'SPITFIRE' Metal 'n' Blues Pedal...

[JebemMajke]

OK, no ups in gain with BF245. Since i don't have time to order and wait for j201 and I do have lots of BF245 (a,b,c) around can i just use them instead or would i have to bias it differently? And again the same question how to get more gain out of this pedal?

[DavenPaget]

OK, no ups in gain with BF245. Since i don't have time to order and wait for j201 and I do have lots of BF245 (a,b,c) around can i just use them instead or would i have to bias it differently? And again the same question how to get more gain out of this pedal?

You could use the same bias , but the gain will drop 25% .
I'm afraid i don't know , J201 are the highest gain FETS i know ... i believe .

[WGTP]

The Spitfire is tuned to have lots of treble boost thru the circuit and then roll it off at the end.  There isn't much left to boost the highs except the R6 change.  You can tweak the 2.2nf caps at the end for treble adjustment, but it won't effect the gain.  I would start with changing R6 to 100k as this should boost all frequencies.  Then try the others.  The others changes will mostly boost mids and lows. 

Suggestions to increase gain that will also alter the tonal balance.  They could also increase oscillation problems:

Change C6 to 68nf or 100nf - more bass
Change R6 to 100k or a 470pf/470k resistor network - more highs
Change C3 and/or C7 to 4.7/10uf - more mids and bass

[deadastronaut]

^what dave and wgtp said:...

imo j201's are the best!...if using other fets you might wanna breadboard it, and experiment.


i think it has plenty of gain, its the eq adjustment like wgtp said really that'll make it 'seem' like theres more gain , and going by my lengthy experiments with different tone controls too i found that to be true!....

[waltk]

Question for Rob (or anyone else who knows)...

Why are R1 (560k) and R8 (1M) different?  Aren't they both there just hanging off of the 10k divider to bias Q1 and Q3 to 1/2 9V?

Edit: Also, why a 10k divider?  Wouldn't a 100k divider work here?

[deadastronaut]

i just went by the russian version setup..and altered the 510k to 560k....
http://www.diystompboxes.com/smfforum/index.php?topic=93909.msg808943#msg808943

no idea on the actual purpose though...

[waltk]

i just went by the russian version setup..and altered the 510k to 560k....

OK.  Anybody?  It wouldn't make much difference if they were both anywhere between 500k and 1M, right?  Are they even neccessary?  What effect would it have to remove them altogether and just bias directly off the voltage divider?

[WGTP]

This bias method is a Mod to the original Mu amp Jack Orman presented by R.G.  It is called "noiseless biasing".  IIRC R.G. used a 1 Meg, but I suspect your right that anything down to 500k would work.  I don't think you can leave that out, or R.G. wouldn't have used it, but I haven't tried it.  The Mu used a 1 Meg to +V and -V without a cap there.  Works fine, but may be more noisy. 

[waltk]

This bias method is a Mod to the original Mu amp Jack Orman presented by R.G.  It is called "noiseless biasing".

Yep.  Thanks for the reminder.  The last time I saw that page, I didn't really understand it, but it makes more sense to me now.  If I understand it correctly, the two 10k resistors in the voltage divider contribute less thermal noise than larger ones would.  The 560k and 1M resistors going to the Q1 and Q3 gates could be just about any high value.

Rob - nice work on this.  Thanks for sharing.  I'm gonna build one. 

[deadastronaut]

@walt:  cool, go for it!...you won't be disappointed...better than a standard bsiab imo..

i'm breadboarding another one just to have to tinker with, i'll try other stacks with it...


tip: that fuzz mode/cap, socket it, its really sick with a 47-100n in there...really deep, almost octave down-ish...just a fun option...

[WGTP]

I forgot.  Try it at 18v.  Use 2 batteries in series.  It's self biasing. 

[J0K3RX]

Anyone who doesn't build this is a sissy girl! This thing will knock yer nuts off

[deadastronaut]

 yeah, you big girls blouse's...


i have this on breadboard again..much to the delight of my cat...

anyway..

i'm doing another build, but with just the funk, setting...sustain on...and just one toggle for modern /classic....just for a simpler build...

tinkering at the mo with wgtp's mods......

