hobbyists's views for hobbyists
Keith Eichmann's Bullet Plug

Page first published on the www June 29, 2001

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The RCA Phono Plug Reinvented:

When I got word from Rob Woodland of Eichmann Technologies of Australia that the RCA phono plug had been reinvented by Keith Louis Eichmann and was going into production, I was very curious of course. What would the new plug be like and would it function better than any other high end phono plug?
When I saw the cutaway of the Bullet Plug - as Keith's invention is called - my curiosity was even greater, but at the same time I saw already one aspect of which I knew that it was beneficial: just the bare essentials and nothing more.
Soundfountain Bullet Plug review



For the least signal loss - especially in analog connections (phono, pre-pre) - I always prefer and use the cheap, plastic RCA phono plugs which have as little metal as possible, instead of the bulky, high-end, luxurious types which suggest the bigger-is-better quality and are attached to many so called high end cables, or have been soldered by hobbyists to their own chosen leads. But as I have found out: Golden shine can blind your eyes but should not fool your ears. It all depends on what is underneath the polished surface.
The very tiny and rather weak signals generated by a phono cartridge should not meander through much metal and loose their integrity. Especially the signals of MC cartridges need great attention. My idea always has been that after the phono signal had been amplified significantly, the more sturdy type of plug could be used.

So, I was pleased to see that the connection of the earth lead, which is a collar normally, had been replaced by just a pin. There is however another significant construction detail of this earth pin. To the eye it is tiny, but one is easily fooled. Indeed it is small in diameter. However Keith Eichmann found that there should be a specific ratio between the earth and the hot signal in loudspeaker cables and interconnects. He calls it rightfully the "Eichmann Ratio" and he appli8es this also to the Bullet Plug. The formula is a ratio between the signal and return conductors, where the return (small pin) has greater cross sectional area and mass than the signal (large pin) – based on the wall thickness of the signal pin. This, notwithstanding the fact that the cutaway of the Bullet Plug may suggest otherwise.


There are more reasons of equal importance why the Bullet plug was designed this way. The classic phono plug lets the signal suffer from “Eddy current” distortion as electrons proceed to and from the RCA socket into the collar through multiple contact points. There also occurs a "Capacitive” distortion where gaps exist between the socket and the collar, the air being the dielectric. And finally there is “Micro-arcing” distortion which is brought about by an electrical short that can occur where gaps exist between the socket and collar. Although these are new to me and to most audiophiles and technicians as well, it explains why already in the nineteen seventies many hobbyists soldered the cables of the sources (especially those of the signal from the turntable) to the amplifier's inputs and also from the outputs straight to the loudspeaker cables in order to achieve a pure as possible contact. They could not explain the technicalities, but certainly had heard the difference.



Except for the true high end brands (like Cardas for instance), most connectors on the market are made of brass. And brass has a very low conductivity. It will transmit only 28% of the signal. It is clear that in order to have a maximum transmission the use of brass should be avoided. The metal which provides undamaged signal transmission, or in more scientific terms: will not inhibit the flow of electrons, is US Tellurium Copper. And why not use copper if the cables you use are highly conductive because they probably are made of copper as well (if you do not use silver conductors). To counteract corrosion the pins are gold plated.
If you have looked carefully at the image, you will have noticed that the earth will not connect with its full length, but just with a small surface over a few square millimeters. This way the flow of electrons is concentrated at that specific point and cannot dissipate and loose its integrity.


There is another novelty. When I asked Robert Woodland about the use of nickel in relation to the gold plating of the pins he answered: "We were able to apply gold plate directly with none of the problems associated with direct gold plating standard copper. You will notice that the gold plate on the Bullet Plug contact pins is quite dull. With a nickel substrate the appearance is very shiny. The gold plate is 20 micro-inches thick, or 0.00005mm. It is purely there to prevent oxidation - not to contribute in the conductive process. In fact gold is less conductive than tellurium copper."

All these details about the design is theory of course, but practical theory as you will find out, and certainly not a formula for the sake of having a formula for marketing purposes. The Bullet Plug works.
As you may know by having visited "Audio & Music Bulletin" (see the link at the top) I am a lover of analog recorded sound. After receiving a pack with 4 Bullet Plugs I cut off the old plugs of the phono cable I had been using and soldered the Bullet Plugs on that same cable. Changing cables would certainly lead to a less objective evaluation. After a few hours already, but certainly after a day or two, the plugs and the very little solder I used, were practically burned in, although I discovered that the signal continued to improve the first days.


Dissipation of the signal in many conventional plugs leads to anomalies in time. That means that the phase of the signal deteriorates and the harmonics of acoustic instruments are being hampered because not all information does reach the amplifier at the same instance so to speak. Now the complete signal seems to be intact, has speed and sounds tight, which means that the phase is correct.

