1960 AMPEG B15-N
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In 1960 Ampeg introduced the B-15 Portaflex combo amplifier. It's innovative design allowed the amplifier head to unlatch, flip over, relatch and be stored upside down inside the speaker cabinet when not in use. Thus the name "Fliptop".
The 1960 B-15 featured a chrome chassis shock-mounted onto the lid and white silkscreened graphics. The original design had two channels sharing tone controls and also a stereo input jack. By October 1960 the design had changed to the two channels having their own dedicated tone controls. Normal and bright input jacks were now included on channel 1. Also the knobs changed from black heptagonal to black stove type. The on/off/standby/polarity knob changed to three metal switches. The fuse moved from the front of the chassis to the back. The blue power light moved from the front of the chassis to the top. The tube cage's texture changed to smaller holes. The tin badge logo with deep blue background changed to a chrome script logo.
Other 1960 Portaflex characteristics: Two large black transformers, black tube cage protecting the tubes and capacitors, two prong power cord, one leather handle, Navy Random Flair vinyl covering, grille cloth, "optional" side port holes, 4 chrome lid latches, 8 pin XLR speaker cable and jack, serial number sticker including tube chart, 15 inch Jensen speaker, matching dolly with wheels.
The serial numbers are 6 digits in length with the following pattern: YMMNNN, where Y denotes the year, MM the month, and NNN the # unit produced that month. The # unit, however, may not have started with 001. Ampeg may very well have used 100 or 101 as the starting point during slow production periods. Nevertheless, for dating purposes, the serial number provides adequate information during this period. For example, an amp with serial number 406123 was made in 1964 (4), during June (06) and was probably the 123rd amp made that month (123).
Caution is needed for dating amps from 1960, as the serial numbers from this year were duplicated in 1965. A serial number 009054 could be from September 1960 or it could be from the second serial number system implemented in 1965. The key is the model and the cosmetics. For instance, an Ampeg from 1960 would be covered in navy random flair vinyl whereas an amp from 1965 would be covered in blue check vinyl. Another check for a 1960 versus a 1965 or later serial number (i.e. numbers beginning with 0) is that the second and third digits of the number denote the month in the first serial number system. Therefore, a serial number where these two digits are greater than 12 must be from the second serial number system (1965-69). For more precise dating cross reference the serial number with the amplifier's transformer, potentiometer, capacitor and speaker codes.