News / Articles

The Manley-Modjeski Letters (Redux) Part 2

In this month’s Roger’s Corner, we present the final installment of the Manley-Modjeski letters. However, before we get to the letters, I want to share some personal recollections recently provided to me by one of Roger’s friends who worked with him during this period. As mentioned in last month’s article, David Manley used the term “nimble” in reference to tube rolling in the RM-9 amplifier. Roger’s tongue-in-cheek response was to refer to himself as, “Chief Spokesman of the Nimble Tube Rollers Society (NTRS).” Roger then took it a step further and put his sense of humor on display by having NTRS pins made and distributing them at the Consumer Electronics Show (CES) in Las Vegas.

It was also noted that the RM-9 was 15 amplifiers in one, based on the tube type and gain (feedback) setting used. Stopping shy of a recommendation, Roger mentioned 6L6 tubes could also be used, with the trade-off of reducing the RM-9’s output power by 50%. So, we now have an amplifier that is 18 amplifiers in one. Through my own personal experience, the only other amplifiers that offered similar flexibility during the RM-9’s run were the Mesa Baron and Cary V12. However, their flexibility was enhanced by the ability to select different modes of operation (e.g., pentode, triode ultralinear, and combinations thereof), while the RM-9 was specifically designed to operate in ultralinear mode.

The last item brought to my attention concerned Roger’s trip to Yugoslavia to visit the Ei factory before the civil war. He came back with a bunch of KT90s and a mixed review, noting that although the factory had manufacturing capabilities, it lacked the equipment or expertise to truly design a new tube. After performing his usual rigorous testing, Roger became frustrated with the performance of the Ei KT90s, and RAM Tubes never endorsed them. This is noteworthy because the KT90 became one of the key topics of the debate.

The final Manley-Modjeski letters were published in the same issue of Stereophile (Vol. 14, No. 6, June 1991), in the Manufacturer’s Comments section, and presented back-to-back in order of submission. The titles and page references are as follows:

1. Modjeski, Music Reference, VTL, & Tubes: Written by Roger A. Modjeski, pp. 289–293.
2. Manley, VTL, & RAM: Written by David Manley, pp. 293–297.
3. VAC on VTL vs RAM: Written by Kevin Hayes, pp. 297–299.

I found it odd that the first series of letters appeared across multiple issues, while the final series was published together. Could Stereophile have been fed up with the debate? Since Kevin Hayes’s letter was an attempt to play peacemaker, perhaps Stereophile felt that running all three letters in the same issue would provide closure and put the matter to rest. I do know one thing: Stereophile asked Roger whether it could share his letter with David Manley before publication and whether he would mind having their letters appear in the same issue. In a letter to the editor dated January 14, 1991, Roger objected to the idea. Nevertheless, it seems evident that Roger’s letter was shared and his letter and David Manley’s response did, of course, appear in the same issue.

As noted previously, Roger visited the Ei factory. Although he found its output tubes to be substandard, except for the 6BQ5/EL84 which was a Philips design, he liked the small-signal tubes such as the 12AX7 (many Telefunken-branded 12AX7s were made at the Ei factory) and the 6DJ8. Roger tried to work with Ei to improve the quality of its output tubes, but in the end, money talked. David Manley placed a large order for KT90s, and because Ei needed the business, it fulfilled the order. Roger’s research and data, along with feedback from others in the industry, supported the view that the tube needed correction. David Manley, however, thought the tube was “...the greatest audio breakthrough of the decade.”

While Kevin Hayes shares a similar philosophy on tube design as David Manley, his commentary on the debate was balanced and everything I would expect from the gentleman he is. One thing I noticed while reading the letters is that each designer discussed not only the physical and electrical characteristics of tubes, but also their sound. One comment from Kevin Hayes that caught my attention was that “...a particular tube’s sonic traits in a particular circuit are largely designed-in, not selected for.” In other words, a tube audio designer does not select a tube because of its “sound” as technically it does not have one. Instead, the tube is selected because its electrical characteristics meet the needs of the designer’s circuit topology.

I would show Roger comments from audiophile forums discussing the sound of tubes. He would eventually laugh, but not before launching into one of his classic rants. Roger liked to say, “It is not as if the factory workers show up in the morning and the floor boss instructs them to get ready because we are making ‘warm’ tubes today.” Of course, the audiophile in you wants to believe tubes have a “sound.” As Roger noted, the tube’s interaction with the circuit, and the resulting distortion characteristics, creates the sound one hears. Roger preferred a transparent, balanced sound, so that is what he designed for in the circuit.

Lastly, I appreciated Kevin Hayes’s comment about a card he received from Vacuum Tube Logic (VTL) introducing the KT90 as something, “...better...that can be plugged into your amplifier in place of either a 6550A or KT88.” Well, I guess that after all the letters and debate, David Manley decided to become a member of the NTRS. That very premise is reminiscent of Roger’s RM-9 design philosophy in that certain tube types could be swapped without any side effects. So, did David Manley really have an epiphany, or did he invest so heavily in KT90s, financially and promotionally, that excess stock dictated he needed to sell more of them and so adapted his tube-swapping philosophy accordingly? This may be one of the great mysteries in audio, and we may never know the answer.

The Manley-Modjeski Letters