Sadly Roger A. Modjeski left us all too soon on December 11, 2019, but at RAM TUBES we hope to continue his legacy and provide our customers with high quality tubes for years to come. While Roger is better known for his innovative tube amplifier and preamplifier circuit designs, he possessed a significant amount of knowledge about vacuum tubes and how to best use them in applications. Even going so far as writing his own applications for specific tubes, such as the EL-84 which he selected for use in the RM-10 amplifier to produce 35 watts per channel, when the norm using the tube text book applications produced roughly half that.

Roger got his first professional opportunity to design tube circuits in 1978 at Harold Beveridge Inc. (HBI) in Santa Barbara, CA. Roger started off as the design consultant for HBI but worked his way up to Chief Engineer. It was at HBI that Roger designed the RM-1 preamplifier (along with its companion RM-2 power supply and RM-3 active crossover). The RM-1 was an all tube direct coupled servo-controlled preamplifier (one of the first to ever use a servo) with not one, but two phono sections. Now building a tube preamplifier that used a lot of tubes in the circuit during this period of time was not out of the ordinary, but with two phono sections it had to be quiet. Roger understood that many designs during this era and to this day used the 12AU7, the 12AT7, and the 12AX7 in preamplifier and phono section circuits. However, while doing his research Roger discovered that the 6DJ8/6922 was a very suitable tube for audio, with its linearity and ability to produce the ideal gain for the RM-1 circuit. In addition, the fact that extremely quiet tubes that would work in the phono section were also readily available encouraged Roger to use the 6DJ8/6922 as the tube of choice for the RM-1.

After leaving HBI, Roger founded RAM LABS (the parent company to RAM TUBES and MUSIC REFERENCE) in 1981. It was during this time that Roger developed the computer signal tube tester using proprietary software that he designed for use on an Apple II computer. Roger was never one to shy away from a challenge, and to that end his first circuit design at RAM LABS was the RM-4 pre pre-amplifier (moving coil head amp), born out of the challenge that a tube head amp for a moving coil cartridge was an “impossibility.” His experience at HBI already told Roger that suitable 6DJ8/6922 tubes could be found for the circuit, and he validated this by developing the equipment to measure what he referred to as the “RAM Factor”, first by hand and then later on, and to this day, by computer. Much of the success of the RM-4, and shortly thereafter the RM-5 full function preamplifier, could not have been achieved without Roger’s extensive research and confidence in the 6DJ8/6922 tube, as well as the RAM Computer Tube Tester that tested and graded them.

Up until this point in his career Roger had not designed a tube power amplifier (the notion that he designed the Beveridge direct drive amps was a myth), mainly due to his not having the proper equipment to test power tubes. This changed in 1984 when Roger added this capability to the RAM Computer Tube Tester. Prior to doing this there were a number of challenges to be overcome. Roger found the process of testing power tubes to be entirely different than testing for low noise preamplifier tubes. Testing power tubes required extreme precision to achieve accurate matching. As such, RAM TUBES was the first to offer a two-parameter match of both bias and transconductance. Roger realized that bias matching alone was worthless unless the matching was done at the precise voltages and currents of the specific amplifier in which the tubes were to be installed. According to Roger, that realization made conventional matching a joke, as his research determined that bias and transconductance matching is the only way to get an output stage to perform optimally.

With the capability to now test power tubes Roger went on to design a number of critically acclaimed amplifiers. Originally destined to be The RM-6, Roger’s first Output Transformerless (OTL) design was instead sold to Mike Elliott and became the Counterpoint SA-4. Roger followed that with what many felt is his finest achievement, the RM-9 dual ultralinear amplifier, designed for the EL-34 tube, but also capable of operating with KT-77, KT-88, and 6550 tubes. The RM-9’s feedback (gain) circuits were an innovation at the time and with the MkII version Roger fused all the output tubes, made all the fuses accessible from the top plate, and provided LED indicators so users would know when a fuse blew and the tube that was responsible for it blowing.

Further innovation came with the RM-10 amplifier that used the EL-84 tube (a pair per channel) in a manner that achieved 35 watts per channel, where previously half that was the norm. The last large production amplifier from Roger was the RM-200. This design used a differential circuit and was a hybrid amplifier using both tube and solid state circuits. Most hybrid amplifiers use a tube input section with a solid state output section. However, Roger flipped it and used a tube output section featuring KT-88 or 6550 tubes. While this was out of the box thinking, the real innovation came from the fact that the amplifier increased power as the speaker load decreased and remained stable down to a 1 ohm load.

While not an extensive history for a man who excelled at his profession for 40 years, we hope this narrative provides a suitable history of Roger’s research with tubes and experience with tube circuit designs. More importantly we hope that it instills confidence in you the consumer that RAM TUBES is uniquely qualified to meet your vacuum tube needs.