Why plastic inside this Male RCA jack?

Discussion in 'Audio Hardware' started by George Blair, Oct 13, 2021.

  1. George Blair

    George Blair Senior Member Thread Starter

    Location:
    Portland, OR
    I have these nice RCA cables from QED, made in the UK. Unlike any others I own, there's a white and red (for R/L channels) plastic part inside the jacks. This makes for a fairly loose connection as they don't insert all the way on to the female connector. What's the reason for this, and why are all other jacks a metal ring instead?

    [​IMG]
     
  2. Carl Swanson

    Carl Swanson Forum Resident

    Why do you call them "nice?"
     
    F1nut likes this.
  3. George Blair

    George Blair Senior Member Thread Starter

    Location:
    Portland, OR
    They reviewed well @ What Hi-Fi?: Home review
     
  4. Dennis Metz

    Dennis Metz Born In A Motor City south of Detroit

    Location:
    Fonthill, Ontario
    That’s a shock
     
    harby and Jim N. like this.
  5. Gibsonian

    Gibsonian Forum Resident

    Location:
    Iowa, USA
    Looks like a design aimed at reducing mass of the negative contacts. There are other designs out there with similar purpose. Likely higher conductivity material than the normal brass used here. Likely copper base.
     
    jfeldt likes this.
  6. Thorensman

    Thorensman Forum Resident

    Theoretically the less brass/ metal
    Making contact the more pressure
    On it.
    Qed obviously done research into
    This part of cable performance.
    I.must have built over 100 cables
    I gave up. Ultimately you can buy better
    Than you build.
    One nice connector i did like was one with spring loaded outer ground.
    No noise whe you unplug.
     
    hi_watt likes this.
  7. George Blair

    George Blair Senior Member Thread Starter

    Location:
    Portland, OR
    Why do say that?
     
  8. Scope J

    Scope J Senior Member

    Location:
    Michigan
    Niiiice!
     
    hi_watt likes this.
  9. George Blair

    George Blair Senior Member Thread Starter

    Location:
    Portland, OR
    What's up with the satirical comments? Is it the word plastic? :sigh:
     
  10. Spin Doctor

    Spin Doctor Forum Resident

    You just have to keep in mind where you're posting. Some people are just, umm "different" here.
     
    Dischord, MassHysteria and Gibsonian like this.
  11. Ripblade

    Ripblade Forum Resident

    Location:
    The Six
    Same principle as the bullet plug: minimise contact area to minimise eddy currents in the connection. The bullet plugs use a single point contact and a lot more plastic.
     
    2channelforever and George Blair like this.
  12. Boltman92124

    Boltman92124 Fish tacos.

    Location:
    San Diego
  13. captouch

    captouch Forum Resident

    Location:
    Bay Area, CA
    Don’t know all the theoretical reasons for why you’d want to minimize the ground contact, but if the net result is a loose connection, it seems like a shaky trade off for whatever theoretical benefit that plastic gives you.
     
    F1nut likes this.
  14. Ripblade

    Ripblade Forum Resident

    Location:
    The Six
    The loose connection almost always happens on the hot pin, in particular the female portion that is sprung to accept different sized pins. The spring contact frequently weakens after time resulting in intermittent connection.
     
    Boltman92124 likes this.
  15. captouch

    captouch Forum Resident

    Location:
    Bay Area, CA
    Yeah, that sounds like an inevitable result of age or frequent use.

    Looking again at the pics posted by the OP, it seems to me that the plastic inner part is part of the mechanical compliant portion of the RCA that will accommodate different sized ground outers. Typically, the outer ground part of an RCA is separated to allow the ground jacket to spread as needed to accommodate the female outer which may vary slightly in size (not necessarily by design, but in reality).

    In the OP’s RCA cables, the outer is solid (no breaks), so it’s gotta be above the typical diameter of a RCA cable and the two metal prongs in conjunction with the two plastic prongs form the compliant part of the jack with the solid outer as a “backstop” to provide mechanical support to those compliant inners that allow for some range of female ground jack sizes.

