High quality in-wall UL-C2 rated 10-gauge A/C wiring ?


I am looking to re-wire my listening area front-wall with a dedicated A/C circuit using 10-gauge UL-C2 rated in-wall wiring.  I know Audience makes a high-quality one however I didn't want to pay $26/foot.  I would need ~60-ft.  I've already purchased two high-quality A/C receptacles and wanted to do 10-gauge to them from a dedicated breaker.  
Anyone have any experience with this or know of other mfg's of 10-gauge A/C UL-C2 wiring ?

Thanks !
30fa39fd 1af9 49c1 a18f 00973f6970ffAg insider logo xs@2xliquidsound
I my current setup I use Synergistic Research provided quantum tunneled Romex -- as I recall it was cheap. Previously in an older installation I used JPS in wall (https://www.thecableco.com/power-ac-in-wall-power-cord-bulk.html) but that costs even more than the Audience ...
I am looking to re-wire my listening area front-wall with a dedicated A/C circuit using 10-gauge UL-C2 rated in-wall wiring. I know Audience makes a high-quality one however I didn’t want to pay $26/foot.


https://www.tweekgeek.com/audience-in-wall-wiring/

If you are wiring a dedicated circuit for your audio sytem, THIS is the wire to use. Audience In-Wall wire is UL rated for in wall use, and is simply the purist, best sounding wire you could use to power your audio system. Robert Harley, and the Head Geek both use it in our listening rooms.

You have 3, 10 AWG high purity stranded copper conductors for the hot, neutral and ground legs. There is an additional drain wire for the shield, and the outer metal jacket offers additional protection from screws, nails, and RFI. Not only does this wiring sound good, it’s safe. The cable is also cryogenically treated to further reduce self-noise by decreasing the physical boundaries between the crystalline structure of the copper.

Features of Hidden Treasure include:
  • UL CL2 approved for 120v and 220v AC in wall applications
  • 10 AWG, 3 conductors
  • Stranded 99.9999% pure OFC, cryogenically treated copper conductors
  • XLPE dielectric with PVC sleeve
  • Foil shielded
  • Flexible
  • 18mm OD
UL listed yes...... For what type of application? ..... UL listed for use as branch circuit power wiring?

CL2: This is a cable jacket fire resistance rating defined in Article 725 of the National Electric Code. It stands for "Class 2 Remote-Control, Signaling, and Power-Limited Circuits" cable, which indicates that the cable is suitable for in-wall installation and use for certain low-voltage applications. Examples of Class 2 circuits include burglar alarm cabling, intercom wiring, and speaker wire. The jacket is designed to protect against voltage surges of up to 150 volts.
https://www.cablewholesale.com/support/technical_articles/confusing_cable_terms.php


Before you buy any so called hi-end in wall branch circuit power wiring/cabling check with your State, County, or local city government AHJ (Authority Having Jurisdiction) that applies to your area. Make sure it meets electrical Code for your area.



https://www.ecmweb.com/cee-news-archive/classification-circuits-under-article-725

.
@jea48 point is well taken. In Southern CA I had no issues having the jacketed JPS cable put in directly in wall but in Portland where (probably in retrospect in error) I had conduit installed my electrician needed to strip the SR Romex into its three constituent cables and run them separately inside the conduit. Suffice it to say consult your local code knowledgable sparky before you set off.
Romex style with two parallel conductors and the earth between them is only bested by twisted LNE in aluminum and twisted LN.

The worst is random wire in steel conduit.

see https://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf p31ff.

https://web.mit.edu/jhawk/tmp/p/EST016_Ground_Loops_handout.pdf

A question for the fancy-pants fans: Electricity comes hundreds of miles, through umpteen transformers, 'suspect' cable & connectors to power meter, panel, breaker, & jack and a few feet of fancy wire is going to 'fix' it?
Not sure if my experience will help, but I recently moved to a new house and had a dedicated AC supply wired with this cable -

https://mcru.co.uk/product/mcru-10mm-shielded-mains-spur-cable/?v=69e1aafeccc5
In my previous place, I also had a dedicated supply but wired with normal romex.  Well, my system (no change before move & now) now sounds quieter with less background hash & noise, the midrange is richer and the top end resolution is better but sounds less sharp.  I need to clarify that the room is obviously different with much higher ceilings (16ft. now vs. 9ft before) but leaving that aside, there is no doubt that the sound now is much much better.Hope this helps. 
A question for the fancy-pants fans: Electricity comes hundreds of miles, through umpteen transformers, ’suspect’ cable & connectors to power meter, panel, breaker, & jack and a few feet of fancy wire is going to ’fix’ it?
Water comes all the way to your house in/through some of the worse conditions imaginable, and yet we filter it before we drink it.

