Rose Morris Vox "30th Anniversary Limited Edition" AC30TB (1990 - 1991)



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Tube Complement
Vox 30th Anniversary Limited Edition AC30

V1
ECC83 (12AX7)
Oscillator for the Vib/Trem Circuit
V2
ECC83 (12AX7)
½ used for preamp of Vibrato channel
½ used as a gain stage for Vibrato circuit
V3
ECC82 (12AU7)
Modulator for the Vib/Trem Circuit
V4
ECC83 (12AX7)
½ used for preamp of Normal channel
½ used for preamp of Brilliant channel
V5
ECC81 (12AT7)
Top Boost Tone Control Circuit
V6
ECC83 (12AX7)
Phase Inverter
V7-V10
EL-84 (6BQ5)
Power Amplifier


Specifications
Vox 30th Anniversary Limited Edition AC30
Size (less hardware): 27.5" W x 20.5" T x 10.4" D
Weight: ~68 pounds
Inputs: 6
Channels: Normal, Brilliant (Top Boost), Vib/Trem
Tube Complement:

Four ECC83 (12AX7)
One ECC82 (12AU7)
One ECC81 (12AT7)
Four EL84 (6BQ5)
Power Rating: 33 Watts RMS
Accessories: Single button foot switch
Offered: 1990 - 1991



Vox Amplification Ltd
Rose Morris utilized three UK electronic sub contractors to produce Vox AC-30 amplifiers between 1979 and 1989. From 1979 through 1984, Dallas Industries of Shoeburyness, Essex UK built the AC-30. Audio Factors, an electronics manufacturer based near Leeds in West Yorkshire, produced the AC-30 from 1984 through 1987. In 1988, AC-30 production was shifted to Precision Electronics of Wellingborough, Northamptonshire.

Rose Morris was so pleased with the quality of work at Precision Electronics that they purchased a major interest in the company in 1989. After hiring an in-house staff of engineers, marketing and production people, Rose Morris established Vox Amplification Ltd. as a solely owned production facility for Vox.

Vox Amplification directed their earliest efforts toward the design and construction of a special limited edition amp to commemorate the 30th anniversary of the AC-30 in 1990. One thousand Vox "30th Anniversary Limited Edition" AC30 amps would be produced in 1990 and 1991.

Get Back
Remember the Beatles lyric that commanded, "Get back to where you once belonged?" Vox wanted the 30th Anniversary AC-30 Limited Edition to "get back" to the sound and appearance of an original 1960s era amplifier.

Cabinet
The cabinet of the AC-30 Limited Edition was constructed of particle board like the AC30TBR - Model 1007 that preceded it. Some of these Limited Edition cabinets would be covered in retro style fawn vinyl produced by Brymor in the UK. The balance of the cabinets were covered in the pebbled black vinyl from the AC-30TBR - Model 1007.

Brown Vox Grill
The introduction of the Limited Edition AC-30 also signaled the return of brown Vox fret (grill) cloth. The reissue brown grill cloth created by Vox for the AC-30 Limited Edition had a coarse weave and the diamonds were stitched in vivid red, green and white threads.

Hardware
In addition to the traditional two-pin corners and pancake feet sourced from Rean of London, the Limited Edition AC-30 featured three oversize stamped steel vent grills finished in gold paint. Three vintage style leather handles with brass hardware were mounted to the top of the amplifier while an embossed brass serial plaque was affixed to the upper rear panel.

Control Panel
The nomenclature on the cherry red anodized control panel was silk screened in white paint and easily subject to scratching. A five position voltage selector and fuse were mounted on the control panel near the toggle style power switch, just like 1960 era Vox AC-30 amps.

Egg Foot Switch
A single button foot switch based on the original cast aluminum JMI Vox "egg" pedal was included to control the Vib/Trem effect on the AC30 Limited Edition amp.

Speakers
The Vox AC-30 Limited was equipped with a pair of 12" 8 ohm Celestion G12-M20 Greenback speakers, wired in series to 16 ohms. In catalog literature for the Limited AC-30, Vox stated that the Celestion G12-M20 was "the best acoustic match to the original blue units." The speakers in the Vox Limited amp pictured at left were replacements.

Chassis
The Vox Limited Edition AC30 utilized the full width rectangular anodized steel chassis pan developed several years earlier for the AC30TBR - Model 1007. The chassis fastened to the sides of the cabinet with four bolts.

Circuit Design
Vox developed a single circuit board for the 30th Anniversary Limited Edition AC30 that incorporated just about everything needed to efficiently construct an AC-30, including all of the tube sockets, controls, and input jacks. This board was also shared by AC30TBR - Model 1007 "Standard" amps built after 1990.

Even though it included a printed circuit board that easily accommodated the addition of reverb, Vox chose to not include it in the 30th Anniversary Limited Edition AC30 amp. I suspect this decision was influenced by the fact that reverb was not included in any AC-30 combo amp produced in the sixties by JMI Vox.

Tube amps built on circuit boards often suffer from 60 cycle hum problems caused by the 6.3 VAC heater supply for the preamp tubes. This hum is normally canceled by braiding or twisting the heater supply wires, something not possible with printed circuit board construction. Vox solved this problem in the AC-30 Limited Edition amp by converting the 6.3VAC filament supply voltage to 6.3 VDC.

The power supply for the original Vox AC-30 amplifier included a 10-20 mH 100mA choke and a GZ34 tube rectifier. A redesign of the AC-30 power supply in 1973 eliminated both the choke and the GZ34 rectifier tube. The GZ34 was replaced by a bridge of four diodes. While a tube rectifier was still not included in the power supply of the AC-30 Limited Edition amp, it did include a 50mH 500mA choke.

Certificate of Authenticty
Each 30th Anniversary Limited Edition AC-30 came with a serialized certificate of authenticity personally signed by Peter Clarke, the managing director of Vox Amplification and Dick Denney, the original designer of the AC-30. The certificate stated:

This Limited Edition 1960 AC30 Top Boost has been hand-built in England by Vox Amplification Ltd. to commemorate the Thirtieth Anniversary of this classic amplifier.

The design has been based, as faithfully as possible, upon the original valve circuitry designed by Dick Denney in 1960 for Jennings Musical Instruments, Dartford, Kent UK.

Issue limited to only 1000 amplifiers worldwide.

Photo Credits
My thanks to John Chambers, Champ Electronics, Nottingham England for graciously allowing the Vox Showroom to present the four photos shown at upper left.





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