Solid State Preamp Reviews

As I write these words in January 1991, we're right in the midst of an annual media feeding frenzy: the "Best of the Year" follies. This usually takes the form of lists compiled in groups of ten for reasons that must hearken back to some obscure Druidic practice. You know the routine: "Ten Best Books of the Year," "Ten Best Films of the Year," "Ten Top Personalities of the Year," "Ten Best Sports Plays of the Year." Every corner of the media seems eager to get into the act. Special-interest magazines are hardly immune. Car enthusiasts can get their fill of "Cars of the Year." Computer literates find their favorite rags full of the "Ten Best Computers/Computer Accessories/Computer Programs." And music magazines regale us with the "Ten Best Recordings of the Year." Everyone with access to a transmitter or printing press has got, it seems, a little list.

Well, almost everyone. The high end of audio doesn't deal much in calendar years. Products are not introduced, allowed to shine, then retired from the scene in a scant 12 months. But if this reviewer were to pick the single most exciting product he has lived with over the past year, the choice would be easy: the Jeff Rowland Consonance. What this new Rowland preamplifier provides is, in my experience, unique: repeatable control—including wireless remote operation—performed in a manner which in no way compromises its top-drawer sound.

I first saw a prototype of the Consonance in 1989, at the Stereophile Hi-Fi Show in San Mateo. It may have been formally brought to market in 1989, but it didn't appear widely until 1990. My experience with it began in mid-1990, and it became an indispensable part of my reference system about an hour after I hooked it up. And therein hangs a tale.

Actually, I knew before I even received it for review that the Rowland Consonance had a strong potential to rope in this reviewer. The reason lies in an important factor which (for me) must be controlled in any critical listening test—playback level. If I listen to a particular piece of music today over a given system and form a particular impression, the impression I form tomorrow or next week will be different unless the level is the same. As it will when comparing equipment in the tried and true audiophile fashion—listening first to one amp/preamp/whatever, swapping leads to another, and repeating the experience. Everyone knows (don't they?) that in a direct A/B the levels must be precisely matched. Less well appreciated is the need to closely control the levels in any type of comparison. "That seems about the same" just isn't good enough.

With a conventional preamplifier, adjusting the level in any sort of precisely controlled or repeatable fashion is not easy to do. Adding outboard networks and auxiliary volume controls is, for the perfectionist audiophile, anathema. Measuring the levels before every selection played (and again when switching components) is more than tedious. The routine can detract seriously from what we hope will be a typical listening experience. In the past I have settled on using an overlay around the volume control (usually part of an index card secured with tape which won't leave a residue) and carefully marking selected levels on this overlay. This does not allow the type of level matching required in an instantaneous A/B, but for less stringent swapping it gets me within 1dB, often less than 0.5dB.

While a stepped volume control may seem to be an answer to this dilemma, it can be a decidedly mixed blessing. The steps on most such controls are often too coarse—frequently more than 1dB. While this is fine for repeating a given volume setting at a later date with the same equipment, it can make matching levels (say between two power amps) next to impossible.

The Rowland Consonance (though certainly designed with day-to-day usage rather than listening tests in mind) gets around this problem by dispensing with rotary controls altogether. All of its controls are light-touch pushbuttons which control (through a microprocessor which is not in the signal path) hermetically sealed, gold-contact relays which in turn control all of the preamp's switching and level-set functions. In the case of the latter, the relays switch in appropriate attenuator resistor-ladder networks. A front-panel, 20-position fluorescent display indicates all of the selected functions of the preamp, including the level setting. The 200 individual level-control steps permit fine adjustments for close level-matching and accurate, repeatable settings. To add icing to the cake, the display indicates the level setting for each channel separately.

Balance adjustment is accomplished by means of the very same relay/resistive ladder, but distinct balance-control pushbuttons (labeled L and R, for left- and right-channel increase) are provided. When the user elects to shift the balance to the left, the first action the Consonance takes is to increase the left channel level by one step. Next, the right channel level is reduced by one step. And so on, until the desired balance adjustment is completed. Thus overall system level is maintained within a fraction of a dB.