Despite the red herring, it’s the condition of the power right where it enters your house/abode, be it at the junction box, or the outlet, depending on what you can afford to do, that matters. That 17,000# transformer outside your house, on your block, kind of makes moot, the whole thing about all that distance it had to travel.

A little filtering here, some better wiring there, ensures better, consistent power.

All the best,
Nonoise


Each transformer in the line adds some distortion. The neighborhood transformer couples the grunge from the neighbors on to mile line.

Filtering I understand.
What is the filtering capacity of a 2m 14ga cable?

One of the claims is better transmission.
Power lines are contaminated with DC, several 10s % HD, RF, etc.
So, the fancy cable is better able to pass the noise and grunge?!?1?!
Thanks to all of you who have responded to my requests !  I have taken the time to quickly review the latest post with links to a great education on power and grounding.  Even though I'm electronically-trained, it was a terrific refresher and really summed up what and more importantly why I should use wiring that will reduce the possibility of adding stray and induced noise.  It appears there is a lot of mis-information out there and "snake-oil".  Perhaps the high-dollar in-wall power cable is good and helps with low-noise, however I believe my choice will be 10-gauge Romex.  
Thanks again to all who have responded !  
The Audience wire is interesting, but I would actually just use cryo'd 10awg Romex myself.  VH Audio sells cryo'd 10-2 Romex for 2.99/foot, or $469 for a 250 foot roll.  The Romex will meet code for running inside walls and through attic areas.  Other wire may or may not (and might have to be run in conduit).  Some people have said they get better results with 8awg THHN, but that is going to be stranded and also needs to be run completely in a conduit.  The Romes is solid core, which is better in my opinion (even if it doesn't quite have the current cabability of 8 awg).
auxinput  

1,651 posts   
06-08-2019 6:00pm  

The Audience wire is interesting


Interesting? That it is not designed, manufactured, or approved, for use as power branch circuit wiring?
Under the electrical code https://www.usawire-cable.com/pdf/nec-ampacities.pdf 14ga wire is good for 20A, 8 for 40A. Continuous.

Other than large Class A amplifiers, 4  nines of HiFi systems don't ever come anywhere near even 20A. With a linear supply, that's ≈1400W.

https://www.usawire-cable.com/pdf/nec-ampacities.pdf


** Unless specifically permitted in Section 240.4(E) through (G), the overcurrent protection shall not exceed 15 amperes for 14 AWG, 20 amperes for 12 AWG, and 30 amperes for 10 AWG copper; or 15 amperes for 12 AWG and 25 amperes for 10 AWG aluminum after any correction factors for ambient temperature and number of conductors have been applied.
Just one example why the NEC should never be used as a design specification or an instruction manual. The NEC is bare minimum electrical safety standards.

NEC 90.1:
National Electrical Code 90.1 Purpose:

    (A) Practical Safeguarding. The purpose of this Code is the practical safeguarding of persons and property from hazards arising from the use of electricity.


    B) Adequacy. This Code contains provisions considered necessary for safety. Compliance therewith and proper maintenance results in an installation that is essentially free from hazard but not necessarily efficient, convenient, or adequate for good service or future expansion of electrical use.


    FPN: Hazards often occur because of overloading of wiring systems by methods or usage not in conformity with this Code. This occurs because initial wiring did not provide for increases in the use of electricity. An initial adequate installation and reasonable provisions for system changes provide for increase in the use of electricity.

    FPN, Fine Print Notes. Suggestions, not mandatory.



    Continuous..... Average..... Doesn’t account for dynamic peaks, spurts, of current draw from an amplifier when amplifying a high dynamic signal. Amplifier power supplies like, need, a steady AC mains Line voltage.

