August 2003

Rothwell In-Line Attenuators
Review by George Papadimitriou (Pappas)
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  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:

What They Do

"High quality, close tolerance attenuators giving a 10dB reduction in signal amplitude. These audiophile devices can be used to attenuate the output from CD players for better pre-amplifier headroom, or to reduce the gain of pre/power amplifier combos to give better control of volume at low levels and improved signal to noise ratio. For more information about these attenuators and other audiophile products, see the Rothwell website.

To attenuate CD players, insert the attenuators into the pre-amplifier's CD input. To attenuate pre/power combos, insert the attenuators into the power amplifier's input sockets."

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.

Many of us audiophiles complain about the harshness of CDs. This is true, but my experience is, after using these attenuators as well as using a Dynaco CDV-1 CD player which has an analogue volume control, that some or perhaps most of this irritating sound comes from sending too high a voltage from the CD player to the pre-amplifier. For example, my volume controlled Dynaco CD player sounds more natural, more relaxed, "closer" to analogue at lower settings of its volume control than at the higher settings. For the same reason, that's why companies like Russ Andrews Accessories in England offer interconnect cables that are attenuated. One can go this route, but obviously it restricts you to using a particular brand of cable - in Russ Andrews case, Kimber Kable, as they are the UK distributor for Kimber. Using the Rothwell attenuators, one can use whatever interconnect one wishes to.

As stated above, the Rothwell In-Line Attenuators can also be inserted between the pre-amplifier and power amplifier. This can also be very useful. Many pre-amplifiers give too much gain or voltage to the power amplifier, or sometimes the power amplifier has an unusually low input voltage to obtain its specified power watt rating. This is exactly what happened when I partnered the pre-amplifier section of my phono integrated 300B Audionote amplifier to the Counterpoint Solid 2A which is a 200 Watt per channel solid-state amplifier.

Plugging the Audionote pre-amplifier section to the Counterpoint amplifier produced too much gain. The sound "came on" loudly even at the lowest volume settings of the pre-amplifier section. This makes adjusting the volume at lower setting much more touchy. Also, as Rothwell points out, the volume control tends not to track very well between channels at these lower volume control settings. Even then, a volume control tends to sound better at higher settings due to the sound having to go through less of the resistive plastic of the volume control. In my case, the Counterpoint was being slightly overloaded as well, sounding somewhat less smooth, but only slightly. The Rothwell attenuators are designed to work here between pre-amplifier and amplifier so that the two can work in better harmony.

Construction

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.

One can clearly hear the benefits of using such a device. It does remove the "overloading" within a system and produces a sound that is less stressed and easier to live with.

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.

With these great benefits, however, came also a cost when this attenuator was inserted. While the sound become warmer, fuller and easier to listen to, it also became excessive. The deepest bass and highs were attenuated as well as the natural transients, the liveliness, the vigour of the music. The sound became more compressed and the dynamic swings were shortened. While the sound was fuller, warmer and easier to listen to, it become too much so, too soft, too mellow, a "Mel Torme" type of sound, pleasant but with little life. The bass, while full sounding became less controlled with less punch and attack, sort of like the sound from a speaker that is designed to give you a fuller more unamplified sound.

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.

However, all this greater detail, articulation and clarity came with a host of nasties. The sound without the Rothwell Attenuators once again became more digital, more stressed with more tension in the music. It was harder to relax into the music. It seemed that the mind had to work too hard to overcome the digital nasties to get to the music. There was a general sense of strain probably due, I suspect, to the overloading of the pre-amplifier stage, although this is just a guess. With this stress, the sound without the attenuators was also more congested and the air and space between instruments that was there with the attenuators in place was not greatly reduced. The soundstage also became flatter, more "cardboard-cut-out" like. The last thing I noticed was that the highlight was now on the mids and lower high frequencies instead of the lower mids and upper lows with the Rothwells. The sound was not as well balanced as with the attenuators in the system.

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.

With the Rothwell Attenuators inserted between the pre-amplifier and power amplifier the sound was basically the same as with them inserted between the CD player and the pre-amplifier. The only difference was that, I would say, the sound changes with the Rothwells "in" and "out" of the system were more obvious when they were inserted between the CD player and the pre-amplifier and slightly, just slightly, less noticeable between the pre-amplifier and power amplifier.

I am pondering the differences in the music when the Rothwells were inserted in the system: their great benefits, but also how they soften the sound, how they dull the transients and lose detail and generally lose information. It occurred to me that this loss of information may be due to the quality of the resistors used inside the attenuators, and to a lesser degree possibly the quality of the metal conductivity of the attenuator itself. It would be interesting, I think, to try this attenuator with better resistors such as the Vishay. Perhaps, one could get the great benefits of this attenuator without the cost in information loss. This can be their Premium or Signature attenuator if this proves to be the case.

In Closing

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.

In the end, when choosing whether this product is for you, or in choosing any product for that matter, is that you TRUST YOUR OWN EARS and rely less on so-called gurus. In the final analysis, don't forget to enjoy the music :-)

Price

UK sales is £39.00 postage free
EC Countries £41 including postage
Rest of the world is £35.19 including Air Mail delivery

Company Information

Rothwell Electronics
180-198 St Georges Road
Bolton, Greater Manchester 
BL1 2PH
England

Telephone: +44 (0) 1204 397788
E-mail: office@rothwell.omnia.co.uk
Website: www.rothwellelectronics.com