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Digital reverb add-on kit for typical DIY amp builds?

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  • Digital reverb add-on kit for typical DIY amp builds?

    With the various digital reverb chips available a small company should come out with a good kit that we can add to our amp builds. Here are a few suggestions for different kits.

    • A Fender/Vox kit with the reverb input signal taken after the first stage, tone stack and volume control. That way the input signal would be fairly clean unless the amp input was overdriven. The reverb signal would be mixed back into the audio signal chain through an op-amp directly ahead of the phase inverter, after the FX loop and an optional cascading overdrive channel. There would be a reverb drive control, a reverb return level control and an input signal treble cut tone control. (These controls could be panel mounted pots or trim pots, the amp builders' choice.)

    • A Marshall style kit similar to the Fender/Vox kit for amps with a tone stack ahead of the phase inverter. For this kit the reverb input signal would be taken after the initial gain stage but would include 2 or 3 tone controls to further shape the reverb input signal.

    • Both designs could be incorporated in the same add-on kit, with headers on the circuit board to be connected to pots and switches.

    • The kit would include a separate power supply module which would provide a regulated voltage from one of the B+ nodes, perhaps the one powering the first stage.

    I would expect the initial kits to retail for around $150-200 but that the price might come down considerably after production was ramped up. What would be included would be 2 or 3 printed circuit boards with th3 switches, pots, jacks and other auxiliary parts provided by the amp builder.



    Any suggestions or comments? I believe that there would definitely be a demand for something like this in the DIY amp building community if someone could put such a design together, perhaps financed by a kickstarter campaign.

    Steve A.

    P.S. There could be a stripped down version of this adding just a buffered solid state FX loop ahead of the phase inverter, perhaps with a series/parallel option.

    P.P.S. These kits would be based on the assumption that an op-amp mixing stage ahead of the phase inverter should be fairly neutral in sound and response.
    The Blue Guitar
    www.blueguitar.org
    Some recordings:
    https://soundcloud.com/sssteeve/sets...e-blue-guitar/
    .

  • #2
    Good idea - and very close to one I've been working on in a desultory way for quite a while.

    My cut on it was to make a mini-tank shaped device with RCA phono jacks in and out that could be plugged in to replace a spring tank. There are a limited number of input impedances and levels for spring tanks, and even fewer output impedances and levels. The Belton BTDR-2 digital reverb gets good reviews for sounding much like a spring reverb. I've done some minor design, adjusting input level and output levels so the interface to the amp would be the same at the ends of the reverb cables.

    The only addition needed would be a source of 5V at up to 200ma. This is a modest PITA in a typical tube amp. Messing with making this from the heater supplies is possible, but frankly the simplest thing would be to wire in one of the 5V output wall warts inside the amp.

    Sadly, my ability to design things is far larger and faster than my time to get prototypes built. The boards are laid out and ready to print, pending only some mechanical mounting issues. I have an amp-tech friend that has squirreled away a couple of dead small-size tanks for me to use in making a proto, but he's out of town, the sun is in my eyes, I have blisters on my fingers....

    On top of that, I have just received my first run of repro Thomas Vox knobs. Chrome, knurled, very, very close to the real thing. Sigh. So many designs to do, so little time.
    Amazing!! Who would ever have guessed that someone who villified the evil rich people would begin happily accepting their millions in speaking fees!

    Oh, wait! That sounds familiar, somehow.

    Comment


    • #3
      R.G. Speaking of spring reverb tanks I sure wish that a boutique company would "spring" up to sell Fender tanks like the old ones, either by rebuilding current production tanks or designing something from scratch.

      As for supplying power for add-on boards and modules inside guitar amps can the "voltage pump" idea in many modern FX pedals be used in creating a regulated DC voltage from the 6.3VAC filament windings?

      Thanks!

      Steve A.
      The Blue Guitar
      www.blueguitar.org
      Some recordings:
      https://soundcloud.com/sssteeve/sets...e-blue-guitar/
      .

      Comment


      • #4
        Ever used one of these?
        Belton BTDR-3H Reverb Modules - Small Bear Electronics

        Comment


        • #5
          Originally posted by olddawg View Post
          Or these? They're for Organs but I'd think a tube amp would be just as accomadating to one of these.
          Fisher Spacexpander and ElectroTone OrganMate (as well as the current Trek II reverb add-on
          nosaj
          soldering stuff that's broken, breaking stuff that works, Yeah!

          Comment


          • #6
            http://diy.smallbearelec.com/Library...ton_BTDR-3.pdf

            Spec sheet. All it seems to need is a 5vdc supply and and external dual pot.

            Comment


            • #7
              there are so many good reverb pedals out there that I just don't bother adding reverb to a build these days. Only if I build an exact clone on request for someone.

              Comment


              • #8
                Originally posted by mac dillard View Post
                there are so many good reverb pedals out there that I just don't bother adding reverb to a build these days. Only if I build an exact clone on request for someone.
                Well yes and no. If you are using overdriving the preamp it can get ugly. A pedal in the effects loop works better.