    But my guess is the loose connection the OP speaks of is due to only half the compliant prongs (the metal ones) having any real strength, with the plastic ones providing some token support, but really, how supportive can plastic really be to form a tight connection.

    Seems to me in the effort to provide some theoretical benefit of reducing the amount of ground connection they created the potential for a less than fully secure mechanical connection.
     
    F1nut and Ripblade like this.
  16. Ripblade

    Ripblade Forum Resident

    Location:
    The Six
    They have to come up with an alternative to avoid patent infringements, possibly.
     
  17. Ilusndweller

    Ilusndweller S.H.M.F.=>Reely kewl.

    Location:
    Columbus, Ohio
    Yep, see diagram here. This also minimizes micro-arcing. Some of the KLE plugs have a similar design.

    ETI Research Bullet Plug RCA - VH Audio

    KLE Copper, Pure, and Absolute Harmony RCA Connectors - VH Audio

    IMHO using plugs of the above style is much more important than using 99.999997% pure, single crystal perfect surface ++++ blahblahblahblahblahblahblah wire.

    Why minimize contact area to avoid micro-arcing? You want to create metallic bonds between the plug and jack. Air gaps in the micrometer size range lead to micro-arcing and thus sound degradation (in theory at least, I have no experience with these plugs but I do believe a very small % of audiophiles could blind ABX pick out these single point/low mass plugs from the standard "maximum apparent area of contact designs" that 99% of us (including me) use.

    "When two surfaces are mated to one another, actual contact only occurs at various isolated points (the asperities) called junctions. When the areas of all the junctions are summed, one obtains the real area of contact. On the other hand, the area of contact which one determines through geometrical considerations of the actual part on a macroscopic level is called the apparent area of contact. The real area of contact is usually much less than the apparent area -- sometimes a thousand or more times less [11]. Typically the real area is about 1% of the apparent area. The diameter of typical junctions has been estimated to range from 1 micrometer to 100 micrometers [12].

    Considering only the real area of contact, it is the protruding asperities which will make contact with the opposing surface (and its protruding asperities). On an atomic level, because a force is being applied to push two surfaces together, bonding will occur somewhere in the junction if the two materials have compatible structures. The extent of cleanliness and other factors such as temperature and environment also play a role. This is due to the nature of atomic forces.

    Figure 1 shows the force versus distance between two surfaces [13] which is similar to the inter-atomic force vs. distance between two atoms [14]. Being in the trough signifies bonding and somewhere in any given junction there will be atoms which are in the trough. Thus there will almost always be some bonding between two unlubricated surfaces when an external force is applied. How much bonding occurs over a given junction depends on many things including the force applied, the compatibility of the crystal structures, material properties such as Young's modulus, how closely the two surfaces mate to one another on an atomic level and how clean the surfaces are. As two surfaces are properly cleaned the friction coefficient can become very large due to adhesion effects, sometimes even exceeding 100 [15]. This type of cleaning can involve sputtering in a vacuum chamber.

    If one considers two surfaces, each containing an infinite number of atoms being pressed together, statistics tells us that at some location in the interface of the two surfaces, the atoms of the opposing materials will be properly positioned and will lie in the trough of Figure 1. This creates a bond. As a tangential force is applied through sliding, the bond may break where it was formed. This does not lead to adhesive wear. If it breaks in the interior of either of the original surfaces though, adhesive wear has occurred. It will generally break in the softer of the two materials. "
     
    Last edited: Oct 13, 2021
  18. Ripblade

    Ripblade Forum Resident

    Location:
    The Six
    I'd like to come up with a connector that uses the aforementioned blah blah wire as the contacts directly....no solder or compression other than between the wire and the connector.

    One can dream...
     
  19. Ilusndweller

    Ilusndweller S.H.M.F.=>Reely kewl.

