Rose Morris Vox AC30 Top Boost and AC30 Top Boost Reverb (1979 - 1984)
A Look "Under the Hood"

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The UK musical distributor Rose Morris (RM) purchased the Vox brand from Dallas Arbiter in 1978.
Shortly after the purchase, Rose Morris established a corporation in the UK called "Vox Limited" to produce new Vox products.

The AC30 Top Boost Reverb amp chassis shown on this page is an example of the first generation AC-30 produced by Rose Morris. RM offered this version of the AC-30 from 1979 through 1984. The component date codes of the chassis shown on this page suggest it was produced in early 1982.

This amp was manufactured for Rose Morris by Dallas Industries in Shoeburyness, Southend-on-Sea, Essex, England. This same facility produced the Vox amps sold by Dallas Arbiter from 1973 through 1978.

This first generation Rose Morris AC-30 chassis featured an anodized steel base to support the weight of the transformers and a vertical aluminum stamping in the shape of an inverted "L" to mount the preamp circuits and control panel. Dallas Arbiter used

this same chassis for their 1973-1978 production of hand wired AC-30 amplifiers. The RM, Dallas and the original JMI AC-30 chassis were all nearly identical except the Dallas and RM chassis versions were slightly taller.

The RM, Dallas and JMI chassis were each bolted to a slider board that allowed the chassis to be removed like a drawer for service. The RM slider board included a foil ground shield and a vent screen under the power tubes to improve flow-through cooling.

Figure 1 - Point to Point Hand Wiring - 1963 JMI Vox AC-30
Hand Wired vs Circuit Board Construction
The original JMI Vox AC-30 amplifier featured hand wired, point-to-point circuit construction (See Figure 1 at left). The leads of all the electronic components were manually wrapped and soldered around lugs mounted to phenolic tag strips. All interconnections between the tag strips, tube sockets and controls were also hand wired and soldered. Building a tube amplifier with hand wired, point-to-point construction offers a number of benefits. In addition to being incredibly durable, hand wired amps provide ease of service not possible with printed circuit boards. However, hand wiring an amp as complex as a top boosted AC-30 was labor intensive and costly to produce.

Stolec Industries produced Vox amplifiers from 1970 to 1972. The redesigned Stolec era Vox AC-30 was built on two large printed circuit boards. One board contained the preamp circuitry, the second contained the power amp. All of the tube sockets were mounted directly to the circuit boards. The heat of ten tubes caused these circuit boards to warp, causing premature failures of the amplifier.

Dallas Industries bought Vox from Stolec in 1972. Dallas recognized that the reputation of the AC-30 had been damaged during the Stolec period. Dallas decided to restore confidence in the AC-30 by taking it back to the original hand wired, point-to-point construction used by JMI Vox in the sixties. The hand wired AC-30 was produced by Dallas Arbiter from 1974 through 1977.

After several years of producing the JMI Vox style AC-30, Dallas discovered they were making little money on the amp due to the high cost of producing the hand wired chassis. It became evident that Dallas needed to return to printed circuit board (PCB) construction to restore profitability. However, Dallas learned the pitfalls of PCB construction several years earlier when they liquidated the troublesome Birch-Stolec AC-30. The engineers at Dallas came up with an innovative solution to incorporate PCB construction into the AC-30 that would not sacrifice quality or dependability. Their ingenious design would combine the best attributes of hand wired and circuit board construction.

Figure 2 - Green PCB Strips - Dallas/Vox Sound Ltd AC-30 (1977 - 1979)

Dallas replaced the three hand wired tag strips in the AC-30 with three strips of translucent green phenolic printed circuit boards (see Fig 2). These PCB strips were the same size and shared the same component layout as the original hand wired tag strips. The hand wired tag strips and their and PCB counterparts were so similar that they were virtually interchangeable. As the tube sockets were mounted to the metal chassis and not to the PCB strips, heat related failures were all but eliminated. Please click here to take a closer view at a Dallas AC-30 with translucent green PCB strip construction.

Dallas Industries sold the Vox brand to Rose Morris, a UK distributor or musical goods, in 1978. Rose Morris extended a manufacturing contract to Dallas Industries continuing production of the AC-30 and other amps in the existing Dallas facility at Shoeburyness.

Figure 3 - Brown PCB Strips - Rose Morris/Vox Limited AC-30
By early 1979, Dallas replaced the three translucent green PCB strips with equivalent PCB strips made of opaque brown phenolic (Fig 3). I believe that most of the AC-30 amps produced by Dallas for Rose Morris (Vox Limited) had these brown PCB strips.

The AC-30 Top Boost Reverb model added a full length Accutronics delay line to the standard AC30 Top Boost model. The reverb circuit was powered by two ECC83 tubes and a hand wired circuit mounted to the inside bottom of the chassis.

No additional holes needed to be provided in the top panel to accommodate a reverb control. To create a position for the "Reverb" control, Rose Morris combined the "Vib/Trem" and "Speed" controls on to one six position rotary switch. The allowed the "Reverb" control to be mounted in the top panel position formerly used for the "Speed" control.

Control Panel
The control panel used on this first generation series of Rose Morris AC30 amps was finished in gray paint. The control nomenclature was silk screened on the panel in gold paint. The gray control panels installed on JMI Vox amps featured an etched and filled finish that offered greater resistance to scratching.

Links to Additional Rose Morris AC-30 Amp Topics in the Vox Showroom
  • The 1979 - 1984 Rose Morris AC30 Top Boost Reverb
  • 1979 Rose Morris Product Catalog
  • 1981 Rose Morris Product Catalog
  • 1985 Rose Morris AC-30 Top Boost Reverb

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