Monthly Archives: December 2009

Custom Console Stereo

For those of you wanting to hear just how good a custom built vacuum tube amp or console stereo will sound, here’s a video from Steve at Custom Tube Art which shows the workmanship of his projects and the quality of the sound.

Steve had this to say about his latest project:

Here is a 1960’s style custom console stereo I built displaying the vacuum tube amplifier right next to the Garrard type A turntable. The 807 tube amplifier has a conservative output of 30 watts per channel and uses 6SN7 and 12AU7 pre amp tubes. The speakers are a pair of Jensen 15″ drivers and a pair of DeForest 3″ tweeters in each cabinet. The entire project took two months to build.

You can see more of Steve’s custom work on his Vacuum Tube Amp web site.

Connector Terms and Glossary

Are you a connector newbie? Below is a collection of terms relating to connectors with their corresponding definitions.

Attenuation – Decrease in power due to resistance or mismatch in transmission line.
Back Mounted – When applied to a coaxial connector it is that connector mounted from the rear of a panel with the fixing nut on the outside.
Bandwidth – Distance between two frequencies over which a RF or microwave device is intended to work.
Between Series Adaptor – An adaptor used to connect two different generic types of connector.
BNC – Bayonet Nut Connector.
Braid – A weave of metal strands used as an electrical shield for an insulated conductor or group of conductors.

Connector

Connector


Bulkhead Mount – The type of connector fitted to a chassis using a single cut-out hole.
Cable Retention – The mechanism that joins the connector to the cable.
Cable Retention Force – The axial force which a connector / cable join can withstand.
Captive – A component such as a contact which is held firmly in position.
Characteristic Impedance – That impedance at which the transmission line is intended to work. A change from the characteristic impedance along its length will cause mismatch and loss of power.
Clamp – The holding of a cable by use of a screw thread action.
Closed Entry Contact – A female contact which is designed to prevent insertion of a contact larger than that specified.
Coaxial Cable – A transmission line where the one conductor is concentric inside another, often abbreviated to “coax”.
Coaxial Termination – A resistive element used to end a coaxial line in its characteristic impedance.
Coaxial Terminator – A device for terminating coaxial cable to a PCB or bulkhead mount (a mechanical device and should not be confused with coaxial termination)
Conhex – Tradename covering SMB and SMC, both in 50 Ohm and 75 Ohm impedance (discontinued)
Connector Durability – The number of times a connector can be physically mated and still maintain its specified performance.
Contact Resistance – The measurement of the DC electrical resistance between a pair of mated contacts. Usually specified as being measured after a given number of mating cycles.
Corona – A discharge of electricity caused by the ionisation of the air around a conductor just prior to total breakdown or flashover.
Crimp – The action of distorting a metal tube to give intimate contact with a conductor; a good crimp should be gas tight and not be impacted by environmental change.
Crimp Dies – The tool inserts which determine the shape of the distortion to create a consistently good crimp.
Crimp Tool – The tool which holds crimp dies to apply the necessary force.
Cross Talk – The amount of signal which may be transferred from one signal carrying line to an adjacent line.
Cut Off Frequency – The frequency at which the loss exceeds a predetermined level.
Decibel (dB) – A unit of measurement of RF power loss.
Dielectric – The insulating medium which holds the center conductor concentric within the connector or cable.
Dielectric Constant – The electrical value of dielectric which determines the impedance in cables or connectors with constant diameters.
Dielectric Withstanding Voltage – The maximum voltage that a dielectric material can withstand without failure.
Direct Solder – A common method of terminating connectors to semi-rigid cable by soldering the cable jacket to the connector.
Discontinuity – A dramatic change in characteristic impedance which gives rise to a reflected wave.
Dissipation – The unused or lost energy in a system e.g. heat.
Distortion – An unwanted change in a signal wave form.
Dummy Load – A device connected to the end of a transmission line to absorb transmitted power and prevent reflected energy.
Dust Cap – A mechanical device attached to the mating face of an unmated connector to prevent ingress of contaminants and provide protection against mechanical damage.
Electromagnetic Compatibility (EMC) – The ability of a device to operate within its intended environment without being effected by or generating electromagnetic interference (EMI).
Engagement and Separation Forces – The forces required to mate and unmate a pair of connectors. The forces are usually specified as a max & min for each action.
Environmentally Sealed – A connector that is provided with seals or other devices to prevent ingress of dust, moisture or other contaminants while mated which might impair performance.
Flexible Cable – A coaxial cable where the outer conductor is flexible (usually braided).
Gigahertz (GHz) – A measure of frequency representing 1 billion Hertz (cycles per second).
Impedance – See ‘Characteristic Impedance’
In-Series Adaptor – An adaptor which enables the connection of two connectors of the same generic type.
Insertion Loss – The loss of power due to a particular component in a transmission line (e.g. cable).
Insulation Resistance – The electrical resistance between two conductors separated by an insulating medium.
Intermodulation – The mixing of two or more frequencies which are not intended to mix.
Interface – The two surfaces of a connector which come into intimate contact when the two halves are mated.
Inter-series Adaptor – See ‘Between Series Adaptor’
Isolation – The measure of interaction between two or more transmission lines.
Jack – One half of a mating pair of connectors. The jack interface normally goes inside the plug interface.
Mean Power – The mean value of the rate at which energy is transmitted from one place to another.
Micro Strip – A transmission line consisting of a flat conductor on a dielectric above a single ground plane. (the ground plane is frequently a metalized face of the dielectric).
UG909B/U Female Bulkhead Clamp Kings Connector

