Month: January 2020

I tried to imagine the sort of custom instrument preamp that a top session player might have brought to a studio in The Seventies. Similar in principle to an Alembic F2B (part of many top players’ rigs for decades) but with many crucial improvements, this compact all-tube preamp starts with a classic Fender blackface low/mid/high/bright/vol feature set but adds the following: *master volume, *hi shift, and most importantly an additional output stage that can reliably drive a 10k input at high levels with no frequency loss.

I learned a ton about the idiosyncratic Fender eq circuit by listening and fine-tuning this unit; the various compromises and ‘sweet spots’ that one can find with different cap and pot values. Basic three-stage filter power supply (output stage at 2nd leg) and c/t grounded AC heaters proved more than sufficient; the thing runs dead quiet (zero hum) other than a minuscule bit of reassuring hiss, as i used all NOS 1960s Allen Bradley carbon-comp resistors throughout (which id never do for a mic pre, but for vintage guitar/bass tone its part of the package, i think). The output stage runs at 350 volts, and the input and makeup stages are around 215, allowing for tons of headroom.

Above: the unit with the top cover removed. You can see the sub chassis with the 12AX7 and the 6C4 output driver; a huge Aerovox output cap; and the rugged fiberglass turret-board point-to-point construction.

Above: another internal view. All of the hardware bits are DakaWare, API, and Smith NOS parts from the 60s and 70s, all from my inventory. Signal wiring (orange) is stranded silver 22ga wire and the ground wire (green) is 18ga solid copper.

How does it sound? With bass guitar its absolutely magical- every classic electric bass sound is just there at your fingertips; very inspiring to play thru. Really sounds like a ‘finished’ bass track with no additional processing. The whole package is compact enough to fit in many gig bags.  As for the name? “Super” as the circuit owes much to my beloved Fender Super Reverbs, and “Hugh” as an homage to one of my all-time favorite session greats Hugh McCracken.

I’ve been developing an all-tube rotary-knob DJ console for the soundsystem at Berlinetta Brewing. One idea I decided to experiment with was building the 4 channels of phono pre amps as little plug-in modules, similar to theatre soundsystems of the 1940s and 50s. This would, in theory, allow me to make just 5 of the modules and have “zero downtime” if/when a channel failed. Anyhow, I made one as a demo, and man what a pain in the ass! The device you see above and below uses the classic RCA circuit from their receiving tube manual RC20 plus an additional 6c4 cathode-follower output stage, all built in a tiny grey Hammond box. All i/o and power (300vdc B+, 7vDC heaters) are on an 8-pin Jones for maximum “fake historical authenticity.” It worked out fine, sounds great, very low noise floor, but it’s just too fussy working in that tiny 4x2x2 inch box I will probably end up going with a different solution. Still an interesting possibility though…

I was recently given this circa 1965 Fairchild model 663 optical compressor module. This unit was sold as part of their modular console range of the era. It requires 7V A/C power and it has a completely passive audio path! Seems incredible, but it’s true. Here’s what I did to ‘lunchbox it’ for standalone use in the studio. More details soon…

Last year I found myself with an excess of nice vintage 1:10 and 1:12 audio transformers, so I figured I would make some “Motown”-style passive DI boxes and see how they sounded. I built all of these using genuine 1960s era transformers, NOS Allen Bradley carbon-comp resistors, and NOS vintage hardware components in order to make something that ‘looked and felt’ like the sort of thing that a studio custom-shop would have built in that era. These aren’t copies of the Motown box – that piece used a particular model of transformer which I did not use, and I had my own aesthetic directions to pursue – but like the original units, they have that higher 1:12 ratio, variable defeatable pad, bi-directional operation (for use as a ‘re-amp’) and ground lift switch.

In the past I generally built my DIs with 1:5 or 1:8 ratios, so I was curious to see if the higher ratio gave a more open, detailed sound while still allowing for a sufficiently good signal-to-noise ratio. After building a half dozen of these things, I can say that yes they sound great. Here are a few examples of the units I built.