Sparkleboost build problem

[adgators89]

I tried to build the sparkleboost, but all i get out of it is a broken up fuzz sound.  anybody have this happen to them?  any possible fix?

[Dragonfly]

I tried to build the sparkleboost, but all i get out of it is a broken up fuzz sound.  anybody have this happen to them?  any possible fix?

well...we need more info...

which layout did you use (or did you make your own) ?

which fet are you using ?

did you check the pinout and verify it's orientation ?

is the fet biased properly (4.5v) ?

any parts substitutions ?

[adgators89]

I followed the schem that you posted.

in to .o022u to transitor socket.  2.2m resistor inbetween the in and the cap going to ground also.  and then 1m resistor going after cap to ground.

where you have listed the 100k trim, is that a pot, or just a 100k resistor.  if it is a pot, is it audio or linear.

I used theNTE458

no part substitutions

I  can not find my mulitmeter as of now, so I can not test for bias (don't really know ho to do that anyway)

any help would be appreciated, thanks

[Dragonfly]

I followed the schem that you posted.

in to .o022u to transitor socket.  2.2m resistor inbetween the in and the cap going to ground also.  and then 1m resistor going after cap to ground.

sounds correct so far...assuming you meant .022u cap, not .0022u ...

where you have listed the 100k trim, is that a pot, or just a 100k resistor.  if it is a pot, is it audio or linear.

its a 100k trim pot. its used to adjust the bias. alternately, you could wire up a 100k linear pot as a variable resistor (connect lugs 1 and 2 together, then connect lug 3 to the battery 9v+, and lug 2 to the "drain" of the fet), set the fets "drain" voltage at 4.5v, measure the resistance, and use a regular resistor of that value in place of the trim pot...but its MUCH easier to just use a trim pot in the first place.

I used theNTE458

good...thats the fet i designed the circuit around....

no part substitutions

if you didnt use a 100k trim pot, than there "is" a substitution...a VERY important one at that ! Different fets need different resistance values to bias proerly, and a 100k resistor will rarely be the correct resistance.

I  can not find my mulitmeter as of now, so I can not test for bias (don't really know ho to do that anyway)

heres how.....

..with a fresh 9v battery hooked up, and a 1/4" plug in your effects input jack......

1)get your multimeter and set it to 20 volts.
2)take the black probe of your multimeter and touch it to ground
3)take the red probe of your multimeter and touch it to the "drain" of the fet

the reading you get will be your voltage...often, you'll get a 0v reading...slowly turn the trim pots dial while watching your multimeters reading carefully. the voltage reading should eventually register, and you want the final reading to be 4.5v

if your voltage is too low of too high, you'll get a very low, fuzzy sound, and very little actual boost...much like the sound you described.

any help would be appreciated, thanks

get the 100k trim pot installed and bias the fet following the directions above...and keep me informed on whats going on

Best of luck,

Andy
Dragonfly FX

[adgators89]

ok, have to get a 100k trimpot and I'll go from there tomorrow.  I will let you know the progress after I try that

[Dragonfly]

ok, have to get a 100k trimpot and I'll go from there tomorrow.  I will let you know the progress after I try that

great !  i think it'll probably solve your problem...

andy
dragonfly fx

[adgators89]

yeah, it works now, I got the trim pot today and it worked right away.  the volume pot definitley works.  However I seem to have some problewms yet

1)  it seems that the other 5k linear pot doesn't do anything.  
2)  overall I think it actually loses volume though.  a

any suggestions on what to tweak or do from here

[Torchy]

crp

[adgators89]

ok, that would make sense then, I am playing through a ss amp at home, but I use a marshall tsl jcm2000 tube amp for live gigs with the band

I'll have to check it out through that amp as well

[Dragonfly]

Glad the trimpot issue solved it for you. As mentioned, the "gain" knob has far more effect when driving a good tube amp...with a solid state amp its fairly "subtle" effect...

on a tube amp, man, its beautiful

let me know how it works with your JCM2000....

Andy
Dragonfly FX

[Alpha579]

andy, have u ever tried removing the 2M2 res from the input? because it doesnt seem to be doing anything useful, it will drop input impedance very slightly....and what about replacing the input cap with a 10K res, make sure RF breakthrough will never be a problem...just some thoughts  

[Dragonfly]

andy, have u ever tried removing the 2M2 res from the input? because it doesnt seem to be doing anything useful

pop protection on true bypass...the pot sends any stray voltage to ground at the end of the circuit, the 2m2 sends it at the beginning....thats the "only" reason its there

and what about replacing the input cap with a 10K res, make sure RF breakthrough will never be a problem...just some thoughts  

havent tried it...the cap blocks any stray dc voltage from entering the circuit, but thats about all it does at that point in the circuit...i might try building one with a resistor up front instead of the cap, see what kind of difference it makes...but to tell the truth, i'm 100% happy with the Sparkle Boost circuit "as-is"  

[Alpha579]

andy, have u ever tried removing the 2M2 res from the input? because it doesnt seem to be doing anything useful

pop protection on true bypass...the pot sends any stray voltage to ground at the end of the circuit, the 2m2 sends it at the beginning....thats the "only" reason its there

and what about replacing the input cap with a 10K res, make sure RF breakthrough will never be a problem...just some thoughts  

havent tried it...the cap blocks any stray dc voltage from entering the circuit, but thats about all it does at that point in the circuit...i might try building one with a resistor up front instead of the cap, see what kind of difference it makes...but to tell the truth, i'm 100% happy with the Sparkle Boost circuit "as-is"  

well as of my knowledge, theres no dc bias on the gate, so pop prevention is unneseccary, as theres no charge on the cap...and the likely-hood of having stray dc on the output of another circuit is highly unlikely, and any that does should be scrapped imediately :wink:

[Dragonfly]

and the likely-hood of having stray dc on the output of another circuit is highly unlikely, and any that does should be scrapped imediately :wink:

while i realize this, the reality is that a cap costs a few cents, so having the extra protection is worth it to me...  

[adgators89]

allright, I drew up a little layout that I made of my perfboard for a visual.
hopefully this will help diagnose any problems.  I used all the values that you had listed in the schematic.

the address is here
http://www.geocities.com/adgators89

[Dragonfly]

allright, I drew up a little layout that I made of my perfboard for a visual.
hopefully this will help diagnose any problems.  I used all the values that you had listed in the schematic.

the address is here
http://www.geocities.com/adgators89

from what i can tell by the drawing, your layout should be fine...try touching up all the solder joints (esp to ground), quadruple check your pinout (DGS, flat side facing you), and make sure that the polarities of the electrolytic caps are correct....the sparkle boost, if built correctly, will give a TON of boost...so somethings not right if you arent getting a good solid boost from it.

have you checked the fets voltages at eack pin ? if so, what are your readings ?

Andy

[adgators89]

is that 20 volts ac or dc ( remember I'm new to this, never used a multimeter before)

[adgators89]

on my multimeter, It reads 10 then 50 then 250 then 500, those are my only choices, I do not have a setting for 20.

is there any other settings I could try?  I have no clue how to use this thing

[Dragonfly]

on my multimeter, It reads 10 then 50 then 250 then 500, those are my only choices, I do not have a setting for 20.

is there any other settings I could try?  I have no clue how to use this thing

"10" will work fine for biasing/reading the voltages on the fet

[adgators89]

where is the "drain" of the fet - is it after the transitor and before the 100k trim pot?