I picked up a broken one cheap -check R31 on the board scan, it's the second one I've seen like this, I'd assume it's caused by a wrong polarity adapter that's been daisy chained with another pedal -toasts the resistor, but the effect will still run on battery power.
that block of epoxy just made me all the more curious to see what what was under it, here's what I got
(http://img.photobucket.com/albums/v282/Axiomdrift/xxlboard.jpg)
(http://img.photobucket.com/albums/v282/Axiomdrift/XXLpn.gif)
Thanks a lot. Looks very interesting. Did yoy tried to breadboard it?
NICE ONE!
Nice! :mrgreen:
How do you know the correct opamp type?
That's pretty amazing. I have one here, but since it's not mine, I didn't have the nerve to remove the epoxy.
Wow! So the warp control just messes with the biasing of the drive opamp, and not a clipper in sight! Now what I would have expected. Can anyone tell us what is happening in there?
Thanks, J.
Ben
My 2 cents:
This Warp control and its surrounding resistors look strange to me. I would expect that on one end of the pot rotation the biasing would be Vcc/2 (symmetrical clipping). In fact, the values shown allow for positive and negative biasing around Vcc/2, which would produce basically the same sound.
Apart from the above, thanks for sharing it :D
STM
P.D. Some logical values in terms of the above would be: 22k for the upper resistor, then the 100K pot, then a 120k resistor. In this way, with the pot at minimum you have 22+100k above the wiper, and 120k below, giving perfect symmetry to the biasing. On the other end, you would have 22k on top, and 100k+120k below, giving a biasing point of 9V * 220/(220+22) = roughly 8V.
EDIT: I checked Tech 21 site and in fact the "middle" or normal position is slightly OFF-CENTER to the left, as the resistor values indicate! Perhaps they left the provision to be able to go to the LEFT of the CENTER position to absorb the tolerance of the pot. For instance, pots are specified usually as +/- 20% tolerance, so a 100k pot could be perfectly between 80k and 120k, which could not allow to get to the "CENTER" biasing in all production units. My approach, if I were to build something like this, would be to include a trimmer to take into account for pot tolerance and make sure one end of the pot is really the CENTER biasing point.
stupid question: what is it? :oops:
Read here:
http://www.tech21nyc.com/xxl.html
Samples are available also.
That 'Warp' thing sounds like a 'Presence' pot being turned fully down.
Whatever the circuit says...
Nice work!!
THanx 4 posting!
T
Thnx for sharin :D
The clips sound pretty cool.
Marcos - no I haven't breadboarded it, it's fairly straightforward and I didn't really have any doubts about my tracing
Arno - once I got to the point where I took the scan, I did some more carefull excavating with a dental pick and got enough of the numbers to make an educated guess. I also measured the current draw of the originals and compared them to others I had on hand. plus I later installed full size sockets to try different opamps and my ear agreed with that combo
STM - yeah, I was a bit puzzled by the "warp" implementation, my guess is it allows two simple "presets" for guitarists averse to knob twiddling - full anti-clockwise is pretty much the sweet spot, clockwise is full blown fuzz, the two sounds most would be looking for basically -if I were to build it I'd use an opamp to set the voltage division for either end of the pot, cheaper than a trimpot
-Jeremy
Jeremy, I agree entirely with your opinion on the preset settings. You did a very nice and thorough job on backtracing the circuit. Thanks again for sharing it.
Now, on another line of thought, everytime I see these Surface Mount guitar circuits I can't believe they will sound as good as if they were made with full-sized through-hole components. I can feel the mojo of through-hole! Of course someone 20 years older than me will make the same comparison between Solid-state and Valve circuits :lol: Does anyone here feel like me?
I spent some time with an XXL a few years back. I remember liking it direct into the fx return of my Rivera. Nice find for cheap, and thanks for the work you put into this.
Kerry M
Quote from: stm, everytime I see these Surface Mount guitar circuits I can't believe they will sound as good as if they were made with full-sized through-hole components. I can feel the mojo of through-hole! Of course someone 20 years older than me will make the same comparison between Solid-state and Valve circuits :lol: Does anyone here feel like me?
Personally, I prefer surface mount! but my commercial products are either through hole or a mixture (some useful components are ONLY made in surface mount now).
I agree certain IC's are mainly available in SMT, but what about metalfilm caps and stuff like that?
Since I have my boards made, I suppose it would be feasible to attempt some SMT circuits, at least with some of the larger SMT parts. It might be an interesting experiment to make a couple simple booster/distortion circuits, making a SMT and a traditional thru-hole version of each, trying to keep the part value differences to a minimum. Then *taste test* them. Which reminds me, I need to get one those desk lamps with the big magnifying glass in the middle.
Kerry M
I got a huge desk mount light/magnifier for Xmas...have no place to install it...has a large countersprung 'elbow arm' so you can bring it in' over the work and away...four screw mounting plate at it's base.
If you're interested in an unused unit, drop me a line...make an offer...It'd be nice, if I had a place for it.
I just got some 14 pin high quality dual op-amps from Ti, unfortunately they are SMD ( only available now in that format )
anyone know a "quick'n dirty" way to expand that out to a 14 pin dip socket ???
"Dead bug" wiring, would that work ?
I'm thinking of a couple of "Craig Anderton" builds.....
Marty
several companies make SMT to DIP adapter pcbs.
One i can think of right off the top is Aries adapters.