[WGTP]

http://www.aronnelson.com/gallery/main.php/v/WGTP/Sweet+16.jpg.html?g2_imageViewsIndex=1

Apologies to Doug and everyone else.  I had the tone stack drawn wrong and didn't figure it out until I was simming it and couldn't get it to work right.  Try it again for a big scooped tone.  Sorry.     :

[deadastronaut]

aha....i'll give this tone a go now then!......i'm sure you'll be forgiven....

[J0K3RX]

Hi Rob, I figured I would give this thread a bump since I think this is THE BEST pedal I have built yet, and I have built a few! I posted a tone sample on the DIY Stompboxes facebook page but since there is only 138 members on there and there are 23768 on here I figured I would post it here as well... As soon as I saw your youtube vid I started building it... First pedal I have built in a long time that I have just sat and played for hours without turning a knob or flippin a switch, just dailed in a tone that I liked and went into wonderland! Had to go deep into my electronics junk pile to find a couple of the parts but I was determined to get it done... The tone pot and a couple of the caps came out of a 1980's boombox stereo that I picked up at a yard sale for $2 that I got just for rippin the guts out of!  Keep in mind that I am playing on a guitar that is slightly out of tune and it's somewhat sloppy but, I think it has "THE TONE!" I recorded it with no mixing of any kind going direct into the USB interface (Line 6 GX) and I am using a software cab sim with celestion 30w impulses, some software delay and lite chorus. I have since really dialed it in and it sounds unbelievable! Best pedal I have built and probably the best pedal I have ever played, period! It can do thrash metal to bluesy Satriani stuff all day long..! It has "The Brown Sound" as in I just crapped in my jockeys when I played it!  So, put those op-amp to the side and build this mutha!!!  
http://dl.dropbox.com/u/11178619/Spitfire%20TEST1.mp3

[deadastronaut]

@jok3rx

sounds really great man, ...nice clip n lick too......still got to check out that impulse lark..interesting stuff!..

glad you got it built...any pics?...


ive been looking into a way of doing away with the toggles and converting the switching to rotary....bit of a nightmare though!...

ive leant mine to a good mate, he's trying it out on his amp/setup...he must be happy, i haven't heard from him...

[J0K3RX]

Thanks Rob..! No pics yet but I will get a few tonight... It's just the guts, I haven't boxed it up and given it a final resting place yet... Waiting for some good parts to come before I seal it up! And "THANK YOU" for stickin with this and getting it to where it is today!!! Great Job to you and all that helped!

[deadastronaut]

@cheers jok3rx  jim..  look forward to seeing it in its full glory!...

+1 on the guys that helped too..

i tried wgtp's modern mod on this.(as i have it breaded)..the 2.2n where the 4.7n on the modern stack is...its nice n punchy...and feels nice and tight under your hand.......its got to be added to it.......its just got too...

hence the need for a rotary switch......still trying to get my head around it switching wise...hmmmmm..nightmare!

so this would be the shopping list for switching options:

modern 1 & 2
classic
hi cut
blues
fuzz

and just doing away with the sustain switch..always on..

but here is the bit that's doing my head in..i want to be able to choose between modern 1 & 2  plus all other options too...and the same with the classic with all other options...arghhhhhhhh my head!!!!!!!!!!!...

i'm sure one of you guys would go about it a better way....ahem!.... ...i would need a 6 pole  ?  way rotary right?....

[andymac1962]

no need for a rotary,   use a toggle   on - off - on
connect a 2n2 from the top of R11 to the top of the tone pot (effectively in parallel with teh switch & tone caps)
change C8 to 2n2,  and C10 to 4n7

in the top switch position the added 2n2 is in parallel with C8,  a total of 4n4   "modern 2"
in the center switch position we have teh added 2n2 only    "modern 1"
in the bottom switch position we have the added 2n2 in parallel with C10,   a total of 6n9   "classic"

i never worked out how to insert a picture into posts on here....