    Location:
    Columbus, Ohio
    I thought up what I believe to be a better idea than both he Eichemann and the KLE connnectors. Have the side connector come in perpendicular and be self tightening. The pin would come to a "fine point" but would need to have some type of hard coating to increase hardness. Tightening the pin would create metallic bonds and make for a very high "real area of contact:apparent area of contact" ratio which would minimize micro-arcing. And I dont think very much "real area of contact" is even necessary. From a scientific point of view(specifically surface science), the standard RCA plug is a piss poor design, albeit one that I think only a very small % of audiophiles could discern differences in SQ vs. a single point/low mass design. A plug like this would need to be designed with a particular wire/cable design in mind of course.
     
    Last edited: Oct 13, 2021
  20. R. Totale

    R. Totale The Voice of Reason

    You mean an F connector?
     
  21. Ripblade

    Ripblade Forum Resident

    Location:
    The Six
    Kind of, but for RCA socket
     
  22. Ilusndweller

    Ilusndweller S.H.M.F.=>Reely kewl.

    Location:
    Columbus, Ohio
    An F connector operates under the same principle I speak of (maximizing the real area of contact:apparent area of contact ratio and IMHO not much real area of contact is needed anyways due to the low current/voltages involved).

    While I think the outer RCA connection could be turned into an F type, turning the center pin of an RCA plug into an F type connection seems like (but possibly not with some fancy engineering) it would involve a complete redesign of the RCA "plug/jack system".

    I think? Cardas might have a (fancy and expensive) RCA phono plug where contact is made via a pin. Or used to.
     
    Last edited: Oct 14, 2021 at 3:24 PM
  23. harby

    harby Forum Resident

    Location:
    Portland, OR, USA
    I just looked this up:

    "Our half-plastic connector allows you to realize minimal electrical contact, developing maximum-path-length synergistic noise-inducing ground potentials over shield conductors, while also ensuring that the shielding encirclement of coaxial connectors is degraded, giving maximum electrical interference possibility for true environmental audio. The asymmetrical connection provides not only limp retention (to avoid pesky connections that stay firmly plugged in), but also at the same time apply torque forces to the RCA pin, ensuring maximum fatigue and permanent deformity in your equipment's receptacles."
    /s

    Solder, molten metal-on-metal, is better than the few actual surface molecules in friction contacts that break through oxidation to come in proximity. Once signals get inside equipment: 100 more solder joints.

    My turntable solves the debate about connectors and mis-specified cables by the cable being soldered to the tonearm board.
     
    C10 likes this.
  24. Ilusndweller

    Ilusndweller S.H.M.F.=>Reely kewl.

    Location:
    Columbus, Ohio
    Fatigue has nothing to do with this. I find some of the other stuff "interesting" as well (show data to back up claims, I bet they cant for the vast majority, but I can see reasons why they may prefer the sound for some of the reasons they speak of and these reasons DONT mean better specs. But Im not necessarily disagreeing with their subjective opinion as Ive also given reasons before why some might easily prefer basic OFC over 99.99999% pure single crystal blahblahblah wire. Same reasons some prefer tube sound over SS even though SS looks better on paper/specs wise. Crimping is also better than soldering(crimping=cold welding=plastic deformation(they say permanent deformity, same thing) =create metallic bonds (crimping=cold welding, Schmaudioquest makes a big deal about it, but QED seems to think soldering is superior to cold welding). You do need to bust through the oxides (and other layers)though.

    "2.3.1 Tribo-Surfaces

    Surface properties are very important and play a major role in determining wear behavior. After all, wear occurs at the surface. As wear progresses, the surface can change in such a way that a transition occurs in the friction and wear behavior. Some important features of the surface include its geometry and its mechanical, physical, and chemical properties.

    Geometrical parameters include the macroscopic shape of the contacting surfaces, as well as the microscopic shape, amount, and distribution of the asperities. An asperity is simply a protruding part on the surface of the material -- a high point. Mechanical properties include macrohardness, microhardness, Young's modulus, shear strength, and fatigue properties. Microhardness is different than macrohardness since a material is often a composite with smaller distinct constituents which have varying hardnesses. Physical characteristics include crystal structure and associated lattice parameters, thermal conductivity, and the ability of a material to work harden. Chemical factors might include chemical composition of the surface or how clean one is able to make a surface. Miedema states "any two metals can be bonded strongly, provided that the initial surfaces are clean" [8]. These are just some examples. In addition, many of these depend on the chemical environment in which sliding occurs.

