Boss DRV-1981

This is a clone of the 1981 Inventions DRV rehoused in a Boss DS-1 enclosure. I used the PedalPCB Informant PCB and the MadBean Softie for this project.

The “Boss” DRV-1981

Why?

Good question! I suppose I saw the ridiculous prices people were paying for the Boss Tone Benders that had come out recently and thought I could just make my own. While I was exploring the idea it seemed it was easiest to three knob Boss enclosures. The cheapest pedals seemed to be the DS-1, SD-1, and the BD-1. So building a three knob was the best option. There are many three knob pedals out there. Big Muff, Tube Screamer etc.

I got a little sidetracked and built a Big Muff in a DS-1 enclosure first, see my post here. The second build was this 1981 DRV. I have a board for a three knob Tone Bender and am planning to work on that next.

The process The process was pretty straight forward.

The Boss enclosure is pretty roomy. Figure you can fit anything that might fit 125B sized box into a Boss enclosure. The donor pedal comes with LED, Jacks, much of the wiring already. No need to drill or install these things.

One thing that needs some work is the power jack. The power jack is mounted to the original DS-1 PCB in my build there was no place to mount this. To solve this I used one of those standard DC jacks with a nut. I needed to ream the enclosure to allow it to fit. I added a couple spare washers so the jack didn’t extend too far out of the enclosure.

Switching

Switching is an area that needed some thought. Boss uses an electronic switching system. The system uses a couple JFET transistors to route the signal either through the effect or from the input to the output. Another part of the circuit turns this off or on. There is also buffer.

A side effect of this system is that your signal is always passing through some electronic components unlike true bypass where the signal is essentially traveling through a wire from the input to the output when the effect is bypassed. I’ve never heard any complaints about The Boss bypass. Another potential problem is the signal is lost when power is lost, even when the effect is bypassed.

I used the MadBean Softie which uses a micro controller and an electronic relay. The relay is an electromechanical switch. It’s a DPDT switch that is activated by an electronic signal. This offers a couple advantages. First, it works with the existing switch in the Boss enclosure. Second, when in bypass it acts as true bypass, the signal is essentially traveling through a wire from input to output when in bypass. Third, if power is lost the relay switches to its default state which bypasses the effect. Last, the relay has a failure rate of 100k cycles so it should outlast a mechanical 3PDT switch, which typically has a failure rate of 30k to 50k cycles.

It isn’t all upside. The cost of the Softie PCB was $4 and you’d need an SPDT monetary switch which is another $2.50. That’s $6.50 compared to $2.50 for one of those standard blue 3PDT switches. In this case the Boss enclosure came witch an SPST.

I thought the Softie worked well. Madbean makes three versions of this board for different sized enclosures. I chose the smallest version that was meant to fit 1590B enclosures. I think I could choose a one of the other boards for the Boss enclosure. The reason the board I chose has a small footprint but mounts parts on both sides of the board making it taller than other boards, which makes it a tighter fit than it would appear.

The Informant/DRV needed three A100K pots. The DS-1 has two B100k and a B20K pot. I could have tried the B100K pots. Since I needed to replace on of the pots I replaced them all.

I used some of those 9- degree PCB mounted pots, two 16mm and one 9mm. I cut a piece of strip board and mounted the post to this. Then ran the wiring from the Strip board to the PCB.

I color coded the wires by the PIN number of the pots to make it easy to get them matched up to the correct holes on the PCB. I just did it alphabetical to make it easy to remember: Brown, Gray, Orange. Notice the center pot is backwards,

Cost

The cost of this project was higher than a typical pedal but not as bad as i was expecting. The cost of the donor DS-1 was the biggest expense. The DS-1 was $40 and it replaces about $10 of other parts. So this was roughly about $30 more than your typical pedal build.

Item Cost
Informant PCB $8
Softie PCB $4
Used DS-1 $40
TC1044 $2
Other parts $6
Total (estimate) $60
DRV-1981 costs estimated

The total cost was about $60 which was not that bad, or at least than I thought it might be when I started. The pedal is pretty solid and works well.

What’s it sound like?

Hopefully like the 1981 Inventions pedal. I haven’t tried one of the originals but this sounds similar to the demos I’ve seen on YouTube. Its a really driven sound with a tight low end. It has a very 80s sound.

The drive control starts at distorted and goes quickly to high gain. I find it sounds best to turn up the Cut control as you increase the gain to “shave” some of the “hair” off as gain increases.

For myself I like the lower range of the Drive control. Everything past 25% (9 o’clock) sounds very similar. I’d like to play with Drive and gain in the future. This might be replacing the Drive pot with a 50k pot, or possibly changing some of the other components to get a more useful feel for this control.

PedalPCB 1981 inventions DRV clone

This is a build of the PedalPCB Informant, it’s a clone of the 1981 Inventions DRV, which is a great sounding evolution of the ProCo Sound Rat. I’d call this a beginner to intermediate level project. The PCB is easy to work with and well laid out with plenty of room to work. The only thing that moves this up from a beginner project is the charge pump. It’s not hard to work with but you do have be careful as these can be blown up easily, there are a few different parts to choose from, and depending on the part number you may need to solder the jumper on the back of the board.

This shares a lot with the Klon but goes further in the drive/distortion range. The DRV and Klon use a charge pump to run on 18 volts. This gives the pedal greater headroom. It also makes it a poor candidate for batteries. They both use a similar clipping architecture with diodes to ground after the op-amp, like a lot of other designs. While the diode arrangement and charge pump are similar the sounds are pretty far apart. The Klon has a deeper mid focused growl and and DRV has tighter sharper mid chunk. It’s the difference between Tom Waits and David Lee Roth.

I used a black powder coated 125B enclosure. I milled the logo and labels into the enclosure with a desktop mill.

Assembly

The PCB is east to assemble and well laid out with plenty of room to work. The pots and LED are mounted to the board which makes for little work wiring and mounts the PCB in the enclosure.

I assembled everything in the enclosure without soldering, fitted the washers and nuts on the pots and bent to LED into position, then soldered the leads on everything.

The docs provide a drilling diagram for a 125B box with the jacks at the top which is a popular arrangement and works well.

Wiring

The PCB makes the off board wiring organized and easy to implement. There are two options to choose either buffered bypass or true bypass. The true bypass option removes the effect entirely from the signal chain and the signal passes from the input to the output through a wire. In the buffered mode one of the op-amps is used as a unity gain buffer when the effect is bypassed. I chose the buffered arrangement for this build which is how the original 1981 DRV works.


Cost

Parts for this project are easy to get and common. The thing of note is the charge pump which are about $2 and can be blown if they get shorted. I’ve burned up a few in the past. It’s this charge pump the boosts the 9 volt power supply up to 18 volts.

Running at 18 volts you’ll want to use 1/4 watt resistors and make sure the caps are rated 25 volts or height.

The other parts are pretty common TL072 op-amps and mostly 10k and 100k resistors. You might have all the parts left over from a previous project!



How Does it Sound?

It sounds like ROCK! This is a total ‘80s rock machine. In some ways it has some of the character of a Klon. But the Klon has a deeper/darker mid range and goes from almost clean to heavy overdrive. The Informant/DRV goes a from distorted to really distorted with with brighter mid range and tighter bass.

Here is a video demo:

PedalPCB Informant Demo

This one is for sale on reverb check out my for sale page