I commissioned Chris Church to build me a custom 4-channel version of his CA-UGLY preamp as part of a long-considered effort to streamline several of my recording rigs. I’m posing to here share the particulars and a few photos of the new setup, and to say thank you to Chris for completing a project that I suspect was something of an interesting diversion for him, but also a PITA with everything else on his plate. Not unexpectedly this took quite a while to bring to fruition, but I want to give big thanks to Chris for making this non-standard odd-ball setup a reality, as well as for his support of this community in general. Thanks again Chris.
As the TS regulars here know, most of my recording setups are atypical multi-channel arrangements used for making both 2-channel stereo and multi-channel surround recordings, so they differ significantly from typical two channel setups used by most members here. Up to this point, combinations of standard gear have done the job, but aren't optimal for a number of reasons. This new preamp is designed for the setup I use most frequently. It greatly simplifies and error-proofs the entire arrangement, makes it easier to use, and makes it more flexible to accommodate a wider range of recording scenarios.
I'd been using two separate CA-UGLYS in this setup ever since I shifted completely to making multichannel surround recordings about 7 or 8 years ago. At that time I was using two completely separate recording rigs in combination, in order to record four channels of information- each rig used two miniature DPA microphones, one CA-UGLY and one Edirol R-09 recorder. Back then I needed to stop and start the two recorders manually, as closely as possible, making a sharp clap at the start and end of each recording as audible "slate-markers" to help with later alignment and sync of the two resulting stereo recordings.
The availability of the Tascam DR2d provided the ability to record all four channels on one hand-held recorder that would fit into a pocket. This was a huge improvement, and the single most important one. However I still needed to manage the two CA-UGLY's and a tangle of wiring, including the four wires from the mics, two microdot-to-stereo-mini-plug 'Y' adapters, and separate interconnects from the preamps to the DR2d. Also, I only had a maximum of ~5dB of gain adjustment easily available (which is the usable range of line-input sensitivity adjustment on the DR2d and can not be changed while recording) because the original CA-UGLYs featured two gain trim-pots for level control, but no global gain control.
The new preamp immediately cuts the preamp and preamp battery count in half, and the wiring simplification greatly reduces the number of intermittency-prone connectors, interconnections and a mess of wiring. It has a single 6-pin mini-XLR input, and a single 6-pin mini-XLR output to the DR2d. All the stereo mini-jack connections have been eliminated up the inputs of the recorder. Cabling is far easier to route and manage, and the rig can be quickly assembled or disassembled as necessary.
Chris built a very nice breakout cable for the mic input side, with four in-line female microdot connectors, staggered to lay flat and not bunch up. That allows me to use standard microdot-terminated miniature DPA mics without chopping and re-terminating them. In this rig that’s four 4060s (In the larger open rig, which I’m also currently reworking, that two 4061s and four 4098s, which will soon be powered by six Naiant PFAs into the DR-680). I only need to plug in the one mini-XLR input and the one mini-XLR output and am ready to go. The breakout cable to the DR2d remains attached to the recorder, reducing wear on the only mini-jack connections remaining in the system.
I’m now considering chopping the four 4060s and terminating them directly to the 6-pin mini-XLR. This would dedicate those mics specifically to this rig, which I’ve previously been reluctant to do, but would allow for customizing the length of each mic lead, completely eliminating the excess cable loop, and eliminating all in-line connections.
Insertion of the 6-pin mini-XLR output connector switches power on to the preamp. Alternately, I can leave everything connected and pop out the 9V battery to power it down. The preamp runs on a single 9V. I like the new battery-tray Chris used, which has spring contacts instead of clamp contacts, less prone to damage over long-term use. We need to relocate the battery tray however, moving the battery so that it extends from the end of the preamp opposite the input/output connectors. That will make the preamp much slimmer and less bulky, about the same thickness as the recorder.
For a few years now, the standard 2-channel CA-UGLY has featured a global rotary gain selection switch in addition to the two channel trim-pots of the original version, and this custom four channel version uses that same configuration. It has two rotary switches (one for ch's 1&2, a second for 3&4). I would prefer a single rotary switch which controlled all four channels simultaneously, but it's easy enough to set both switches identically. They are located adjacent to one another and the switch positions are detented. The switches allow for easy change of overall gain through the preamp to suit different recording situations.
The individual channel trim-pots are retained and are located adjacent to each other, next to the rotary switches. Adjusted individually, these are critical for setting up the correct inter-channel level balance between the four channels. Adjusted together, they also serve to fine-tune the throughput gain of the switch positions, so that the switch positions are properly calibrated to suit the input sensitivity of the DR2d with respect to various recording scenarios. It takes some time to find a comfortable global-gain setting in combination with the appropriate trim-match from channel to channel. In the past I arrived at these settings by trial and error, making slight re-adjustments between recording dates. This time I measured gain through the "entire chain" for each channel using the settings I had arrived at with two original CA-UGLYs, and transferred those settings to the new four channel version. I did this by sending a test tone through each mic in turn (Behringer cable tester as tone generator, driving airline ear-bud headphones, with the small 4060 capsule placed into the silicone flange of one of the ear-buds) and recorded the resulting peak levels numerically indicated on the DR2d. I then did the same after switching to the new preamp, with the two rotary switches placed in a middle position. I then achieved the same gain-staging as before, mapped to a middle position on the gain switches. I can now increase or decrease gain as necessary for very loud or very quiet recording situations using the switches, without touching the trims or needing to adjust the very limited input gain range available on the DR2d.
Here’s some photos of the preamp and its breakouts connected and ready for use with a DR2d and its remote (the photo perspective makes it look larger than it actually is in relation to the recorder in the last couple photos) -