UG909B/U Female Bulkhead Clamp Kings Connector

Microwave – Very short electromagnetic waves. Frequency range above 1 GHz.
MIL-C-39012 – The generic specification covering USA Military coaxial connectors.
MIL-C-17 – The generic MIL spec covering coaxial cables.
Mismatch – The condition in which the impedance of the source and load are not the = same. This reduces power transfer and causes reflections.
Mounting Plan – The design of the PCB or panel cut-out used to mount the connector. N Connector – This was the first true microwave connector capable of working to 18GHz, initially designed for test applications.
Nanohex – Trade name covering SSMB & SSMC (discontinued)
Noise – An external electromagnetic signal which interferes with the desired signal.
Non-captive – A component such as a contact which does not have a retention feature.
Passivation – This is a surface treatment applied primarily to stainless steel. The process removes contaminating iron particles and produces a passive surface.
Peak Power – Is the maximum power which may be handled by a connector or cable.
Plug – One half of a mating pair of connectors. The plug interface normally goes outside the jack interface.
POSNS – Abbreviation for “positions”.
PTFE – Abbreviation of polytetrafluorethylene. This is the most commonly used dielectric (insulator) used in professional coaxial connectors.
QPL – Qualified Parts List. Parts approved to MIL-C-390 12 specification.
Receptacle – A term used to describe a connector assembly usually bulkhead or PCB mounted.
Return Loss – A reason for loosing RF energy due to signals being reflected due to a mismatch in a transmission line.
RF Leakage – The RF power lost from a transmission line or device. Measured in dB.
RG – The traditional prefix for MIL spec coaxial cables.
Screw-on – The mating action of connectors which are joined using a screw thread (e.g. SMC)
Sealflex2â„¢ – Cannon trade name for a flexible microwave cable assembly which has a performance similar to semi-rigid cable.
Semi-rigid Cable – A coaxial cable where the outer conductor is a solid metal tube.
Skin Effect – The tendency of alternating currents to flow near to the surface of a conductor; this increases resistance and becomes more marked the higher the frequency.
SMD – Sometimes used as an abbreviation for slide-on variants of SMB. This is a misnomer, the more common use is for Surface Mount Device.
Snap-on – A term used to describe the mating action of SMB and SSMB connectors.
Solderless SMA – An SMA connector that can be connected to semi-rigid cable by compressing the inner body rather than by soldering (sometimes referred to as semi-rigid ‘crimp’ connectors).
Stripline – A method of building a microwave circuit. The circuitry is sandwiched between 2 ground planes. Sometimes referred to as Tri-plate.
Teflonâ„¢ – DuPont tradename for PTFE.
Tensile Strength – The greatest force a device can withstand without tearing or pulling apart. This is frequently the method of determining the effectiveness of a crimp.
TNC – Thread Nut Connector same size as BNC; the only obvious difference is the coupling nut.
Tri-plate – See Stripline.
UG Symbol – Used to indicate a connector made to US government spec.
Voltage Standing Wave Ratio (VSWR) – A way of expressing the resultant loss of power as a result of signal reflections due to discontinuity.

The Titan – Newest (and biggest) Vacuum Tube Amp from Steve

Just in from our friend Steve W. in Canada (who constructs the most amazing vacuum tube amplifiers)…

The best way to describe this next amplifier is it’s a Titan. It has to be the biggest, baddest, heaviest and most powerful amplifier I’ve made to date! Weighing in at just under 60 lbs. this push-pull-parallel EL-34 / 6L6 is conservatively rated at 110 watts per channel using EL-34 tubes. Capable of driving 4 or 8 ohm speakers via a switch on the back panel, this amp is a tube roller’s dream.

Simply by plugging in which rectifier tubes you want to use, be it a pair of 5Y3’s, 5R4’s, 5U4’s or even 5AR4’s you can match the correct plate voltage with what ever power tubes you choose, be it a set of 6V6’s, 6L6’s, 5881’s Kt-66’s, Kt-77’s, EL-34’s, or even 7591’s.

You also have the choice of running the amp in push-pull instead of push-pull-parallel simply by not installing the front four power tubes and switching off one of the two rectifier tubes via a switch located on the right hand side of the chassis. The signal and phase-inverter pre amp tubes used are my favourite large dual triodes 6SN7’s.

Now, about the transformers, seeing that this amplifier has to drive thirteen tubes, I thought it only made sense to use a separate filament power transformer. The transformer right next to the larger power transformer is the 20 amp filament transformer. By doing this, I’ve removed the heater load off of the main power transformer which now only has to supply the high voltages the amp needs.

Along with a hefty octet of 470 mfd 400 volt capacitors bought from West Florida Components, there is more than enough capacitance to keep this amp in the black during those high current moments when the music demands it.

By sharing the load this way, the main power transformer will not be taxed nearly as much. The output transformers are massive Hammonds that can easily handle the wattage this amp delivers.

You will notice a volume control knob located right smack in the middle of the mirror in front of the amp that’s surrounded in pure copper foil, and that is because this is a fully integrated power amp with a line stage pre amplifier built into it. That means you do not need to buy a separate pre amplifier. You only need to plug in your CD player, satellite, MP3, I-pod, or what ever type of line stage device you like to use, directly into the amplifier.

There are two benefits to an integrated amp, one, you don’t have to go out and spend money on a separate pre amp, and two, you are amplifying completely with tubes throughout the whole amplifying process from pre amp to power amp, and that makes it sound better, way better!

Once again – amazing job, Steve! Thanks for sharing this with our readers.