Belton Brick ungooped -- it's what we thought

[culturejam]

Okay, now I understand it a bit more. They have it set up like a typical Schmitt/integrator LFO, but they used an actual Schmitt IC and then the op amp integrator, instead of just using two regular op amps for both parts. Not sure why, as that would make the footprint a lot bigger. Maybe better performance?

Anyway, it could be done with a dual op amp. Maybe they did that on the smaller bricks.

[micromegas]

It seems to me that certain builder already knows the answer...

Here are the guts of a famous reverb pedal:

[Thomas_H]

Which one is that?

The layout does look a little homemade.

[micromegas]

Which one is that?

The layout does look a little homemade.

[selfdestroyer]

I believe the Malekko Chicklet was the same way also.

[destro]

Cool! Thanks!!

Did seeing the guts unveil how the modulation is being introduced into the circuit? There has been discussion of whether the short bricks have it verse the long. Would be another nice thing to have control over.

As was mentioned a few posts up, the larger older brick is the one that was degooped. That one doesn't seem to have nearly the same level of modulation as the newer smaller bricks.

Check out this hand-drawn trace from the same Russian thread:
http://i.imgur.com/9lfFsu8.jpg

The interesting thing (to me) is the single Schmitt Trigger connected pins 13/14 on the middle PT2399 (but not the others). I haven't really had a deep look at the whole schematic, but it would seem that Schmitt is set up as a dead-simple relaxation oscillator that is (maybe?) filtered by the internal op amp on pins 13/14, which is then used to oscillate pin 6 (delay time). Not exactly sure yet how it all works together, but it will be something fun to chew on for a while.

That alone is a really cool thing to explore. But I would be careful in proceeding with that because the circuit is covered under a real-deal patent. 

[Ettore_M]

Oh indeed it's patented! I read that on FSB a long time ago! 
However, we could do a reverb project that uses 3 PTs, based on the existing DIY PT2399 reverb projects which are out there, and not use this patented scheme. Maybe like the Merlin's Equinox and another design that I can't remember at the moment, Solstice. 

Hector

EDIT: I checked the Equinox and I don't know if the two circuits are any comparable in terms of circuit design logic. If you know what I mean.

[Ettore_M]

It seems to me that certain builder already knows the answer...

Here are the guts of a famous reverb pedal:

BTW, I think the Malekko reverb is nearly as old as the Belton brick. Or am I wrong?
How could he know and design the thing almost identical, from what it seems? 

Hector

[jkokura]

Mostly because I don't think it's ever been a well kept secret that the Belton Unit was based on cascading PT2399 chips. It's not a new idea. I remember seeing this posted on 6 or 7 years ago at DIY Stompboxes, and other guys saying that this had already been a topic of discussion before.

Jacob

[RobA]

What about that circuit is patentable? It's the freaking spec sheet applied to a standard digital implementation of a reverb effect. They are certainly ways to do this better with cheaper parts too.

[midwayfair]

What about that circuit is patentable?

Well, you CAN patent implementation (see: Mesa Boogie). That doesn't mean it's a robust patent that will stand up to challenge. Thus, the goop.

Interesting tidbit: Once again, goop was used to hide something that wasn't exactly original. People still would have used the bricks if they'd known what was in there ... the things are super convenient.

[icecycle66]

I wonder if the goop wasn't just for hiding, but for protection and uniformity of the single item.

I would rather the gooped box with the not very scary pins poking out that a little computer chip with a bunch of stuff on it. Since most of the user are not deconstructors and the security of a patent (no matter how weak or strong), this particular case of gooping may be just as much of part of the product as it is in securing against reverse engineering and cloning. 

[RobA]

What about that circuit is patentable?

Well, you CAN patent implementation (see: Mesa Boogie). That doesn't mean it's a robust patent that will stand up to challenge. Thus, the goop.

Interesting tidbit: Once again, goop was used to hide something that wasn't exactly original. People still would have used the bricks if they'd known what was in there ... the things are super convenient.

Well, part of the concept of patenting was specifically to stop people from gooping things to hide them. Thus the name. Really, the goop should automatically invalidate the patent -- not that anything about the way patents are currently regulated gives me any hope that it would happen that way. I do understand that you can patent pretty much any implementation, no matter how lame, but I have a moral problem with the practice of patenting things that really shouldn't be. This just made me kinda grumpy.

I agree with you too. The goop was pointless both from a copying and marketing standpoint. It wouldn't have stopped anyone from copying them and it wouldn't have significantly altered their sales. Maybe it was just to make it feel more physical, more spring tank like.

[jkokura]

Except, you guys keep looking at it as 'goop,' meant to hide things from sneaky people. I don't think that's the case at all.

The original purpose of these things were standalone reverb additions for amplifiers. Certainly the use was expanded to pedals as well. The smaller form factor works better for pedals and was released less than 2 years ago.

I think the 'goop' as you call it is more about packaging and protection. These units are meant to work, as they are, in one form. Exposing the circuit makes for a less reliable, less identifiable device, and exposing it adds no benefit to anyone. It's not about hiding from hackers, but hiding from the elements (read inept technicians). As I said before, Belton never really was about 'hiding' things. It's not really like they're hoping nobody figures it out, they've sort of been saying it for a long time - three cascaded delays create a spring like reverb.

Jacob

[RobA]

I certainly see that as an angle, especially if they are more potted than gooped, but I really can't see how potting it is any better than just putting it in the little case. The little case makes perfect sense to me. It is designed to be a replacement for a spring tank after all. But, I still can't see even attempting to patent this circuit.