1969 AMPEG SVT
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On June 22 1969 Ampeg debuted the Super Vacuum Tube "SVT" amplifier at the National Association of Music Merchants "N.A.M.M." convention in Chicago. This amp was a milestone design utilizing 300 watts of power specifically designed for larger venues.
The preamp and chrome chassis were usually hand numbered (with matching numbers). However we've seen early year 1969 SVT's without any hand numbering. By October the two front power switches began changing from plastic to metal (with one being black). Both versions have been seen throughout 1969. The inside of the wooden box was unpainted but by October occasionally sprayed black.
In 1969 Ampeg manufactured three different types of removable back panels for the SVT. The first version was painted black with white silkscreening and was produced in June and July. The serial number was stamped into the right side of the back panel. The second version of removable back panel was introduced in June. This version was chrome, still with white silkscreening and serial number stamped into the right side. By October serial numbers began to be stamped into the chassis, between the standby switch and the external amp jack. This change prompted a third version of back panel, which now had a "cutout" in the middle of the panel for viewing that serial number on the chassis underneath.
Other 1969 SVT characteristics: "Blueline" silkscreened graphics with detail etched into the metal, two channels, small black "D shaft" knobs with silver tops, black plastic tone adjustment rocker switches, small round red power light, silver grille cloth with no badge logo, exposed plastic fan, two prong power cord and outlet on back, fuse, 4 pin female XLR speaker cable, Linden manufacturing name on backplate, two metal cord wraps, (3) black transformers: power, filament and output, 6146B "bottleneck" power tubes, circuit boards, capacitors, CTS (Chicago Telephone Supply) potentiometers with both plastic and metal "D shafts", vinyl handles, smooth vinyl covering, tube chart sticker, manila envelope containing schematic, six rubber feet, eight chassis connector bolts, CTS speakers, 8x10 inch speaker cabinet with three handles and matching dolly, literature.
Ampeg 1969 serial numbers used the prefixes 080xxx through 092xxx. We were informed by a retired Ampeg employee that 1969 number stamping sequentially corresponded to the 12 manufacturing months of the year. Leftover units at the end of 1968 used the 080xxx prefix, January 1969 started at 081xxx, Feb 082xxx, March 083xxx, April 084xxx, May 085xxx, June 086xxx, July 087xxx, August 088xxx, September 089xxx, October 090xxx, November 091xxx and December 092xxx. The SVT was introduced in June 1969, therefore the first units should have an 086xxx serial number. Two of the 1969 SVT's that we've owned had the serial numbers: 08677x (June) and 08710x (July). For more precise dating cross reference the serial number with the amplifier's transformer, potentiometer, capacitor and speaker codes.
Component code dating vintage SVT's: As with all vintage gear, the manufacture date is determined by the newest component/date stamp on the unit. On vintage SVT's, the newest date code on the unit is usually the four digit white ink stamp on the large output transformer. The first two numbers indicate the year, the third and fourth numbers indicate the production week of that year. Example: 6937 means a transformer made in the 37th week of 1969. However we have seen early 1969 SVT's where some transformers have NO date codes at all.
Other codes to determine the manufacture date: The other large power transformer and the adjacent smaller filament transformer usually have six digit codes stamped into the metal. The first three digits indicate the company's personal manufacturing code. Those should be 682, which indicate the Electrical Windings Company. The fourth number indicates the year. The fifth and sixth numbers indicate the production week of that year. Example: 682920 means a transformer made by Electrical Windings Company in the 20th week of 1969.
Potentiometers are also date encoded. There is a seven digit code stamped into the metal. The first three digits indicate the company's personal manufacturing code. Those should be 137, which indicate Chicago Telephone Supply or CTS. The fourth and fifth numbers indicate the year. The sixth and seventh numbers indicate the production week of that year. Example: 1376915 means a pot made by CTS in the 15th week of 1969. Capacitors and speakers can also be dated in a similar manner.
At the beginning of the Rolling Stones Los Angeles rehearsals for the 1969 U.S. Tour, The Stones blew up all their U.K. Fender amplifiers, due to failed power conversion transformers. At road manager/keyboardist Ian Stewart's request, Ampeg gave the Rolling Stones all five of their prototype SVT heads to use as their entire backline. The tour ran from Nov. 7 to the infamous Dec. 6 1969 show in Altamont, California. Other than those five prototypes (and subsequent replacement amps) given to the Stones during that tour, there were very few actual 1969 SVT amplifiers manufactured. The Rolling Stones endorsement helped turn the SVT into the world's premier concert bass amp.