The Formula № 5 was inspired by old tweed amps, most notably the 5E3 circuit. The character of the 5E3 is very unique. It has very minimal power filtering, low plate voltages, elemental tone stack, and does next to nothing to control the low end between gain stages, not to mention the under-rated output transformer and speaker. The entire system runs inefficiently resulting in a loose bass, greasy mids, cutting treble, and incredible grit – none of these qualities were ideal or intentional back in the day. In spite of this, over the past five decades the amp inspired some of the coolest, most sought after guitar tones ever recorded.
We’ve captured the unique qualities of these amps in the Formula № 5. For this circuit we felt cascaded JFET gainstages yielded the best result. They have a softer sound than MOSFETs. JFETs also have much more natural attack/decay than diode clipped rigs which are pingy on the attack and fizzy on the decay. We chose capacitor types that enhanced the midrange and burnished the treble.
We’ve captured the unique qualities of these amps in the Formula № 5. For this circuit we felt cascaded JFET gainstages yielded the best result. They have a softer sound than MOSFETs. JFETs also have much more natural attack/decay than diode clipped rigs which are pingy on the attack and fizzy on the decay. We chose capacitor types that enhanced the midrange and burnished the treble.
This versions has been modified slightly to make one of the stock resistors switchable. With the 2M2 in circuit you have "Formula No 5 mode", with it removed you have higher gain "More mode".
So the orange 100n and 1n caps are they supposed to be ceramics? i see there are other 100n's and 1n's in red. are they to be metal film or poly film?
ReplyDeleteI've seen some polystyrene capacitors in catalinbread pedals before... i love subbing polystyrenes in amps in place of the ceramic treble caps, much smoother than ceramic and not super edgy like silver mica's. I guess the original tweeds used ceramics though!
i'd love to see the catalinbread treble booster! I've decided I can afford to buy half and build half of these new pedals from them, very cool. one day i'll buy em all
I only use the ceramic symbol because there is only a 2.5mm pitch for those caps and if I use the red poly symbol at that pitch the text gets obscured. So I'd use poly for all of them, a box capis quite good for a 2.5mm pitch because you can bend a leg back then back out again to the correct gap, and it's all covered up when soldered by the box casing.
Deleteverified. try the more switch on a footswitch rather than a toggle, you can use it much better (nearly go from a mild crunch clean boost to a full on dirt channel)
ReplyDeleteTop man, thanks mate
DeleteI built this and tested it without connecting the switch, I guessed it should be the same as the switch in the off position (without the resistor connection). But it ended up sounding like a weird fuzz with an octave down effect. Is my mistake in omitting the switch or something else?
ReplyDeleteYes that's what it sounds like! With the resistor in circuit you get the Formula Number 5 sound, this was just an added bonus! :o)
DeleteI was hoping I might have come up with an original fuzz circuit by mistake :(
DeleteThanks for the help Mark
Can I omit the switch and just hard wire the 2m2 resistor on the board?
ReplyDeleteYes no problem, you just won't get the glitch fuzzy mode but that'll give you a stock Formula No 5.
DeleteOk, cool. So do I just place each end of the 2m2 where the switch wires leave the board (2m2 jumping over the ground wire)?
DeleteYep
DeleteMade this,Sound very good. Not sure what Vasil is getting with the 'weird fuzz'. I get a sharp full on distortion on the 'more' position. Sounds awesome, better than the stock to be honest.
ReplyDeletehttp://img10.imageshack.us/img10/8536/dsc001492.jpg
Nice one Vince, thanks for the pic
DeleteHi
ReplyDeleteCan J201s be used instead of the 2N5457s ?
extremely underrated, I built one and it sounds amazing in both modes, has some very thick chewy gain in the "more" setting. I'll try to get a video of it up tomorrow! Thanks again for what you do for the DIY community, you're helping me learn the basics quite easily.
ReplyDeleteThis comment has been removed by the author.
ReplyDeleteI'm wanting the dual foot switch and not a flip switch. Thanks again!
DeleteWhere abouts in the world are you doc?
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ReplyDeleteCould anybody please tell me how to get rid off that overwhelming bass response;-)? Would lowering the input(2u2)/coupling(100n) caps do the trick? My tone pot is almost always at max, how could i squeeze a little bit more treble out of it? Thanks!
ReplyDeleteHeiko
This is a good sounding pedal. I really like it a lot. Quick question - what does the 470p cap doing? I didn't have one and I have been trying different values in it. Thanks
ReplyDeleteIt creates the filter for the tone control, but I just noticed it should be a 47p anyway. Doh! As with most tone controls though, it's always worth experimenting to get the best tone sweep for your own taste that works well with your own gear.
DeleteActually just reading the FSB thread and it could be 470p (which is probably why I used that value in the layout). But socket and experiment would still be the best thing to do I reckon
DeleteThanks, I'll try it.
DeleteHey I built this today and it works, but the gain pot cuts out after 9 oclock and the tone knob seems to control gain more than it does tone. Any obvious place I should start troubleshooting?
ReplyDeleteI checked it out a bit and the gain knob doesn't work at all when the 2.2M resistor is in the circuit. I've checked for solder bridges and can't find any. Is it possible that my pot is just bad?