The Consonance also provides a unique memory and recall mode. It is possible to select and store a specific level for any or all of the six inputs. By entering the recall mode, the selected level is automatically entered upon switching to that input. If you're into instantaneous A/Bs, I don't need to explain the value of this capability. If you're not, it's still a useful feature.

Every front-panel control is duplicated on the substantial (metal, not plastic) hand-held, wireless remote control included as standard equipment. Other front-panel or remote-controllable features, in addition to the above-mentioned volume and balance functions, are input selection, left-cut and right-cut (useful for system setup and troubleshooting), mono, absolute phase reversal, mute, and display-blanking (in case you prefer not to have that display illuminated all of the time—though a single small figure remains illuminated in the blanking mode). Selection of the input to be fed to the tape output jacks may also be made from the front panel or the remote; it need not be the same input being fed to the main outputs. The obvious use for this capability is to enable the user to listen to one source while recording another. But an additional use suggests itself: by routing to the record output a different input from that being fed to the main outputs, a connected tape deck's input circuitry will not load down the primary source during critical listening (the tape output is unbuffered).

Since those 200 level settings are rather fine (each step was measured to be between 0.1dB and 0.25dB), two additional level-set controls (up-fast and down-fast) on the remote raise and lower the level 10 steps at a time. (These "coarse" adjustments are also available on the front panel by using a slightly different procedure). Three additional controls on the remote, labeled I, II, and III, have no apparent current function, but are there to provide for future additional capabilities which can be incorporated into existing units by updating the microprocessor.

Two ergonomics problems are worth noting. The first, a potential source of confusion, involves the input (and record) select indications on the fluorescent display. These merely indicate the selected input numbers, 1 through 6. You must remember what you plugged into each input; the numbers won't tell you (except for 1, which is always phono when the preamp is phono-equipped).

The second quirk is potentially more troublesome, but applies only to early samples of the Consonance, ours included. Suppose that you have a tuner connected to input 5 and your tape deck hooked up to input 6. Normally you would select 5 for the playback source (the signal to be fed to the main outputs) and 5 for the record source (the signal to be fed to the tape outputs. Want to monitor off the tape? No problem, select 6 as the playback source and, assuming you have your tape deck set up properly, you will hear the tape playback of the radio program. But if you then inadvertently select 6 as the record source (there's no reason for you to want to do this, but suppose Murphy has dropped over to hear the show), you'll very likely be subjected to system-busting feedback.

You should never be able to select a functioning tape recorder as its own recording source. I've seen this undesirable configuration in other high-end preamps. The ergonomics of the Rowland, however, with its numbered, unlabeled inputs and easy remote-control access, make such an accident more likely than with any of the others. Fortunately, Rowland has informed us that shortly after we received our sample, a change was made in the Consonance effectively "locking out" input 6. That is, it is impossible to select input 6 as the feed to the tape outputs. A tape deck which is to be used for recording should, therefore, always be connected to input 6. If you own an older sample of the Consonance and use a tape deck, exercise caution (or contact Rowland about a modification to your unit).

It's impossible to fully appreciate the value of having all of these features—especially volume, balance, phase reversal, and mute—controllable from the listening position until you've actually tried it for yourself. I don't know what's kept high-end manufacturers from designing remote control into their preamps, but it's likely been market-driven. To be sure, Rowland was not the first to come out with such a product. The Meitner preamp (and its newer Melior cousin) has been on the market for some time, and Meridian provides extensive remote control in some of its products, notably the 208 CD player/preamplifier and their new D-6000 amplified loudspeakers. But none of these products provides quite the flexibility (or fine control of level) of the Consonance.

Other high-end manufacturers are treading lightly into remote-control territory, perhaps concerned that their customer base is not yet ready to accept the concept. Rowland themselves have related to me an interesting story concerning the Consummate preamp (their top-of-the-line unit having control and readout functions similar to those of the Consonance). On a visit to one of their dealers, they found it being displayed and demonstrated without the remote—which was still hidden away in the shipping carton. Was the dealer lazy, careless, or simply trying to "hide" the existence of remote-control capability?

