A good client wanted to know if I could build him a '55 Super. Or maybe a '54 Pro. Or maybe a '57 Deluxe. So I came up with the 61 South, that gets the exact circuitry of the Pros, Supers, and Deluxes from '53 through '57. Here is a whole lot of vintage Tweed tone in one modern high quality amplifier. Galactic ground scheme, decoupled stages, extremely high quality low noise long life electrolytics, Vishay/Dale 1W resistors, and a combination of Sozo and Wima caps. Vintage goodness without the vintage problems. --- Start with the basics. Ceramic tube sockets securely mounted with stainless locking nuts to a good quality chassis. Also stainless steel standoffs for the board. --- Rubber grommets for the transformer wires, bayonet bases in place for the preamp tubes. While I don't personally like tube shields, I use high quality ones. --- "Bear trap" retainers for the octal tubes. This amp can use 6L6s, 6V6s, EL34s, 5881s, pretty much any octal tube out there. And because it's cathode biased, you can mix and match if you want. --- Board in progress. Custom board, everything military spec, through hole plating, heavy duty traces, separate shield and grounding, galactic ground scheme, etc. Everything can easily be serviced - even the electrolytic caps can be replaced without removing the board. PCB with the serviceability of eyelet board construction. --- Mercury Magnetics transformers ('59 Bassman power, Radio Spares OT). The original Fender designs used way too low a primary impedance for the 6L6s being run in cathode bias. I chose a 45W MM Radio Spares output transformer so I could offer both the Fender 4K primary impedance and a much more correct 8K primary. The amp is much louder and more dynamic at 8K. --- PEC and CTS pots, shielded connections where necessary, everything "just so." As this was the first build, some parts of the circuit were tweaked, so there are about three wires and one "flying" cap that won't be present in future builds. While this build used Sozo coupling caps, due to Sozo's unpredictable availability, future builds will use Cornell Dublier WMF coupling caps (same high quality, same "correct" construction for the desired tonal response). --- Rear panel. Note the ability to switch between 450V and 350V for the plate voltage. The old amps used 5U4 rectifier tubes and had a low plate voltage. As the amp is cathode biased with a fairly steady current draw, I skipped a tube rectifier as "sag" was not an issue and all the tube would offer was more noise and a weak link in terms of ruggedness. At the 350V setting the amp has the B+ of the 5U4 (and you can use old 6V6s safely). But it's nice to get the most out of 6L6s, so the 450V is there. You can also choose between a choke and a resistor for filtering, and between the old and a more correct primary impedance for the output transformer. --- The channel selection and trem can be controlled either from the front panel or remotely. The V1 socket is wired so that if the client uses a 12DW7 tube, Channel 1 (no tone control) has more gain than Channel 2 (tone control). This makes it really easy to go from clean to dirty with the touch of the foot switch. V1 can be 12AU7, 12AY7, 12DW7, or 12AX7, depending on the amount of gain desired. --- Steel inserts hold all the screws securely to the cabinet. --- The finished amp. I chose the "carbon fiber" fabric as a nod to the tweed Fender used, but clearly this is not trying to be a "vintage amp." --- OK, the magic switches... V1 bias chooses between grid leak bias (as on the early 5C Fenders which is more compressed with more low end and not as much note to note separation) and cathode bias (as found on almost all amps made since '55 or so). Channel Mixer chooses between the early Fender channel blend (with very interactive controls and a ton of gain) and the later mixer as used on the Bassman, which has more channel separation and a lot more clean headroom. Nice to have both. Inverter chooses between the early Paraphase phase inverter and the later Cathodyne, which has a little more output and a different kind of overdrive. The NFB (Negative Feedback) switch is a 3 way switch, which offer no nfb in the center (like the old Fenders), slight negative feedback to the left (slightly cleaner sound), and a good bit of feedback in conjunction with a (preset) Presence control (as introduced on the Bassman) which offers a gain increase with more brightness. And while the old Supers, Pros, and Deluxes didn't offer it, I put in a Bias Tremolo of my own design. Because they are cool. My trem circuit uses a solid state oscillating circuit to save heat and tube failure, but the solid state components are not in the audio path. Also note the "Voltage" knob instead of a Master Volume. This is my own version of power scaling and it works fantastically for cathode biased amps. The Speed LED always flashes in time with the Trem, and is slightly dimmer when the Trem is not on. So the player can set the speed visually before turning on the Trem. Nice not to have to guess. --- The rear. This amp is using two Weber Alnico 12A125As at 20W each. A perfect match for this amp. The cab is my design and was built to my spec by Lopo Line - they did a great job. Void-free birch plywood, dado joints. Solid as they come. The cab has wonderful low end response and a huge, detailed sound. Note the rear jack on the top panel - this allows the cab to be used as a 2x12 with any amp. Plugging in here bypasses the connection from the 61 South. The 61 South can be had in the 2x12 version shown, a 1x12, or a head version. Silver (shown) or black carbon fiber finishes. --- The foot switch for the 61 South, which connects to the chassis with any 5 conductor DIN (MIDI) cable.