duhvoodooman
December 3rd, 2008, 08:37 PM
No, Duh Voodoo Man has not decided to drop pedal-making and try out for the Top Chef series. What I'm referring to here is the delightful and cheap (part of why it's delightful!) Danelectro Chicken Salad vibrato pedal. Turns out you can get under the hood of this puppy and have some fun!
First, I want to thank Tone2TheBone for turning me on to this possibility. I had really never considered trying to modify such an inexpensive little effect pedal, but then Tone passed along some info that blew my mind: Amazingly, the Chicken Salad uses the same basic phase-shifting technology as the legendary Univox Uni-Vibe! I had always thought that it was just a cheapy knockoff of any of a number of vibrato or phaser circuits, but that's not the case. The heart of the Uni-Vibe is its "lighthouse"--a small enclosure containing a lamp source and 4 light-dependent resistors (LDR's). The intensity of the light souce is modulated by a low-frequency oscillator (LFO) circuit that causes the light brightness to change at an adjustable rate of speed. As the light intensity changes, so does the resistance of each of the LDR's--and this swing of the resistance up and down is what causes the out-of-phase signal "notch" to sweep up and down in frequency and gives the Uni-Vibe it's characteristic swirly, watery modulation. You can buy the Dunlop reissue version for $200 or so. Original vintage Uni-Vibes will run you quadruple that or more.
Well, guess what? The little $30 Danelectro Chicken Salad uses lighthouse phase sweep technology, too. I was floored when Tone told me this, basically telling him he must be wrong. Well, he wasn't. He gave me a couple of web links and off I went in search of "the truth" (it's out there). Turns out that inside the CS on one of its two small PCB's is mounted that lighthouse (a small, square plastic box about 1/4" high) and--just as importantly--a trimpot that adjusts the base voltage supplied to the LED light source inside. The LFO circuit then allows you to adjust the magnitude (intensity control) and speed (rate control) of the LED voltage modulation. The fun comes in twiddling that trimpot. In the stock setup, the magnitude of the voltage swing (i.e. from min. to max.) is pretty conservatively set. But by dialing the base voltage up, the magnitude of the swing increases and the sound of the phasing gets more pronounced....and noticeably more Uni-Vibe-like. Go too far and it starts to sound strange in a not-so-good way, but you can easily tweak it up and down until you get the sound that's best to your ear. For mine, an increase of about 30 degrees was optimal. You can also visually see the effect of the trimpot adjustment, since the lighthouse is not light-tight--the glow of the LED inside can be seen from a couple of different angles. To adjust it, I turned the intensity knob all the way up and the rate knob all the way down. This gives you a nice slow, accentuated pulse from the internal LED.
If you want to go nuts with this, you can also line the inside of the top of the lighthouse (it's epoxied on, but can be removed--carefully--with an exacto knife) with aluminum foil. This supposedly reflects the light back toward the LDR's and further increases the depth of the effect. Haven't tried that yet, so I don't know how effective that is, on top of the trimpot adjustment.
Getting into the CS pedal is fairly straightforward. Remove the bottom, and then 4 small screws hold the first PCB in place (the one with the I/O and power jacks), and another 3 hold the 2nd PCB mounted above the first. You will need to remove the two control knobs to be able to lift out the PCB's and work on them, and they don't come off easily. I just gripped them firmly with a pair of pliers and pulled straight up. Once you have the PCB's removed, just plug into the I/O jacks as you usually would and use an AC adapter or a battery for power. Below are a couple of photos I took, along with a link to a clip I recorded. It's a popular Pink Floyd riff often used for phaser and Uni-Vibe clone demos. Recorded with my Xaviere 870 Strat copy at the meck/middle pickup setting through the CS and into my Valve Jr/2x12 cab. The first section is the Chicken Salad at the stock trimpot setting and max. intensity. The remainder is the same Floyd riff played longer with the CS tweaked for "maximum warble". With the intensity knob dimed, it's a bit overdone, but the idea was to accentuate the differences. This trimpot setting gives a more irregular modulation which is one of the key characteristics of the Uni-Vibe sound, from what I've read.