I think DIgikey, mayB Mouser, sell them.
Little on the pricy side.
Google "smt adapter" & C what U come up with.
I designed an adapter for 16pin SMT to 16pin DIP for a TI
headphone amp, but never etched it cause i ended up buying
an evaluation pcb.
Also, i discovered, i couldn't solder the SMT---ultra small..
staydownsized
tone
Quote from: MartyMartthey are SMD ( only available now in that format )
anyone know a "quick'n dirty" way to expand that out to a 14 pin dip socket ???Marty
For 'cheap' go 'ghetto'!
that is, get an old computer board with smt parts, remove the components with a heat gun, and cut off a chunk that has the pattern you want. Then you solder your smt chip to the board fragment and either glue it to the main board & run wires off to the relevant places, or soleder on stiffer wires & pretend they are legs.
You DID say CHEAP right? (yeah, i have done it for protos..)
Does anybody know what's the FET transistors used in this stompbox to make the bypass circuit?
Thanks,
Wagner.
I don't know anything about the XXL specs but typically the J111 is used in similar switching arrangements... you can also use the J113 --- DOD uses both of these for switching.
Boss uses the 2SK30A and Ibanez sometimes uses the 2SK118.
regards, Jack
Quote from: stm
Now, on another line of thought, everytime I see these Surface Mount guitar circuits I can't believe they will sound as good as if they were made with full-sized through-hole components. I can feel the mojo of through-hole! Of course someone 20 years older than me will make the same comparison between Solid-state and Valve circuits :lol: Does anyone here feel like me?
I don't like the look of them either, my Korg DT-10 tuner has them too, but then again I just think about how frickin small electrons are and I don't really worry about it.
You could always make it true bypass, or use mechanical switching in place of the FETs.
The Insanity pedal was designed after I had an XXL here. (of course) I liked the Insanity a lot better than the XXL.
Maybe now I can figure out how to clean it up. I like the tone of the XXL, but even at the lowest gain setting, it's way too dirty for me.
Roger
i've used that pedal a few times
i had the chance to compare with a bd-2 , green bigmuff, vintage bigmuff, and ds-2, including a classic tech 21.(in realtime)
it's not really special, sounds buzzy and has one sound for it.
it's gainy and buzzy without an special character.
Quote from: RodgreMaybe now I can figure out how to clean it up. I like the tone of the XXL, but even at the lowest gain setting, it's way too dirty for me.
(Assuming the J. Luja draw is 100% accurate) The first stage has a default gain of 100, and the second stage can't go any lower than a gain of 10 (albeit with a bit of attenuation between stages). No wonder it never really cleans up. Perhaps replacing R8 with 10k instead of 3k3 might help.
Um, are you sure those component values are right? With C10 = 47nf and R8 = 3k3, that gives a low end rolloff of 1026hz. While this is sort of counterbalanced by the high end rolloff at 4.8khz caused by C7, I'm not quite sure those components would yield anything more than a whiny tone. Is it possible that C10 = 470nf? Not questioning anyone's integrity, just the limits of the human eye when it comes to those SMT parts.
Wagner, I didn't make note of the fet part number, sorry, but as Jack has pointed out, there are several substitute parts that should work fine.
Roger, I agree with you there's not much range in the drive control, a good mod would be to add another gain control for the first stage. though all the important parts are under a brick of epoxy, you're better off building a clone and modding that.
Mark, I'm fairly certain of the component values, each of the caps were unsoldered and measured one at a time (there's no label, you wouldn't want a mix up) and the resistors are very clearly marked, especially on my high resolution scan. also a 470nf cap would be farily large for a ceramic smt I think they would more likely choose a tantalum package, as they did on the double drive. check out the interesting tone control though, it seems to compensate for the pre-emphasis and attempts to keep the perceived volume the same throughout its range.
-Jeremy
Well, you're right about the interesting tone control. Kinda clever. I like clever tone controls.
If my calculated roloff is accurate, boy oh boy that's a weird one.
If I'm reading this correctly, the input cap/resistor (C12/R21) form a high pass filter with a corner frequency of 590Hz. That not only feeds the circuit, but it feeds the bypass. I think I'll true bypass this one.
Quote from: Khas EvetsIf I'm reading this correctly, the input cap/resistor (C12/R21) form a high pass filter with a corner frequency of 590Hz.
nah, you got the math right, but you're reading it incorrectly. R21 is in series with R20 and R10, which (ignoring C11,C8, R12 ,the position of the warp control and the input impedance of the opamp for simplicity) makes the coner frequency at around 12Hz.
Quote from: RodgreMaybe now I can figure out how to clean it up. I like the tone of the XXL, but even at the lowest gain setting, it's way too dirty for me.
While I had the XXL on loan, I was considering using it just for it's high-gain, smooth *lead* tone (somewhere between Santana and Fusion), using other methods for edge-of-breakup and *crunch* sounds. But I found the GT2 I already had to be much more versatile overall, as it will actually clean up with the guitar volume.
Kerry M
G'day all,
To build this pedal true bypass would I be right in assuming that I would
leave out the two fets along with the input buffer and just hard wire the
level pot to the output buffer.
Cheers Ken.
I was about to ask the same question. Is the output buffer required? I was thinking about just putting a coupling cap and a pull down resistor.
I was also thinking about using one side of the TCL2262 to replace the TL072, but that will probably change the character of the circuit.