Ampeg is the exception that proves the rule about amplifier dating: the company published a guide to its own serial numbers, organised by era, and that guide admits that two of those eras cannot be dated from a serial number at all. Work through the eras in order, and be prepared to hear "no data" from this site rather than an invented year.
1. Before 1953: there is no serial number
The earliest Ampeg amplifiers carry no serial number. The only dating evidence is the EIA component codes inside them — see EIA codes explained — combined with model history. Our decoder answers these with the component route, not with a fabricated range.
2. 1953 to mid-1965: YMMNNN
Seven digits in the form YMMNNN: the first digit is the year, the next two are the month, the last three are the sequence within that month. The sequence could start at 100 or 101, so a low number is not necessarily an early one. Because the system repeats every ten years, the leading digit is ambiguous wherever the decades overlap: 3 reads as 1953 or 1963, 4 as 1954 or 1964, 5 as 1955 or 1965.
Documented ranges include 301001–312999, 401001–412999 and 501001–512999, while the 1960s numbers look different again: 1960 runs 1001–12999, 1961 runs 101001–112999 and 1962 runs 201001–212999.
The resolvers come straight from the sources: blue check vinyl rules out 1954 and points to 1964; navy "random flair" vinyl rules out 1965 and points to 1960; a Mercury circuit with 6V6 valves points to 1960. Model history, circuit, cosmetics, number structure and component codes, in that order, is the documented disambiguation method.
3. Early 1965 to 1969: sequential six-digit numbers
Ampeg then moved to a straight sequence: 1–20000 = 1965, 20000–49000 = 1966, 49000–75000 = 1967, 75000–80000 = 1968 and 80000–92000 = 1969. Sources disagree on the top of the last range — the official knowledge base and one dealer guide give 092000, Blue Book gives 090000 — and we show both rather than choosing silently. A serial beginning with 0 late in the decade belongs to this second system when its second and third digits are greater than 12.
4. 1970–1979 and 1981–1985: no data, so read the features
Under Magnavox (1970–79) and MTI (1981–85) the serial numbers are not datable from published records. The era is identified from the amplifier's features instead. Documented markers:
- Blue control-panel graphics, 1968–72.
- Black graphics with square corners, 1972–75.
- Black graphics split horizontally with rounded corners: solid-state amplifiers 1973–79, valve amplifiers 1976–79.
- A distortion control knob, 1976–79.
- White rocker switches from 1973–79 on solid-state and 1976–79 on valve amplifiers, against black rocker switches 1968–75.
- A metal "A" logo 1968–75 against a plastic one 1973–79.
Three or four of these together usually narrow an amplifier to a few years, which is a better answer than a fabricated serial range.
5. 1985–2005: the SLM ten-character serial
SLM-era serials are ten characters, LLLCYMNNNN: three letters, a country letter, a year letter, a month character and a four-digit sequence. Country letters: U = U.K., Y = Europe, W = worldwide, D = domestic or U.S. Year letters from 1988: A = 1988, B = 1989, C = 1990, D = 1991, E = 1992, F = 1993, G = 1994, H = 1995, I = 1996, J = 1997, K = 1998, L = 1999, M = 2000 and onward. Months: 1 to 9 for January to September, then 0 = October, A = November, B = December. The official example is AJYDB60626 = United States, June 1989, number 626.
One warning catches people out. From 2006 Ampeg used a different table with the same letters: C is 1990 in the SLM era but 2010 in the later one, and F is 1993 against 2013. The tables must never be mixed.
6. 2006 onwards
From 2006 the serial is XXXXBBYMNNNN, where BB is the place of assembly and the month is given in half-month steps, A being the first part of January and so on. Codes up to 2023 are documented; the source has nothing for 2024–2026 and we do not extrapolate.
Safety, before you go looking
Ampeg's own text carries an explicit warning: lethal voltage remains stored inside valve amplifiers after they are switched off and unplugged. The SVT, SVT-CL, SVT Pro and V-series in particular should not be opened by anyone without experience — read the serial from the outside. The same warning sits on the model cards, including the SVT.
What this means in practice
A 1950s or early-1960s Ampeg gives you a month, a late-1960s one a year, a 1970s one nothing but its features, and an SLM one a month and a country. Enter what is on the plate in the Ampeg decoder and you will get the era, the rules that applied then, the candidates where a digit is ambiguous, and an honest no-data answer where records do not exist. One source disagreement belongs on the record: guitarserialnumbers.com states that Ampeg never published an amp chart and that factory logs are lost. That holds for the guitar line; for amplifiers the guide is published by Ampeg itself at ampeg.com/kb, and that is what we follow.