DeleteI have just built the circuit and agree with the general opinion that it is true to the original which is a great crunchy Fenderish sound and that the More option gives you a fairly high gain distortion bonus. I had no problem with lack of treble or gain although as it uses a Fender tonestack the tone and gain controls are quite interractive.
DeleteI tried 2N5458 jfets but they clipped too harshly giving a brittle sound but when I got my 2N5457's from Tayda and installed them the sound became just right. I like this one a lot.
Just finished this one up and it is quite nice. I think I'll box it up soon with the 2m2 on a stomp switch instead of a toggle. Can anyone help me understand how I would wire it if I wanted a second LED to indicate when the "more" mode is engaged?
ReplyDeleteJust built this. A lovely overdrive. I added a 250k pot at the input of this circuit, as I found it opens up the circuit to much lower gain settings. A necessary addition, as the without it, the lowest gain setting is still pretty distorted.
ReplyDeleteFinished this a few days back. Just wanted to add to the feedback. For me, this is a very organic sounding overdrive. I haven't been able to get a bad sound out of it. One of my favorite Catalinbread builds to date - heck one of my favorites overall. I do get some squeal when the "more" switch is engaged and the gain knob is maxed out, but I very seldom use the "more" setting, the gain range being pretty sufficient in normal mode.
ReplyDeleteNot too bright, not too dark - just right. And i don't know that I have ever had a tone circuit that allowed me to use the whole range of the tone knob like I can here. It is voiced perfectly to my ear. Very happy with this build....
I finished it today and sincerely it's one of the best overdrive I've ever played in my life!
ReplyDeletedo these jfets need to biased? i didnt see anything about the typical 4.5v at the drains and i'm getting anywhere from 3.8v on Q1 4.5v on Q3 and 9.3v on Q2 and Q4.
ReplyDeleteLooks like a mu amp topology - these usually don't need biasing - I think.
ReplyDelete9v on Q2 and Q4 is correct since theirs drains are sitting right on the 9v rail.
would it be possible to get the schematic for this? I imagine is coming from the fsb thread but I cannot decide which is the final one
ReplyDeleteHi there!
ReplyDeleteI just finished this, it sounds great, but the gain and tone pot both have no effect whatsoever..
I cut all the traces, checked the parts and all seems to be in order.
Any idea what part in the circuit could be the reason for this?
hm.. after reflowing some joints the gain starting working. After the tone as well. Probably some stray piece creating a bridge though i'm sure i checked very thorough.
ReplyDeleteNot really my cup of tea unfortunately. I like grainy, but even on low gain settings you still have that heavier grain sound in the background. Works great with volume, but not my type of gaincharacter I guess. It's funny, wasn't convinced by the youtube video but thought: In real life im sure it's better and i'll like it. This being the 3rd where I made that same mistake, i'm apparently good at judging pedals through youtube videos now haha
Actually seems like a simple On-Off switch would be all that's needed for engaging the 'More'-circuit? The DPDT isn't necessary unless you are going for a dedicated LED, but then the wiring would need to be different... Am I missing something? Tx!!
ReplyDeleteSo I got this working but I have a few questions
ReplyDelete1. It has been asked before but I am not sure if the answer was definitive. Should trimpots be used for biasing?
2. I am not sure if the response I am getting from the interaction of the drive and tone controls is right. First, if I have maximum gain the tone pot seems to have much less effect than if the gain is set to minimum. Also, in general, I find this to cut a bit darker sounding than the bypassed signal in any setting. Is this normal?
thanks
Is that a (on off) dpdt switch or a (on on)? thanks
ReplyDeleteOn/on
DeleteI put it all together but all i get us a squeal when it's on and it won't pass signal when its off. Any ideas?
ReplyDeleteI put it all together but all i get us a squeal when it's on and it won't pass signal when its off. Any ideas?
ReplyDeleteIf it won't pass signal when bypassed then you have a problem with your offboard wiring. Post the highest resolution photos of your build possible in the debugging section of the forum and we'll help you out
ReplyDeleteCould I use a 3M3 resistor instead more position in the switch to get a setting with less gain?
ReplyDeleteShouldnt there be a jumper between the bottom two lugs of the more switch?
ReplyDeleteIs the input cap drawn backwards on the layout? The schematics I found have the negative side facing the input.
ReplyDeleteDoes it matter?
http://web.fc2.com/jump/?url=http://homemadefx.web.fc2.com/formula5.BMP
http://3.bp.blogspot.com/-O3_NYJeXWw0/TxxRtec1RGI/AAAAAAAAAqA/2y4TQcCbMfU/s1600/Formula+No+5+Fixed.png
Built it, sounds great, but wasn't crazy about the treble cut tone control. So I replaced it with a Baxandall tone stack.
ReplyDeletehttp://guitar-fx-layouts.42897.x6.nabble.com/Catalinbread-Formula-5-with-Baxandall-Tone-Stack-tp38778.html
Help please needed.
ReplyDeletemade this twice on vero now and once on a pcb and got same result every time,nice clean sound but no gain,changed jfets pots etc same result,cant seem to get to the bottom of it.
Is this a preamp?
ReplyDelete