KPFA-FM  94.1

1990-1991 (David Carroll Electronics, Inc.)

Customer: KPFA
Project Engineer:  Tim McGovern (now CE at Skywalker)
Installation supervisor:  Keith, Jason
Scope of work: Audio control rooms, master control, studios

KPFA Fact Sheet, mostly written by Tim McGovern:

We were retained by KPFA in 1990 to consult on the construction aspects of the new facility. DCE, working with the architect, electrical engineer, and acoustical consultant, helped specify the base building subsystems required to support the broadcast operations. This included proper AC power and grounding, low voltage signal conduit and tray, equipment space planning, and other issues. In February 1991, we began the process of a complete technical systems design/build. The design process included broadcast equipment specification, technical furniture design, audio and control subsystem design, office telephone and data interconnect, broadcast telephone interfacing, and coordination with KPFA staff and construction efforts. The design process proceeded in phases, allowing us to begin the process of cable prefabrication, furniture construction, and equipment procurement in stages. KPFA on-air control room was the first room up and we went on the air with it as scheduled on October 4, 1991. 

GENERAL INFORMATION 

There are five Control Rooms, four small interview Studios, and one large production recording Studio at KPFA. The main KPFA On-Air control room, the KPFB control room, and the News control room all utilize Auditronics 210 series broadcast consoles. KPFA's main Production control room uses an Auditronics 210 for its broadcast side as well as an Otari Soundworkshop 34C mixing console for its music and theater recording purposes. The fifth control room is primarily set up for music and theater production only, so it does not have a broadcast-style board, but uses an Otari Soundworkshop 34C. That room is for the National Asian American Telecommunications Association (NAATA) which is a Corporation for Public Broadcasting consortium. The four interview studios are designated -A-, -B-, -C-, and News. All audio and control signals to and from the studios terminate at a DCE System Five surface mount panel chase. The signals are carried from there to their final destinations in the studio. Each studio is equipped with a wired table which is removable and interchangeable with any other studio's table. Table turrets are fitted with Luxo-mounted microphones, cough and talkback buttons, headphone outputs for four persons, and timer display and telephone. The large recording Studio is designated -D-. It is set up for music and theater recordings as well as for larger interview or roundtable discussion productions. The music/theater side of studio -D has direct interface to the KPFA Production control room's 34C and a separate and direct interface to NAATA's 34C.

Studios -A-, -B-, -C-, and the interview side of -D- can be easily connected to any of the control rooms by using the Multi-Pin Patch (MPP) system. The only exception is News, where that control room and the News studio were designed to be an isolated operation in that regard. The MPP is located in the Master Control room and allows all logic and audio signals to be re-routed using a single patch cord.

KPFA ON-AIR CONTROL ROOM

The KPFA ON-AIR control room was setup to allow for normal Disc Jockey combo operation; for a board operator to engineer for talent located in anyone or more of the studios; and for a board operator/personality to host with guests sitting across from them in the room. The room was also designed to accommodate wheelchair access. The board operator could be in a wheelchair and still have plenty of maneuvering room.

ON-AIR has a 24-channel Auditronics 210 console, three Otari MX55NM reel-to-reel tape decks on rollaround stands, two Panasonic SV-3700 Rdat decks, two Tascam 122MKII cassette decks, two Technics SL-P1300 compact disc players, two Technics SP-10MKII turntables with Audio Technica ATP-12T tone arms and Stanton 681EEE cartridges and Stanton 310B preamps, one 360 Systems Digicart , two Gentner Autonull telephone hybrids, one Loftek TS lRMX test set, Sony MDR-V6 headphones, Electrovoice RE-27 microphones, Meyer HD-l monitor speakers, and four DCE ultra-patch patchbays. The transmitter remote control and status and the Emergency Broadcast System are accomplished with TFT units.

The console overbridge is equipped with various DCE custom panels. These allow for KPFA and KPFB RF modulation meters and peak indicators; Durroughs stereo loudness meters; transmitter program switcher control for KPFA and KPFB; a MPP Studio Active indicator (this shows the operator which physical studios are patched into their console, there is a similar indicator in the studios telling which console has control); studio -A- and studio -B- headphone mixing; front door "doorbell" indicator and door open pushbuttons; status indicators for technical, burglar, and fire alarms; and opto-isolators for interfacing on-air signals and News-ready-to-broadcast signals.

Provision was made for two guests to be comfortable in this control room. They sit across the console from the board operator's position. Each guest position has a microphone, a "Mic On" indicator, a "cough" button, and a headphone jack with volume control. Guest headphones are normalled at the patchbay to receive KPFA air, this feed is isolated from the control room monitor system and from the two studios' monitor systems. This guest feature is commonly used during KPFA's live talk and music programs where the board operator is also the talent. When this area is not being used for guests, it will accommodate a producer for telephone call-in or other more complicated live shows.