    Initially two tribo-surfaces (disk and counterface in this research) are covered with layers of oxides, sulfides, and other solid compounds. On top of these compounds there are films of adsorbed gases and hydrocarbons. Without these surface layers, the mating surfaces could bond more strongly. Once sliding occurs, tangential motion at the interface disperses these contaminants at the contact points and cold welding can occur at these junctions. As sliding continues, these junctions are sheared and new junctions are formed. Wear debris is formed by this continuing adhesion and fracture of the mating surfaces. This is one example of a possible wear process.

    The act of wearing is a dynamic process, that is, the system is constantly changing and the process of wear can change some of the factors mentioned above. While the surface parameters affect the wear behavior, wear can also affect the surface parameters. In a stable or steady state wear situation, the change in the surface properties is negligible as wear progresses. To properly design a stable tribosystem one needs to understand the interrelationships between friction and wear and their effects on the tribo-surface.

    2.3.2 Stresses Involved in Tribotesting

    The stresses a material is subjected to during a sliding test (or for that matter rolling or impact also) can be considered on a macroscopic level as well as a microscopic level. The "macrostresses" are related to the overall geometry of the contacting members. The overall geometry is sometimes referred to as the "apparent area of contact". The "microstresses" relate to the local geometry of the asperity contacts. These local contacts define the "real area of contact".

    Considering the "macrosystem" of stresses, there are two general contact situations. An example of a conforming contact is a flat surface rubbing against another flat surface. An example of a nonconforming contact situation, is a sphere rubbing against a flat surface. For a conforming contact with normal forces only, the pressure distribution across the surface is uniform. The stress level is maximum on the surface. In a nonconforming contact situation, the stress level is not maximum on the surface. The Hertz contact theory predicts that the pressure is greatest in the middle of the contact and that the maximum shear stress is actually below the surface [9]. The distance below the surface has been estimated to be equal to one-third of the radius of the apparent contact area. Its value has been estimated to be approximately one-third of the maximum contact pressure [10]. So, in the case of a non-conforming contact situation, which is the case for this research (although it changes towards a conforming contact situation as the tribotest progresses), the maximum shear stresses are actually below the surface.

    The "macrostress" system and "microstress" system are really just ways of thinking about stresses. In reality a given contact has elements of both of these theories. The pressure distribution associated with a macrosystem can affect the load distribution across the asperities. As mentioned earlier, for nonconforming contacts, asperities in the center of the contact region will be loaded more than asperities near the edges of the contact region. When the asperities are loaded elastically, the stress field for a given asperity is similar to that of a nonconforming contact area since asperities usually have curvature. When the asperities are loaded at higher loads which cause plastic deformation, the stress field for the asperity approaches that of a conforming contact area situation. It should also be noted that as wear occurs, the stresses involved in the contact, both macrostresses and microstresses, can change -- it is a very dynamic process. An example of this is that a contact which was originally nonconforming can become a conforming contact as wear progresses. That is the case for this research.

    2.3.3 Adhesive Wear

    This type of wear has also been termed "sliding wear". Though sliding wear has also been used as a more general term which includes adhesive wear as just one of many components involved. Before describing this wear mode, it should be made clear that just because material of opposing surfaces is found adhered to one another after a wear test does not necessarily imply that chemical adhesion has occurred and one cannot jump to the conclusion that adhesive wear was occurring. "

    The above quote comes right before my quote in #17 (part of my thesis where I was studying the friction and wear properties of a Cr23C6 coating and Cr-Si coating that are environmentally friendly to produce and we were hoping would have better tribological (friction and wear) properties than electroplated chrome (nasty to make, carcinogenic hexavalent chromium, lots of nasty waste to dispose of as well).

    "Our half-plastic connector allows you to realize minimal electrical contact"

    The Eichemann and KLE plugs do a better job. A "pointy pin" like I speak of would do a better job than the Eichmann and KLE in this regard.
     
    Last edited: Oct 15, 2021 at 6:00 AM

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