BD955 Broadcast Delay - Eventide Audio

The BD955 Broadcast Audio Delay Line was specifically made for policing live talk shows and became an almost indispensable tool for radio stations at the time of its release. It was also the pioneering product in our long line of profanity delays, paving the way for the BD800, BD600, and more.

The BD955 replaced unreliable tape loop devices with solid state digital reliability. Stereo was also possible with two BD955s, with no degradation in the phase performance.

It was available in two frequency ranges:

7.5 kHz for the reproduction of telephone audio.

15 kHz for quality reproduction of the full audio spectrum.

A Range of Delay Times

It came with three maximum delay times: 1.6, 3.2, or 6.4 seconds. When the BD955 was first produced, its board came with two rows of 1977 memory chips, twice as many as that of the 1745M delay line or the H949 HarmonizerĀ®. Each board provided 800 ms of delay, but when eight boards were arranged together, 1.6 ms could be achieved, long enough to catch short phrases of obscenities, and more boards meant longer maximum delay times. Nowadays, a thumb-nail-sized chip could hold the amount of data of half a million of these boards!

DUMP feature

At the time, it was a common practice in radio stations to wait 7 seconds while the delay tape wound its way through the second machine. But because the BD955 was a digital delay, the DUMP feature eliminated the obscenity with the touch of a finger.

Catch-Up Mode

After removing the obscenity, the BD955’s unique “Catch-Up” was able to automatically rebuild the delay safety margin after objectionable material had been dumped, which eliminated the need to fill time with a taped jingle or announcement. The delay period is able to gradually build while the announcers talked until the station was protected again.

Doubling as Production Tool

The BD955 was also used as a production effects tool and provided delay times from 6.5 ms to the maximum delay time of 1.6, 3.2, or 6.4 seconds. Because of the range of delay times, it was used for “doubling” (giving the impression of multiple singers or instrumentalists) to create unusual echo effects and provide delay for echo chamber feed. Outside of production, it could also be used in television for delaying landline transmission of audio to match the delay introduced in video signals when they are transmitted by satellite!

Front view of the BD955 with the “DUMP” button

BD955 Images

1984 Feldon Audio Eventide Products Ad from Studio Sound Magazine
BD955 Ad in Studio Sound Magazine, October 1978





  • Standard 19″ (48.26cm) rack width.
  • Height equals one rack space – 1 3/4″ (4.45 cm).
  • Depth 12 1/2″ (31.75cm).
  • 10 lbs.

Want More?

Interested in more BD955 history? Check out our Flashback blog.