    Nelson Pass https://www.passlabs.com/press/power-supplies-commentary-consumers


    Post by Ralph - Manufacturer, Atma-Sphere Music Systems
    https://www.audioasylum.com/audio/cables/messages/17/174988.html

    The subject matter is for a power cord. The same would hold true for branch circuit wiring. Even more so for a convenience outlet branch circuit where other loads are connected to the same circuit as an audio system.
    Jim
    .
    @jea48 
    The breaker limits the current below the wire ampacity. A 15A circuit has 5A current reserve capacity in the wire according to the NEC.

    From Pass:

    Typically, a Class AB stereo amplifier rated at 200 watts per channel continuously should be capable of delivering 700 watts or so, and this means a transformer rating of about 2000 watts. Anything less means non-continuous operation. This might be alright for a class AB amplifier where maximum continuous operation is not required.
    Confirms that most systems do not require 20A. Any humongo transient that occurs when the 120v line is 0v is going to suck down the caps regardless of the transformer size. The supply capacitors need to be of sufficient capacity and low ESR to handle the transients supplying the required current without falling below the required voltage.

    Toroids are somewhat fan-boy sales bait. They are not a free lunch.
    http://www.soundstagenetwork.com/maxdb/maxdb071998.htm

    I'd read Ralph's post and agree with him.
    Post removed 
    Table 310.15(B)(16):
              60°C     75°C      90°C
              TW       THWN    THHN
    14ga  15A        20A         25A

    Encore Wire NM-B : Color-coded Polyvinyl Chloride (PVC) compound meeting the required thickness of Type THHN or THWN-2 with a heat-stabilized Nylon jacket rated for 90°C in dry locations.
    https://www.encorewire.com/wp-content/uploads/EncoreWire-NMB.pdf

    The NEC de-rates 14ga to 15A per circuit by breaker.

    Table 310.15(B)(2)(b) allows increasing a 90°C current rating by 14% below 25°C in some installation types.

    The bottom line is 14ga is not going to starve the typical HiFi.

    What will gum up the works are ’sh.tty’ daisy chain ’quick-connects’ so typical of modern construction.
    ieales

    356 posts
    06-10-2019 1:46pm

    Table 310.15(B)(16):
    60°C 75°C 90°C
    TW THWN THHN
    14ga 15A 20A 25A


    Encore Wire NM-B : Color-coded Polyvinyl Chloride (PVC) compound meeting the required thickness of Type THHN or THWN-2 with a heat-stabilized Nylon jacket rated for 90°C in dry locations.
    https://www.encorewire.com/wp-content/uploads/EncoreWire-NMB.pdf

    The NEC de-rates 14ga to 15A per circuit by breaker.

    Table 310.15(B)(2)(b) allows increasing a 90°C current rating by 14% below 25°C in some installation types.

    The bottom line is 14ga is not going to starve the typical HiFi.

    What will gum up the works are ’sh.tty’ daisy chain ’quick-connects’ so typical of modern construction.
    None of your post addresses Voltage drop.

    You throw out a Link for NM-B and disregard the footnotes below the chart. Did you even check them out?

    Here is some reading material for you.
    https://www.ecmag.com/section/codes-standards/sizing-conductors-0

    What will gum up the works are ’sh.tty’ daisy chain ’quick-connects’ so typical of modern construction.
    But don’t worry the wire is rated for 20 amps. As long as the insulation is rated 75C, and all of the termination connections are rated 75C.  No need to worry about VD, Voltage Drop, for what ever reason on the branch circuit. The 15 amp circuit breaker will pass a continuous load of 15 amps all day long without tripping. If the Voltage is bouncing around due to a power amplifier being driven hard playing a high dynamic music source Just blame the distortion heard solely on the amplifier.

    Food for thought. When using the formula for single phase voltage drop on a circuit the temperature rating for the insulation covering of the wire is not part of the equation.
    Example:
    http://www.adamselectric.coop/wp-content/uploads/2015/02/Voltage-Drop.pdf
    .
    We're getting lost in the weeds. 14ga wire will power most any HiFi without any problems providing the wiring is up to snuff.

    Most modern houses have ’sh.tty’ daisy chain ’quick-connects’  and a
    fancy power cable at the end of a series of ’sh.tty’ daisy chain ’quick-connects’ ain't gonna do jack. 