A weakness of my active speaker system, which I attributed to an incorrect adjustment, was entirely gone. There is no make belief openness and space which are often displayed by bulky plugs. Now the orchestra sounds straight. Transient response is exemplary, also because the midband is in phase now. The sound has become more dynamic and articulate, which is specifically apparent in the brass section in symphonies. Playing Rachmaninoff's 3rd Symphony for example, conducted by Walter Weller on an original DECCA, the timpani has a firm attack and the brass players stand out with warmth and clear sonority.


Massed strings have more texture. Cymbals have that build up and presence which one hears in the concert hall. Henryk Szeryng playing "Kreisler Favorites" (a beautiful Mercury recording on a even beautiful Fontana pressing by Philips) displays a violin tone with uncanny realism and sharpness. The variations in pressure of the bow on the strings have significantly improved.
Phase is a very important aspect. If the phase is not correct, people with sensitive ears can easily feel a sort of nausea.
Now there is complete acceptance of the displayed sound by every and each listener.
The improved signal transmission has its effect on every recorded instrument in all sorts of music. The grand piano of Ingrid Haebler is more real and has more felt on the hammers. The bass of Ray Brown on a Contemporary record playing with Barney Kessel and Shelly Manne is more snug. Voices in choirs are broad and articulate. The quality of pressings and the way the recordings are made is more evident than before.

The significant improvement came about by just starting at the turntable side.


If you consider to go for the Bullet Plug, I would suggest that you start with a 4 pack and treat the front end signal of  CD-player or phono cartridge. That is: if you have become interested enough.
If after this trial you are as satisfied as I am, you can procure more Bullet Plugs and continue to improve more signal paths in your hi-fi system. After connecting my MC phono lead with Bullet Plugs I have continued improving the connections between my active crossover and the two main amplifiers. For these connections I originally did use Isoda Hybrid Cable which I had chosen several years ago because of its cleanness, but which I have changed for another type.


The Bullet Plug accepts the Isoda cable easily. At one end I always solder the shielding together with the earth wire (black) to the Bullet Plug. At that end I connect the cable to the source, in this case the crossover. In this way the shielding of the housing of the crossover is extended all the way to the power amp. Making the connections with the Bullet Plug meant not only a further improvement of detail and strength, but contributed significantly to a deeper and wider stage, for example when listening to Les Brown and His Band of Renown. It must be that through the Bullet Plugs the transmission of the low and high section signals gained in equality. This of course can be attributed to the precise physical properties of the connectors.
Soldering is generally very easily done. And in case you are not satisfied with the cable you initially used with the Bullet Plug, do not worry, the Bullet Plug is easily removed and reused of course. The plug's body is made of a very hard quality plastic which does not deform or melt easily (like the plastic of the ordinary type of plug). The design is such that it procures a snug fit on all apparatus. That is why it is advised to gently heat the red/black flange with a hairdryer before fitting the plug to large RCA sockets.

Now is the time that you will hear the quality and characteristics of specific cables more than ever. Now a cable choice is more significant. The Bullet Plug accepts cables with a maximum diameter of 9 mm. And to finish of the construction of your own interconnects, you may want to use a (clear) heat shrink wrap over the outer housing where the cable enters the housing. This may provide a more secure, long term fitting.


The Bullet Plug lets you also hear the design of circuits and the sound characteristics of amplifiers instead of blurring the information. Except for the interconnects of my Tandberg 10X tape recorder and Denon DCD 2560 CD-player all leads have been fitted with Bullet Plugs. And I am very happy with the improvement in precision, detail and cleanliness of the sound. 'Recommended' is my verdict. The improvement made me think and wonder what the next step would be. That is: what about female plugs and the RCA sockets on the chassis of the various components? Robert Woodland told me that a concept is on the drawing table. So, in due time we will have another surprise.

The image below shows the generally adopted way to make the connections inside the Bullet Plug or any RCA phono plug. The preamplifier is the central point in the chain. There the shielding (earth) has to be connected to the negative conductor. At the end of the power amplifier the shield is not connected. The idea is that the chassis of the preamplifier extends to the chassis of the power amplifier through the shielding of the interconnecting cable. So in case of phono cartridges, pre-preamplifiers and step-up transformers, CD-players, etc. the plug at the preamplifier has the shielding connected to the negative. This method can only be used if you have a cable with two conductors (leads) plus a shielding.

Rudolf A. Bruil, June 29, 2001

Audio&Music Bulletin - Rudolf A. Bruil, Editor - Copyright 1998-2011 by Rudolf A. Bruil and co-authors