I first heard of the Rothwell In-line Attenuators by reading a review of them in a British hi-fi magazine called "Hi Fi +" (Hi-Fi Plus) which incidentally is an exceptional magazine, well worth obtaining, reading and enjoying. The Rothwell attenuators are quite simple really. They are a male RCA plug on one end, and a female RCA at the other. Inside the attenuator is a "ladder type" resistor network that reduces the attenuation by 10dB through this plug. They are designed to attenuate levels and be inserted in one of two places; in between a line level source, such as a CD player, and the pre-amplifier and/or between the pre-amplifier and power amplifier. This is what the tiny owner's manual says about them:
There is good reason for using these attenuators. Many CD players produce outputs of
2 to 4 volts or more. This is considerably higher than the usual 1V output which was the generally accepted norm before CD players came around. This higher voltage from a source component often overloads the pre-amplifier stage and produces a harsh, strident and edgy sound. Even though a particular pre-amplifier input overload is "rated" higher than the 2 to 4 volt range in the "specifications", many times this higher voltage still overloads or at least distresses the pre-amplifier input stage. This tends to happen often especially if the pre-amplifier is solid state. In my experience, tube pre-amplifiers generally can handle these higher voltages better than solid state ones can.
These attenuators are made by taking a male RCA plus barrel and soldering a female RCA plug to the other end of this barrel. Inside the barrel there are two tiny resistors, one soldered from the hot centre pin of the male to the hot inner sleeve of the female. The other resistor is soldered in "shunt" which means it goes across the connector. This resistor connects the hot centre pin of the male RCA to its ground section. Then the resistors are siliconed inside the barrel. The connector can be opened by unscrewing the barrel from the male RCA end. Use a wide rubber band on both these surfaces to get a better grip and unscrewing the male RCA jack from the barrel. These two resistors, one in "series" and the other in "shunt" produce the 10dB attenuation through the attenuator.
How They Sounded
The attenuators were tried at both positions; between the CD player and the pre-amplifier as well as between the pre-amplifier and power amplifier. In both positions, the Rothwells changed the sound significantly. I'll give you general description first, and then describe the subtleties in both locations. The
Rothwells, in general, made a very obvious change in the sound when inserted in the system. The outcome was that the sound became less stressed, easier on the ears, had more body, less edge, more mass and solidity, but also conversely become softer, less direct, less transparent with the transient dealing edges becoming more subdued and the highs less airy.
The Sonic Details
Let us start by describing the sound of the Rothwell attenuators when inserted between the CD player and pre-amplifier. With the Rothwells in place the sound from my tube output stage Audio Electronics Supply (AES) CD player made by Cary's other division had a blacker background and was more spacious. There was also more space and air around the instruments. The lower midrange and mid to lower bass were more prominent in the frequency mix. This range was brought up in level producing a sound that had more "meat", more body, more solidity, and very easy to listen to. It was more analogue-like, mellower, smoother and had greater separation of instruments in the mix. This made CD's very easy to listen to. This resulted in a less stressed, warmer, fuller balance. It seemed that there was less "overload" on the pre-amplifier section and a better match between the CD player and the pre-amplifier.
Removing the Attenuators
What was lost with the Rothwells is the detail from the music. The sound lost its life, its direct sound, and its quickness. Taking the attenuators out of the loop produced improvement in some areas, but detriments in others. The sound without the attenuators was more detailed, snappier and more articulate. The leading edges of the music were better reproduced. The sound now regained some of its life, zest, snap and vibrancy. The soundstage also was larger and taller, generally bigger. The music was more open, more extended, especially at the highs and the deeper bass. Over all, the music was more articulate, better detailed, with greater microdynamics. The attacks of the music were not only quicker but better integrated with the rest of the music. It was like looking through a clear glass as opposed to a slightly diffused one. The bass now became more punchy, more articulate and tighter but less full sounding…like a speaker designed to have unamplified bass.
Between Pre-Amplifier And Power Amplifier
What about when the Rothwells are inserted between the pre-amplifier and the power amplifier? Well, let's look at my listening notes. Hmm…with the attenuators, my notes read, "more even frequency balance, greater depth, greater decay, less stressed sound, a better sense of ease, greater reproduction of the lower registers of the music such as the lower fundamentals and the lower natural resonances of the piano, warmer sounding, a fuller sound." Continuing, my notes read all is not positive. Notes..."less airy highs, music was softer, electric guitar plucks were softer, drums lacked their attack and quickness, their percussive quality, a fattening and thickening of the music, transients were softened in their attack, robbing the music of its snap and excitement." Well, I think you get the picture.
The Rothwell In-Line Attenuators (they come in both RCA and XLR types) have great benefits when inserted between a CD player and a pre-amplifier and/or between the pre-amplifier and the power amplifier. They make the music less stressful, less edgy, fuller and warmer. This is exceptionally beneficial when playing CDs that can often sound hard, edgy and harsh... the typical
"digititus" type of sound. The Rothwells, I believe, would be an excellent choice to use in a system, especially if one uses a more modest CD player. The attenuators' benefits would be maximized in such a system. In a better system the benefits are less clear, because the Rothwells also lose detail and articulation, and reduce the leading edge of the transients. They lose the life and vitality, the directness of the music. I recommend, however that you try them in you system to see if the
Rothwells' many benefits work in synergy with your particular system. I strongly recommend them if you have a modestly priced or older CD player, or if the gain in your system is too high. I will not use our standard rating system because most of it doesn't apply here.
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