This control room can have up to three telephones on the air simultaneously. An Auditronics 210 telephone module and DCE custom switching is used for hybrid interface. At this time only two hybrids are dedicated to this room, however wiring is in place for a third which can be borrowed from another control room. (It is not unusual for some of KPFA's talk show personalities to "phone their part in" and have a guest who "phones their part in" which means the third set can be used for the listeners to "phone their part in").

Miscellaneous features include a DCE custom universal adapter tie line panel, separate volume control for each headphone location, ADC Icon QCP punch block for interconnecting to Master Control, DCE custom swing out equipment racks, provision for a local computer and/or terminal, two video tie lines, custom studio furniture designed by DCE.

PRODUCTION CONTROL

The production control room is basically the same as the KPFA ON-AIR Control Room with the major exception that this room was set up to allow for full-blown recording studio operations as well. After searching for a console to replace the hand-made "recording-style / broadcast -style" console that KPFA was accustomed to using, we decided two consoles was the best way to meet their requirements. The minimal interfacing between the two boards allows for the stereo audio of one to be brought up on the other, and for the SW34C's control room monitor to be muted by the announcer's microphone logic in the Auditronics.

NEWS and KPFB CONTROL

The NEWS and KPFB control rooms are basically scaled-down versions of PRODUCTION and KPFA control. They both use 12-channel Auditronics 210 consoles, and Tannoy PBM8 monitor speakers. Unlike On-Air and Production, these rooms are wired to deal with only one studio at a time, although the second studio's facilities are brought out to the patch bay.

CUSTOM CONSOLE MODIFICATIONS

Sound Workshop 34C The Production Control Soundworkshop console was modified in only two ways. One was to allow pushbutton control of On-Air lights for the Control Room, Studio -D- (the big recording room), and for an interview studio should one be used with the SW34C. We interfaced to unused switches in the ARMS section of the console. The second modification was to allow for the SW34C's control room monitor feed to be muted by Auditronics logic upon operation of a local microphone. This was accomplished using logic controlled relays.

Auditronics 210 The Communications/Studio Module (CSM) was modified thusly: to allow for individual selection of the source feed for monitoring in studios -A- and -B-; to extract pre-fader audio for use with the Headphone 1 feed (one for Studio -A- and one for Studio -B-); extraction of the talkback signal and one-button control ofTB logic for use with the Headphone 2 feed (one for studio -Aand one for Studio -B-).

The console was further modified to balance the provided Cue Buss direct output; to provide for a balanced Cue Buss input; to buffer the Program Buss output so that signal to the transmitter chain is more direct and isolated from feeds used for various utility purposes; to extract individual "Mic On"" tallies for use with the table turrets.

Headphone Feeds Headphone audio is distributed at power amplifier output level and is level/impedance matched a) at the jacks on the studio wall panel, b) at the jacks in the interview tables, and c) at studio breakout boxes for use with musicians. This allows for an almost unlimited number of headphones to be driven with virtually no degradation of quality. It also takes care of the problem of different impedance headphones being used at the same time. The Studios are equipped with two separate stereo headphone feeds. Each of the four headphone jacks on the interview tables can select either HPI feed or HP2 feed. The HPI feed is the no frills version and gets whatever is selected by the Studio's monitor switch bank. The HP2 is the same except that the right channel is a mix of "program"" (monitor switchbank output), "inject" (a patchbay input point that will accept any line level audio), and "talkback" (the output of the control room announcer's microphone activated by the TB pushbutton). HP 1 and HP2 feeds appear in all studios. In studio -D- there are two additional HP feeds. HP3 is the "studio cue" output (stereo) of the Production SW34C, and HP4 is the "studio cue" from the NAATA SW34C.

This is just a partial list of highlights. Any questions regarding the computer network, the non-lA2 phone system, the cable runs, acoustical considerations, various RF and remote systems, ground system, etc. are more than welcome.

Modular Panel System

DCE made extensive use of our Modular Panel system at KPFA. Each studio has at least one panel appearance with several common features. A modular multipin patch system in the master control room was connected to the studios through these panels and allows engineers to reconfigure at will the relationship between control room and studio. A single connector carries microphones, headphones, talley, and telephone information for the studio, enabling quick reconfiguration of the facility. A portable interview table plugs into the MPS panel as well.

Studio Configuration Patch

Multipin patch bay. Each panel mounted connector represents a control room (Some control rooms had two studio capability) and each male cable mount connector represents a studio MPS location.

It's located in the Master Control room.

Swing Racks and cabinetry

We also made extensive use of custom Swing Racks at KPFA to solve the omnipresent problem of no rear access. Most of the control rooms were cramped and the racks had to be built right into the walls. We designed and commissioned all of the cabinets, including the console and racks, and built in the custom steel swing frames where required. This was another project where we advanced the state of the art of our own in-house products, ultimately resulting in the Signal Transport swing rack design.

For some reason we involved an outside cabinet shop on KPFA. Muller-Nichols, basically a large production shop in Oakland, was brought in. Rob must have been busy.