    Just FYI, I removed all the ’sh.tty’ daisy chain ’quick-connects’  in my house [100s of them] because they eff-up everything from my espresso machines, to our waffle makers, to the missus iron, blow-dryer, etc.

    I had a 3v drop form one side of our media room to the other just due to the ’sh.tty’ daisy chain ’quick-connects’  on a lightly loaded HT circuit.

    Removed the oxidation, and screwed the terminals down gas tight and now nary a VD to be found.

    PAX
    @ieales - I disagree.  I did testing with a double-run of 14awg romex (that's 2x14awg which makes an 11awg total).  The result was just not as good as a standard 12awg or 10awg romex.  The smaller 14awg just cannot respond to on-demand current as well as the larger awg romex.
    auxinput said:


    I did testing with a double-run of 14awg romex (that’s 2x14awg which makes an 11awg total)

    @auxinput,
    Though you doubled the size of the conductors there is a good chance you also increased the chance of inducing a voltage from the current carrying loaded conductors onto the equipment grounding conductor of the opposing Romex cable. To prevent this from happening you would have to keep the two paralleled Romex cables separated from one another. You may have also doubled the chance of picking up AC noise on the two Romex cables you installed from other nearby/close Romex branch circuit conductors.

    Read pages 31 thru 36.

    https://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf

    There is no doubt though 12/2 with ground Romex is better than #14 if installing a new branch circuit to power an audio system. The labor cost will be the same. The only additional cost will be the Romex cable. It’s a no brainer, imo.

    .
    About 4 months ago I ran 2 runs (40' each) of the Audience Hidden Treasure in-wall AC cable to my system. I paid $18 per foot for it and used 2 Furutech GTX-D NCF (R) outlets. Audience is located in San Diego, Ca. and I live in Los Angeles, Ca. Big step up from the standard #12 wire I had replaced. Very expensive but if you don't have a long run it's worth considering.

    @ron17

    Had you hired a reputable licensed electrician for the install he would have told you it does not meet the National Electrical Code for branch circuit wiring.
    CL2, Class 2 cable.


    CL2: This is a cable jacket fire resistance rating defined in Article 725 of the National Electric Code. It stands for "Class 2 Remote-Control, Signaling, and Power-Limited Circuits" cable, which indicates that the cable is suitable for in-wall installation and use for certain low-voltage applications. Examples of Class 2 circuits include burglar alarm cabling, intercom wiring, and speaker wire. The jacket is designed to protect against voltage surges of up to 150 volts.
    https://www.cablewholesale.com/support/technical_articles/confusing_cable_terms.php

    The jacket is designed to protect against voltage surges of up to 150 volts.
    The branch circuit wiring in your home has a 600V rating.

    NEC Article 725
    https://www.ecmweb.com/cee-news-archive/classification-circuits-under-article-725


    https://www.thecableco.com/power-ac-in-wall-power-cord-bulk.html

    Specifications are easily met at 30 amps with heavy duty 600V, 105C rated (UL) VW-1, (CSA) FT-1, 2 x 10 AWG (5.27 mm2) current carrying conductors, plus ground (3 conductors total). Outer diameter is approx. 0.6 inches (1.5 cm) overall but flexible and easy to install. This unique AC cable noticeably improves performance and resolution in any quality installation, and once installed as a dedicated run to the main panel avoids the need for extensive conditioning within the room. Please specify and install JPS Labs Power AC In-Wall cable into your critical audio or video room, recording studio or editing room for the finest possible results without the worry of ground loop hum and noise affecting audio and video quality. Do it once, right!



    The above information is from the manufacturer.


    This cable meets the NEC. (Verify with your local AHJ for your area. Note the red outer jacket. Not required by the NEC to be orange in color because the conductors are #10awg.) Color coding of NM cable is a NEMA manufacturer thing.

