Slapback Echo

[bluebunny]

Will you be selling PCBs at Druid HQ, Tom?

[ElectricDruid]

Will you be selling PCBs at Druid HQ, Tom?

I might do in due course. The first-draft PCB I used is in a 1590B, which is pretty tight. Possible, but tight. I was thinking about doing a redesign for a 125B which would give people a bit more space and make the build a lot easier. Plus the jacks could go at the top in a 125B without the controls finishing up in the middle of the pedal.
I've got a couple of spare boards, so email me if you want to have a go with the little board.

[Mark Hammer]

Are you assuming 1/4W resistors or 1/8W?  Horizontally or vertically mounted?  And would using a SIP TL072 make for an easier fit?

[ElectricDruid]

Are you assuming 1/4W resistors or 1/8W?  Horizontally or vertically mounted?  And would using a SIP TL072 make for an easier fit?

I'm assuming big resistors, horizontally. You could certainly get it smaller, and to be fair I think either you or Bunny or similarly experienced types around here would have no problem building this as it stands.

Here's what mine looked like (not fitted DC wires yet):



It's not impossible, but there's quite a few things with tolerances you need to watch out for. I used those little square Lumberg Jacks, for instance, and something larger would be probably be too big. Simialrly, the electro caps are all 10mm tall, and they're level with the top of the enclosure. Anything taller and you wouldn't get the back on.
Like you, I've been doing this pedal-building thing for a while and I knew to watch out for those things, but I'd like to make the project more beginner-friendly if possible. Making the box larger makes that much easier and gives a lot more leeway for everything.

[Mark Hammer]

An entirely reasonable approach.  And yes, choice of in/out jacks can often make the jack placement and machining of an enclosure easier or harder.

I still insist that the principle reason that MXR used tantalum caps, instead of upright electrolytics, is because the tantalums were much easier to lay on their sides, so that the enclosure back would fit.  Now that electros have gotten much smaller, it's not an issue.

[Ben N]

I think your approach makes more sense, Tom, but, interestingly, EHX claims that "the GAIN knob boosts your dry signal before it hits the BLEND knob and the echo circuitry." I'm not sure how they do that without overloading the BBD, unless they have a compander in there, and that makes even less sense--boosting into a compander. Then again, they also say "the dry and wet signal are both boosted by the GAIN knob," so make of all this puffery what you will.

[ElectricDruid]

I think your approach makes more sense, Tom, but, interestingly, EHX claims that "the GAIN knob boosts your dry signal before it hits the BLEND knob and the echo circuitry." I'm not sure how they do that without overloading the BBD, unless they have a compander in there, and that makes even less sense--boosting into a compander. Then again, they also say "the dry and wet signal are both boosted by the GAIN knob," so make of all this puffery what you will.

Meh...if they contradict themselves, you can kind-of choose which version you want to believe, can't you?!?

I suspect "Boost after" is more likely, but if they've got a 15V power supply inside the box and a full-voltage BBD, I suppose a x10 boost before the BBD is just about possible. If you assume a 1Vpp input, then x10 gain isn't a total disaster. What's the headroom through the BBD on 15V, do you think? 10 or 12V, maybe? So it's possible, at least. It has the advantage of giving you a better S/N ratio through the BBD␈.

Anyway, *I'm* not going to all that trouble. I'll keep my version nice and basic and simple, thanks.

[Ben N]

Here's what mine looked like (not fitted DC wires yet):

I just get comfort from knowing that the Electric Druid's box caps sometimes bear the scars of too-close-for-comfort- encounters with a soldering iron, just like mine! 

[ElectricDruid]

I just get comfort from knowing that the Electric Druid's box caps sometimes bear the scars of too-close-for-comfort- encounters with a soldering iron, just like mine! 

Lol, yep, I'm not immune! Was trying to solder that damn switch in and not focussing on everthing else!