Danelectro BLT Slap Echo – Guitar Pedal Bending

Guitar pedal circuit bending

After getting my feet wet with my Danelectro T-Bone Distortion Pedal I wanted to keep up the momentum. My next victim would be my Danelectro BLT Slap Echo mini pedal. Like the T-bone the Danelectro BLT Slap Echo pedal is an extremely low cost and relatively simple pedal which makes it a perfect candidate for circuit bending.

guitar pedal circuit bending

The BLT Slap Echo consists of two circuit boards. The lower board (brown) is dedicated to driving the inputs and operating the foot switch. This lower board is identical to the one found on the T-Bone Pedal. Because it is not involved in effects creation I will be ignoring it while circuit bending.

The upper green board is where the magic happens. The upper board is driven by a PT2399S Digital Delay Analog Echo chip which is where I found the majority of the bend points. The second smaller IC is a simple TL072 op-amp which I largely ignored. One thing you will notice about these Danelectro mini pedals which makes them extremely pleasant to work with is that there are unused solder points throughout the circuit which can be easily connected to to create bends.

guitar pedal circuit bending

After probing the circuit board and some experimentation I settled on the points shown above. I soldered leads to each of these points using different colors to distinguish the different bends. Once the soldering was completed I also applied some glue to each solder point to hold the wires in place. This glue will keep the wires from tearing off the (admittedly weakly constructed) solder board and also prevent them moving around and touching other points.

From here I ran the wires out through the hole in the pedal case I had drilled and through the lid of the container I would use to house the switches. This container will likely be a temporary housing as it lacks the durability you need in a pedal. Down the road when I have the materials available I will create a post where I rehouse both the T-Bone pedal and the BLT Slap Echo into their own custom pedal boxes.

The first bend here is made by connecting the green and blue wires. This produces something of an infinite echo. rather than the echo decaying over time as it normally would it will continue until the bend is disconnected.

Next I used an on – off – on switch to connect the blue wire to either of the yellow wires. This bend creates a crunchy distorted echo effect. One of the yellow wires will give you a more treble base distortion, and the other will give you a more bass distortion. I have not tried it yet but I would be interested to know what happens if you wire the blue to the wiper on a potentiometer with the yellow on either side. You may be able to tune the pitch of the distortion this way. I expect I will attempt this when I rehouse the pedal.

Third I connected the red wires together. This is probably my favorite bend on this pedal. It is more subtly then some of the others but creates a really satisfying slow reverb effect that I really love.

The final bend was to connect the black and green wires. during testing this created a nice white noise effect behind the pedal output. Unfortunately though now that I have wired everything up it does not appear to be working. I’m not sure if I mixed up the solder points or if something came disconnected while I was closing up the circuit, but I will do some troubleshooting and provide an update if I can get it working again.

Guitar pedal circuit bending

From there all that’s left is to box everything back up and get playing with it. I will be creating a video within the next few days to demonstrate the bends on both my T-Bone Distortion Pedal and this BLT Slap Echo pedal. Overall I’ve found these Danelectro pedals to be really rewarding and great way to initiate myself into the world of guitar pedal bending. Hope you all enjoyed and have a great week.

Share and Enjoy

  • Facebook
  • Twitter
  • LinkedIn
  • Reddit
  • RSS
  • Pinterest

Danelectro T-Bone Distortion – Guitar Pedal Bending

guitar pedal circuit bending

I decided to try something new this week. I have a couple old guitar pedals laying around my shop and I wanted to open them up and see what I could do as far as circuit bending them. The first I bent was a Danelectro T-Bone Distortion mini pedal. I chose this as my first because it is small, relatively uncomplicated and most importantly cheap. I have a second Danelectro mini pedal (A BLT Slap Echo) which I will be bending next but before I do I wanted to get some practice with pedal bending. Also this distortion pedal will give me a better understanding of how these devices are put together as the two pedals are constructed very similarly.

After opening the T-Bone Distortion pedal up my suspicions about it’s simplicity were confirmed. The pedal is made up of two separate boards connected by a short ribbon cable. The lower board (brown board in this image) appears to primarily handle the functionality of the switch and the inputs and as such I will be largely ignoring it. A quick look in my BLT pedal confirmed that this lower board is shared between all pedals in this series and is therefore not involved in the effects production. I will be focusing my efforts on the upper (green) board.

The effects board on the T-Bone Distortion pedal appears to be built around an LM324 quad op-amp chip. This chip is essentially four op-amps (LM741s) arranged on a single chip with shared power and ground. Another helpful thing I found with this board is that there are numerous unused solder points throughout the circuit which made experimentation and modification extremely easy. Likely this board was developed to serve multiple purposes or be used in multiple pedals depending on which components or points were used.

By feeling around on these unused solder points I was able to find a number of areas which created additional effects though the majority of these effects were very similar to each other. In the end I decided to keep things simple for this project and settled on three soldering points. When these points are used in combination they allowed me to create two new effects which I found interesting and fairly unique. By connecting the blue wire shown above to either of the green wires (through a potentiometer) you can create these effects.

For the first (using the green wire on the left side of the board) I used a 200K ohm potentiometer. This creates a high gain bass boost effect. As you get closer to 0 ohms of resistance this boost devolves into a crunchy noisy mess and the melody for your guitar (or other inputs) is all but lost. That being said if that is the effect you are after it is quite pleasing. As you raise the resistance up close to 200K though you can get a very nice (if still a bit crunchy) bass boost added onto the melody you are playing.

The second bend is a bit harder to describe. For it I used a 10K pot and added a 27K resistor in series. With this bend the pedal will die if you lower the resistance below about 25-26K so the extra resistor stops this from happening. with no inputs going to the pedal this bend will create a smooth square wave oscillation, the pitch of which can be adjusted with the potentiometer. Once this is connected with inputs going to the pedal though things get a bit strange. The oscillation and the audio playing through the pedal begin to modulate each other and create some very fun and interesting effects.

Since there is very little free space in these pedals I opted to run the wires out to a small container I had on hand. I drilled a small hole in the side of the pedal and ran the wires out through there prior to attaching the switches and pots. This is not a very permanent solution and I expect I will be re boxing this pedal down the road. That being said it works for the time being. To protect the wires I loosely wrapped them with electric tape (heat shrink tubing will give a cleaner effect if you have some on hand) and created plugs for the holes on the pedal and box using hot glue. This will prevent the wires from being tugged which could disconnect the solder points. With that my Danelectro T-Bone Distortion was ready to play!

That’s it for today, I hope you guys enjoyed this project. Once I have finished the BLT echo pedal I will upload a video showing off the effects. Until next time, happy soldering!

Share and Enjoy

  • Facebook
  • Twitter
  • LinkedIn
  • Reddit
  • RSS
  • Pinterest