Hermida/GGG Reverb

LooseCannon · Post by **LooseCannon** » 30 May 2011, 01:19

Hey guys, anyone have a perfboard layout for this?

reneshelle · Post by **reneshelle** » 30 May 2011, 23:38

You can convert the vero to perf if you like. Not perfect, but it will work

LooseCannon · Post by **LooseCannon** » 31 May 2011, 02:28

Thanks reneshelle.

How do I convert it to perf?

reneshelle · Post by **reneshelle** » 31 May 2011, 12:40

It's a pain... you make the 'tracks' yourself! But it can be done. You don't have to make all the tracks, only where a connection is needed.

Buy some vero?

LooseCannon · Post by **LooseCannon** » 31 May 2011, 14:01

Thanks man.

Yeah I guess I should buy some vero, i'm a noob and haven't worked with it before.

LooseCannon · Post by **LooseCannon** » 16 Jun 2011, 00:01

Just finished this build today with the vero layout, I built it into a 125 sized enclosure with no footswitch and battery. The reverb isn't working, I get a signal but it's like a bypassed signal- no effect no matter where the knob is.

Any ideas what could be wrong?

Thanks!

Steven_M · Post by **Steven_M** » 16 Jun 2011, 00:07

LooseCannon wrote:Just finished this build today with the vero layout, I built it into a 125 sized enclosure with no footswitch and battery. The reverb isn't working, I get a signal but it's like a bypassed signal- no effect no matter where the knob is.

Any ideas what could be wrong?

Thanks!

Did you remember the reverb brick?

LooseCannon · Post by **LooseCannon** » 16 Jun 2011, 00:10

Steven_M wrote:
LooseCannon wrote:Just finished this build today with the vero layout, I built it into a 125 sized enclosure with no footswitch and battery. The reverb isn't working, I get a signal but it's like a bypassed signal- no effect no matter where the knob is.

Any ideas what could be wrong?

Thanks!
Did you remember the reverb brick?

Of course I did, just didn't take a picture of it

LooseCannon · Post by **LooseCannon** » 18 Jun 2011, 18:08

Turns out I put the voltage regulator one hole too low

So now it's working and sounds great, didn't have much time with it but it doesn't seem to change the tone like other reverbs do.
I've compared it to my fender's reverb and the fender's decay sounds more like a splash because of the tank, and sounds a bit more washed out and less clean because of that (you might like that and you might not), the hermida reverb sounds pretty similar but is cleaner and there isn't a "splash" in the decay, you actually hear the trails, which might sound a bit fake.

LooseCannon · Post by **LooseCannon** » 19 Jun 2011, 00:44

Is it possible to add a dwell control to the reverb?

Thanks

monkeyxx · Post by **monkeyxx** » 07 Jul 2011, 03:04

LooseCannon wrote:Just finished this build today with the vero layout, I built it into a 125 sized enclosure with no footswitch and battery. The reverb isn't working, I get a signal but it's like a bypassed signal- no effect no matter where the knob is.

Any ideas what could be wrong?

Thanks!

which vero layout did you use?? could you post it here? that would be terrific

reneshelle · Post by **reneshelle** » 07 Jul 2011, 06:27

He used the same one as I used as a startingpoint

http://www.sabrotone.com/wp-content/upl ... Reverb.gif

monkeyxx · Post by **monkeyxx** » 07 Jul 2011, 06:40

thanks! your layout is amazing as well. I always seem to like Harald's layouts, too, good luck with those so far

gonzo1999 · Post by **gonzo1999** » 24 Oct 2011, 16:56

Maybe i missed it somewhere in this thread, but does anyone know which brick is used in the GGG/Hermida reverb? I see Small Bear offers 3 versions of the brick, with short, medium, and long decays. Thanks for any info!

monkeyxx · Post by **monkeyxx** » 24 Oct 2011, 20:03

that's up to your preference... I'm not sure about the Hermida/GGG... I think a lot of people, GGG, use medium... I ordered the Long, because that tends more toward my general preference, but the clips I've heard of Medium sounded really nice

LooseCannon · Post by **LooseCannon** » 24 Dec 2012, 20:51

I've noticed that the reverb adds brightness when the pedal is on, any way to get rid of that issue?

Thanks

gefi · Post by **gefi** » 04 Jan 2013, 13:51

un chitarist wrote:if anyone does need pcb (or layout in pdf format) for this reverb can contact me.

I need pcb and layout in pdf format
thanks

gfigliola@hotmail.com

danielzink · Post by **danielzink** » 04 Jan 2013, 20:08

gefi wrote:
un chitarist wrote:if anyone does need pcb (or layout in pdf format) for this reverb can contact me.
I need pcb and layout in pdf format
thanks

gfigliola@hotmail.com

That guy is long gone.

He got pissed when he asked for 10$ per layout emailed any everyone shot him down.

He had his account deleted..

I did this one - feel free to give it a shot (for free even !)

Dan

induction · Post by **induction** » 18 Jan 2013, 23:26

If anyone's still interested, it's pretty simple to add a dwell control to this pedal.

