In my opinion, the most significant items are JBL speakers. Early Jerry used D120's. Then E120's and eventually K120's. I personally have two E's and two K's. They are slightly different but both deliver a signature tone. The second significant trick is to use a single coil middle pickup and a Fender style preamp with the Treble at 10, Bass at 1 and Mid at 6 or 7. When Dino turned me on to this, I was blown away. A Fender twin is so bright and brittle. The notion of cranking the Treble and killing the Bass seemed insane to me. Well by god, it nails the Jerry tone. This works for a couple of reasons. First, a twins native eq curve isn't flat. By cranking Treble and killing Bass you essentially flatten the eq of a twin. Second, by having less bass in the guitar tone, it really slices through the mix. Guitars are mid-range instruments and by clearing the bass frequencies, it removes the mud from the mix. Let the bassist play bass and not have the guitar interfere. After learning these tricks, I was intrigued and wanted to nail more of the Garcia tone.
Jerry had an onboard buffer in his Wolf, Tiger, Rosebud and Bolt guitars. This was helpful to allow him to run long cables without noise. To explain further, his guitars had an effects loop within the guitar. People often see the two jacks and assume it was a stereo guitar. It is not. The first jack is a stereo jack that is an insert loop. This out and back in loop happens before the volume knob. That way when the volume knob on the guitar is used, it's post FX. To help you understand I'll give an example. On a normal guitar, when the volume knob is turned down, you are lowering the signal that is coming from the instrument to the FX pedals. When using a distortion pedal for example, it lowers the signal to that pedal and very much alters the way the pedal sounds. On Jerry's rig, the signal comes off the pickup at 100% and is buffered, then sent to the FX pedals. Then it returns back to the guitar, hits the volume and tone pots and then goes to the final output jack which goes to the amp. So when you turn down the volume knob on his guitar, it's after the FX pedals. The FX always get 100% of the pickup signal and the volume knob doesn't affect how the pedals respond. When using his Mutron Envelope Filter (wah), this is critical. The signal to trigger the envelope is fixed. By having a consistent signal to that unit, it always triggers properly without volume knob interference. This setup is commonly referred to as OBEL or on board effects loop.
Jerry used a variety of effects over the years but although the brands changed a bit, it was a pretty consistent chain. It was Octave, Mutron, Distortion, Phaser and later Delay was added. His first octave was a Musitronics and later it was a Boss OC2. His distortion pedal was an MXR Distortion + and later various Boss pedals. Boss OD1 and HM3. Using multiple distortions can really add to the tonal possibilities. His early delay was an MXR and later he used Lexicon rack units.
After getting a bit of this knowledge, I tapped my gear guru, Dave Taylor, to help me design and build a copy of this signal path. I'm on my second version of this rig and it's a pretty amazing unit. We took the various pedals out of their stomp box cases and put their circuits all into a single rack space unit. The FX are each powered on all of the time and their signals are inserted into the FX chain with audio relays that are triggered via MIDI. So we control analog FX using MIDI signals. The brain to handle the midi is a small microcontroller called an Arduino. We chose the Arduino Pro Micro for our latest version because it handles USB. So I can plug USB into the back of the rack and update the functionality of the controller as well as handle MIDI over USB. I have a traditional MIDI jack for the foot pedal, however I use the USB MIDI to send controls to my iPad for synth sounds.
My chain of FX is the Boss OC2 Octave, Boss OD1 Distortion, Mutron 3 Envelope Filter, MXR Distortion +, MXR Phase 90, Analog Delay. I have two addition FX spots on the unit to plug in external pedals if so desired. One is first in the chain and one is last. In addition, each distortion unit runs out to a 6 band eq. This helps me shape the tone of the distortions. For example the Boss OD1 boosts about 800Hz. Sometimes I like to boost other spots in it to make it sound more natural. The MXR D+ is a flatter eq and sometimes I like to boost its 800Hz to balance it with the OD1. The knobs for these eq units are on the back of the rack unit.
The phase 90 that I use isn’t accurate. Garcia used a phase 100. I had the 100 in my version 1 rig and I thought I could switch to the 90 for version 2 and no one would know the difference. Well, I can tell the difference so I’m considering swapping that however space is tight in my single rack unit so for now, I’m dealing with it. In both of these versions I modded the phaser like Garcia. I removed the speed knob and ran it out to a pedal on the floor. That way I can alter the speed with my foot. This is super handy because turning knobs during a show is never convenient. This speed knob is a pull-pot on the rack. When not pulled it’s getting a value from the pedal. When I pull it out it performs like the stock knob.
My analog delay had a knob for time. I developed a system to turn it into a tap delay. I made the time knob a pull-pot. When I pull it out, it performs like the stock knob. When it’s not pulled, I’ve attached a digital potentiometer integrated circuit to the unit. I wrote code on my foot pedal to measure tap times, convert those to a MIDI value between 0-255 and send that data back to the rack. The code on the rack interprets the MIDI value and tells the digital potentiometer how much resistance to apply. This is a programmatic way of turning the speed knob. The end result is I can tap my foot to the tempo of the song and my delay adjusts to that time. This was super complicated for me to code but it works nicely now.
After running through the FX portion of my signal path, I enter a separate rack unit that handles pre-amp, power amp and reverb. We copied Leo Fender's AB763 circuit. This is the fundamental circuit in many Fender amps. Jerry's version of this circuit was modified a bit. He removed the 68K resistor at the input for example. Dave tried to be faithful to this when building my rig. In addition, my version 2 pre-amp has additional tube stages that I can use for tube overdrives. This is not Jerry faithful. The notion was to give me a switch to flip to turn off the Garcia stuff. After all, I have lots of bands and sometimes its more desirable to escape the Jerry tone. I call this my Dumble switch since Dave modeled the circuit after Dumble Overdrive Specials. When playing Dead, I leave this section off, but in other bands I can turn the rig into a dirty tube amp. All told there are 4 tube stages in the pre-amp. Two for the twin sound, one for the Dumble and one for the reverb.
The reverb is a digital reverb that is then run through a tube stage. I avoids the noise spring of an old school reverb but retains the tube warmth. All of this is then run through a solid state power amp. Many people are immediately turned off by the term "solid state" however this is what Jerry used. He used a Mcintosh MC2300 which back in his day was one of the cleanest high power amps available. He liked the solid state power because tubes respond so differently to different voltages. When on the road traveling, you never know what the house power will be like. His tone changed too much with tube amps so he went to a tube pre/solid state power setup. I've copied this. My version 1 rig used a solid state Rocktron Velocity 300 as was recommended to me by Brad Sarno. It was a good choice and sounded like what I needed however it was 20lbs. My new version 2 rig uses lightweight Class D power. Class D is common for bass players these days but is just now gaining ground with guitar players namely through a company called Quilter. Well we adopted the Class D model however we bought our own circuit board instead of a Quilter unit. I'm very pleased with the outcome. It's stable loud clean power under 1lb.
I'm going to make a video of this rig and post it very soon.
Garcia's signal path: Center pickup Dimarzio Super 2 in single coil mode, onboard buffer, FX chain, volume/tone knobs, pre-amp, reverb, power amp, JBL. Cabinet is mic'd with a Sennheiser 421