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I build a lot of guitar effects, and that community is even worse when it comes to attachement to obsolete components. The discontinuation of J201 JFETs (in TO-
by PeanutNore 10y ago
I build a lot of guitar effects, and that community is even worse when it comes to attachement to obsolete components. The discontinuation of J201 JFETs (in TO-92 through hole package at least) by Fairchild has caused a lot of upset. My perspective, not widely shared, is that JFETs in general have been made obsolete by depletion-mode MOSFETs, at least in audio circuits.
Part of the reason, I think, is that a lot of "designers" of guitar pedals don't understand the math that determines component values for a particular transistor in a particular circuit so they don't know how to either select a modern transistor to replace an obsolete one based on datasheet parameters or to change the collector / emitter / source / drain / etc resistor values to work right with a new part.
- blackguardx 10y agoJFETs main application these days is for when you need very low noise, usually for precise measurements. A depletion mode MOSFET has similar behavior, but not specs.
- PeanutNore 10y agoYeah, I see them used for that purpose and for VHF / UHF applications. A lot of precision op-amps also have JFET inputs. In guitar effects land JFETs are popular because as a class-a amplifier in common source configuration they bias the same way that a triode does. Ironically when people try to replicate tube preamp circuits by cascading JFET stages the result is anything but "very low noise". Depletion-mode MOSFETs can be cascaded like triodes without creating unacceptable (for a guitar pedal) noise levels.
- bsder 10y ago> My perspective, not widely shared, is that JFETs in general have been made obsolete by depletion-mode MOSFETs, at least in audio circuits. A guitarist friend decided to "test" me once and put this in front of me and ask what it would sound like: http://el34world.com/charts/Schematics/files/randall/Randall%20RG100.PNG http://el34world.com/charts/Schematics/files/randall/Randall... My immediate response was: "That looks like a really great amp from the mid 1980's--looks like it was designed by someone who actually understands electrical engineering. It should have a pretty clean. But if you overdrive it, the clipping on those JFET's is gonna sound like fscking buzzsaw trash." He, of course, laughed knowing that Dimebag Darrell used the amp for precisely that buzzsaw sound. You would have to add lots of "clipping" components to get the same sound out of depletion mode MOSFET's. Now, whether that's a good sound is open to debate. :)
- PeanutNore 10y agoThere definitely are people who want that buzzsaw sound. The Boss HM-2 pedal "chainsaw" sound is also having a moment right now. I'm not really into either, but I do like really saturated high gain sounds with a lot of compression.
- retrogradeorbit 10y agoHM-2 on bass is really good. If my memory serves, Kevin Shields used the HM-2 on bass on some My Bloody Valentine tracks.
- jwatte 10y agoADC, MCU, DAC, done. Cheaper, too -- I think 50 cent ARMs can do that these days. Any pedal that isn't digital today is just nostalgia (like tube headphone amps and the like.) Digital is the clear better choice even for sound shaping.
- mb_72 10y agoNostalgia sells, yet another 'that digital crap' pedal may not. And many, many guitar players are dead keen on recreating classic tones of the 60's and 70's with period-authentic designs.
- ssalazar 10y agoIts not really that simple. Does the 50 cent ARM have accelerated floating point (though 32-bit fixed point is usually fine)? Does the analog design have a realizable digital model (not always possible/practical with non-linear systems)? Can a 50 cent ARM run the digital model at a high sample rate (needs to be 4-8x higher than normal audio rates to be able to filter out aliasing)?
- TylerE 10y agoA lot of times the "magic" is in the variance... the subtle things like drifting resistance values with temperature. Digital never does that right.
- busterarm 10y agoGuitar d00ds having obscure, nonsensical reasons for things because "mah tones!"? Say it ain't so. I mean, nearly every tube head on the market has an essentially pointless standby/bypass switch because of the mistaken belief that you need to warm up your tubes for some arbitrary amount of time in a modern amp and keep them warm. I forget which manufacturer it was that dropped the switch on one model and saw sales plummet and got freaked out support calls asking why the switch wasn't there. Next iteration had the switch back.
- failrate 10y agoIf I ever made analog audio equipment professionally, I would add an entire series of switches and dials that weren't wired up to anything.
- jandrese 10y agoYou could label them like "warmth", "aggressiveness", "heart", and have people go apeshit trying to figure out the best setting for their song.
- PeanutNore 10y ago"Girth"
- failrate 10y agoZest, Ennui, Anticipation
- zimpenfish 10y agoFrobulator on iOS has "orbit", "vexity", "doubt".
- WalterBright 10y agoBack in the 70's, a friend of mine created a formula where the inputs were number of switches, number of dials, and number of meters and would output the price. It was remarkably close at predicting the price of most any stereo receiver/amplifier in the stereo store. One standout anomaly was the Heathkit 250W amp, which just had an on/off switch and 2 meters.