http://www.box.net/shared/okxigbq80g
http://duhvoodooman.com/miscimages/musical/CS_apart.jpg http://duhvoodooman.com/miscimages/musical/CS_PCB's.jpg http://duhvoodooman.com/miscimages/musical/CS_PCB_labeled.jpg
First, I want to thank Tone2TheBone for turning me on to this possibility. I had really never considered trying to modify such an inexpensive little effect pedal, but then Tone passed along some info that blew my mind: Amazingly, the Chicken Salad uses the same basic phase-shifting technology as the legendary Univox Uni-Vibe! I had always thought that it was just a cheapy knockoff of any of a number of vibrato or phaser circuits, but that's not the case. The heart of the Uni-Vibe is its "lighthouse"--a small enclosure containing a lamp source and 4 light-dependent resistors (LDR's). The intensity of the light souce is modulated by a low-frequency oscillator (LFO) circuit that causes the light brightness to change at an adjustable rate of speed. As the light intensity changes, so does the resistance of each of the LDR's--and this swing of the resistance up and down is what causes the out-of-phase signal "notch" to sweep up and down in frequency and gives the Uni-Vibe it's characteristic swirly, watery modulation. You can buy the Dunlop reissue version for $200 or so. Original vintage Uni-Vibes will run you quadruple that or more.
Well, guess what? The little $30 Danelectro Chicken Salad uses lighthouse phase sweep technology, too. I was floored when Tone told me this, basically telling him he must be wrong. Well, he wasn't. He gave me a couple of web links and off I went in search of "the truth" (it's out there). Turns out that inside the CS on one of its two small PCB's is mounted that lighthouse (a small, square plastic box about 1/4" high) and--just as importantly--a trimpot that adjusts the base voltage supplied to the LED light source inside. The LFO circuit then allows you to adjust the magnitude (intensity control) and speed (rate control) of the LED voltage modulation. The fun comes in twiddling that trimpot. In the stock setup, the magnitude of the voltage swing (i.e. from min. to max.) is pretty conservatively set. But by dialing the base voltage up, the magnitude of the swing increases and the sound of the phasing gets more pronounced....and noticeably more Uni-Vibe-like. Go too far and it starts to sound strange in a not-so-good way, but you can easily tweak it up and down until you get the sound that's best to your ear. For mine, an increase of about 30 degrees was optimal. You can also visually see the effect of the trimpot adjustment, since the lighthouse is not light-tight--the glow of the LED inside can be seen from a couple of different angles. To adjust it, I turned the intensity knob all the way up and the rate knob all the way down. This gives you a nice slow, accentuated pulse from the internal LED.
If you want to go nuts with this, you can also line the inside of the top of the lighthouse (it's epoxied on, but can be removed--carefully--with an exacto knife) with aluminum foil. This supposedly reflects the light back toward the LDR's and further increases the depth of the effect. Haven't tried that yet, so I don't know how effective that is, on top of the trimpot adjustment.
Getting into the CS pedal is fairly straightforward. Remove the bottom, and then 4 small screws hold the first PCB in place (the one with the I/O and power jacks), and another 3 hold the 2nd PCB mounted above the first. You will need to remove the two control knobs to be able to lift out the PCB's and work on them, and they don't come off easily. I just gripped them firmly with a pair of pliers and pulled straight up. Once you have the PCB's removed, just plug into the I/O jacks as you usually would and use an AC adapter or a battery for power. Below are a couple of photos I took, along with a link to a clip I recorded. It's a popular Pink Floyd riff often used for phaser and Uni-Vibe clone demos. Recorded with my Xaviere 870 Strat copy at the meck/middle pickup setting through the CS and into my Valve Jr/2x12 cab. The first section is the Chicken Salad at the stock trimpot setting and max. intensity. The remainder is the same Floyd riff played longer with the CS tweaked for "maximum warble". With the intensity knob dimed, it's a bit overdone, but the idea was to accentuate the differences. This trimpot setting gives a more irregular modulation which is one of the key characteristics of the Uni-Vibe sound, from what I've read.
http://www.box.net/shared/okxigbq80g
http://duhvoodooman.com/miscimages/musical/CS_apart.jpg http://duhvoodooman.com/miscimages/musical/CS_PCB's.jpg http://duhvoodooman.com/miscimages/musical/CS_PCB_labeled.jpg