“This is my favorite amplifier of yours, Jason. It sounds great.” Ken Fischer

“With a little practice, you might just have Kenny beat!” Eliot Jacobs

JCA Circuits “Purpleheart” Amplifiers. This is THE amplifier which began it all for me. It’s the first one I felt that I truly “got right”. Previously, I quite literally built 75+ more or less semi-disastrous attempts at different guitar amplifier designs before I understood this was the “right” one. It got me off. Honestly, it’s among the best amplifiers I’ve ever experienced to date (I’m posting this November 7, 2024). As are every other amplifier I’ve created since this one because I use it as THE benchmark as to whether or not other amps I design/build possess the “IT” factor in the same way. Different amps/designs may or may not sound alike, but the quality of performance does have to meet THIS standard. When I first build an amp, it’s rare that they come off the line meeting my standards. I often spend many additional days/weeks/months in some cases perfecting (even rebuilding) them. Everything which emerges from this shop has to perform on the level of the Purpleheart/Inferno amps or else it’s shit.

Back when I got serious about playing guitar in the late 1980’s, I quickly realized that nearly every single guitar amplifier I tried appeared different from one another and I wanted to understand why that was. I love a variety of music so I understood that there was an infinite palette of sounds/moods/atmospheres within music. In the late 1980’s and early 1990’s, there existed a very limited amount of information available on this subject Pre-Internet. I used to happily scour used bookstores for anything I could get my hands on. For instance, I spent years looking for my own copy of the RCA Radiotron Designer’s Handbook F.L. Smith 4th Ed. i.e. “Big Red”. I settled for a 3rd Edition after diligent searching. I also lucked into a nice original 4th edition eventually and scored a minty second 3rd edition to add to my library after several years! I will pontificate on my very nice “in-print” library on this subject some other time…

I built a total of [3] Purpleheart amps circa 1997 thru 2002. The top gallery shows #1; the prototype which is sitting on the Two Rock cab. The next gallery shows #3 (final build) which sits atop the Mesa Boogie 112 Thiele cabinet. Yes, the joinery is a little rough on #3 with some tearout along the edges…don’t sue me. I currently own #1, a local player presently owns #3, and unfortunately #2 no longer exists. The fellow I whom built #2 for owned (and loved) it for over a decade but wound up eventually selling it. Number #2 had a solid purpleheart cabinet, solid bubinga valence, and ebony JCA inlay. I will post a snapshot sometime. Unfortunately, the USPS wound up destroying it during shipping transit between its first and second owner. This was a very heartbreaking event for all three of us. It’s one of the primary reasons I refuse to ship most of my amplifiers. I offer in-person demos or white glove delivery only now for most of my one off/custom creations except for builds which I can readily get cabinetry/parts for. I’ll ship the Vibe, 5F1, 18 Watt, and 5E3’s no problem since this all is common and presently available.

Matt Friedman of Acacia Instruments (Custom Basses) built all of the Purpleheart’s cabinets. His shop was located a half a mile from where I attended high school. I would often stop in there afterwards to hang out. Matt was a GREAT guy all around. He quite literally helped put JCA Circuits on the map. I had never even heard of Mouser Electronics until I met him in the early 90’s! He wound up giving me one of his older Mouser catalogs way back then. I’ll also thank George Alessandro for giving/recommending me a MOJO Tone catalog when Nate Kramer & Family still owned MOJO. Thus began the madness… Most may not believe this but my orders were among the FIRST placed with Mouser when they began carrying Mallory 150 caps. Those were used in these amps as well as the first GR1.6’s back then in the late 90’s/00’s. I’d literally spend hours between Mallory and Mouser corresponding with and trading part numbers in order to buy them. I recall publishing the part numbers for my homies on Ampage back then.

Matt built 3 cabinets out of solid purpleheart wood. He created a CNC machine to do inlay on his custom basses. He wound up programming my wife’s hand-drawn JCA logo and inlayed it on the front valence panels of each cabinet. The inlay is Pau Amarillo (yellow) for #1 and #3, and Ebony for #2. The joinery uses biscuits for a smooth looking joint. Biscuit joints are NOT recommended for the road. They look nice.

The chassis are solid 1/8″ thick aluminum using aluminum flat stock and U channel. This is a very cool, strong, and industrial type of design. It’s also a REAL PAIN IN THE ASS to build. It’s like 4D chess with layout due to the way wires need to be routed. My insistence to utilize thicker than average chassis material and youthful Ego constrained myself to using specific unusual chassis design/layout/construction. These constraints actually wound up forcing me to redo the builds several times which did lead to a better result, overall. In the end, it turned out exceptionally well. Believe me, the first couple of iterations were less than stellar. But I persevered and eventually decoded it. I also learned something significant in this process. These amplifiers perform at the VERY top of the performance curve due to being forced to fix critical design/layout issues during the first attempts. This ultimately led to more happy accidents which I then pursued further which further lead me to uncover several more. I learn from mistakes. They almost always turn out to be Golden mistakes. I’ve learned to not be afraid of failure and to fail better next time!

Ken Fischer really liked the prototype (#1). I used Trainwreck Climax Iron for that build. I am INTIMATELY familiar with the story behind the Kendrick-Trainwreck Climax amplifier project. I was very fortunate to acquire the Pacific Transformer Power and Outputs for use in #1. It utilizes a 285-0-285VAC @300ma Center Tapped PT and 5.8k/35Watt Output. I also used several Elna Cerafine power filters, Mallory 150 series capacitors, Ohmite RCN series 750 VDC Carbon Film signal resistors, Angela Instruments (Azuma) ceramic/gold/silver sockets, NKK 10A DPST switches, Alpha Oxygen Free Copper/Silver Teflon 600V wire, and several other really nice quality parts. The design also utilizes a fast recovery full wave solid state rectifier (Recticon FR307’s) plus an adjustable fixed bias. The fixed bias is unique because it utilizes a “brute force” filtering approach with a single 1,200uF/100V Mallory reservoir. I also installed a 10 turn Clarostat wirewound voltage divider & test points to monitor plate + screen grid currents for lazy tube swaps. It theoretically shouldn’t work as well as it does. The primary output impedance is such that EL-34’s lie within a fairly linear region of their transfer curves (close to Hiwatt DR103 impedances) and 6V6’s lie closer to the knee portion (lower than average-and less linear). Honestly, I haven’t experienced much in the way of decreased lifespan on the 6V6’s running them a bit low here. They sound extraordinary with a stiff power supply, stiff fixed bias supply, etc. This amp laid the groundwork for what I want to accomplish by furthering the state of the art with this unique work. Always more to come…

JCA