Another BTDR Reverb

[samhay]

The resurrection of Rob's 'Dead Astronaut Reverb' thread got me thinking about the BTDR bricks again.
It seems that all the designs I have seen are, quite understandably, based on the data sheet example. I figured I would start from scratch and this is what I have came up with this evening.

- The mix pot lets you pan between ~100% dry to ~100% wet, which gives you more of an 'effect' than a reverb in places - the totally wet signal can do some nice swell effects
- I figured the 2 outputs on the brick must be good for something, so I used one for the feedback, which is 100% wet, and the other for the mix. It will just self-oscillate when maxed. Using only 1 output knocks the signal down, which is why the dry signal is also halved before the mix pot. The second op-amp make up the gain
- The filtering, which is minimal, is a switchable low-pass before the brick. This makes sense to me as you tend to lose the highs first with reverb. This differs from the data sheet, which uses a ~ 700 Hz HP before the brick and then most 'tone' knobs put a LP after the brick.

It's getting late. Will endeavour to post some sound clips tomorrow. In the mean time, any comments are most welcome.



Edit - did my usual trick of drawing it with the op-amps upside down again. Schematic has been updated.

[John Lyons]

It will just self-oscillate when maxed.
Interesting!

[samhay]

It will just self-oscillate when maxed.
Interesting!

Actually, it is probably better to think of it as an infinite repeats option, which the other BTDR designs with feedback can be made to do. It does seem to self-oscillate some times, but this is probably a consequence of the mess of wires on the breadboard.

[deadastronaut]

ahhh cool so you have a brick on breadboard too...

i like the cap switch idea, as it can get  thin on the fully wet..

[samhay]

I do now - thanks for the motivation.

With the 47n cap in the filter, it can get pretty dark, so the 3 options - no filtering, 10n and 47n - seem to cover most of the basses. However, there is minimal HP filtering into the brick, so with a wet signal and the feedback/regeneration turned up it can get a bit muddy. I may end up with 2 filter switches - one HP and the other LP.

I came across another design this morning - the 'All-Star' reverb by induction (try the other forum), which also uses one of the bricks outputs for feedback and the other for the wet signal out. It doesn't do 100% wet like mine, but the demo here is not bad: http://www.youtube.com/watch?v=pnz_mtDOYkk

[deadastronaut]

yeah thats pretty cool...^

i really love the fully wet on mine but when fully wet it gets thin....it is a nice option though.


look forward to your clips man..

[samhay]

^i really love the fully wet on mine but when fully wet it gets thin

Yeah, I realised a few days ago that the filtering into the brick was a little different to how I would have done it - hence the breadboard adventures.
While you have yours on the breadboard, try replacing C5 (22n) with a larger cap - maybe 100n or even 220n.

[deadastronaut]

oh yeah...220-470n does it, thats more like it..

nice and thick lushness..

thank god for my cap sub box..

[samhay]

now you can add a dark switch too.

[samhay]

I have tweaked the design slightly to add a second filter switch - there are now independent LPF and a HPFs. The schematic has been updated.

I haven't recorded anything yet, but Rob somewhat beat me to it, and this should give you an idea of what it can sound like when mix is near fully wet and the filtering is minimal:
http://www.diystompboxes.com/smfforum/index.php?topic=101126.msg939381#msg939381

[deadastronaut]

looking good man, what does the regen do...act as a feedback from output 2.?

[samhay]

Yeah, regen(eration) is the positive feedback of the wet signal back to the brick.