Synthrotek VERB- DIY Build

As described by the Synthrotek site, “the Synthrotek Verb is a reverb module like no other. This three PT2399 unit offers a warm tape saturated spring reverb like sound but with the added flair of the subtle modulation which truly makes it shine.” This was enough for us to decide to take on the VERB on for the next build of September 2020.

Unlike a lot of other reverb modules, this one does not require a “tank” to produce its reverb. It relies on the x3 PT2399 circuits that were previous utilized in other delay modules. 

The PT2399 is back … again.

We won’t go into all of the technical jargon like we have in previous builds (see Synthrotek DLY and Waveform Magazine Delay builds), but we will say that the PT2399 is a very versatile IC. It can be used for delay’s, echo’s and even reverbs (as this module uses them).

To keep it simple, the IC takes in analog audio input and converts it into digital stream of bits to add a digital delay to it. This audio delayed audio signal is then provided as output (ie. perfect for these module types).

On with the build ...

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As with other Synthrotek builds, we will start off by saying the kits are neatly organized. The components of the Synthrotek VERB are all taped together to almost match the BOM perfectly. We still use a component tester to spot check resistors, but it is definitely not needed to build the module. Start by laying out your PCB and your components.

We recommend using a pair of “helping hands” to help keep the PCB in place as you begin to layout the resistors and other components. We also used a solder pump, IC pin chip tool and our Synth DIY Toolset to help tighten down the panel to the PCB.

Synthrotek VERB - Time Lapse Build

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Resistors and Diodes:

Measure out the size/spacing of the components and begin placing the resistors, one at a time according to the BOM and/or silkscreen. We used a top down soldering method with a final reflow on any leg that didn’t get tacked down enough. This made for a pretty fast build overall.  Keep in mind that this kit is for intermediate or advanced builders due to the soldering pads being close and some tight spaces that require a very steady hand. 

Once the resistors have been placed, make sure take notice of the orientation of the diodes. Crucial to the module, diodes can make or break a module depending on orientation. As for the capacitors, which are next, their orientation does not matter (same with resistors).

One thing you want to watch for with the caps is that you allow enough space between the disc and the PCB. Do not push the cap all the way down as some of the ceramic coating could block solder from flowing into the pads as it should. If this occurs, the module will not function correctly. 

Take a break … that was 61 resistors and 5 diodes already… 

IC Socket headers are next. Make sure that they are placed in the correct orientation based upon the silkscreen and the little “U” at the top of the header. There are 8 of them total, so take your time and place each one at a time.  Be aware you will not be placing the IC’s at this time, so keep those on the side and ignore them for now.

Transistors, Voltage Regulator and Trimmer Potentiometer…

Next up are the two transistors, and the 5v regulator. These are all polarized, so make sure when populating them that you align the flat edge of the component with the corresponding flat line on the silkscreen. Pay close attention to the number on the side of the component, as it is very easy to mix up the voltage regulator with the transistors, as they all look alike.

When populating the trimmer potentiometer, orient the flat side (the side with two legs) up with the matching side on the PCB. (opposite the callout). Once everything is in it’s proper place according to the BOM, carefully flip your project over and solder everything in place, clipping any excess leads on the bottom.

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Electrolytic Capacitor and Power Header…

If you have to choose between which one of these components you tack down first, make it the electro caps. You will want to make sure they are orientated correctly as well. The stripe on the capacitor should be facing away from the ‘+’ symbol on the PCB silkscreen.

Once these are in place correctly, tack them down and move onto the shrouded header. This too has an orientation that matters. Just match the notch in the header to the notch on the silkscreen and solder that bad boy down.

When it comes to the pots and the jacks, place the parts where they go via the BOM and then flip the PCB over to tack down the center pin on each. This will allow the pots and jacks to maneuver around as you line up the front panel and hand tighten it down.

Once the panel is in place and everything looks to be lined up, tack down the rest of the legs on the pots and jacks. This will ensure that everything is where it needs to be when it is all said and done. Before you jump into patching, place the supplied knobs (or change the color and use your own) and get ready to calibrate. 

The Completed DLY Module

Calibration and Testing...

Prior to patching, you need to go through the calibration process which is listed on the assembly guide on Synthroteks’ website or below.

Locate the trimmer potentiometer at R62. This trimmer controls the gain on the input stage. Turning this trimmer CW will decrease the gain (lowering the level), and turning it CCW will increase the gain (raising the level). We will patch and adjust accordingly via the trimmer pot. 

Calibrate with the following patch:

  • VCO patched into a VCA (triangle wave is best for hearing audible differences)
  • Relatively slow gate patched into an envelope
  • Envelope on linear taper
  • Output of Envelope patched into CV control of VCA.
  • Output of VCA patched into the Verb
  • Output of Verb patched into an output module of some sort.
  • Basically, you want a short-ish ‘pulse’ going through your Verb so that you can clearly hear the reverb effect.
  • Once everything is set up, turn your MIX knob and Level Knob to 3 o’clock position. Then adjust the trimmer CW to adjust the Verb until you are satisfied with the output.
  • Because everyone’s tastes are different, there isn’t one ‘right’ position for the trimmer, but we’ve found adjusting it to the position shown below sounds on point.
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Features and Specifications

Features:

  • CV in over MOD and MIX
  • Buffered Input and Output
  • CV In for the MIX is additive to the knob.
  • Very low signal DC offset at -0.073V
  • Trimmer to adjust input gain
  • No tank needed

Current Draw:

  • 18mA @ -12V
  • 87mA @ +12V
  • 0mA @ +5V

Dimensions:

  • Module Height: 3U
  • Module Width: 4HP
  • Depth: 54mm
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Sythrotek VERB - Purchasing Options

Synthrotek has a couple different options when it comes to purchasing the VERB module. We wanted to keep it simple by just placing images of the options and linking out to the direct purchase. The prices are excellent and the quality of this build is way worth it! Head on over to SR and tell them we sent ya!

$150.00 - Assembled
$99.99 - DIY Kit
$29.99 - Panel/PCB Combo
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Sythrotek VERB - Documentation

Our Final Thoughts . . .

The Synthrotek VERB is an outstanding module in the legacy lineup. This reverb module, with its triple PT2399 ICs allows one to attain a sharp reverb that can be used throughout ones performance or recordings. The build itself is not for the timid. Coming in strong with 8 IC’s and 61 resistors… the VERB kit is one that takes time. Calibration is quick and easy which nice thanks to the guide. 

As one of the “legacy” modules from Synthrotek, the VERB pairs well with its counterparts, the DLY and the ECHO. Together these three modules can really add some much needed dynamics to your audio compositions. If you decided to head on over to the Synthrotek store to pick one up, tell the gang we said hello!

Comments or Suggestions?

If you have questions about the build process or suggestions/feedback about this article, feel free to let us know by contacting us  We look forward to hearing from you!

Until the next build … 

~ f i N

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