Jeff Rowland Design Group Model 7/II power amplifier
A careful examination of the chassis, however, goes a long way toward explaining the stratospheric asking price. A huge 2kVA toroidal transformer occupies a big chunk of the available space, the power supply reservoir caps are impressive looking, and parts quality throughout is excellent. The amp obviously strives for a state-of-the-art appellation. Does it succeed? Well...
Circuitry FETs are used in the input stage for voltage amplification, while bipolars are used in the output stage in a sliding bias configuration. The output stage operates in class-A at low power levels, sliding to -AB as current demand increases. Feedback is used only around individual stages; there's no overall feedback from output to input. Theoretically, this should make this amp immune from transient intermodulation distortion.
The amp is also DC-coupled from input to output, meaning there are no capacitors in the signal path. DC coupling does have one potential disadvantage: any DC offset at the preamplifier outputs will be amplified and fed to the speakers. A slight amount would bias the woofer cones, making them nonlinear, while slightly more could, with an amplifier that puts out this much current, quite possibly burn out the voice coils. To prevent this, the same DC servo circuits that keep the operating voltages at the right levels under no-signal conditions also compensate for any small DC offsets coming from the preamp. If the offset becomes too big for the servos to correct, they simply shut down the power supply. In other words, the amp just refuses to operate under conditions which could do damage, which allows it to embody all the advantages of DC-coupling with none of the hazards.
Most of my listening to the Rowland 7s was done through the MartinLogan Monolith speakers, though I also listened using dynamic speakers. The series II designation refers to current production. Our original sample (series I) mysteriously started blowing fuses after several weeks of use, at which point the series II amps were hand-delivered by designer Jeff Rowland. Several minor changes had been incorporated into the latest version, including modifications to the DC-offset servo so that low frequency 3dB point was changed from 1Hz to 0.2Hz. This latter change, amazingly enough, brought about a noticeable improvement in the amp's bass performance. Admittedly, the Monoliths' low end is not reference quality, tending to be slightly on the loose and lumpy side. At least that's the way it always sounded until the little Eagle 2 amplifier came along. With the Eagle 2, the bass of the Monoliths tightened up significantly and took on a good measure of impact, to the point where it is now quite respectable.
With the Model 7/II, the bass performance on the Monoliths began to approach the Eagle 2's, becoming firmer and better defined in character. It could be argued that the Rowlands simply expose the bass weaknesses of the Monoliths, and to a large extent I think that's a reasonable argument. But the bottom line (pun intended), however, is that the Rowlands still do not control an underdamped low end as well as does the little Eagle (which costs only $995).
Unquestionably, the Rowlands possess a gorgeous high end. The extreme top is, in fact, the best I've ever heard from any ampeither tubed or solid-state. It is very clean and airy in character, with a touch of sweetness, not syrupy and rolled-off as I've heard from some tubed amps. The mid-treble and presence regions, down to about 4kHz, are also exemplary: clean, very smooth, and a little on the soft ide. All of this is quite remarkable for a solid-state amp. My first reaction to these amps after a quick listen was, Gee, they might just cure me of tubophilia (footnote 1).
And close they did come, but no cigar. The Rowland's midband tonal character works against them on the Monoliths, as well as on any other speakers I was able to try them with. The Model 7/IIs are just too laid-back. The midrange is sufficiently distant to make the sound a bit lifeless and uninvolving. I wouldn't go so far as to say that their midband performance on the Monoliths is less than good, but certainly the palable realism offered by the best tubed competition is missing here. This highlights the need to match these amps with speakers somewhat on the forward side of neutral, something I wasn't able to do. I understand that the Model 7/IIs work very well with Dave Wilson's WAMMs (which incorporates an equalizer, making tonal balance problems of the sort noted here relatively unimportant) and the Sound Lab Model A-1 electrostatics.
No matter what speakers I used these amps with, the impression was always of excellent resolution and clarity from top to bottom, together with an effortless quality about the sound that I find very attractive. The Rowland's retrieval of low-level detail in the midrange is outstanding, but somehow they do not appear quite as transparent to me as a bridged pair of Spectrascan model BPA-101s. There's no doubt in my mind that, with the right speakers, I could happily live with these amps. The big question is, though: are they right for your speakers?
If your pockets are deep enough to consider this sort of expenditure, I would advise an audition of the Rowlands. They certainly do not represent value for the dollar, but they are not intended to. The Rowlands attempt to scale the state-of-the-art barrier, where cost is no object. They do so at the high end, but there are still problems through the rest of the range. The high end is where solid state has always had problems, so I have high hopes.Dick Olsher
An Addendum from J. Gordon Holt
But that's not the end of the story. Shortly after Dick Olsher wrote the foregoing, Jeff Rowland paid us another visit withyou guessed ityet another couple of modifications.
These were worth the effort. The result was a virtual transformation; the sucked-out middle range came up, the low end took on added authority and heft, and the already superb high end was unchanged. The amp now sounded superb on every loudspeaker I had on hand, including the MartinLogan Monoliths, with which the laid-back midrange of the Rowlands had mated so poorly in earlier incarnations.
As a result of these latest improvements, I was prepared to give the Rowland 7 an alone-at-the-top recommendation, despite its seemingly outrageous price, but something changed my mind. That something was my exposure to the new SA-1 from Threshold (see Sidebar).
As of now, I can only say that the Rowland Seven/II (or is it III?) is only one of the best amplifiers money can buy.J. Gordon Holt
Footnote 1: An irrational love for tubed audio gear.Dick Olsher