ROTHWELL in-line RCA audio attenuators (pair)(Model:10dB)
Here's the solution to a problem from which far too many audiophiles suffer - too much gain in the system. The symptoms are easy enough to spot - the volume is plenty loud enough with the volume control set to the 9 o'clock position, too loud with the volume control at 10 o'clock, and fine control at low levels is impossible. This may seem like nothing more than a minor irritation, but in truth the performance of the system is being compromised. Although potentiometers work reasonably well over most of their operating range, they are notoriously problematic at extreme settings. The most obvious problem is channel imbalance - one channel will fade out (or fade in) quicker than the other, causing the stereo image to shift to one side - but on a more subtle level, the music may sound veiled and indistinct with the volume control turned down to the point where it is nearly off. Some people have tried to cure the problem by fitting a more expensive volume control only to find that it doesn't do much good. That's because the volume control isn't really the problem.
It's the excess gain in the system which is the real problem. That in turn forces you always to use the volume control over a very limited portion of its travel. What's needed is a way to reduce overall system gain without compromising sound quality and without major modifications to the equipment itself.
The Rothwell In-Line Attenuators are the answer. These audiophile devices simply plug into any input sockets and reduce signal levels by 10dB. They can be used with integrated amps or pre/power amps, and are compatible with equipment over the entire price spectrum, from budget to extreme high end.
When used with integrated amps (simply plug them into any input sockets, then plug the source component into the attenuators) the volume control will be two or three "hours" further round its range than it was before, giving better control at low levels and operating well away from the end stops. When used with pre/power amps, there is an added benefit.
Although the attenuators can be used on the inputs of the pre-amp in exactly the same way as they would be used on an integrated amp (with the same benefits), alternatively they can be used between the pre-amp and the power amp to even greater effect. When used this way, not only is system gain reduced by 10dB, but the signal to noise ratio is improved by 10dB. This pushes the noise floor down enough to create an inky black silent background from which the music can emerge with better resolved fine detail and transparency. This applies to even very high-end and very expensive pre/power amps.
So, if you recognise the symptoms of excess gain in your system, the Rothwell attenuators are the answer. Don't be put off by the fact that you could pay much more money for an audiophile tweak such as a set of spikes. These attenuators give real, measurable as well as audible improvements and are perfectly at home between pre and power amps costing as much as the family car! And for users of balanced equipment we now have a balanced version available.
"The sole role of your Hi-Fi system is to extract the information recorded on your source material and generate sufficient power to drive your chosen loudspeakers.
Ideally, apart from any required equalisation, nothing should be added and nothing should be taken away. Of course the signal chain adds both noise and distortion. One source of distortion arises from feeding one component in the chain with too large a signal from its preceding component.
A common problem occours when the power amp is matched to speakers of such high sensitivity, that the signal from the preamplifier need only be a small fraction of the maximum obtainable in order to drive the loudspeakers to the required volume. This results in the volume control being set at close to its lower limit, where often the channel matching is not at its best.
A more effective volume control setting can be achieved by attenuating the signal either to the preamplifier or power amplifier. The key to this approach is to reduce the signal strength without modifying it in any other way, either by creating impedance imbalance, adding noise or causing distortion.
Rothwell sell attenuators for exactly this purpose. These are simple devices based on potential dividers housed in otherwise straight-through female-male phono plugs. The trick in making these work well is the choice of resistors so that there is close channel matching (claimed to be 0.1 dB) and appropriate input and output impedance. These devices therefore are designed to provide a purely passive resistive load that gives 10dB signal attenuation.
In my system I had a very specific application in mind when I was asked to test these accessories. I have a heavily modified active system based around Naim audio boards, recovered from very early components. That is to say that the frequency filtering is performed between the pre and power amps by an active crossover. The active crossover provides third order filtering with both input buffers and output amplification to compensate for the 3dB per order loss in the filters.
Whilst this set up provides a wonderfully fast, pure and powerful sound, the active crossover does increase the noise floor such that with no signal it is just audible when seated in the listening position. Not a major issue but a little annoying when listening to quite passages.
With the attenuators placed at the input to the power amplifiers, the background hiss was inaudible except when a few inches from the tweeters. In the listening position the system was silent - exactly the result I was hoping for.
But the real test was whether there was any audible degradation in the sound quality. After a number of A/B testing sessions with and without the attenuators in place I could discern no change in signal quality.
The only difference was that the volume control had to be set to about 2 o'clock with the attenuators in place rather than the normal 10 o'clock. In my system this is not an issue as there is plenty of headroom in the amplifiers. Additionally, as the volume control is normally set between 10 and 12 o'clock, well away from the lower limit, I did not expect to benefit from any improved resistance matching in the channels.
In conclusion then, these are very useful devices for improving signal to noise. In some systems that suffer from a large excess in signal (unlike my own which is well-matched) there might be much larger gains to be had. They are certainly very effective in my system and as far I can tell simply reduce the signal and nothing more - exactly as it should be! Whilst it may be possible to DIY such a device, I hardly think it worth it since channel and impedance matching will take some time and a good selection of resistors. A well finished and effective device from Rothwell offered at a sensible price that in some systems could be the most cost effective up-grade on the market."
© Copyright 2002 Steve Davey - http://www.tnt-audio.com
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