                Comment


                • #9
                  Originally posted by olddawg View Post
                  Well yes and no. If you are using overdriving the preamp it can get ugly. A pedal in the effects loop works better.
                  It is pretty much blues guitarists who really want or need reverb built in to an amp. A long time ago I figured that I needed reverb or sustain from overdrive, but not necessarily both.

                  In rewiring my already-butchered 1965 Pro Reverb with a D.... clean channel and an OD channel based on a 2204 Marshall I gave up trying to get a decent OD sound running through the 3M3/12pf reverb splitter so I ran it like the stock Normal channel directly to the PI... much better.
                  (The Dumble clean channel through the Fender reverb circuit sounded like angels on high.)

                  Hence my specification that the reverb signal be taken early in the circuit and mixed in right at the phase inverter. Blending in a clean reverb signal with an overdriven signal can be cool.

                  Steve A.

                  P.S. Attached below is the Son of Promaniac schematic from 1999 which without mention included my D mods for the Normal Channel as a Halloween bonus. Shhhh... don't tell anybody!


                  .sopm_1.pdf
                  Last edited by Steve A.; 06-05-2018, 04:18 AM.
                  The Blue Guitar
                  www.blueguitar.org
                  Some recordings:
                  https://soundcloud.com/sssteeve/sets...e-blue-guitar/
                  .

                  Comment


                  • #10
                    Steve,

                    There are several circuits available based on Belton Reverb modules. Why can't you use one of them?
                    Also, FV-1 chip is often used. And they are available as a small module. I designed a programmable effect using this chip: GalleryGaleria - Eagle AudioEagle Audio . It mimics The Shadows band sound but it is too complicated compared to what you need.
                    I suggest looking at the Belton modules.

                    Mark

                    Comment


                    • #11
                      Originally posted by Steve A. View Post
                      R.G. Speaking of spring reverb tanks I sure wish that a boutique company would "spring" up to sell Fender tanks like the old ones, either by rebuilding current production tanks or designing something from scratch.
                      That may be tough. I wound up getting some of the last Accutronics tanks before they were bought out when I did the protos for the Workhorse amps. They didn't sound right, and in talking to some tech people at Accutronics, they let slip that they could no longer get the same damping material that the driver/pickups ran in. The replacements didn't sound right. I don't know how that got solved, but it was a long time ago and maybe Belton has figured it out. It's funny that the exact material in a plug of stuff made them sound way different.

                      As for supplying power for add-on boards and modules inside guitar amps can the "voltage pump" idea in many modern FX pedals be used in creating a regulated DC voltage from the 6.3VAC filament windings?
                      Sure. You can make 7-8V that way, and run it through a 7805 regulator to make the necessary power. But it's a PITA, like all the ad-hoc schemes to make low voltage DC from heaters. A single lightweight lump that takes in 120Vac and puts out 5V DC without a lot of muss and fuss seems both conceptually and practically simpler. Maybe I'm just getting lazy.
                      Amazing!! Who would ever have guessed that someone who villified the evil rich people would begin happily accepting their millions in speaking fees!

                      Oh, wait! That sounds familiar, somehow.

                      Comment


                      • #12
                        Last I looked at the Acutronics reverb tanks.... the reason for the poor sound was the spring material ... The old original springs made in the 60's and 70's had a significant % nickel content...
                        Reverb springs made today are much lighter and no nickel content.... totally different cheaper metal..
                        The mechanical resonance of the springs are just too bright and nasty sounding.... all the damping wont do much except band-aide a crappy spring..
                        As for selling to Fender...that would never happen ... They would get the first spring unit, copy it and never pay you..then a few months later send you a "cease and desist" claiming they own the spring IP...
                        I designed a stereo Digital Reverb with a Sharc processor a few years back for major pedal company...they still have never paid me and they are selling this pedal in high volume....

                        Comment


                        • #13
                          Originally posted by cerrem View Post
                          Last I looked at the Acutronics reverb tanks.... the reason for the poor sound was the spring material
                          Whilst we're properly slagging the last-of-the-run US Accutronics tanks, let's not forget the last 5 or so years of production when they treated us to rapidly failing transducer coils. One customer went through half a dozen Accu tanks over the course of 2 or 3 years. He hasn't been back to see me for anything since, that was about 14 years ago.

                          Has anyone tried the "new" Belton made Accutronics tanks? Or are they the s.o.s., just up priced because they have the revered brand name on them?
                          This isn't the future I signed up for.

                          Comment


                          • #14
                            Originally posted by Leo_Gnardo View Post
                            Whilst we're properly slagging the last-of-the-run US Accutronics tanks, let's not forget the last 5 or so years of production when they treated us to rapidly failing transducer coils. One customer went through half a dozen Accu tanks over the course of 2 or 3 years. He hasn't been back to see me for anything since, that was about 14 years ago.

                            Has anyone tried the "new" Belton made Accutronics tanks? Or are they the s.o.s., just up priced because they have the revered brand name on them?
                            I got a tank from Antique Electronic Supply recently, think its stamped "Accutronics". Sounds pretty stinky.
                            The only good solid state amp is a dead solid state amp. Unless it sounds really good, then its OK.

                            Comment


                            • #15
                              Reverb sound is a matter of taste, but I've used the Mod tanks with good results. You may or may not like them.
                              "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

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