    *** I am not recommending the cable one way or the other. ***

    Note: The maximum branch circuit breaker size is 20 amp for 2 or more 15 amp outlets or for a 20 amp outlet/s

    Jim
    .
    @jea48 - interesting read, but the problem I had did not relate to ground loop buzz / voltage inducement. I believe now it had to do with the voltage in the tiny 14awg wire being restricted by the high dielectric constant on the insulation (something I have definitely found on small gauge wires). On a larger 10/12awg conductor, there is less percentage of voltage restriction with more area/mass of conductor. My result of 2x14awg romex was weak bass/midbass punch. A single 12awg gave much better impact/sound.
    I did testing with a double-run of 14awg romex (that's 2x14awg which makes an 11awg total
    Please describe the 'test' in detail from start to finish

    Unless you were able to compare the original to the new, in real time, any perceived change is pure fantasy

    voltage in the tiny 14awg wire being restricted by the high dielectric constant on the insulation
    ROTFLMFAO!!!
    @ 60Hz?
    Gimme a break!

    Yeah, seriously.  I have experienced this same exact thing in power cord conductors (which transfer the same 60hz A/C).
    As far as the 2x14awg romex test was concerned:
    1. Take two 50 foot lengths of 14awg romex.
    2. Take the two black hot leads of both cables and connect them to the same 15A/20A circuit breaker.
    3. Take the two white neutral leads and connect to neutral bar in sub-panel.
    4. Take the two bare ground leads and connect to ground bar in sub-panel.
    5. Run the two 14awg romex cables to outlet.
    6. Connect the two black hot leads to hot connection on outlet.
    7. Connect the two white neutral leads to neutral connection on outlet.
    8. Connect the two bare wire ground to outlet ground.

    So, essentially, I am doubling the size of the wiring from circuit breaker to outlet. This is the same thing that happens inside larger power cords.

    auxinput

    1. Take two 50 foot lengths of 14awg romex.
    2. Take the two black hot leads of both cables and connect them to the same 15A/20A circuit breaker.
    You'd need to check NEC on this as well as your local code. Also, note that only breakers designed for such a two-wire connection would be permitted.
    This is the same thing that happens inside larger power cords.
    No it's not.

    Even if R were the same, L&C are vastly different.

    In the 'test' did you also have the heavier ga single wire connected to the same side of the transformer and routed closely so you could listen to each with minimal delay? If not, there innumerable changes possible on the A/C
    Yup, I totally know that it's not to code.  My point was that 14awg is really not enough to supply good current to audio equipment.  The on-demand current draws are just restricted by the small 14awg wire along with the high dielectric insulation (this is not anything like foamed polyethelyne or teflon found on many good power cords).  While ieales seems to think that 14awg is perfectly okay for 20 amps of current (and it may be for general purposes, but highly not recommended!!!), is it definitely not acceptable for the fast current draws required by audio equipment for good sound.  You guys can laugh at me all you want, I really don't care because I know what works and what doesn't.
    Headroom loss for 14ga vs 10ga is less than ¼db @ ≈14A / ≈1600W
    See http://ielogical.com/Audio/CableSnakeOil.php#ACWiring
    Voltage drop calculator.
    http://www.windsun.com/Hardware/Voltage_Calc.htm

    Distance or Conductor Size: .... (Distance)

    Single or Three phase: ........... (Single)

    Conductor Type: .... (Copper)

    Installation: ............. (Conduit)   .... Same for Romex
    Voltage: .................... (120V)

    Maximum Voltage Drop: ... (Already set for 3%. You can change the percentage to what ever you want.)
    3% of 120V = 3.6V VD
    2% of 120V = 2.4V VD

    Conductor size: ...... (14 gauge)

    Current: ...................(12 amps)

    Max length of branch circuit for a 3% VD (Voltage Drop) 55.97ft.
    Max length of branch circuit for a 2% VD 37.32ft

    Remember, up, down, and all around when figuring the entire length.

    Dynamic Headroom:
    https://forum.audiogon.com/discussions/dynamic-headroom

    Here’s a quote from a Pro Audio web site, old post.
    Around 1984 when I bought my first QSC power amp I called QSC after reading that it has 3db of headroom. I was told that the 300 watt rms rated amp could produce 600 watts of peak power when needed.


    That means if I did a rim shot on the snare drum to make it louder or kick the bass drum harder when hitting a crash cymbal there would be enough power reserve for this and the amp would not clip. I remember the guy telling me its like snapping my fingers and then waiting a few seconds and snapping them again.
    https://forums.prosoundweb.com/index.php?topic=139460.10

    .

