Blue Note Music

Amplifier Authentication & Evaluation Checklist

 

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BASIC INFORMATION

Manufacturer: Ampeg

Model: GS - 12 R

Serial Number: 038891

Circuit Designation: Reverb rocket II

Estimated Production Year: mid to late 1966

Country of Manufacture: USA

PRIMARY AUTHENTICATION

Serial Number Verification

Chassis Inspection: No stamp, no added holes, no modifications

Circuit Verification: early circuit distinguished by the 6U10 Compactron Tube

Circuit Identified As: GS-12-R

Power Transformer: PT-110V 682623

Output Transformer: OP-151A 682622

Potentiometer Codes: 1376623 137 CTS 23rd week of 1966

Tube Chart / Factory Labels: Present and original

CABINET AUTHENTICATION

Construction: Original not modified - Pine

Covering: Original

Type: Tolex

Grill Cloth: Original

Hardware

Handle: Original

Corners: Original

Feet: Original

Logo: Original

TRANSFORMERS

Power Transformer: PT-110V 682623 is consistent with mid to late 60’s

Output Transformer: No EIA manufacturer or date code visible

SPEAKER SYSTEM

Speaker Configuration: 1x12

Speaker Manufacturer: CTS

Speaker Codes: 137

Speaker Assessment: Original in good working order

ELECTRONICS AUTHENTICATION

Capacitors

Filter Capacitors: Yellow axial electrolytic caps are replacements. Green Cornell Dubilier film caps are replacements. One blue resistor appears newer than the others. The large red electrolytic cap is a replacement

Coupling Capacitors: Partial replacement

Wiring Harness: Original

Solder Joints: Original with Caps exception

TUBE COMPLEMENT

Power Tubes: Sylvania 7591 correct for the era, appears original

Preamp Tubes: Amperex 12ACX7 ECC83 - appear original

MODIFICATIONS

Functional Modifications: None 

STRUCTURAL CONDITION

Cabinet: Minor wear

Chassis: Excellent

FINAL EVALUATION

Condition Grade: B

A+ — Exceptional / Collector Grade

Outstanding originality and condition. Among the finest examples likely to be encountered.

A — Excellent

Highly desirable example with only minor wear and no significant issues.

B — Very Good

Strong vintage example with normal wear and minor repairs or service replacements.

C — Good Player Grade

Functional amplifier with noticeable modifications, repairs, or originality loss.

D — Project Grade

Requires significant repair, restoration, or maintenance.

F — Parts / Salvage Grade

Major damage or missing components make restoration impractical.

Originality Grade: 02 - Mostly original

Structural Grade: S1 - Excellent

Repair Grade: R0 -  no work recommended

Authentication Confidence: High -  John Maynard

FINAL NARRATIVE SUMMARY

The 1966 Ampeg GS-12R Reverb Rocket II is an authentic and highly desirable vintage American tube amplifier that represents one of Ampeg's most respected mid-1960s designs. Authentication confirms the amplifier retains its original pine cabinet, tolex, grille cloth, hardware, chassis, wiring harness, factory labels, CTS speaker, and the distinctive early Reverb Rocket II circuit featuring the sought-after 6U10 Compactron tube, making it an excellent example of this model. The amplifier has received thoughtful maintenance over its lifetime, including replacement filter and select coupling capacitors along with one resistor—common and desirable service items that enhance long-term reliability while preserving the originality of the circuit. It also retains what appear to be its original-era Sylvania 7591 power tubes and Amperex ECC83/12AX7 preamp tubes, further adding to its authenticity and collectability. Graded B (Very Good) for condition with an Originality Grade of O2 (Mostly Original), Structural Grade S1 (Excellent), and Repair Grade R0 (No Work Recommended), this amplifier offers an outstanding balance of originality, reliability, and investment potential. With its rich Ampeg clean tones, lush tube-driven reverb, and warm vintage character, this Reverb Rocket II is equally appealing to collectors, recording musicians, and players seeking a genuine mid-1960s American tube amplifier that is ready to enjoy immediately while remaining highly collectible.