Granted, it's expensive to implement a remote in a way which meets high-end concerns. But Rowland has met that challenge here. I don't mind telling you that the remote control is not only addictive, but surprisingly beneficial sonically. Fine adjustments—one or two steps (less than 0.5dB) at a time—can make a significant difference in the satisfaction level of the overall reproduction. Not dramatic. Not earthshaking. But significant and worthwhile. To refer to the capability as akin to having an audio focus control would not be far off the mark. And being able to do such fine-tuning from the listening chair means that you can accurately and instantaneously assess the subjective effect of the change. As a listener I find such a capability enticing. As a reviewer I find it invaluable—especially when combined with the front-panel readout (footnote 1). To get a better idea of just why I like the latter two features so much, see the accompanying sidebar.

Although one might argue that relay-activated controls can be troublesome, I can only observe that in several months of use none of the relays in my sample have malfunctioned. Rowland states that the relays are guaranteed for 100 million activations, a claim that I, for one, do not plan to verify.

Both inverting and non-inverting RCA outputs are provided on the rear panel of the Consonance, as are fully balanced XLR outputs. Nearby is the socket for the remote-control receiver (located in its own, separate chassis for flexibility of placement), the detachable power cord, and the on-off switch. Rowland recommends that the Consonance be left powered-up at all times (it consumes only 30W in idle). Turn-on, turn-off surges are prevented by temporary muting during power application, power drop, or power interruption. And whenever the Consonance is powered up, its fluorescent display puts on a little show. First it reads "The Consonance." Then, before reverting to the normal operating display (which begins in an all-zero mode at power-up), it reads "phono-equipped" if the phono module is installed (it may be deleted, if desired).

The inside story
Internal inspection of the Consonance revealed the expected (at this price) high-quality layout and construction. Banks of relays are visible, as are the DIP switches used for impedance matching. Two other DIP switches adjust the remote's speed of operation. (The latter feature is not discussed in the owner's manual, nor is the fact that the remote can be adjusted to operate on an alternate frequency should interference occur with the remotes of other equipment.)

Both the phono and the line stages of the Consonance are encapsulated onto plug-in circuit boards. The phono module, if installed, may be configured via DIP switches (located under the module) for either moving-coil or moving-magnet pickups. Other internal DIP switches provide 12 different settings for cartridge loading (11 low-impedance settings plus 47k ohms), three line-input impedances (600 ohms, 10k ohms, and 100k ohms), two output impedances (150 and 300 ohms), and adjustable line-stage gain (located, as with the phono-stage gain adjustment, beneath the module).

An internal six-position terminal block permits the Consonance to be easily configured for worldwide power compatibility. The 100VA power transformer has separate secondaries for the analog stages and the microprocessor control section. The analog supply provides rectification and filtering; local regulation is provided within the phono and line modules themselves. The supply for the microprocessor functions (footnote 2), following its own rectification and filtering, is regulated with a circuit which shuts down the "digital" functions and mutes the output of the preamp if the supply voltage drops to less than 95V (for the 120V configuration). This so-called "watchdog" regulator is followed by additional regulators for the digital display and relays.

All amplification stages in the Consonance are FETs operated in class-A mode. The phono amplifier module is divided into two stages. The first stage is comprised of paralleled, high-transconductance FETs operating at a total of 40mA without negative feedback. The user-adjustable switching (to select MC or MM gain) is located at this stage, as is the 75µs portion of the RIAA equalization (that portion which performs the high-frequency rolloff). The second stage operates in a current feedback mode; the feedback elements here provide the 3180 and 318;us portions of the equalization (the 3180µs portion provides the RIAA low-end boost, the 318µs provides the required slope below 1kHz with a knee at 500Hz). The phono stage is direct-coupled (as is the rest of the preamp), with DC servos incorporated to correct for DC drift. It should be noted that this phono stage provides an inverted polarity signal to the tape monitor outputs (though not to the main outputs).

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Footnote 1: A number of high-end manufacturers showed prototypes of remote-controllable preamps at the recent 1991 Winter CES. These seemed to be invariably implemented with motor-driven pots, and did not provide the precise repeatability and informative display of the Rowland.

Footnote 2: Rowland refers to this as the digital supply, which is technically accurate but potentially misleading: the "digital" functions of the Consonance are strictly of the switching variety.