    I guess if all you listen to is elevator music at a moderate listening level #14 wire is all you need.

    .

    Note:
    When a load is known the NEC says the wire shall be sized at 125% of the connected load. Again when the load is known. Using #14awg copper wire, #14 has an ampacity rating of 15 amps. 80% of 15 = 12 amps.
    (For a continuous load. Continuous load is defined by the NEC for a load lasting 3 hours or more.)

    (ieales there’s your reserve you are looking for. )

    That does not mean you can’t load a convenience receptacle outlet circuit to the 15 amp max until the 15 amp breaker trips..... If it trips..... With a receptacle convenience outlet circuit the loads are not known. The limiting factor is the circuit breaker.

    In a dwelling unit there is no limit on the number of receptacle outlets that can be installed on a 15 or 20 amp branch circuit.


    .
    Other than Class A, HiFi is not a continuous load. A ’typical’ tube amp is about 1A per 70W sum of both channels.

    Peak power can be a numbers game. The 1974 FTC rule mandated an amplifier provide 1/3 rated power for 1 hour @ rated distortion without shutting down. Peak power is the greater of power supply or protection circuit voltage and current. Into a complex load, i.e. loudspeaker and cables, rated power maybe a fantasy.

    Most every home over 1500ft² in America fails the 3% rule in some area, being wired with 14/2. Obviously if one has a very heavy continuous draw, a heavier circuit should be installed.

    However, for the vast majority of systems, the load is neither heavy or continuous.

    I guess if all you listen to is elevator music at a moderate listening level #14 wire is all you need.
    and if you listen to Def Leppard @100db, your hearing is so screwed as to make HiFi irrelevant ~<;-P

    For nearly ½ century, I’ve used an oscilloscope to determine undistorted power at the load. Musical peaks of 100db are handled easily. Said oscilloscope also determines that line voltage is always more than sufficient to keep the power supplies at full charge!

    As mentioned previously: A large transient at line zero crossing depends 100% on amplifier power supply. 4/0 cable will not make one iota difference.

    And 3% drop is only about -¼db
    ieales

    361 posts
    06-17-2019 8:59am

    Other than Class A, HiFi is not a continuous load. A ’typical’ tube amp is about 1A per 70W sum of both channels.

    No kidding? I would never of known that without you telling me.

    Is that what you took away from reading my entire post?
    Hell, in the link you provided the guy used 14 amps for a purely resistance load for his bench tests for testing of dynamic headroom of a power amp. Why didn’t he use a real world testing? You know a power amp, connected to a load like speakers. Push the amp feeding it with a high dynamic source. Maybe the sound track from the John Wick Movie. That’s pretty intense.


    Much ado is made in some circles about the inadequacy of 14ga wiring and how it will diminish dynamics.

    14ga Copper wire has an ampacity of 28 amps. The U.S. National Electrical Code [NEC] rates 14ga THHN for 20A @ 75°C. Romex 14/2 is electrically equivalent to THHN. NEC limits 14ga to 15A circuits for a very adequate safety margin. See NEC 310.15(B)(16).

    To find how much loss is incurred on a heavily loaded 14ga circuit, a Semi Professional espresso machine, plugged into the first socket on a circuit and the only device, was measured. It has a 1600w heating element with a resistance of ≈8.25Ω or ≈14A current draw. The heating element is PID controlled. This duty cycle is a square wave and presents transients far in excess of anything in a HiFi system. Using a digital sampling oscilloscope [DSO], 100%, ≈50% and 0% duty cycle load voltages were recorded.

    No load measured 117.81vrms, load 114.02vrms integrating samples over 1 period for periods

    with the highest and lowest peaks respectively. Over several minutes, 50% or 100% duty cycle made no difference in the loaded voltage peaks.


    14ga Copper wire has an ampacity of 28 amps. The U.S. National Electrical Code [NEC] rates 14ga THHN for 20A @ 75°C. Romex 14/2 is electrically equivalent to THHN. NEC limits 14ga to 15A circuits for a very adequate safety margin. See NEC 310.15(B)(16).
    Another guy that doesn’t understand how to read the NEC.

    14ga copper wire is rated for 28 amps...... Maybe in free air. What is the length of the circuit for a 2% VD or even a 3% VD at 28 amps? Use the VD calculator... What is it at 20 amps.

