVE the "small connector"...all there is is an input jack and an output cable. and the battery door, the battery was originally an "m" size...3.2v, obviously this one is set up to run for 9v...so no, i guess we still don't have the original circuit.

funny...i just finished a couple circuits and was ready to go for this...

Actually, what battery is in Synthi's ?

[Gus]

I would try two alkaline AA or AAA cells and see where the collector voltage ends up not changing anything else.

EDIT if I was to build a Si PNP treble booster I would use something like a TIP30
http://www.fairchildsemi.com/ds/TI/TIP30C.pdf

[pinkjimiphoton]

molded on the plastic case, it says an m size battery, and some other presumably brit number for the same thing.

i bet at 3v it will be fine. will have to try. i could go with the m size and see what happens, just hate to waste the bread on an 9 buck battery if i don't need to.

the original pictures synthy posted are apparently a different revision from the one i've got.

[LucifersTrip]

haha...sounds cool...so, just to be clear, we're doin' Synthi's version that has a 9V supply, which is this:


then, there's your box which has a 3V supply....which actually could be the same circuit, but we have no idea yet.

either way, I'll try it out later tonight

[pinkjimiphoton]

cool, lu,
lookin' forward to the results of your experiment.

i LOVE the sound of mine at 9v, i bet it gets a little fuzzier at 3.

[LucifersTrip]

just got done with a ton of experimentation...

I started with a low leak 80 hfe ge, 80uA leakage with 9.6V adapter. K = K from base to (-). All voltages below are (-)

The transistor turns on at around 2V (collector), which for me was 38K (250K pot subbed for the 68K). The V increases along with K. I actually got a decent tone all the way from 2.5V to to 8.6V (250K), but there is sweet spot in the 5 - 6.5V range (~60 - 90K). The 68K gave me 5.2V.  If you raise the V into the 6's, 7's, etc there's some treble loss...which might be better if you think it's too harsh at lower V.

With a lower gain transistor, you'll get a higher voltage on the collector, so you have to lower the K to get that 5 - 6.5V range.  The lower gain ones (< 50 hfe) in the circuit are totally predictable...less volume, less sharpness, etc, but still sound decent. ...and it's the opposite with higher gain. In the end, I went with a 2N398A with gain 110 and leakage 100uA. It was a little louder & brighter.

Don't use anything with higher leakage. Just like with the Rangemaster, it adds hiss.

I tried silicon with hfe ~ 130  and the collector voltage was higher than with ge with the same K. So, you have to lower the K to hit the 5 - 6.5V range.  For that transistor, I was in the 50 - 55K range for the sweet spot.  It really wasn't as bad or harsh as I expected, but I didn't like it nearly as much as the ge transistor.

The silicon turned on around 20K (2.5V), so I can't see any way that 6.8K can be correct if the other values are accurate.

I tried a 3V supply with the 110 hfe ge and it worked right off. The K value for the sweet spot was the same as with 9V supply (~60 - 90K) and the voltage sweet spot was around 2V.  Similar to using a low gain transistor, it simply wasn't as loud, sharp or bright...but still decent.

Final version:

[Gus]

A little off topic
I use an external bias control when I build a Si treble boost.  The resistor I adjust causes less of a change of input resistance and the high pass frequency.  Second image shows the change with different input caps

[pinkjimiphoton]

cool. well done guys.


now i just gotta work up a mojo layout for it.