Dallas Vox AC-30 Control Panel - 1973-1979

Dallas Industries Vox AC-30/6 Top Boost 1976-1978
Dallas Industries Vox AC-30/6 Top Boost w/Reverb 1976-1978
PCB "Strip" Construction

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Dallas Vox AC-30 - Front View
Dallas Vox AC-30 - Rear View

Fig 1 - Twin rows of slender vents on early Dallas AC-30 amps

Fig 2 - Larger Rean vents from later Dallas AC-30 amps

Fig 3 - Two position voltage selector switch concealed under the back panel

Fig 4 - Printed circuit tag strip construction

Fig 5 - 12" Fane "Blue" speakers

Dallas inherited quite a mess when they purchased Vox Sound Ltd from Birch-Stolec in 1972. During their ownership of the Vox brand, Birch-Stolec reduced the Vox product line to just a few items that still had some appeal in the market. Amp production was limited to a few solid state models such as the Defiant, Supreme and Foundation Bass. Birch-Stolec also produced a redesigned AC-30 based on two fragile and undependable printed circuit boards (PCB). By 1972, Vox sales in Europe had flat lined.

To make matters worse, Birch-Stolec didn't employ an engineering staff to develop new products. The innovative engineers from Jennings, including Dick Denney, had all moved on to other employment. Birch Stolec couldn't even turn to the US Vox operation for ideas. US Vox sales had dropped to the point that Thomas Organ, the manufacturer of Vox amps for North America, withdrew developmental support for new products.

Dallas Industries was no stranger to the music business. Prior to their acquisiton of Vox in 1972, Dallas had been appointed the Fender distributor for the UK. Dallas also manufactured and distributed the "Sound City" line of guitar amplifiers and the iconic "Fuzz Face" distortion pedal.

Dallas offered Vox the opportunity to regain the ground lost during the Birch-Stolec ownership period. Dallas provided Vox a technical staff for product development and even gave JMI founder Tom Jennings an advisory role in the company. The "Vox Sound Ltd" corporate name was retained. Production was moved to the Dallas facility in Shoeburyness, Essex UK.

Before new production could start, Dallas had to liquidate an unsold supply of printed circuit AC-30 amps passed down from the Birch-Stolec purchase. These remaining printed circuit AC-30s were featured in a 1973 Dallas Vox sales flyer.

Even as Dallas was selling off the remaining stock of Birch-Stolec amps, they were busy preparing a new version of the AC-30 for production. The new Dallas AC-30 would dump PC boards in favor of JMI style tag strips and hand wired, point-to-point construction. Aside from a bridge of diodes replacing the GZ34 rectifier tube and an additional roll of slender vents to improve ventilation (see Fig 1), the new Dallas AC-30 amp was close to identical to the original JMI design.

When Dallas purchased Vox from Stolec, they received about one hundred 12" Celestion Vox Alnico Blue speakers in the deal. This is significant because Celestion had discontinued producing this speaker a year earlier due to high costs. The first fifty or so of the new Vox AC-30 Top Boost amps produced by Dallas had the original Vox Alnico Blue speaker installed. After the stock of Alnico Blue speakers was depleted, Dallas Industries switched to a pair of 12" Celestion Green Backs.

Dallas offered this hand wired AC-30 from 1974 to 1977. A second hand wired AC-30 that included Accutronics spring reverb was introduced in the 1976 Vox catalog.

Dallas was building a superb JMI style AC-30 but the high cost of producing the hand wired chassis meant that the amp wasn't making any money for the company. It became evident that Dallas might need to return to printed circuit board (PCB) construction to restore profitability. 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 without sacrificing quality or dependability.

Dallas replaced the three hand wired tag strips in the AC-30 with three strips of green phenolic printed circuit boards. These PCB strips were the same size and shared the same component layout as the original hand wired tag strips (see Fig. 4). 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 PCB strip construction.

Dallas produced models of the AC-30 PCB strip amp with and without reverb. The amp had six inputs and three channels: Normal, Brilliant and Vib/Trem. The power section of the amp produced close to 40 watts through four cathode biased EL84 tubes operating in parallel push-pull mode. Power supply rectification was handled by a bridge of four IN1007 diodes.

A two position voltage selector slide switch, mounted vertically on the rear edge of the chassis, toggled between 220 and 120 VAC mains. The switch was normally concealed by the upper back panel (Fig. 3).  

The cabinet was constructed of particle board and included eight "two-pin" black plastic Rean corners, no logo handles, black basketweave vinyl and black Vox grill. Most amps featured six slim air vents (Fig. 1). In later production, Dallas replaced the slim air vents with a trio of large plastic Rean air vents (Fig. 2).

The AC-30 PCB strip amp was originally supplied with a pair of 12" Celestion Green Back speakers. Dallas made a change to a Fane 12" speaker in later production (Fig. 5), probably as a cost saving move.

Dallas offered the AC-30 with PCB strip construction until they sold the Vox brand to Rose Morris in 1978. Rose Morris extended a manufacturing contract to Dallas to continue production on the PCB strip AC-30 through 1983.


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