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Brian Wampler just released an interesting video on designing an overdrive pedal from scratch. Might be interesting for us DIY pedal types. I am watching today but if I have time after work I might have a crack at breadboarding the circuit along with the video.
https://www.youtube.com/watch?v=F-WHBgIowmU
Great Vid. Watched it all the way through. Maybe one day I'll get to play around a bit more like this on the breadboard.:cool:
Sometimes I wish I wasn’t such an (anti) op-amp snob =). But that looks like a fun project to try!
I find it interesting to read forum posts by people asking something like "what pedals did Tony Iommi* use on Paranoid?" only to be surprised that most of the answer is "none, they just recorded the amp at hell raising volume". But for those of us who can't just crank a tube amp, op amps, pedals, and modelling amps are a good solution.Quote:
Originally Posted by Joe Garfield
But hey, at least op amps are still analog. So it's possible to embrace op amps and still turn your nose up at digital :)
Myself, I love a good op amp. They are the basis of most dirt pedals on the market (except maybe for fuzz).
(Edit: hopefully this isn’t taking away from the thread - it looks like a cool project!)
Good points - my shortcoming (well, one of many) is not knowing what a ‘good’ op amp is. I know they exist in recording studios and stuff, but I also know cheap consumer ones can sound like crap.
Maybe in a pedal it doesn’t matter as much, and ‘cheap’ op amps might even have desirable sound!
I wonder if one of these would work:
https://sparkoslabs.com/discrete-op-amps/
Thanks for the link - I’ve never built a pedal and this looks like one I might try in the future.
It's not taking away from the thread at all. I enjoy these conversations wherever they might lead. While expensive op amps with "better" specs definitely exist (lower noise, tighter tolerances etc), they are not always that helpful in effect pedals, particularly overdrive pedals. My $200 modded tubescreamer sounds fantastic, as does my Barber CDD that I build recently. The op amp in both cost less than $2. I swapped them for a $0.30 4558D op amp I bought on eBay and couldn't hear a difference. In soft-clipped overdrives, the clipping diodes can make a much larger difference to the sound. In fact, it's all the stuff that surrounds the op amp (tone circuits, filtering capacitor choices, clipping diodes, number of gain stages etc) that makes most of the difference in sound.Quote:
Originally Posted by Joe Garfield
Also this: https://www.youtube.com/watch?v=PH2uj9bWfM4&t=2s
That makes sense - also the whole point is to add dirt! My bias came from putting together a hi-fi audio system for music (hybrid dual triode /discrete AB power with discrete resistor ladder converter) but it’s probably not the right approach to think what’s good for one is good for the other. Also the second video reminded me that guitar amps / cabinets naturally roll off high frequency which is where (I find) op amps show their shortcomings, so actually it’s probably the ideal place to use an op-amp!
Ah yes, high end hi-fi is another thing altogether. The stuff I build is decidedly lo-fi
An op-amp is an op-amp. It does what it does very well within its designated limits. That is, amplify a signal cleanly and with very low distortion. They all have slightly different operating parameters and need different support resistors and caps to make them work properly, but once you do, they work with very low noise and distortion (except maybe some of the early op amps like the classic 741, which was rather noisy).
Those discrete op-amps are basically a waste of money. They certainly aren't a drop-in replacement for the majority of existing op-amps, which will be chosen for their specific attributes, such as bipolar or jfet input stage. They are obviously much larger and so are unlikely to fit in as a replacement anyway. And as standard op-amps are so good anyway, any small improvement in the %THD figure would never be heard.
I think you are getting mixed up between an op-amp and a pre-amp.Quote:
Originally Posted by Joe Garfield
Almost all op-amps are cheap, typically well under $1 each when bought in bulk. They are just small chips, typically with 2 op-amps within each chip (though many other configurations are available). Most (unless designed for a specific purpose) have a bandwidth of at least 100kHz (and it is generally far greater), so it's not the op-amp that looses high end, it's the rest of the circuitry. And in the majority of drive pedals, the op-amp output signal remains clean, and is just used to raise the signal level into other devices that provide the actual distortion.
Either that, or it’s all the snake oil I was raised on :) It was either that or Diet Coke. Apparently if you drink enough of it, you hear magical things that don’t really exist. =)
Do these breadboard DIY pedals fit inside normal size stomp boxes?
You use a breadboard to try out designs and change components easily. They have push-fit connection terminals that make for quick assembly but not for long-term robustness. Once you're happy with the design, they you'd either make your own PCB, or transfer it to strip-board. It all depends on how compact you can make the design as to how big a box you need to fit it in.
All the micro-pedals do without a battery ability, and use surface-mount components for the most compact footprint. With mostly discrete, and all hand-soldered components, you're unlikely to ever get down to that generic micro-size box, but you should be able to manage to squeeze most pedals with 1-3 knobs in a small MXR/Boss sized box. If you've got 6 knobs on a pedal, then their physical size, and the spacing need to cleanly access each knob, determines the minimum size of box you'll need.
Simon has it right. Breadboards are used for prototyping or for building temporary circuits. They are noiser, prone to picking up radio signals, and fragile. But they are non-destructive, components can be reclaimed and used again. They are also easy to modify, letting a pedal designer quickly explore ideas: how would it sound with hard clipping?, what if I used a different tone circuit?, this is too bright, lets swap that capacitor. Last night I built a temporary circuit for testing JFETs then tore it down again. They also let me test a circuit to see if I like it enough to commit to a permanent build.
I don't etch my own circuit boards. For simple to moderate circuits I use stripboard where copper tracks are cut and links are added to make a circuit board for a specific layout. You can see the process in my recent build threads, such as the current Phase 45 build. They require more concentration to avoid mistakes compared to a circuit board as there are not so many guides to the correct location for a component. But they are significantly cheaper and quite fast to prepare. For more complex circuits I prefer to buy a PCB. I find very large stripboard builds exhausting.
Most micro pedals come in a 1590A enclosure. I built my buffer in one of those, but the circuit is tiny, there is no battery, no footswitch, and no pots.
I put most of my other builds in a larger 125B enclosure as they have lots of room for all the hardware. 6 pots and a footswitch will fit with care. But even though this box is larger, the fact that it has room to top-mount the input, output, and power jacks means the pedals can fit very close together on a board:
Attachment 34945
All up, it's a great hobby, and a great distraction from the time I have available to do other things, like play guitar.
Geez pedals have gotten a lot smaller in the past 10 years! Those look tiny!
They are not that small, it's just a bad photo. They are roughly the size of a Boss pedal, or maybe a bit chunkier. 122mm x 66mm x 39.5mm.Quote:
Originally Posted by Joe Garfield