I breadboarded the BYOC 2-knob (I used a TL074 and a BTDR-2 medium brick), and the tone was nice, but I found that the reverb was pretty overwhelming at most settings (a miniscule pot rotation takes you from no reverb to too much), and the dwell knob didn't change the sound much but caused oscillations at higher settings. At very high reverb settings, the original signal disappears and you get reverb only, so there's a noticeable latency in the signal. Also, the circuit generated a noticeable amount of hiss.

Then I breadboarded the GGG and found that it behaved much better - much less reverb (though plenty is available at max setting) and no hiss - but alas no dwell control.

The two circuits are very similar:

I'm not an EE, but here's my shot at analyzing the differences. Please correct me if I screwed this up (I had to look up differential amplifiers on Wikipedia), and feel free to skip this part if you only care about how to add the dwell control:

There are some differences in regulator filtering/grounding and some different coupling caps, but they don't affect the sound very much. The only substantial difference in topology comes at the brick output. The BYOC uses both brick outputs and the reverb signal goes through an extra op-amp (inverting amplifier) stage before splitting the signal between the subsequent differential amplifier and the dwell control, which feeds back into the preceding inverting amplifier. If I've calculated it correctly, that extra inverting amplifier has a gain of about 8.3. The differential amplifiers both give unity gain to the dry signal, but BYOC gives unity gain to the reverb signal as well, while the GGG gives a gain of about 1/4. Finally, the GGG feeds an inverted reverb signal to the differential amplifier, while the BYOC reverb signal is not inverted. This means that GGG adds the wet signal to the dry in a 1:4 ratio, while BYOC subtracts the wet from the dry at 1:1, which might explain why the dry signal disappears at high reverb settings with the BYOC. When you combine the effects of both op-amp stages, the BYOC offers about 32x more reverb signal than the GGG. I'm not sure why the BYOC hisses so much, even with the knob turned way down (maybe it's just the extra op-amp), or why the dwell control doesn't do very much. Maybe someone can fill me in. If you want more reverb from the GGG at max setting, I imagine that the resistors in the differential amplifier section are what you would change. You'd probably want to keep unity gain on the dry signal and find another gain for the wet signal. One way to do that would be to use the BYOC values. If you want to reduce the reverb in the BYOC, you could reduce the gain of the inverting amplifier, or play with the wet gain on the differential amplifier.

My solution for adding a dwell control to the GGG is very simple, but works well. I start with the GGG circuit, and simply feed the extra output from the brick into an inverting buffer (with the unused opamp), through the dwell pot/caps/resistor from the BYOC circuit, and back into the first inverting amplifier that feeds the brick input:

It's kind of a hybrid GGG/BYOC circuit now, and I like it a lot. With the dwell knob at zero, it's pure GGG: nice springy reverb. Crank up the dwell and you get a new kind of reverb that doesn't sound so much like a spring. It's a shimmery, ethereal reverb that's useful for ambient sounds (if that's your thing), especially on clean tones. Definitely worth the $2 in extra parts, IMHO.

One good thing about this mod is that you're only adding to the circuit, not changing anything that's already there. So if you've already built it and you don't mind some point-to-point in your pedal (call it extra mojo if it makes you feel better) or maybe a small daughterboard, you can do it without starting from scratch. If that idea makes you cringe, you can at least audition the mod without much hassle and see if it's worth it.

You can get tails if you forgo true bypass: wire the input jack directly to the circuit input and put the stomp switch after the input buffer between points A and B (in this case you only need a DPDT stomp, or an SPDT if you don't want an LED). If you prefer true bypass, I would add a pulldown resistor to the input. Switch pop + reverb = yuck. (Unless that's your thing.) If you're indecisive, you can use merlin's trick and switch between tails and mechanical bypass with an SPDT toggle (in this case, don't use a pulldown). It won't really be true bypass because the input jack is always attached to the circuit, but the input impedance of op-amp buffers is high enough that it probably doesn't matter.

If you want to be able to switch tails and actual true bypass, you can use a 4PDT stomp and a DPDT toggle. I'll leave that as an exercise for the reader.

When I tried the tails switch with the BYOC, the difference between mechanical and buffered bypass was obvious because of the hiss. When I tried it on the modified GGG, I couldn't tell the difference. No hiss. YMMV.

Sooner or later I'll make a vero and post it here. Maybe someone else will beat me to it.

Something similar could be done to the Box of Hall, which is a pretty similar circuit, though it uses the extra brick output for the Damp control, so it won't be exactly the same. You could insert an inverting buffer (if you don't buffer Vref, you'll have an extra op-amp available; or you could add a TL071 or something) after the Damp pot, and split the output of that between the Reverb pot and back into the first inverting amplifier. I haven't tried it, so I can't say how it sounds or if it hisses. It's almost the same trick I used here, so it should be pretty straightforward, but if anyone's interested I can post a schem in the Box of Hall thread.

Hope this helps somebody.

induction · Post by **induction** » 07 Feb 2013, 18:44

As promised, here is a vero for the GGG digital reverb with dwell control. It is unverified. This layout accommodates buffered bypass with tails, or switchable buffered/mechanical bypass using the tails switch from my previous post. For true bypass, jumper A and B, use standard true bypass wiring, and add a pulldown resistor to the input. You can put it on the stomp switch between the circuit input and ground lugs, or add a column on the left hand side of the vero and run it to power ground (should be ok, I think; I haven't tried it).

Let us know if you build it.