- earlz 10y agoI'm a noob builder (constructed my first pedal a week ago, woo) but I can kinda understand this. Most effects tend to overdrive their components. This by definition means that they operate beyond what a datasheet and the manufacturer specifies. Tiny differences that aren't noticeable when going by the specs can become much more obvious when hearing it overdriven. Yes, the community is really based in "older is always better" kind of mentality, but there is a reason some old components are so valued, and why respected pedal manufacturers commonly hand-pick parts that meet their designed specs best (especially fuzz and overdrive effects), and this includes everything from picking transistors with ideal leakage etc, to hand picking resistors (though the resistor bit I'm not sure on why they don't just buy high precision ones for a few cents more)
- PeanutNore 10y agoThere's a difference between overloading components and overdriving them. If you overdrive an amplifier (the circuit element, not the finished product) all you are doing is presenting it with an input signal with a greater amplitude than it can faithfully reproduce at the output, causing it to distort. It can still be operating perfectly happy within the manufacturer's specs as stated on the datasheet. I think you're thinking of overload, which isn't something you would typically find or hear outside of a power amp stage, typically a valve one.
- guitarbill 10y ago> (though the resistor bit I'm not sure on why they don't just buy high precision ones for a few cents more) high precision resistors can get expensive, aren't always readily available (depending on your volume), or simply might not be available in the power rating you need. especially if you don't need absolute precision you might consider it wasteful. so it's good to know how to match resistors when you're designing/prototyping the circuit. because of that, it's probably become hearsay and superstition, and is consequently overused.
- busterarm 10y agoSeparate from my other comment. I'm pretty much switched over entirely to AxeFX for my guitar & bass setup these days but I've been building circuits lately and figure instrument & vocal effects would be cool projects. Any places I should get started looking?
- mdb333 10y agoI'm still resisting the AxeFx but being short on space and a growing stack of rack gear waiting to get fixed might push me over the edge soon :-] There's a pretty classic book called Electronic Projects for Musicians that might be of interest: https://msu.edu/~dougl126/Electronic%20Projects%20for%20Musicians.pdf https://msu.edu/~dougl126/Electronic%20Projects%20for%20Musi...
- busterarm 10y agoSold all my heads, pedals, cabs. Have just the Axe and a FRFR wedge now. Best decision I ever made.
- mdb333 10y agofolks are digging the kemper profiler too. Can't argue with the results but i guess im still addicted to analog.
- busterarm 10y agoThe profiler is okay and is likely preferred for people who already have a sample of the tone they want and aren't the kind that will want to fiddle.
- TylerE 10y agoThese days I'm mainly playing through my PC (Decent USB interface for input, my stereo via a good DAC for output). I've got a decent tube combo amp, but it's just easier and more flexible to do it digitally. I mostly run S-Gear, which I find has by _far_ the best amp modeling, it's the only VST that really gets moderate overdrive right.
- mdb333 10y agoTrue but i think a lot of that is in adherence to the original design/specs they're emulating (or straight up ripping off). Folks went nuts over the XVive BBD revivals or even still pay ridiculous sums for original panasonics. Sometimes there simply aren't alternatives to achieve the same circuit or you're repairing something very specific (although that's probably outside the scope of the article's PoV). As well there's the vintage issue...Sure, I buy NOS caps from the 50-70s for guitar tone circuits. I doubt side by side they sound noticeably better but if you're building vintage it only makes sense to keep the 'tronics true to the time period.
- cr0sh 10y ago> I doubt side by side they sound noticeably better but if you're building vintage it only makes sense to keep the 'tronics true to the time period. In vintage radio repair, they sometimes will replace old caps (usually electrolytics) with new ones, but put the new ones inside the old cans - to preserve the look of the device. Obviously, though, this won't work with all parts...
- PeanutNore 10y agoThis works well with electrolytic caps because modern ones are so much smaller for the same voltage and capacitance rating than older ones were. You can also hollow out old carbon comp resistors and put metal film resistors inside them. As a bonus you could use resistor shells on the outside with color bands that don't at all represent the actual value of the resistor inside as a practical joke on anyone trying to clone the circuit.
- WalterBright 10y agoOld car dash instruments are often upgraded the same way. They use new parts to drive the original indicators so it all looks correct, but is actually accurate. There are even kits to replace the guts of old car radios with modern stereos while preserving the controls and dials and their function.
- cr0sh 10y ago
- tawayway 10y agoDepletion MOSFETs seem to have availability problems. My local distributors only have a dozen or so models, mostly SOT-23. I can see why DIYers are not all over them.
- PeanutNore 10y agoIt's definitely true that there just aren't nearly as many depletion mode parts as there are enhancement mode. I've never tried getting them from anywhere other than Mouser. For my purposes I stick with LND150s and DN25XX / DN35XX parts.
- tnecniv 10y agoYeah I've also seen a lot of voodoo talk in that community as well. I'd buy some things, like germanium vs silicon transistors, but most of it I think is cargo cult behavior.