My "Digital Reverb Pan" Project

[Paul Marossy]

As I mentioned in another post, I went ahead and installed the GGG D-Verb digital reverb circuit into my Gregory "Mark X" tube amp, and I must say that amp sounds really sweet now!

Here are a few pictures with some details:

This is a view of the outside of the enclosure I fabricated specifically for this digital reverb circuit. I wasn't too concerned with looks as it's kind of hidden away inside the amp.


In keeping with tradition, I decided to use RCA cables to connect to my "digital reverb pan".


This is showing how all the parts are arranged inside the enclosure. The enclosure is actually 3-pieces of aluminum. One piece is from the bottom of a long RadioShack plastic project enclosure, which I bent as required. The other two pieces are 1"x1" aluminum angle left over from my recent pedalboard project.


The bottom of the pan is just a piece of card board covered with aluminum tape for shielding. When everything is together, it forms a nice shielded enclosure. Shielding this thing well is very important when it's around power and output transformers in a tube amp. When I first tested it, I didn't have it in an enclosure, and man that thing buzzed!


Here is a section of RCA cable ready for installation into the amplifier. I simply inserted this circuit between the input jacks and the first preamp tube. That way it's a permanent part of the amp, and I don't have to give up any real estate on my already crowded pedalboard.


Here it is inside the amp. The level control knob is easily accessed by reaching around the amp. Since I pretty much leave my reverb setting at one place, it's a "set and forget" kind of thing. I also added an emergency bypass switch just in case it's ever needed.


Powering the circuit was a snap since I already added a second power transformer for a DC powered cooling fan. All I had to do was add a new power cord from the transformer to a DC jack I mounted on the enclosure. In between the PCB and the DC jack is an LM317 adjustable voltage regulator set at 9.5V, just like what a new 9V battery will typically measure.

What I think is cool about this project is that when I first heard about the GGG D-Verb digital reverb kit, I instantly thought that it would be a perfect application for this particular amp and kind of an interesting experiment to try - but it actually working out so well is what is the coolest part of it all. Overall, I am very pleased with it, it sounds great! Now I have the best of both worlds, a great vintage tone with cutting edge technology mixed into it. I know some tube amp purists wouldn't approve,  but I think this is a lot simpler and less expensive than trying to add a tube reverb circuit and a spring reverb pan to an existing amp. Sometimes the way the amp is constructed really restricts what you can do in terms of adding tube reverb, so I think this is a good compromise.

[biggy boy]

Nice job Paul!!
The digital reverb sure sounds nice.
Do you get any power supply noise through the reverb?
I need to get mine off of batteries! I've eaten through three Duracells in about 3 hours of use.


Glen

[Paul Marossy]

Nice job Paul!!
The digital reverb sure sounds nice.
Do you get any power supply noise through the reverb?
I need to get mine off of batteries! I've eaten through three Duracells in about 3 hours of use.


Glen

No noise, I had that second power supply filtered pretty well already. Wow, it eats batteries quick! 

[mike_a]

Really nice work (as always), Paul!

From what I understand, you put the reverb BEFORE the preamp (and please correct me if I'm wrong).
Doesn't that cause problems when you overdrive it?
I mean, reverb before an overdrive can be quite nasty.

am I missing something here, or are you always running it clean?

[Paul Marossy]

Really nice work (as always), Paul!

From what I understand, you put the reverb BEFORE the preamp (and please correct me if I'm wrong).
Doesn't that cause problems when you overdrive it?
I mean, reverb before an overdrive can be quite nasty.

am I missing something here, or are you always running it clean?

Thanks. It's basically going to operate exactly like I use all of my other amps, my pedals will supply all of the overdrive & distortion sounds. I run all my amps clean and use pedals for the overdrive/distortion sounds that I want. Since it's the last thing in the signal chain before the first preamp tube, it's very similar to what I would have if I use any of my other amps in terms of the sound. Not optimum in terms of where the reverb circuit gets injected into the signal path, but it's acceptable.

My normal pedal order is this: Colorsound wah, AMZ Mini-Booster, Fulltone '69 clone, TS808 clone, Boss DD-5 delay w/ tap tempo box & Boss Super Chorus. The reverb will be after everything just like it is when I use any of my other amps. I will be playing it more and doing some testing with various pedals to see how it performs. I think it will be fine, but I need to spend a little more time with it.

[Paul Marossy]

I tried it with my normal pedal board arrangement today, and it sounded good. I think I can definitely live with it. 

[biggy boy]

I tried mine with a IC big muff in front of it, sounds wicked.
The dirty boost really makes it come alive.

[Paul Marossy]

I tried mine with a IC big muff in front of it, sounds wicked.
The dirty boost really makes it come alive.

I agree, but in my case a TS808 clone.

[d95err]

From what I understand, you put the reverb BEFORE the preamp (and please correct me if I'm wrong).
Doesn't that cause problems when you overdrive it?
I mean, reverb before an overdrive can be quite nasty.

In all the classic Fender amps, distortion is generated after the reverb (i.e. last gain stage, phase inverter, power tubes) and it seems to work pretty well... 

[Paul Marossy]

From what I understand, you put the reverb BEFORE the preamp (and please correct me if I'm wrong).
Doesn't that cause problems when you overdrive it?
I mean, reverb before an overdrive can be quite nasty.

In all the classic Fender amps, distortion is generated after the reverb (i.e. last gain stage, phase inverter, power tubes) and it seems to work pretty well... 

Hmm... if that's the case, then I am in very familiar territory! 

[wavley]

Boy that is pretty cool, I might have to try that!

[Paul Marossy]

Boy that is pretty cool, I might have to try that!

Glad you think so. 

If you do try it, please also check out this post: http://www.diystompboxes.com/smfforum/index.php?topic=77130.0
I think changing the 1M input resistor to a 100K might help lower the noise in the circuit, but I have not verified that yet.

Here is how it looks when the amp is completely back together again:

[ahermida]

Paul:

Very cool project! 

I want to make one observation: the board is simply supported by the pins coming out of the reverb module.  The opposite end doesn't have any support at all.  Since you're putting it next to the speaker, I'm concerned that the vibrations are going to weaken those pins as the pcb flaps up and down.  Please consider adding some support on the "floating" end of the pcb to handle the vibrations.  Maybe some material to dampen the motion of the pcb.  Recall that this board was designed to be inside a pedal where the vibrations are minimal.

Alf

[Paul Marossy]

Paul:

Very cool project! 

I want to make one observation: the board is simply supported by the pins coming out of the reverb module.  The opposite end doesn't have any support at all.  Since you're putting it next to the speaker, I'm concerned that the vibrations are going to weaken those pins as the pcb flaps up and down.  Please consider adding some support on the "floating" end of the pcb to handle the vibrations.  Maybe some material to dampen the motion of the pcb.  Recall that this board was designed to be inside a pedal where the vibrations are minimal.

Alf

Thanks. You bring up a good point, it would be pretty easy to do that. Although it's pretty solid as soldered, I guess that what you say could happen over time...

[Paul Marossy]

I just thought I'd give an update on this. I've been playing regularly at about 50% volume since I installed this in my amp and it hasn't given me any problems whatsoever. The vibration from the amp cabinet doesn't appear to have any adverse affects on the Belton reverb module.