should i change v1 preamp tube or phase inverter ac15

The circuit diagram for the AC-30/4 is found on JMI schematic OA/032, dated April 29, 1960. The AC-30/6 had a new and unique circuit design that was prefered by Vox lead engineer Dick Denney. Finally, the unique design of the AC-30/6 was not merely an adaptation from the AC-15. This eliminated the problems with microphonics common to the AC-30/4. Secondly, the AC-30/6 circuitry did not include the troublesome EF-86 tube. Having three channels with individual volume controls, the AC-30/6 offered the ability for three instrumentalists to play through the amp simultaneously. First, it was not unusual for an English band to pool their money to buy one good guitar amplifier and share it. The AC-30/4 made no appearances in Vox catalogs and price lists after 1961.Ī number of opinions have been offered why JMI would decide to retire the AC-30/4 in favor of the AC-30/6. The AC-30/4 continued to be offered in the 1961 price list, probably to reduce existing inventory. By the time the 1961 Vox catalog was released in mid 1961, the AC-30/6 was included but the AC-30/4 was not. Thoroughout the first part of 1961, AC-30/4 and AC-30/6 amps were sold concurrently by JMI.

This facilitated the addition of a third channel in the AC-30/6. The AC-30/6 replaced the single element EF86 preamp tube used in the AC-30/4 with a dual element 12AX7.

When JMI introduced the four input AC-30/4 in mid 1960 it was their 'top of the line' amplifier but it was joined by the six input AC-30/6 before the end of the year. As the AC-30/4 and AC-15 shared the same preamp circuitry, the AC-30/4 also included an EF86 tube in the preamp stages of the Normal channel. Vox head engineer Dick Denney so liked the higher gain and rich harmonics of the EF86 pentode tube that he designed it into the preamp circuits of Vox AC-4, AC-10 and AC-15 amplifiers.

Should i change v1 preamp tube or phase inverter ac15