    Not continuous, ........ but say for a quick short draw of 28 amps or even 20 amps. Now please use a realistic number for the distance, length, of the circuit conductors.

    Professional espresso machine
    Really, an espresso machine? Does that espresso machine have a power transformer,  bridge rectifier and electrolytic caps in it?
    I wonder if Ralph Karsten would agree you can substitute an espresso machine for one of his power amps for such a test.

    No load measured 117.81vrms, load 114.02vrms integrating samples over 1 period for periods
    with the highest and lowest peaks respectively. Over several minutes, 50% or 100% duty cycle made no difference in the loaded voltage peaks.
    What was the length of the wire in the circuit? Did I miss it?
    117.81V - 114.02V = 3.79V VD. What’s that going to do to the power supply of a power amp as the caps are trying to recharge? Read Ralph Karsten quoted material below.

    .


    I should have never mentioned the part about the NEC and the definition of continuous load for the 125% for sizing a branch circuit when the load is known. Way too much info for you. I should have left that whole thing out.

    The VD calculator was meant to shown how current and the length of the wire are directly proportional to VD. NOTICE: No mention of the type of insulation used on the wire. NO 60C or 75C or 95C. Why? Because the copper conductor in 60C wire is exactly the same as the copper conductor in 75C and 95C insulated wire.
    VD on THHN 75C insulated wire will be the same as TW 60C insulated wire.


    What the hell do you think the rest of my post was about? Continuous load of a power amplifier? NO it was not!

    The second issue is the high frequency current limiting. This is a bit trickier to understand, but its not quite rocket science. Almost any power supply consists of a power transformer, rectifiers and filter capacitors. When the the transformer voltage is higher than the capacitor voltage, the rectifier commutates (a fancy word for turns on and conducts). At that point the filter capacitors can charge up and will do so until the power transformer voltage falls low enough that the rectifiers cut off.

    At that point the circuit using the power supply drains the filter caps. Since this happens 60 times a second, the drain is usually not very much at all, so its only at the very peaks of the AC waveform that the caps are be replenished. There might be only a few microseconds or milliseconds that this can happen, and quite a bit of current might have to flow during that time, essentially a high frequency event.

    If the power cord limits current during this period, the performance of the circuit using the power supply might suffer, possibly due to increased IMD since the DC might have a bit more of a sawtooth on it than if the current was not limited.


    That means if I did a rim shot on the snare drum to make it louder or kick the bass drum harder when hitting a crash cymbal there would be enough power reserve for this and the amp would not clip. I remember the guy telling me its like snapping my fingers and then waiting a few seconds and snapping them again.

    Can you see any correlation in the two quotes? Any?

    .


    ieLogical is my domain.

    I used an espresso machine precisely because it is a resistor and a near constant load. I wasn't testing the dynamic headroom of an amp. That is a property of the amplifier and not the line. I could run the identical test on my HiFi, but it's much more of a PITA. Additionally, amplifier peak output has the inconvenient habit of occurring when the A/C line is not at peak, so the line cruises merrily along unperturbed. BTDT.

    3.79V VD What’s that going to do to the power supply of a power amp as the caps are trying to recharge?
    A 200w power amp is going transform that down to about 2V on the caps. 10ga is going to give +1V more on the caps @ 14A line draw

    So assuming the transpistors are full on and running off the transformer because the caps are flat, which they never are, instead of 40V at the speaker, there will be 39V. 20log(39/40) = -0.22db <OUCH!>

    There might be only a few microseconds or milliseconds that this can happen, and quite a bit of current might have to flow during that time, essentially a high frequency event.
    The line provides 60Hz. Full stop. It does not know diddly about any other frequency, distortion components aside. The power supply provides DC. The control devices modulate that DC to provide the AC to the speaker.

    When the load current drops as the signal alternates phase, the draw from the capacitors decrease and the capacitors charge. If the load amplitude peaks when the line is 0v,all the current is supplied by the capacitors.

    Please have a look at http://ielogical.com/assets/CblSnkOil/HFoverLine.png to see what is happening with high frequency and the line. The capacitors supply ALL the power when the transformed voltage is below the capacitor voltage + the diode drop.