VOX - Model V807 ECHO REVERB
and the story about disc-echoes:
“ Ray Lubow and the Electrostatic Storage System Tape based echo effects units for guitar were growing in popularity in the late 1950s. These units recorded the original or "dry" signal from a guitar onto a loop of audio tape that passed over a series of playback heads, creating the "wet" effect of an echo. However, tape based echo units required frequent head cleanings and periodic replacements of the tape loop. Electronic technician and entrepreneur Ray Lubow invented an echo device in 1958 that eliminated the need for audio tape and multiple tape heads. Lubow's motor driven "electrostatic storage system" and "delay apparatus" were granted US patents in 1960. Ray Lubow and his brother Marvin founded "Tel-Ray," a company located in Gardena CA dedicated to the production of tapeless echo effects devices for musical instruments. At the heart of Lubow's "tapeless echo" design was a spinning platter oriented vertically inside a steel can. The specially treated metallic surface of the platter acted as a capacitor, allowing charges to be stored on it's surface. Several neoprene brushes made contact with the spinning platter. One brush recorded the audio signal onto the platter in the form of an electrostatic charge while several other brushes spaced around the platter played the sound back. The delay in playback caused by the rotation of the platter created an echo effect. Lubow's patent called for adding about a tablespoon of oil to the inside of the steel can to improve performance. A slight oil coating on the platter lubricated the brushes and helped the recorded signal from discharging prematurely. As a result, Lubow's electrostatic memory disk earned the nickname "oil can delay." The Thomas Organ "Electrostatic Memory Disk" Prior to acquiring the trademark rights for the Vox brand in 1965, Thomas Organ developed an echo circuit including an "electrostatic memory disk" for their home organs. Thomas adapted this echo circuit from their home organs for the Vox V807 Standard Echo Reverb. While Fender, Gibson and others were willing to pay Tel-Ray a license fee to utilize the tapeless echo design, Thomas Organ was not. The engineers at Thomas Organ designed an motor driven electrostatic echo storage device similar to the unit detailed in Lubow's patents but the Thomas version eliminated the need for oil. This small change may have been all that was necessary to work around the patents. The photo above of the rear of the V807 Standard Echo Reverb chassis offers a view of the rear plastic cover of the belt driven Thomas electrostatic memory unit. The thick wire located at the 2 o'clock position of the rear cover connected to the brush that recorded the electrostatic audio signal onto the spinning platter. The playback signal was picked up by wires mounted to brushes located at the 9, 10 and 3 o'clock positions on the plastic cover. The black grounded wire at the 4 o'clock position appears to connect to an "erase" brush. Grounding an area of the the disk would remove the electrostatic charge, erasing the recorded signal.“
cred: voxshowroom.com